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  • 1. Allakhverdiev, Suleyman I.
    et al.
    Zharmukhamedov, Sergey K.
    Rodionova, Margarita V.
    Shuvalov, Vladimir A.
    Dismukes, Charles
    Shen, Jian-Ren
    Barber, James
    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).
    Govindjee,
    Vyacheslav (Slava) Klimov (1945-2017): A scientist par excellence, a great human being, a friend, and a Renaissance man2018In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, no 1, p. 1-16Article in journal (Other academic)
    Abstract [en]

    Vyacheslav Vasilevich (V.V.) Klimov (or Slava, as most of us called him) was born on January 12, 1945 and passed away on May 9, 2017. He began his scientific career at the Bach Institute of Biochemistry of the USSR Academy of Sciences (Akademy Nauk (AN) SSSR), Moscow, Russia, and then, he was associated with the Institute of Photosynthesis, Pushchino, Moscow Region, for about 50 years. He worked in the field of biochemistry and biophysics of photosynthesis. He is known for his studies on the molecular organization of photosystem II (PSII). He was an eminent scientist in the field of photobiology, a well-respected professor, and, above all, an outstanding researcher. Further, he was one of the founding members of the Institute of Photosynthesis in Pushchino, Russia. To most, Slava Klimov was a great human being. He was one of the pioneers of research on the understanding of the mechanism of light energy conversion and of water oxidation in photosynthesis. Slava had many collaborations all over the world, and he is (and will be) very much missed by the scientific community and friends in Russia as well as around the World. We present here a brief biography and some comments on his research in photosynthesis. We remember him as a friendly and enthusiastic person who had an unflagging curiosity and energy to conduct outstanding research in many aspects of photosynthesis, especially that related to PSII.

  • 2.
    Beckmann, Katrin
    et al.
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Badger, Murray Ronald
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Wydrzynski, Tom
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Hillier, Warwick
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    On-line mass spectrometry: membrane inlet sampling2009In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 102, no 2-3, p. 511-522Article in journal (Refereed)
    Abstract [en]

    Significant insights into plant photosynthesis and respiration have been achieved using membrane inlet mass spectrometry (MIMS) for the analysis of stable isotope distribution of gases. The MIMS approach is based on using a gas permeable membrane to enable the entry of gas molecules into the mass spectrometer source. This is a simple yet durable approach for the analysis of volatile gases, particularly atmospheric gases. The MIMS technique strongly lends itself to the study of reaction flux where isotopic labeling is employed to differentiate two competing processes; i.e., O2 evolution versus O2 uptake reactions from PSII or terminal oxidase/rubisco reactions. Such investigations have been used for in vitro studies of whole leaves and isolated cells. The MIMS approach is also able to follow rates of isotopic exchange, which is useful for obtaining chemical exchange rates. These types of measurements have been employed for oxygen ligand exchange in PSII and to discern reaction rates of the carbonic anhydrase reactions. Recent developments have also engaged MIMS for online isotopic fractionation and for the study of reactions in inorganic systems that are capable of water splitting or H2 generation. The simplicity of the sampling approach coupled to the high sensitivity of modern instrumentation is a reason for the growing applicability of this technique for a range of problems in plant photosynthesis and respiration. This review offers some insights into the sampling approaches and the experiments that have been conducted with MIMS.

  • 3. Bossmann, B
    et al.
    Knoetzel, J
    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).
    Screening of chlorina mutants of barley (Hordeum vulgare L.) with antibodies against light-harvesting proteins of PS I and PS II: Absence of specific antenna proteins1997In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 52, no 2, p. 127-136Article in journal (Refereed)
    Abstract [en]

