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  • 1. Bishop, NI
    et al.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    CORRELATION OF THE PHOTOSYSTEM-I AND PHOTOSYSTEM-II REACTION CENTER CHLOROPHYLL-PROTEIN COMPLEXES, CP-AI AND CP-AII, WITH PHOTOSYSTEM ACTIVITY AND LOW-TEMPERATURE FLUORESCENCE EMISSION PROPERTIES IN MUTANTS OF SCENEDESMUS1980In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 49, no 4, p. 477-486Article in journal (Refereed)
  • 2. Björn, Lars Olof
    et al.
    Sundqvist, Christer
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    A tribute to Per Halldal (1922-1986), a Norwegian photobiologist in Sweden.2007In: Photosynthesis Research, ISSN 0166-8595, Vol. 92, no 1, p. 7-11Article in journal (Other academic)
  • 3. Borodich, A
    et al.
    Rojdestvenski, I
    Cottam, M
    Anderson, J
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Segregation of the photosystems in higher plant thylakoids and short- and long-term regulation by a mesoscopic approach2003In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 225, no 4, p. 431-441Article in journal (Refereed)
    Abstract [en]

    In this paper we consider the relationship between the lateral segregation of photosystems I and II in the grana and characteristics of the short- and long-term regulation in thylakoids following the mesoscopic approach. Our study is thermodynamic; it is based on the Flory-Huggins theory for binary mixtures and the McMillan-Mayer theory of heterogeneous solutions. We demonstrate that state transitions promote rearrangement of photosystems by either favoring their mixing after LHCII phosphorylation or enhancing their segregation after LHCII dephosphorylation. This regulation influences the entire system properties locally. We also demonstrate that the variations of the photosystem ratio promote rearrangement of the photosystems preserving their segregation. This regulation influences the entire system properties globally. The studies presented are another indication of the importance of the segregation of the photosystems in the grana thylakoids of higher plants. Segregation of PSIs and PSIIs is a signature of the spinodal decomposition, which is a fine regulatory mechanism, related to both the short- and long-term adaptations of the photosynthetic apparatus in higher plant thylakoids. (C) 2003 Elsevier Ltd. All rights reserved.

  • 4. Borodich, A
    et al.
    Rojdestvenski, I
    Cottam, M
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Segregation of the photosystems in thylakoids depends on their size2003In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1606, no 1-3, p. 73-82Article in journal (Refereed)
    Abstract [en]

    Lateral segregation of two types of photosystems in thylakoid membranes of green plants is one of the key factors that provide the stability and fine-tuning of the light quanta supply by pigment proteins and non-cyclic electron transport. Due to this specific feature of the membrane structural organization, the photosynthetic units function in the green plants with optimal performance. In this report a mesoscopic theory is outlined to address the physical aspects of segregation phenomenon. Results of theoretical studies and computer simulations suggest that charge mismatch and the size difference between two photosystems in grana are most responsible for their lateral segregation, which is driven by the screened electrostatic and lipid-induced interactions. Comparative simulations of photosystems of different sizes show the crucial dependence of their ordering on a geometrical parameter. It seems that the size effect alone may prevent photosystems from segregated arrangement in cyanobacterial thylakoids. (C) 2003 Elsevier B.V. All rights reserved.

  • 5. BRUNES, L
    et al.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    ELIASSON, L
    ON THE REASON FOR THE DIFFERENT PHOTOSYNTHETIC RATES OF SEEDLINGS OF PINUS-SILVESTRIS AND BETULA-VERRUCOSA1980In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 66, no 5, p. 940-944Article in journal (Refereed)
  • 6. Campbell, D
    et al.
    Bruce, D
    Carpenter, C
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Two forms of the photosystem II D1 protein alter energy dissipation and state transitions in the cyanobacterium Synechococcus sp PCC 79421996In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 47, no 2, p. 131-144Article in journal (Refereed)
    Abstract [en]

    Synechococcus sp. PCC 7942 (Anacystis nidulans R2) contains two forms of the Photosystem II reaction centre protein D1, which differ in 25 of 360 amino acids. D1:1 predominates under low light hut is transiently replaced by D1:2 upon shifts to higher light. Mutant cells containing only D1:1 have lower photochemical energy capture efficiency and decreased resistance to photoinhibition, compared to cells containing D1:2. We show that when dark-adapted or under low to moderate light, cells with D1:1 have higher non-photochemical quenching of PS II fluorescence (higher q(N)) than do cells with D1:2. This is reflected in the 77 K chlorophyll emission spectra, with lower Photosystem II fluorescence at 697-698 nm in cells containing D1:1 than in cells with D1:2. This difference in quenching of Photosystem II fluorescence occurs upon excitation of both chlorophyll at 435 nm and phycobilisomes at 570 nm. Measurement of time-resolved room temperature fluorescence shows that Photosystem II fluorescence related to charge stabilization is quenched more rapidly in cells containing D1:1 than in those with D1:2. Cells containing D1:1 appear generally shifted towards State II, with PS II down-regulated, while cells with D1:2 tend towards State I. In these cyanobacteria electron transport away from PS II remains non-saturated even under photoinhibitory levels of light. Therefore, the higher activity of D1:2 Photosystem II centres may allow more rapid photochemical dissipation of excess energy into the electron transport chain. D1:1 confers capacity for extreme State II which may be of benefit under low and variable light.

  • 7. Campbell, D
    et al.
    Clarke, A K
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oxygen-dependent electron flow influences photosystem II function and psbA gene expression in the cyanobacterium Synechococcus sp PCC 79421999In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 105, no 4, p. 746-755Article in journal (Refereed)
    Abstract [en]

    During acclimated growth in Synechococcus sp, PCC 7942 a substantial proportion of the electrons extracted from mater by photosystem II ultimately flow back to oxygen, This flow increases rapidly under high light, which allows Synechococcus to maintain photosystem II centers largely open, even under excessive excitation, The electron flow to oxygen with increasing light accounts for the progressive discrepancy between the light response curve of measured oxygen evolution, and the light response curve of photosystem II activity estimated from fluorescence measures. In cells under anoxia this flexible electron sink is lost and photosystem II centers suffer partial closure at the growth light intensity, with closure becoming more severe under excess light. As predicted from earlier work this PSII closure results in rapid loss of psbAI message, encoding the D1:1 protein of PSII, and induction of psbAII/AIII encoding the alternate D1:2 protein. The changes in the mRNA pool are not, however, reflected at the protein level, and D1:1 remains in the thylakoid membranes. There is no accumulation of D1:2, despite some continued synthesis of other proteins. PSII closure, therefore, results in repression of psbAI and induction psbAII/AIII expression, but D1:1/D1:2 exchange is blocked by anoxia, downstream from transcription. D1:1 protein and PSII activity are quite stable under anoxia and moderate illumination, Nevertheless, upon recovery under oxygenic conditions, the existing D1:1 is lost from the membranes, resulting in a transient drop in PSII activity. This suggests that under normal conditions the cells use oxygen to facilitate preemptive turnover of D1 proteins.

  • 8. Campbell, D
    et al.
    Eriksson, Mats-Jerry
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Clarke, A K
    A cyanobacterium resists UV-B by exchanging Photosystem II D1 proteins.1997In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 114, no 3, p. 30004-30004Article in journal (Refereed)
  • 9. Campbell, D
    et al.
    Eriksson, Mats-Jerry
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Clarke, A K
    The cyanobacterium Synechococcus resists UV-B by exchanging photosystem II reaction-center D1 proteins1998In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 95, no 1, p. 364-369Article in journal (Refereed)
    Abstract [en]

    Current ambient UV-B levels can significantly depress productivity in aquatic habitats, largely because UV-B inhibits several steps of photosynthesis, including the photooxidation of water catalyzed by photosystem II, We show that upon UV-B exposure the cyanobacterium Synechococcus sp, PCC 7942 rapidly changes the expression of a family of three psbA genes encoding photosystem II D1 proteins, In wild-type cells the psbAI gene is expressed constitutively, but strong accumulations of psbAII and psbAIII transcripts are induced within 15 min of moderate UV-B exposure (0.4 W/m(2)), This transcriptional response causes an exchange of two distinct photosystem II D1 proteins, D1:1 is encoded by psbAI, but on UV-B exposure, it is largely replaced by the alternate D1:2 form, encoded by both psbAII and psbAIII, The total content of D1 and other photosystem II reaction center protein, D2, remained unchanged throughout the UV exposure, as did the content and composition of the phycobilisome, Wild-type cells suffered only slight transient inhibition of photosystem II function under UV-B exposure, In marked contrast, under the same UV-B treatment, a mutant strain expressing only psbAI suffered severe (40%) and sustained inhibition of photosystem II function, Another mutant strain with constitutive expression of psbAII and psbAIII was almost completely resistant to the UV-B treatment, showing no inhibition of photosystem II function and only a slight drop in electron transport, In Synechococcus the rapid exchange of alternate D1 forms, therefore, accounts for much of the cellular resistance to UV-B inhibition of photosystem II activity and photosynthetic electron transport, This molecular plasticity may be an important element in community-level responses to UV-B, where susceptibility to UV-B inhibition of photosynthesis changes diurnally.

  • 10. Campbell, D
    et al.
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Clarke, A K
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Chlorophyll fluorescence analysis of cyanobacterial photosynthesis and acclimation1998In: Microbiology and molecular biology reviews, ISSN 1092-2172, E-ISSN 1098-5557, Vol. 62, no 3, p. 667-+Article, review/survey (Refereed)
    Abstract [en]

    Cyanobacteria are ecologically important photosynthetic prokaryotes that also serve as popular model organisms for studies of photosynthesis and gene regulation. Both molecular and ecological studies of cyanobacteria benefit from real-time information on photosynthesis and acclimation. Monitoring in vivo chlorophyll fluorescence can provide noninvasive measures of photosynthetic physiology in a wide range of cyanobacteria and cyanolichens and requires only small samples. Cyanobacterial fluorescence patterns are distinct from those of plants, because of key structural and functional properties of cyanobacteria. These include significant fluorescence emission from the light-harvesting phycobiliproteins; large and rapid changes in fluorescence yield (state transitions) which depend on metabolic and environmental conditions; and flexible, overlapping respiratory and photosynthetic electron transport chains. The fluorescence parameters F-V/F-M. F-V'/F-M', q(p),q(N), NPQ, and phi PS II were originally developed to extract information from the fluorescence signals of higher plants. In this review, we consider how the special properties of cyanobacteria can be accommodated and used to extract biologically useful information from cyanobacterial in vivo chlorophyll fluorescence signals. We describe how the pattern of fluorescence yield versus light intensity can be used to predict the acclimated light level for a cyanobacterial population, giving information valuable for both laboratory and field studies of acclimation processes. The size of the change in fluorescence yield during dark-to-light transitions can provide information on respiration and the iron status of the cyanobacteria. Finally, fluorescence parameters cart be used to estimate the electron transport rate at the acclimated growth light intensity.

  • 11. Campbell, D
    et al.
    OQUIST, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Predicting light acclimation in cyanobacteria from nonphotochemical quenching of photosystem II fluorescence, which reflects state transitions in these organisms1996In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 111, no 4, p. 1293-1298Article in journal (Refereed)
    Abstract [en]

    An important factor in photosynthetic ecophysiology is the light regime that a photobiont is acclimated to exploit. In a wide range of cyanobacteria and cyano-lichens, the easily measured fluorescence parameters, coefficient of nonphotochemical quenching of photosystem II variable fluorescence (q(N)) and nonphotochemical quenching, decline to a minimum near the acclimated growth light intensity. This characteristic pattern predicts the integrated light regime to which populations are acclimated, information that is particularly useful for cyanobacteria or cyano-lichens from habitats with highly variable light intensities. q(N) reflects processes that compete with photosystem II photochemistry for absorbed excitation energy. In cyanobacteria, we find no evidence for energy-dependent quenching mechanisms, which are the predominant components of q(N) in higher plants. Instead, in cyanobacteria, q(N) correlates closely with the excitation flow from the phycobilisome to photosystem I, indicating that q(N) reflects the state transition mechanism for equilibration of excitation from the phycobilisome to the two photosystems.

  • 12. CAMPBELL, D
    et al.
    ZHOU, GQ
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    CLARKE, AK
    ELECTRON-TRANSPORT REGULATES EXCHANGE OF 2 FORMS OF PHOTOSYSTEM-II D1 PROTEIN IN THE CYANOBACTERIUM SYNECHOCOCCUS1995In: EMBO Journal, ISSN 0261-4189, E-ISSN 1460-2075, Vol. 14, no 22, p. 5457-5466Article in journal (Refereed)
    Abstract [en]

    Synechococcus sp, PCC 7942 modulates photosynthetic function by transiently replacing the constitutive D1 photosystem II protein, D1:1, with an alternate form, D1:2, to help counteract photoinhibition under excess light, We show that a temperature drop from 37 to 25 degrees C also drives D1:1/D1:2 exchange under constant, moderate light, Chilling or light-induced D1 exchange results from rapid loss of psbAI message coding for D1:1 and accumulation of psbAII and psbAIII messages coding for D1:2, During chilling, a large pool of a novel form, D1:2*, transiently accumulates, distinguishable from normal D1 by an increase in apparent molecular mass, D1:* is not phosphorylated and is probably a functionally inactive, incompletely processed precursor, After acclimation to 25 degrees C, D1:2* disappears and D1:1 again predominates, although substantial D1:2 remains, Partial inhibition of electron transport under constant, moderate light also triggers the D1 exchange process, These treatments all increase excitation pressure on photosystem II relative to electron transport, Therefore, information from photosynthetic electron transport regulates D1 exchange without any requirement for a change in light intensity or quality, possibly via a redox sensing mechanism proximal to photosystem II.

  • 13. Chow, Wah Soon
    et al.
    Fan, Da-Yong
    Oguchi, Riichi
    Jia, Husen
    Losciale, Pasquale
    Park, Youn-Il
    He, Jie
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Shen, Yun-Gang
    Anderson, Jan M.
    Quantifying and monitoring functional photosystem II and the stoichiometry of the two photosystems in leaf segments: approaches and approximations2012In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 113, no 1-3, p. 63-74Article, review/survey (Refereed)
    Abstract [en]

    Given its unique function in light-induced water oxidation and its susceptibility to photoinactivation during photosynthesis, photosystem II (PS II) is often the focus of studies of photosynthetic structure and function, particularly in environmental stress conditions. Here we review four approaches for quantifying or monitoring PS II functionality or the stoichiometry of the two photosystems in leaf segments, scrutinizing the approximations in each approach. (1) Chlorophyll fluorescence parameters are convenient to derive, but the information-rich signal suffers from the localized nature of its detection in leaf tissue. (2) The gross O-2 yield per single-turnover flash in CO2-enriched air is a more direct measurement of the functional content, assuming that each functional PS II evolves one O-2 molecule after four flashes. However, the gross O-2 yield per single-turnover flash (multiplied by four) could over-estimate the content of functional PS II if mitochondrial respiration is lower in flash illumination than in darkness. (3) The cumulative delivery of electrons from PS II to P700(+) (oxidized primary donor in PS I) after a flash is added to steady background far-red light is a whole-tissue measurement, such that a single linear correlation with functional PS II applies to leaves of all plant species investigated so far. However, the magnitude obtained in a simple analysis (with the signal normalized to the maximum photo-oxidizable P700 signal), which should equal the ratio of PS II to PS I centers, was too small to match the independently-obtained photosystem stoichiometry. Further, an under-estimation of functional PS II content could occur if some electrons were intercepted before reaching PS I. (4) The electrochromic signal from leaf segments appears to reliably quantify the photosystem stoichiometry, either by progressively photoinactivating PS II or suppressing PS I via photo-oxidation of a known fraction of the P700 with steady far-red light. Together, these approaches have the potential for quantitatively probing PS II in vivo in leaf segments, with prospects for application of the latter two approaches in the field.

  • 14. CLARKE, AK
    et al.
    CAMPBELL, D
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    DYNAMIC-RESPONSES OF PHOTOSYSTEM-II AND PHYCOBILISOMES TO CHANGING LIGHT IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC-79421995In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 197, no 3, p. 553-562Article in journal (Refereed)
    Abstract [en]

    We have examined the molecular and photosynthetic responses of a planktonic cyanobacterium to shifts in light intensity over periods up to one generation (7 h). Synechococcus sp. PCC 7942 possesses two functionally distinct forms of the D1 protein, D1:1 and D1:2. Photosystem II (PSII) centers containing D1:1 are less efficient and more susceptible to photoinhibition than are centers containing D1:2, Under 50 mu mol photons m(-2). s(-1), PSII centers contain D1:1, but upon shifts to higher light (200 to 1000 mu mol photons m(-2). s(-1)), D1:1 is rapidly replaced by D1:2, with the rate of interchange dependent on the magnitude of the light shift. This interchange is readily reversed when cells are returned to 50 mu mol photons m(-2). s(-1). If, however, incubation under 200 mu mol photons m(-2). s(-1) is extended, D1:1 content recovers and by 3 h after the light shift D1:1 once again predominates. Oxygen evolution and chlorophyll (Chi) fluorescence measurements spanning the light shift and D1 interchanges showed an initial inhibition of photosynthesis at 200 mu mol photons m(-2). s(-1), which correlates with a proportional loss of total D1 protein and a cessation of growth. This was followed by recovery in photosynthesis and growth as the maximum level of D1:2 is reached after 2 h at 200 mu mol photons m(-2). s(-1) Thereafter, photosynthesis steadily declines with the loss of D1:2 and the return of the less-efficient D1:1. During the D1:1/D1:2 interchanges, no significant change occurs in the level of phycocyanin (PC) and Chl a, nor of the phycobilisome rod linkers. Nevertheless, the initial PC/Chl a ratio strongly influences the magnitude of photoinhibition and recovery during the light shifts. In Synechococcus sp. PCC 7942, the PC/Chl a ratio responds only slowly to light intensity or quality, while the rapid but transient interchange between D1:1 and D1:2 modulates PSII activity to limit damage upon exposure to excess light.

  • 15. CLARKE, AK
    et al.
    HURRY, VM
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    2 FUNCTIONALLY DISTINCT FORMS OF THE PHOTOSYSTEM-II REACTION-CENTER PROTEIN D1 IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC 79421993In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 90, no 24, p. 11985-11989Article in journal (Refereed)
    Abstract [en]

    The cyanobacterium Synechococcus sp. PCC 7942 possesses a small psbA multigene family that codes for two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We showed previously that the normally predominant D1 form (D1:1) was rapidly replaced with the alternative D1:2 when cells adapted to a photon irradiance of 50 mumol/m-2.s-1 are shifted to 500 mumol.m-2.s-1 and that this interchange was readily reversible once cells were allowed to recover under the original growth conditions. By using the psbA inactivation mutants R2S2C3 and R2K1 (which synthesize only D1:1 and D1:2, respectively), we showed that this interchange between D1 forms was essential for limiting the degree of photoinhibition as well as enabling a rapid recovery of photosynthesis. In this report, we have extended these findings by examining whether any intrinsic functional differences exist between the two D1 forms that may afford increased resistance to photoinhibition. Initial studies on the rate of D1 degradation at three photon-irradiances (50, 200, and 500 mumol.m-2.s-1) showed that the rates of degradation for both D1 forms increase with increasing photon flux density but that there was no significant difference between D1:1 and D1:2. Analysis of light-response curves for oxygen evolution for the mutants R2S2C3 and R2K1 revealed that cells with photosystem II reaction centers containing D1:2 have a higher apparent quantum yield (almost-equal-to 25%) than cells possessing D1:1. Further studies using chlorophyll a fluorescence measurements confirmed that R2K1 has a higher photochemical yield than R2S2C3; that is, a more efficient conversion of excitation energy from photon absorption into photochemistry. We believe that the higher photochemical efficiency of reaction centers containing D1:2 is causally related to the preferential induction of D1:2 at high light and thus may be an integral component of the protection mechanism within Synechococcus sp. PCC 7942 against photoinhibition.

  • 16. CLARKE, AK
    et al.
    SOITAMO, A
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    RAPID INTERCHANGE BETWEEN 2 DISTINCT FORMS OF CYANOBACTERIAL PHOTOSYSTEM-II REACTION-CENTER PROTEIN-D1 IN RESPONSE TO PHOTOINHIBITION1993In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 90, no 21, p. 9973-9977Article in journal (Refereed)
    Abstract [en]

    We have studied photoinhibition of photosynthesis in the cyanobacterium Synechococcus sp. PCC 7942, which possesses two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We report here that when cells adapted to a growth irradiance of 50 mumol.m-2.s-1 are exposed to an irradiance of 500 mumol.m-2.s-1, the normally predominant D1 form (D1:1) is rapidly replaced with the alternative D1:2. This interchange is not only complete within the first hour of photoinhibition but is also fully reversible once cells are returned to 50 mumol.m-2.s-1. By using a mutant that synthesizes only D1:1, we show that the failure to replace D1:1 with D1:2 during photoinhibition results in severe loss of photosynthetic activity as well as a diminished capacity to recover after the stress period. We believe that this interchange between D1 forms may constitute an active component in a protection mechanism unique among photosynthetic organisms that enables cyanobacteria to effectively cope with and recover from photoinhibition.

  • 17. DELUCIA, EH
    et al.
    DAY, TA
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    THE POTENTIAL FOR PHOTOINHIBITION OF PINUS-SYLVESTRIS L SEEDLINGS EXPOSED TO HIGH LIGHT AND LOW SOIL-TEMPERATURE1991In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 42, no 238, p. 611-617Article in journal (Refereed)
    Abstract [en]

    The effect of high light and root chilling on gas exchange, chlorophyll fluorescence, and bulk shoot water potential (PSI-shoot) was examined for Pinus sylvestris seedlings. Transferring plants from low light (200-mu-mol m-2 s-1, PAR) and a soil temperature of 15-degrees-C to high light (850-mu-mol m-2 S-1) and 1-degrees-C caused > 90% decrease in net photosynthesis and leaf conductance measured at 350 mm3 dm-3 CO2, and a decrease in the ratio of variable to maximum fluorescence (F(v)/F(m)) from 0.83 to 0.63. The decrease in F(v)/F(m) was, however, only marginally greater than when seedlings were transferred from low to high light but kept at a soil temperature of 15-degrees-C. Thus, photoinhibition was a minor component of the substantial decrease observed for net photosynthesis at 1-degrees-C soil temperature. The decrease in net photosynthesis and PSI-shoot at 1-degrees-C was associated with an increased in calculated intracellular CO2 concentration, suggesting that non-stomatal factors related to water stress were involved in inhibiting carbon assimilation. Measurements at saturating external CO2 concentration, however, indicate that stomatal closure was the dominant factor limiting net photosynthesis at low soil temperature. This interpretation was confirmed with additional experiments using Pinus taeda and Picea engelmannii seedlings. Decreases in gas-exchange variables at 5-degrees-C soil temperature were not associated with changes in PSI-shoot. Thus, hormonal factors, localized decreases in PSI-needle, or changes in xylem flux may mediate the response to moderate root chilling.

  • 18. Ensminger, Ingo
    et al.
    Sveshnikov, Dmitry
    Campbell, Douglas A.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Lloyd, Jon
    Shibistova, Olga
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Intermittent low temperatures constrain spring recovery of photosynthesis in boreal Scots pine forests2004In: Global Change Biology, ISSN 1354-1013, Vol. 10, no 6, p. 995-1008Article in journal (Refereed)
    Abstract [en]

    During winter and early spring, evergreen boreal conifers are severely stressed because light energy cannot be used when photosynthesis is pre-empted by low ambient temperatures. To study photosynthetic performance dynamics in a severe boreal climate, seasonal changes in photosynthetic pigments, chloroplast proteins and photochemical efficiency were studied in a Scots pine forest near Zotino, Central Siberia. In winter, downregulation of photosynthesis involved loss of chlorophylls, a twofold increase in xanthophyll cycle pigments and sustained high levels of the light stress-induced zeaxanthin pigment. The highest levels of xanthophylls and zeaxanthin did not occur during the coldest winter period, but rather in April when light was increasing, indicating an increased capacity for thermal dissipation of excitation energy at that time. Concomitantly, in early spring the D1 protein of the photosystem II (PSII) reaction centre and the light-harvesting complex of PSII dropped to their lowest annual levels. In April and May, recovery of PSII activity, chloroplast protein synthesis and rearrangements of pigments were observed as air temperatures increased above 0°C. Nevertheless, severe intermittent low-temperature episodes during this period not only halted but actually reversed the physiological recovery. During these spring low-temperature episodes, protective processes involved a complementary function of the PsbS and early light-induced protein thylakoid proteins. Full recovery of photosynthesis did not occur until the end of May. Our results show that even after winter cold hardening, photosynthetic activity in evergreens responds opportunistically to environmental change throughout the cold season. Therefore, climate change effects potentially improve the sink capacity of boreal forests for atmospheric carbon. However, earlier photosynthesis in spring in response to warmer temperatures is strongly constrained by environmental variation, counteracting the positive effects of an early recovery process.

  • 19. FALK, S
    et al.
    LEVERENZ, JW
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    CHANGES IN PHOTOSYSTEM-II FLUORESCENCE IN CHLAMYDOMONAS-REINHARDTII EXPOSED TO INCREASING LEVELS OF IRRADIANCE IN RELATIONSHIP TO THE PHOTOSYNTHETIC RESPONSE TO LIGHT1992In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 31, no 1, p. 31-40Article in journal (Refereed)
    Abstract [en]

    The effects of a 60 min exposure to photosynthetic photon flux densities ranging from 300 to 2200-mu-mol m-2 s-1 on the photosynthetic light response curve and on PS II heterogeneity as reflected in chlorophyll a fluorescence were investigated using the unicellular green alga Chlamydomonas reinhardtii. It was established that exposure to high light acts at three different regulatory or inhibitory levels; 1) regulation occurs from 300 to 780-mu-mol m-2 s-1 where total amount of PS II centers and the shape of the light response curve is not significantly changed, 2) a first photoinhibitory range above 780 up to 1600-mu-mol m-2 s-1 where a progressive inhibition of the quantum yield and the rate of bending (convexity) of the light response curve can be related to the loss of Q(B)-reducing centers and 3) a second photoinhibitory range above 1600-mu-mol m-2 s-1 where the rate of light saturated photosynthesis also decreases and convexity reaches zero. This was related to a particularly large decrease in PS II(alpha) centers and a large increase in spill-over in energy to PS I.

  • 20. FALK, S
    et al.
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    TEMPERATURE-DEPENDENT PHOTOINHIBITION AND RECOVERY OF PHOTOSYNTHESIS IN THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII ACCLIMATED TO 12 AND 27-DEGREES-C1990In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 78, no 2, p. 173-180Article in journal (Refereed)
  • 21. Greer, DH
    et al.
    Ottander, Christina
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Department of Science and Mathematics Education.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Photoinhibition and recovery of photosynthesis in intact barley leaves at 5 and 20°C1991In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 81, no 2, p. 203-210Article in journal (Refereed)
    Abstract [en]

    Photoinhibition of photosynthesis and its recovery were studied in intact barley (Hordeum vulgare L. cv. Gunilla) leaves grown in a controlled environment by exposing them to two temperatures, 5 and 20-degrees-C, and a range of photon flux densities in excess of that during growth. Additionally, photoinhibition was examined in the presence of chloramphenicol (CAP, an inhibitor of chloroplast protein synthesis) and of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Susceptibility to photoinhibition was much higher at 5 than at 20-degrees-C. Furthermore, at 20-degrees-C CAP exacerbated photoinhibition strongly, whereas CAP had little additional effect (10%) at 5-degrees-C. These results support the model that net photoinhibition is the difference between the inactivation and repair of photosystem II (PSII); i.e. the degradation and synthesis of the reaction centre protein, D1. Furthermore, the steady-state extent of photoinhibition was strongly dependent on temperature and the results indicated this was manifested through the effects of temperature on the repair process of PSII. We propose that the continuous repair of PSII at 20-degrees-C conferred at least some protection from photoinhibition. At 5-degrees-C the repair process was largely inhibited, with increased photoinhibition as a consequence. However, we suggest where repair is inhibited by low temperature, some protection is alternatively conferred by the photoinhibited reaction centres. Providing they are not degraded, such centres could still dissipate excitation energy non-radiatively, thereby conferring protection of remaining photochemically active centres under steady-state conditions. A fraction of PS II centres were capable of resisting photoinhibition when the repair process was inhibited by CAP. This is discussed in relation to PS II heterogeneity. Furthermore, the repair process was not apparently activated within 3 h when barley leaves were transferred to photoinhibitory light conditions at 20-degrees-C.

  • 22. Hendrickson, Luke
    et al.
    Vlcková, Alexandra
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Cold acclimation of the Arabidopsis dgd1 mutant results in recovery from photosystem I-limited photosynthesis.2006In: FEBS Letters, ISSN 0014-5793, Vol. 580, no 20, p. 4959-68Article in journal (Refereed)
    Abstract [en]

    We compared the thylakoid membrane composition and photosynthetic properties of non- and cold-acclimated leaves from the dgd1 mutant (lacking >90% of digalactosyl–diacylglycerol; DGDG) and wild type (WT) Arabidopsis thaliana. In contrast to warm grown plants, cold-acclimated dgd1 leaves recovered pigment-protein pools and photosynthetic function equivalent to WT. Surprisingly, this recovery was not correlated with an increase in DGDG. When returned to warm temperatures the severe dgd1 mutant phenotype reappeared. We conclude that the relative recovery of photosynthetic activity at 5 °C resulted from a temperature/lipid interaction enabling the stable assembly of PSI complexes in the thylakoid.

  • 23. HETHERINGTON, SE
    et al.
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    MONITORING CHILLING INJURY - A COMPARISON OF CHLOROPHYLL FLUORESCENCE MEASUREMENTS, POST-CHILLING GROWTH AND VISIBLE SYMPTOMS OF INJURY IN ZEA-MAYS1988In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 72, no 2, p. 241-247Article in journal (Refereed)
  • 24. HODGINS, RRW
    et al.
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    PORPHYRIN METABOLISM IN CHILL-STRESSED SEEDLINGS OF SCOTS PINE (PINUS-SYLVESTRIS)1989In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 77, no 4, p. 620-624Article in journal (Refereed)
  • 25. Huner, Norman P A
    et al.
    Ivanov, Alexander G
    Sane, Prafullachandra Vishnu
    Pocock, T
    Król, Marianna
    Balseris, A
    Rosso, Dominic
    Savitch, Leonid V
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Photoprotection of Photosystem II: Reaction center quenching versus antenna quenching2006In: Photoprotection, Photoinhibition, Gene Regulation and Environment, Springer , 2006, p. 155-174Chapter in book (Other academic)
    Abstract [en]

    Photoprotection, Photoinhibition, Gene Regulation, and Environment examines the processes whereby plants monitor environmental conditions and orchestrate their response to change, an ability paramount to the life of all plants. "Excess light", absorbed by the light-harvesting systems of photosynthetic organisms, is an integrative indicator of the environment, communicating the presence of intense light and any conditions unfavorable for growth and photosynthesis. Key plant responses are photoprotection and photoinhibition. In this volume, the dual role of photoprotective responses in the preservation of leaf integrity and in redox signaling networks modulating stress acclimation, growth, and development is addressed. In addition, the still unresolved impact of photoinhibition on plant survival and productivity is discussed. Specific topics include dissipation of excess energy via thermal and other pathways, scavenging of reactive oxygen by antioxidants, proteins key to photoprotection and photoinhibition, peroxidation of lipids, as well as signaling by reactive oxygen, lipid-derived messengers, and other messengers that modulate gene expression. Approaches include biochemical, physiological, genetic, molecular, and field studies, addressing intense visible and ultraviolet light, winter conditions, nutrient deficiency, drought, and salinity. This book is directed toward advanced undergraduate students, graduate students, and researchers interested in Plant Ecology, Stress Physiology, Plant Biochemistry, Integrative Biology, and Photobiology.

  • 26. HUNER, NPA
    et al.
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    HURRY, VM
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    KROL, M
    FALK, S
    GRIFFITH, M
    PHOTOSYNTHESIS, PHOTOINHIBITION AND LOW-TEMPERATURE ACCLIMATION IN COLD TOLERANT PLANTS1993In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 37, no 1, p. 19-39Article in journal (Refereed)
    Abstract [en]

    Cold acclimation requires adjustment to a combination of light and low temperature, conditions which are potentially photoinhibitory. The photosynthetic response of plants to low temperature is dependent upon time of exposure and the developmental history of the leaves. Exposure of fully expanded leaves of winter cereals to short-term, low temperature shifts inhibits whereas low temperature growth stimulates electron transport capacity and carbon assimilation. However, the photosynthetic response to low temperature is clearly species and cultivar dependent. Winter annuals and algae which actively grow and develop at low temperature and moderate irradiance acquire a resistance to irradiance 5- to 6-fold higher than their growth irradiance. Resistance to short-term photoinhibition (hours) in winter cereals is a reflection of the increased capacity to keep Q(A) oxidized under high light conditions and low temperature. This is due to an increased capacity for photosynthesis. These characteristics reflect photosynthetic acclimation to low growth temperature and can be used to predict the freezing tolerance of cereals. It is proposed that the enhanced photosynthetic capacity reflects an increased flux of fixed carbon through to sucrose in source tissue as a consequence of the combined effects of increased storage of carbohydrate as fructans in the vacuole of leaf mesophyll cells and an enhanced export to the crown due to its increased sink activity. Long-term exposure (months) of cereals to low temperature photoinhibition indicates that this reduction of photochemical efficiency of PS II represents a stable, long-term down regulation of PS II to match the energy requirements for CO2 fixation. Thus, photoinhibition in vivo should be viewed as the capacity of plants to adjust photosynthetically to the prevailing environmental conditions rather than a process which necessarily results in damage or injury to plants. Not all cold tolerant, herbaceous annuals use the same mechanism to acquire resistance to photoinhibition. In contrast to annuals and algae, overwintering evergreens become dormant during the cold hardening period and generally remain susceptible to photoinhibition. It is concluded that the photosynthetic response to low temperatures and susceptibility to photoinhibition are consequences of the overwintering strategy of the plant species.

  • 27.
    Hurry, Vaughan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Keerberg, O
    Parnik, T
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Cold-hardening results in increased activity of enzymes involved in carbon metabolism in leaves of winter rye (Secale-Cereale L)1995In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 195, no 4, p. 554-562Article in journal (Refereed)
    Abstract [en]

    Light- and CO2-saturated photosynthesis of nonhardened rye (Secale cereale L. cv. Musketeer) was reduced from 18.10 to 7.17 mu mol O-2.m(-2).s(-1) when leaves were transferred from 20 to 5 degrees C for 30 min. Following cold-hardening at 5 degrees C for ten weeks, photosynthesis recovered to 15.05 mu mol O-2.m(-2).s(-1), comparable to the non-hardened rate at 20 degrees C. Recovery of photosynthesis was associated with increases in the total activity and activation of enzymes of the photosynthetic carbon-reduction cycle and of sucrose synthesis. The total hexose-phosphate pool increase by 30% and 120% for nonhardened and cold-hardened leaves respectively when measured at 5 degrees C. The large increase in esterified phosphate in cold-hardened leaves occurred without a limitation in inorganic phosphate supply. In contrast, the much smaller increase in esterified phosphate in nonhardened leaves was associated with an inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase and sucrose-phosphate synthase activation. It is suggested that the large increases in hexose phosphates in cold-hardened leaves compensates for the higher substrate threshold concentrations needed for enzyme activation at low temperatures. High substrate concentrations could also compensate for the kinetic limitations imposed by product inhibition from the accumulation of sucrose at 5 degrees C. Nonhardened leaves appear to be unable to compensate in this fashion due to an inadequate supply of inorganic phosphate.

  • 28.
    Hurry, Vaughan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Keerberg, O
    Parnik, T
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Effect of cold hardening on the components of respiratory decarboxylation in the light and in the dark in leaves of winter rye1996In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 111, no 3, p. 713-719Article in journal (Refereed)
    Abstract [en]

    In the dark, all decarboxylation reactions are associated with the oxidase reactions of mitochondrial electron transport. In the light, photorespiration is also active in photosynthetic cells. In winter rye (Secale cereale L.), cold hardening resulted in a P-fold increase in the rate of dark respiratory CO2 release from leaves compared with nonhardened (NH) controls. However, in the light, NH and cold-hardened (CH) leaves had comparable rates of oxidase decarboxylation and total intracellular decarboxylation, Furthermore, whereas CH leaves showed similar rates of total oxidase decarboxylation in the dark and light, NH leaves showed a 2-fold increase in total oxidase activity in the light compared with the dark. Light suppressed oxidase decarboxylation of end products of photosynthesis 2-fold in NH leaves and 3-fold in CH leaves in air. However, in high-CO2, light did not suppress the oxidase decarboxylation of end products. Thus, the decrease in oxidase decarboxylation of end products observed in the light and in air reflected glycolate-cycle-related inhibition of tricarboxylic acid cycle activity. We also showed that the glycolate cycle was involved in the decarboxylation of the end products of photosynthesis in both NH and CH leaves, suggesting a flow of fixed carbon out of the starch pool in the light.

  • 29.
    Hurry, Vaughan M.
    et al.
    Cooperative Research Centre for Plant Science, The Australian National University, Canberra ACT 2601, Australia.
    Strand, Åsa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Tobiaeson, Maria
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Cold hardening of spring and winter-wheat and rape results in differential-effects on growth, carbon metabolism, and carbohydrate content1995In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 109, no 2, p. 697-706Article in journal (Refereed)
    Abstract [en]

    The effect of long-term (months) exposure to low temperature (5 degrees C) on growth, photosynthesis, and carbon metabolism was studied in spring and winter cultivars of wheat (Triticum aestivum) and rape (Brassica napus). Cold-grown winter rape and winter wheat maintained higher net assimilation rates and higher in situ CO2 exchange rates than the respective cold-grown spring cultivars. In particular, the relative growth rate of spring rape declined over time at low temperature, and this was associated with a 92% loss in in situ CO2 exchange rates. Associated with the high photosynthetic rates of cold-grown winter cultivars was a P-fold increase per unit of protein in both stromal and cytosolic fructose-1,6-bisphosphatase activity and a 1.5- to 2-fold increase in sucrose-phosphate synthase activity. Neither spring cultivar increased enzyme activity on a per unit of protein basis. We suggest that the recovery of photosynthetic capacity at low temperature and the regulation of enzymatic activity represent acclimation in winter cultivars. This allows these overwintering herbaceous annuals to maximize the production of sugars with possible cryoprotective function and to accumulate sufficient carbohydrate storage reserves to support basal metabolism and regrowth in the spring.

  • 30.
    Hurry, Vaughan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Malmberg, Gunilla
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Effects of a short-term shift to low-temperature and of long-term cold hardening on photosynthesis and ribulose-1,5-bisphosphate carboxylase oxygenase and sucrose-phosphate synthase activity in leabves of winter rye (Secale-Cereale L)1994In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 106, no 3, p. 983-990Article in journal (Refereed)
    Abstract [en]

    The effect of a short-term (hours) shift to low temperature (5 degrees C) and long-term (months) cold hardening on photosynthesis and carbon metabolism was studied in winter rye (Secale cereale L. cv Musketeer), Cold-hardened plants grown at 5 degrees C exhibited 25% higher in situ CO2 exchange rates than nonhardened plants grown at 24 degrees C. Cold-hardened plants maintained these high rates throughout the day, in contrast to nonhardened plants, which showed a gradual decline in photosynthesis after 3 h. Associated with the increase in photosynthetic capacity following cold hardening was an increase in ribulose-1,5-bisphosphate carboxylase/oxygenase and sucrose phosphate synthase activity and 3- to 4-fold increases in the pools of associated metabolites. Leaves of nonhardened plants shifted overnight to 5 degrees C required 9 h in the light at 5 degrees C before maximum rates of photosynthesis were reached. The gradual increase in photosynthesis in leaves shifted to 5 degrees C was correlated with a sharp decline in the 3-phosphoglycerate/triose phosphate ratio and by an increase in the ribulose bisphosphate/3-phosphoglycerate ratio, indicating the gradual easing of aninorganic phosphate-mediated feedback inhibition on photo-synthesis. We suggest that the strong recovery of photosynthesis in winter rye following cold hardening indicates that the buildup of photosynthetic enzymes, as well as those involved in sucrose synthesis, is an adaptive response that enables these plants to maximize the production of sugars that have both cryoprotective and storage functions that are critical to the performance of these cultivars during over-wintering.

  • 31.
    Hurry, Vaughan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Tobiaeson, M
    Kromer, S
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Mitochondria contribute to increased photosynthetic capacity of leaves of winter rye (Secale-Cereale L) following cold-hardening1995In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 18, no 1, p. 69-76Article in journal (Refereed)
    Abstract [en]

    Cold-hardening of winter rye (Secale cereale L. cv. Musketeer) increased dark respiration from -2.2 to -3.9 mu mol O-2 m(-2)s(-1) and doubled light- and CO2-saturated photosynthesis at 20 degrees C from 18.1 to 37.0 mu mol O-2 m(-2) s(-1). We added oligomycin at a concentration that specifically inhibits oxidative phosphorylation to see whether the observed increase in dark respiration reflected an increase in respiration in the light, and whether this contributed to the enhanced photosynthesis of cold-hardened leaves, Oligomycin inhibited light- and CO2-saturated rates of photosynthesis in non-hardened and cold-hardened leaves by 14 and 25%, respectively, and decreased photochemical quenching of chlorophyll a fluorescence to a greater degree in cold-hardened than in non-hardened leaves, These data indicate an increase both in the rate of respiration in the light, and in the importance of respiration to photosynthesis following cold-hardening, Analysis of metabolite pools indicated that oligomycin inhibited photosynthesis by limiting regeneration of ribulose-1,5-bisphosphate, This limitation was particularly severe in cold-hardened leaves, and the resulting low 3-phosphoglycerate pools led to a feed-forward inhibition of sucrose-phosphate synthase activity, Thus, it does not appear that oxidative phosphorylation supports the increase in photosynthetic O-2 evolution following cold-hardening by increasing the availability of cytosolic ATP, The data instead support the hypothesis that the mitochondria function in the light by using the reducing equivalents generated by nan-cyclic photosynthetic electron transport.

  • 32.
    HURRY, VM
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    REDUCED SENSITIVITY TO PHOTOINHIBITION FOLLOWING FROST-HARDENING OF WINTER RYE IS DUE TO INCREASED PHOSPHATE AVAILABILITY1993In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 190, no 4, p. 484-490Article in journal (Refereed)
    Abstract [en]

    The possibility of a role for phosphate metabolism in the photosynthetic regulation that occurs during frost hardening was investigated in winter rye (Secale cereale L. cv. Musketeer). Leaves of frost-hardened and non-hardened winter rye were studied during photosynthetic induction, and at steady state after being allowed to take up 20 mM orthophosphate through the transpiration stream for 3 h. At the growth irradiance (350 mumol.m-2.s-1) frost-hardening increased the stationary rate Of CO2-dependent O2 evolution by 57% and 25% when measured at 5 and 20-degrees-C, respectively. Frost-hardening also reduced the lag phase to stationary photosynthesis by 40% at 5-degrees-C and decreased the susceptibility of leaves to oscillations during induction and after interruption of the actinic beam during steady-state photosynthesis. These responses are all indicative of increased phosphate availability in frost-hardened leaves. As reported previously by Oquist and Huner (1993, Planta 189, 150-156), frost-hardening also decreased the reduction state of Q(A), the primary, stable quinone acceptor of PSII, and decreased the sensitivity of winter rye to photoinhibition of photosynthesis. Non-hardened rye leaves fed orthophosphate also showed an increased photosynthetic capacity (25% at 20-degrees-C and light saturation), lower reduction state of Q(A), a reduced sensitivity to photoinhibition and lower susceptibility to oscillations resulting from a brief interruption of the actinic light. Thus, the data indicate that phosphate metabolism plays a key role in photosynthetic acclimation of winter rye to low temperatures.

  • 33.
    HURRY, VM
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    KROL, M
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    HUNER, NPA
    EFFECT OF LONG-TERM PHOTOINHIBITION ON GROWTH AND PHOTOSYNTHESIS OF COLD-HARDENED SPRING AND WINTER-WHEAT1992In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 188, no 3, p. 369-375Article in journal (Refereed)
    Abstract [en]

    The effect of repeated exposure to high light (1200 mumol . m-2 . s-1 photosynthetic photon flux density, PPFD) at 5-degrees-C was examined in attached leaves of cold-grown spring (cv. Katepwa) and winter (cv. Kharkov) wheat (Triticum aestivum L.) over an eight-week period. Under these conditions, Kharkov winter wheat exhibited a daily reduction of 24% in F(V)/F(M) (the ratio of variable to maximal fluorescence in the dark-adapted state), in contrast to 41% for cold-grown Katepwa spring wheat. Both cultivars were able to recover from this daily suppression of F(V)/F(M) such that the leaves exhibited an average morning F(V)/F(M) of 0.651 +/- 0.004. Fluorescence measurements made under steady-state conditions as a function of irradiance from 60 to 2000 mumol . m-2 . s-1 indicated that the yield of photosystem II (PSII) electron transport under light-saturating conditions was the same for photoinhibited and control cold-grown plants, regardless of cultivar. Repeated daily exposure to high light at low temperature did not increase resistance to short-term photoinhibition, although zeaxanthin levels increased by three- to fourfold. In addition, both cultivars increased the rate of dry-matter accumulation, relative to control plants maintained at 5-degrees-C and 250 mumol . m-2 . s-1 PPFD (10% and 28% for Katepwa and Kharkov, respectively), despite exhibiting suppressed F(V)/F(M) and reduced photon yields for O2 evolution following daily high-light treatments. Thus, although photosynthetic efficiency is suppressed by a long-term, photoinhibitory treatment, light-saturated rates of photosynthesis are sufficiently high during the high-light treatment to offset any reduction in photochemical efficiency of PSII. We suggest that in these cold-tolerant plants, photoinhibition of PSII may represent a long-term, stable, down-regulation of photochemistry to match the overall photosynthetic demand for ATP and reducing equivalents.

  • 34. Ivanov, A G
    et al.
    Park, Y I
    Miskiewicz, E
    Raven, J A
    Huner, N P A
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Iron stress restricts photosynthetic intersystem electron transport in Synechococcus sp, PCC 79422000In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 485, no 2-3, p. 173-177Article in journal (Refereed)
    Abstract [en]

    Although exposure of Synechococcus sp. PCC 7942 to iron stress induced the accumulation of the isiA gene product (CP43') compared with non-stressed controls, immunodetection of the N-terminus of cytochrome (Cyt) f indicated that iron stress not only reduced the content of the 40 kDa, heme-binding, Cyt f polypeptide by 32% but it also specifically induced the accumulation of a new, 23 kDa, non-heme-binding, putative Cyt f polypeptide, Concomitantly, iron stress restricted intersystem electron transport based on the in vivo reduction of P700(+), monitored as DeltaA(820)/A(820) in the presence and absence of electron transport inhibitors, as well as the inhibition of the Emerson enhancement effect on O-2 evolution. However, iron stress appeared to be associated with enhanced rates of PS I cyclic electron transport, low rates of PS I-driven photoreduction of NADP(+) but comparable rates for PS II+PS I photoreduction of NADP(+) relative to controls. We hypothesize that Synechococcus sp, PCC 7942 exhibits a dynamic capacity to uncouple PS II and PS I electron transport, which may allow for the higher than expected growth rates observed during iron stress. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

  • 35. Ivanov, A. G.
    et al.
    Rosso, D.
    Savitch, L. V.
    Stachula, Paulina
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Rosembert, M.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huener, N. P. A.
    Implications of alternative electron sinks in increased resistance of PSII and PSI photochemistry to high light stress in cold-acclimated Arabidopsis thaliana2012In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 113, no 1-3, p. 191-206Article in journal (Refereed)
    Abstract [en]

    Exposure of control (non-hardened) Arabidopsis leaves to high light stress at 5 A degrees C resulted in a decrease of both photosystem II (PSII) (45 %) and Photosystem I (PSI) (35 %) photochemical efficiencies compared to non-treated plants. In contrast, cold-acclimated (CA) leaves exhibited only 35 and 22 % decrease of PSII and PSI photochemistry, respectively, under the same conditions. This was accompanied by an accelerated rate of P700(+) re-reduction, indicating an up-regulation of PSI-dependent cyclic electron transport (CET). Interestingly, the expression of the NDH-H gene and the relative abundance of the Ndh-H polypeptide, representing the NDH-complex, decreased as a result of exposure to low temperatures. This indicates that the NDH-dependent CET pathway cannot be involved and the overall stimulation of CET in CA plants is due to up-regulation of the ferredoxin-plastoquinone reductase, antimycin A-sensitive CET pathway. The lower abundance of NDH complex also implies lower activity of the chlororespiratory pathway in CA plants, although the expression level and overall abundance of the other well-characterized component involved in chlororespiration, the plastid terminal oxidase (PTOX), was up-regulated at low temperatures. This suggests increased PTOX-mediated alternative electron flow to oxygen in plants exposed to low temperatures. Indeed, the estimated proportion of O-2-dependent linear electron transport not utilized in carbon assimilation and not directed to photorespiration was twofold higher in CA Arabidopsis. The possible involvement of alternative electron transport pathways in inducing greater resistance of both PSII and PSI to high light stress in CA plants is discussed.

  • 36. Ivanov, A G
    et al.
    Sane, P
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Krol, M
    Sveshnikov, D
    Huner, N P A
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Low-temperature modulation of the redox properties of the acceptor side of photosystem II: photoprotection through reaction centre quenching of excess energy2003In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 119, no 3, p. 376-383Article in journal (Refereed)
    Abstract [en]

    Although it has been well established that acclimation to low growth temperatures is strongly correlated with an increased proportion of reduced Q(A) in all photosynthetic groups, the precise mechanism controlling the redox state of Q(A) and its physiological significance in developing cold tolerance in photoautotrophs has not been fully elucidated. Our recent thermoluminescence (TL) measurements of the acceptor site of PSII have revealed that short-term exposure of the cyanobacterium Synechococcus sp. PCC 7942 to cold stress, overwintering of Scots pine (Pinus sylvestris L.), and acclimation of Arabidopsis plants to low growth temperatures, all caused a substantial shift in the characteristic T-M of S(2)Q(B)(-) recombination to lower temperatures. These changes were accompanied by much lower overall TL emission, restricted electron transfer between Q(A) and Q(B), and in Arabidopsis by a shift of the S(2)Q(A)(-)-related peak to higher temperatures. The shifts in recombination temperatures are indicative of a lower activation energy for the S(2)Q(B)(-) redox pair and a higher activation energy for the S(2)Q(A)(-) redox pair. This results in an increase in the free-energy gap between P680(+)Q(A)(-) and P680(+)Pheo(-) and a narrowing of the free energy gap between Q(A) and Q(B) electron acceptors. We propose that these effects result in an increased population of reduced Q(A) (Q(A)(-)), facilitating non-radiative P680(+)Q(A)(-) radical pair recombination within the PSII reaction centre. The proposed reaction centre quenching could be an important protective mechanism in cyanobacteria in which antenna and zeaxanthin cycle-dependent quenching are not present. In herbaceous plants, the enhanced capacity for dissipation of excess light energy via PSII reaction centre quenching following cold acclimation may complement their capacity for increased utilization of absorbed light through CO2 assimilation and carbon metabolism. During overwintering of evergreens, when photosynthesis is inhibited, PSII reaction centre quenching may complement non-photochemical quenching within the light-harvesting antenna when zeaxanthin cycle-dependent energy quenching is thermodynamically restricted by low temperatures. We suggest that PSII reaction centre quenching is a significant mechanism enabling cold-acclimated organisms to acquire increased resistance to high light.

  • 37. Ivanov, A G
    et al.
    Sane, P V
    Zeinalov, Y
    Malmberg, G
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, N P A
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Photosynthetic electron transport adjustments in overwintering Scots pine (Pinus sylvestris L.)2001In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 213, no 4, p. 575-585Article in journal (Refereed)
    Abstract [en]

    As shown before [C. Ottander et al. (1995) Planta 197:176-183], there is a severe inhibition of the photosystem (PS) II photochemical efficiency of Scots pine (Pinus sylvestris L.) during the winter. In contrast, the in vivo PSI photochemistry is less inhibited during winter as shown by in vivo measurements of DeltaA(820)/Delta (820) (P700(+)). There was also an enhanced cyclic electron transfer around PSI in winter-stressed needles as indicated by 4-fold faster reduction kinetics of P700(+). The differential functional stability of PSII and PSI was accompanied by a 3.7-fold higher intersystem electron pool size, and a 5-fold increase in the stromal electron pool available for P700(+) reduction. There was also a strong reduction of the QB band in the thermoluminescence glow curve and markedly slower Q-A re-oxidation in needles of winter pine, indicating an inhibition of electron transfer between QA and QB. The data presented indicate that the plastoquinone pool is largely reduced in winter pine, and that this reduced state is likely to be of metabolic rather than photochemical origin. The retention of PSI photochemistry, and the suggested metabolic reduction of the plastoquinone pool in winter stressed needles of Scots pine are discussed in terms of the need for enhanced photoprotection of the needles during the winter and the role of metabolically supplied energy for the recovery of photosynthesis from winter stress in evergreens.

  • 38. Ivanov, A G
    et al.
    Sane, P V
    Zeinalov, Y
    Simidjiev, I
    Huner, N P A
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Seasonal responses of photosynthetic electron transport in Scots pine (Pinus sylvestris L.) studied by thermoluminescence2002In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 215, no 3, p. 457-465Article in journal (Refereed)
    Abstract [en]

    The potential of photosynthesis to recover from winter stress was studied by following the thermoluminescence (TL) and chlorophyll fluorescence changes of winter pine needles during the exposure to room temperature (20 degreesC) and an irradiance of 100 mumol m(-2) s(-1). TL measurements of photosystem 11 (PSII) revealed that the S(2)Q(B)(-) charge recombinations (the B-band) were shifted to lower temperatures in winter pine needles, while the S(2)Q(A)(-) recombinations (the Q-band) remained close to 0 degreesC. This was accompanied by a drastically reduced (65%) PSII photochemical efficiency measured as F-v/F-m and a 20-fold faster rate of the fluorescence transient from F-o to F, as compared to summer pine. A strong positive correlation between the increase in the photochemical efficiency of PSII and the increase in the relative contribution of the B-band was found during the time course of the recovery process. The seasonal dynamics of TL in Scots pine needles studied under field conditions revealed that between November and April, the contribution of the Q- and B-bands to the overall TL emission was very low (less than 5%). During spring, the relative contribution of the Q- and B-bands, corresponding to charge recombination events between the acceptor and donor sides of PSII, rapidly increased, reaching maximal values in late July. A sharp decline of the B-band was observed in late summer, followed by a gradual decrease, reaching minimal values in November. Possible mechanisms of the seasonally induced changes in the redox properties Of S-2/S(3)Q(B)(-) recombinations are discussed. It is proposed that the lowered redox potential Of Q(B) in winter needles increases the population Of Q(A)(-). thus enhancing the probability for non-radiative P680(+) Q(A)(-) recombination. This is suggested to enhance the radiationless dissipation of excess light within the PSII reaction center during cold acclimation and during cold winter periods.

  • 39.
    Ivanov, AG
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sane, PV
    Simidjiev, I
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Park, Y-I
    Huner, NPA
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Restricted capacity for PSI-dependent cyclic electron flow in Delta petE mutant compromises the ability for acclimation to iron stress in Synechococcus sp PCC 7942 cells2012In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1817, no 8, p. 1277-1284Article in journal (Refereed)
    Abstract [en]

    Exposure of wild type (WT) and plastocyanin coding petE gene deficient mutant (Delta petE) of Synechococcus cells to low iron growth conditions was accompanied by similar iron-stress induced blue-shift of the main red Chl a absorption peak and a gradual decrease of the Phc/Chl ratio, although Delta petE mutant was more sensitive when exposed to iron deficient conditions. Despite comparable iron stress induced phenotypic changes, the inactivation of petE gene expression was accompanied with a significant reduction of the growth rates compared to WT cells. To examine the photosynthetic electron fluxes in vivo, far-red light induced P700 redox state transients at 820 nm of WT and Delta petE mutant cells grown under iron sufficient and iron deficient conditions were compared. The extent of the absorbance change (Delta A(820)/A(820)) used for quantitative estimation of photooxidizable P700(+) indicated a 2-fold lower level of P700(+) in Delta petE compared to WT cells under control conditions. This was accompanied by a 2-fold slower re-reduction rate of P700(+) in the Delta petE indicating a lower capacity for cyclic electron flow around PSI in the cells lacking plastocyanin. Thermoluminescence (TL) measurements did not reveal significant differences in PSII photochemistry between control WT and Delta petE cells. However, exposure to iron stress induced a 4.5 times lower level of P700(+), 2-fold faster re-reduction rate of P700(+) and a temperature shift of the TL peak corresponding to S-2/S(3)Q(B)(-) charge recombination in WT cells. In contrast, the iron-stressed Delta petE mutant exhibited only a 40% decrease of P700(+) and no significant temperature shift in S-2/S(3)Q(B)(-) charge recombination. The role of mobile electron carriers in modulating the photosynthetic electron fluxes and physiological acclimation of cyanobacteria to low iron conditions is discussed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. (C) 2012 Elsevier B.V. All rights reserved.

  • 40. Ivanov, Alexander G
    et al.
    Hendrickson, Luke
    Krol, Marianna
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P A
    Digalactosyl-diacylglycerol deficiency impairs the capacity for photosynthetic intersystem electron transport and state transitions in Arabidopsis thaliana due to photosystem I acceptor-side limitations.2006In: Plant Cell Physiology, ISSN 0032-0781, Vol. 47, no 8, p. 1146-57Article in journal (Refereed)
    Abstract [en]

    Compared with wild type, the dgd1 mutant of Arabidopsis thaliana exhibited a lower amount of PSI-related Chl–protein complexes and lower abundance of the PSI-associated polypeptides, PsaA, PsaB, PsaC, PsaL and PsaH, with no changes in the levels of Lhca1–4. Functionally, the dgd1 mutant exhibited a significantly lower light-dependent, steady-state oxidation level of P700 (P700+) in vivo, a higher intersystem electron pool size, restricted linear electron transport and a higher rate of reduction of P700+ in the dark, indicating an increased capacity for PSI cyclic electron transfer compared with the wild type. Concomitantly, the dgd1 mutant exhibited a higher sensitivity to and incomplete recovery of photoinhibition of PSI. Furthermore, dgd1 exhibited a lower capacity to undergo state transitions compared with the wild type, which was associated with a higher reduction state of the plastoquinone (PQ) pool. We conclude that digalactosyl-diacylglycerol (DGDG) deficiency results in PSI acceptor-side limitations that alter the flux of electrons through the photosynthetic electron chain and impair the regulation of distribution of excitation energy between the photosystems. These results are discussed in terms of thylakoid membrane domain reorganization in response to DGDG deficiency in A. thaliana.

  • 41. Ivanov, Alexander G
    et al.
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sane, Prafullachandra Vishnu
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P A
    Reaction centre quenching of excess light energy and photoprotection of photosystem II2008In: Journal of Plant Biology, Vol. 51, no 2, p. 85-96Article in journal (Refereed)
    Abstract [en]

    In addition to the energy dissipation of excess light occurring in PSII antenna via the xanthophyll cycle, there is mounting evidence of a zeaxanthin-independent pathway for non-photochemical quenching based within the PSII reaction centre (reaction centre quenching) that may also play a significant role in photoprotection. It has been demonstrated that acclimation of higher plants, green algae and cyanobacteria to low temperature or high light conditions which potentially induce an imbalance between energy supply and energy utilization is accompanied by the development of higher reduction state of QA and higher resistance to photoinhibition (Huner et al., 1998). Although this is a fundamental feature of all photoautotrophs, and the acquisition of increased tolerance to photoinhibition has been ascribed to growth and development under high PSII excitation pressure, the precise mechanism controlling the redox state of QA and its physiological significance in developing higher resistance to photoinhibition has not been fully elucidated. In this review we summarize recent data indicating that the increased resistance to high light in a broad spectrum of photosynthetic organisms acclimated to high excitation pressure conditions is associated with an increase probability for alternative non-radiative P680+QA − radical pair recombination pathway for energy dissipation within the reaction centre of PSII. The various molecular mechanisms that could account for nonphotochemical quenching through PSII reaction centre are also discussed.

  • 42. Ivanov, Alexander G
    et al.
    Krol, Marianna
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    Sane, Prafullachandra Vishnu
    Sveshnikov, Dmitry
    Park, Youn-Il
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    Huner, Norman P A
    The induction of CP43' by iron-stress in Synechococcus sp. PCC 7942 is associated with carotenoid accumulation and enhanced fatty acid unsaturation.2007In: Biochimica et Biophysica Acta, ISSN 0006-3002, Vol. 1767, no 6, p. 807-13Article in journal (Refereed)
    Abstract [en]

    Comparative lipid analysis demonstrated reduced amount of PG (50%) and lower ratio of MGDG/DGDG in iron-stressed Synechococcus sp. PCC 7942 cells compared to cells grown under iron sufficient conditions. In parallel, the monoenoic (C:1) fatty acids in MGDG, DGDG and PG increased from 46.8%, 43.7% and 45.6%, respectively in control cells to 51.6%, 48.8% and 48.7%, respectively in iron-stressed cells. This suggests increased membrane dynamics, which may facilitate the diffusion of PQ and keep the PQ pool in relatively more oxidized state in iron-stressed compared to control cells. This was confirmed by chlorophyll fluorescence and thermoluminescence measurements. Analysis of carotenoid composition demonstrated that the induction of isiA (CP43′) protein in response to iron stress is accompanied by significant increase of the relative abundance of all carotenoids. The quantity of carotenoids calculated on a Chl basis increased differentially with nostoxanthin, cryptoxanthin, zeaxanthin and β-carotene showing 2.6-, 3.1-, 1.9- and 1.9-fold increases, respectively, while the relative amount of caloxanthin was increased only by 30%. HPLC analyses of the pigment composition of Chl–protein complexes separated by non-denaturating SDS-PAGE demonstrated even higher relative carotenoids content, especially of cryptoxanthin, in trimer and monomer PSI Chl–protein complexes co-migrating with CP43′ from iron-stressed cells than in PSI complexes from control cells where CP43′ is not present. This implies a carotenoid-binding role for the CP43′ protein which supports our previous suggestion for effective energy quenching and photoprotective role of CP43′ protein in cyanobacteria under iron stress.

  • 43. Ivanov, Alexander G
    et al.
    Krol, Marianna
    Sveshnikov, Dimitri
    Malmberg, Gunilla
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P A
    Characterization of the photosynthetic apparatus in cortical bark chlorenchyma of Scots pine.2006In: Planta, ISSN 0032-0935, Vol. 223, no 6, p. 1165-77Article in journal (Refereed)
    Abstract [en]

    Winter-induced inhibition of photosynthesis in Scots pine (Pinus sylvestris L.) needles is accompanied by a 65% reduction of the maximum photochemical efficiency of photosystem II (PSII), measured as F v/F m, but relatively stable photosystem I (PSI) activity. In contrast, the photochemical efficiency of PSII in bark chlorenchyma of Scots pine twigs was shown to be well preserved, while PSI capacity was severely decreased. Low-temperature (77 K) chlorophyll fluorescence measurements also revealed lower relative fluorescence intensity emitted from PSI in bark chlorenchyma compared to needles regardless of the growing season. Nondenaturating SDS-PAGE analysis of the chlorophyll–protein complexes also revealed much lower abundance of LHCI and the CPI band related to light harvesting and the core complex of PSI, respectively, in bark chlorenchyma. These changes were associated with a 38% reduction in the total amount of chlorophyll in the bark chlorenchyma relative to winter needles, but the Chl a/b ratio and carotenoid composition were similar in the two tissues. As distinct from winter pine needles exhibiting ATP/ADP ratio of 11.3, the total adenylate content in winter bark chlorenchyma was 2.5-fold higher and the estimated ATP/ADP ratio was 20.7. The photochemical efficiency of PSII in needles attached to the twig recovered significantly faster (28–30 h) then in detached needles. Fluorescence quenching analysis revealed a high reduction state of Q A and the PQ-pool in the green bark tissue. The role of bark chlorenchyma and its photochemical performance during the recovery of photosynthesis from winter stress in Scots pine is discussed.

  • 44. Ivanov, Alexander G
    et al.
    Krol, Marianna
    Sveshnikov, Dmitry
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    Sandström, Stefan
    Koochek, Maryam
    Park, Youn-Il
    Vasil'ev, Sergej
    Bruce, Doug
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    Huner, Norman P A
    Iron deficiency in cyanobacteria causes monomerization of photosystem I trimers and reduces the capacity for state transitions and the effective absorption cross section of photosystem I in vivo.2006In: Plant Physiology, ISSN 0032-0889, Vol. 141, no 4, p. 1436-45Article in journal (Refereed)
    Abstract [en]

    The induction of the isiA (CP43') protein in iron-stressed cyanobacteria is accompanied by the formation of a ring of 18 CP43' proteins around the photosystem I (PSI) trimer and is thought to increase the absorption cross section of PSI within the CP43'-PSI supercomplex. In contrast to these in vitro studies, our in vivo measurements failed to demonstrate any increase of the PSI absorption cross section in two strains (Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803) of iron-stressed cells. We report that iron-stressed cells exhibited a reduced capacity for state transitions and limited dark reduction of the plastoquinone pool, which accounts for the increase in PSII-related 685 nm chlorophyll fluorescence under iron deficiency. This was accompanied by lower abundance of the NADP-dehydrogenase complex and the PSI-associated subunit PsaL, as well as a reduced amount of phosphatidylglycerol. Nondenaturating polyacrylamide gel electrophoresis separation of the chlorophyll-protein complexes indicated that the monomeric form of PSI is favored over the trimeric form of PSI under iron stress. Thus, we demonstrate that the induction of CP43' does not increase the PSI functional absorption cross section of whole cells in vivo, but rather, induces monomerization of PSI trimers and reduces the capacity for state transitions. We discuss the role of CP43' as an effective energy quencher to photoprotect PSII and PSI under unfavorable environmental conditions in cyanobacteria in vivo.

  • 45. Ivanov, Alexander G
    et al.
    Sane, Prafullachandra V
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P A
    Photosystem II reaction centre quenching: mechanisms and physiological role.2008In: Photosynthesis Research, ISSN 0166-8595, Vol. 98, no 1-3, p. 565-74Article in journal (Refereed)
    Abstract [en]

    Dissipation of excess absorbed light energy in eukaryotic photoautotrophs through zeaxanthin- and DpHdependent photosystem II antenna quenching is considered the major mechanism for non-photochemical quenching and photoprotection. However, there is mounting evidence of a zeaxanthin-independent pathway for dissipation of excess light energy based within the PSII reaction centre that may also play a significant role in photoprotection. We summarize recent reports which indicate that this enigma can be explained, in part, by the fact that PSII reaction centres can be reversibly interconverted from photochemical energy transducers that convert light into ATP

    and NADPH to efficient, non-photochemical energy quenchers that protect the photosynthetic apparatus from photodamage. In our opinion, reaction centre quenching complements photoprotection through antenna quenching, and dynamic regulation of photosystem II reaction centre represents a general response to any environmental condition that predisposes the accumulation of reduced QA in the photosystem II reaction centres of prokaryotic and eukaryotic photoautotrophs. Since the evolution of reaction centres preceded the evolution of light harvesting systems, reaction centre quenching may represent the oldest photoprotective mechanism.10.1007/s1120-00

  • 46. Ivanov, Alexander G
    et al.
    Sane, Prafullachandra Vishnu
    Krol, Marianna
    Gray, G R
    Balseris, A
    Savitch, Leonid V
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    Huner, Norman P A
    Acclimation to temperature and irradiance modulates PSII charge recombination.2006In: FEBS Letters, ISSN 0014-5793, Vol. 580, no 11, p. 2797-802Article in journal (Refereed)
    Abstract [en]

    Acclimation of wild type and the chlorina F2 mutant of barley to either high light or low temperature results in a 2- to 3-fold increase in non-photochemical quenching which occurred independently of either energy-dependent quenching (qE), xanthophyll cycle-mediated antenna quenching or state transitions. Results of in vivo thermoluminescence measurements used to address this conundrum indicated that excitation pressure regulates the temperature gap for Click to view the MathML source and Click to view the MathML source charge recombinations within photosystem II reaction centers. This is discussed in terms of photoprotection through non-radiative charge recombination.

  • 47.
    Jansson, Stefan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    VIRGIN, I
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    ANDERSSON, B
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    LIGHT-INDUCED-CHANGES OF PHOTOSYSTEM-II ACTIVITY IN DARK-GROWN SCOTS PINE-SEEDLINGS1992In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 84, no 1, p. 6-12Article in journal (Refereed)
    Abstract [en]

    Both chlorophyll a and b and polypeptides of the photosynthetic apparatus are found in gymnosperm seedlings germinated and grown in absolute darkness. The photosystem II (PSII) activity is, however, limited, probably due to an inactive oxygen evolving system. In the present study dark-grown seedlings of Scots pine (Pinus sylvestris I..) were transferred to light and changes in antenna size and the activation process of PSII were investigated using fluorescence measurements and quantitative western blotting. It was found that the activation process is rapid, requires very little light and that strong light inhibits the process. It takes place without any changes in the primary reactions of PSII. Furthermore, all polypeptides except the major light-harvesting chlorophyll alb-binding protein complex of PSII (LHCII) were present in dark-grown seedlings in amounts comparable to the light treated control. The dark-grown seedlings had the same LHCII polypeptide composition as light treated seedlings, and the LHCII present seemed to be fully connected to the reaction centre. The results indicate that activation of PSII in dark-grown conifer seedlings resembles the photoactivation process of angiosperms. This implies that the fundamental processes in the assembly of the photosystem II complex is the same in all plants, but that the regulation differs between different taxa.

  • 48. KALLA, SR
    et al.
    LONNEBORG, A
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    LIGHT-MODULATED ANTENNAE ACCLIMATION IN THE CYANOBACTERIUM ANACYSTIS-NIDULANS - EFFECTS OF TRANSCRIPTIONAL AND TRANSLATIONAL INHIBITORS1986In: JOURNAL OF GENERAL MICROBIOLOGY, ISSN 0022-1287, Vol. 132, p. 3195-3200Article in journal (Refereed)
  • 49. Krivosheeva, A
    et al.
    Tao, D L
    Ottander, Christina
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Department of Science and Mathematics Education.
    Wingsle, Gunnar
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Dube, S L
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Cold acclimation and photoinhibition of photosynthesis in Scots pine1996In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 200, no 3, p. 296-305Article in journal (Refereed)
    Abstract [en]

    Cold acclimation of Scots pine did not affect the susceptibility of photosynthesis to photoinhibition. Cold acclimation did however cause a suppression of the rate of CO2 uptake, and at given light and temperature conditions a larger fraction of the photosystem Il reaction centres were closed in cold-acclimated than in nonacclimated pine. Therefore, when assayed at the level of photosystem II reaction centres, i.e. in relation to the degree of photosystem closure, cold acclimation caused a significant increase in resistance to photoinhibition; at given levels of photosystem II closure the resistance to photoinhibition was higher after cold acclimation. This was particularly evident in measurements at 20 degrees C. The amounts and activities of the majority of analysed active oxygen scavengers were higher after cold acclimation. We suggest that this increase in protective enzymes and compounds, particularly superoxide dismutase, ascorbate peroxidase, glutathione reductase and ascorbate of the chloroplasts, enables Scots pine to avoid excessive photoinhibition of photosynthesis despite partial suppression of photosynthesis upon cold acclimation. An increased capacity for light-induced de-epoxidation of violaxanthin to zeaxanthin upon cold acclimation may also be of significance.

  • 50. KROL, M
    et al.
    GRAY, GR
    HURRY, VM
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    OQUIST, G
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    MALEK, L
    HUNER, NPA
    LOW-TEMPERATURE STRESS AND PHOTOPERIOD AFFECT AN INCREASED TOLERANCE TO PHOTOINHIBITION IN PINUS-BANKSIANA SEEDLINGS1995In: Canadian Journal of Botany, ISSN 0008-4026, E-ISSN 1480-3305, Vol. 73, no 8, p. 1119-1127Article in journal (Refereed)
    Abstract [en]

    The capacity to develop tolerance to photoinhibition of photosynthesis was assessed in jack pine seedlings (Pinus banksiana Lamb.). Photoinhibition induced at 5 degrees C in control jack pine seedlings grown at 20 degrees C was saturated above an irradiance of 1000 mu mol . m(-2). s(-1) but was detectable at an irradiance as low as 25 mu mol . m(-2). s(-1). However, 20 degrees C seedlings shifted to 5 degrees C were 2-fold more tolerant to photoinhibition than 20 degrees C unshifted control seedlings, as detected by either the light-dependent decrease in photochemical efficiency or the apparent quantum yield of O-2 evolution. The extent of this tolerance of photoinhibition was dependent upon time, photoperiod, and irradiance during exposure to the low-temperature shift. Furthermore, the tolerance of photoinhibition was correlated with anthocyanin accumulation in 20 degrees C grown seedlings shifted to 5 degrees C. In addition, seedlings shifted to 5 degrees C and an 8-h photoperiod exhibited a 2-fold higher yield of photosystem II electron transport, which was associated with an increased capacity to keep Q(A), the first stable quinone electron acceptor of photosystem II, oxidized at high irradiance. This was consistent with a 2-fold higher rate of photosynthesis on a chlorophyll basis. We propose that the combination of light attenuation by anthocyanin in the epidermis and enhanced rates of photosynthesis may, in part, account for the reduced sensitivity of jack pine to photoinhibition at low temperature.

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