    Twenty-three chlorina (clo) mutants from the barley mutant collection of the Carlsberg Laboratory, Copenhagen, were tested for the presence of the four light-harvesting chlorophyll (Chl) a/b-binding proteins (LHC) of Photosystem I (Lhcal-4) and the PS II antenna proteins Lhcb1-3 (LHC II), Lhcb4-6 (CP29, CP26, CP24) and PsbS (CP22) using monospecific and monoclonal antibodies. Mutants allelic to barley mutant clo-f2, impaired in Chi b synthesis, provided evidence that Lhca4, Lhcb1 and Lhcb6 are unstable in the absence of Chi b, and the accumulation of Lhcb2, Lhcb3 and Lhcb4 is also impaired. Mutants at the locus chlorina-a (clo-a(117), clo-a(126) and clo-a(134)) lack or have only trace amounts of Lhca1, Lhca4, Lhcb1 and Lhcb3, whereas a mutant at the locus chlorina-b (clo-b(125)) had reduced amounts of all Lhca proteins. These two mutations could have an effect in protein import or assembly. Evidence is presented that Lhcb5 is the innermost LHC protein of PS II, and that Lhca1 and Lhca4, which have been supposed to be intimately associated in the LHCI-730 complex, can accumulate independently of each other. 77 K fluorescence emission spectra taken from leaves of clo-f2(101), clo-a(126) and clo-b(125) indicate that chlorophyll(s) emitting at 742 nm are coupled to the presence of Lhca4 that is bound to the reaction centre, and those emitting around 730 nm are located on Lhca1.

  • 4. 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.

  • 5. 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.

  • 6. Chow, Wah Soon
    et al.
    Lee, Hae-Youn
    He, Jie
    Hendrickson, Luke
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia.
    Hong, Young-Nam
    Matsubara, Shizue
    Photoinactivation of photosystem II in leaves2005In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 84, no 1-3, p. 35-41Article in journal (Refereed)
    Abstract [en]

    Photoinactivation of Photosystem II (PS II), the light-induced loss of ability to evolve oxygen, inevitably occurs under any light environment in nature, counteracted by repair. Under certain conditions, the extent of photoinactivation of PS II depends on the photon exposure (light dosage, x), rather than the irradiance or duration of illumination per se, thus obeying the law of reciprocity of irradiance and duration of illumination, namely, that equal photon exposure produces an equal effect. If the probability of photoinactivation (p) of PS II is directly proportional to an increment in photon exposure (p = kDeltax, where k is the probability per unit photon exposure), it can be deduced that the number of active PS II complexes decreases exponentially as a function of photon exposure: N = Noexp(-kx). Further, since a photon exposure is usually achieved by varying the illumination time (t) at constant irradiance (I), N = Noexp(-kI t), i.e., N decreases exponentially with time, with a rate coefficient of photoinactivation kI, where the product kI is obviously directly proportional to I. Given that N = Noexp(-kx), the quantum yield of photoinactivation of PS II can be defined as -dN/dx = kN, which varies with the number of active PS II complexes remaining. Typically, the quantum yield of photoinactivation of PS II is ca. 0.1micromol PS II per mol photons at low photon exposure when repair is inhibited. That is, when about 10(7) photons have been received by leaf tissue, one PS II complex is inactivated. Some species such as grapevine have a much lower quantum yield of photoinactivation of PS II, even at a chilling temperature. Examination of the longer-term time course of photoinactivation of PS II in capsicum leaves reveals that the decrease in N deviates from a single-exponential decay when the majority of the PS II complexes are inactivated in the absence of repair. This can be attributed to the formation of strong quenchers in severely-photoinactivated PS II complexes, able to dissipate excitation energy efficiently and to protect the remaining active neighbours against damage by light.

  • 7. Conlan, Brendon l
    et al.
    Govindjee,
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry - Ångström, Uppsala University, Uppsala, Sweden.
    Thomas John Wydrzynski (8 July 1947-16 March 2018)2019In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 140, no 3, p. 253-261Article in journal (Refereed)
    Abstract [en]

    With this Tribute, we remember and honor Thomas John (Tom) Wydrzynski. Tom was a highly innovative, independent and committed researcher, who had, early in his career, defined his life-long research goal. He was committed to understand how Photosystem II produces molecular oxygen from water, using the energy of sunlight, and to apply this knowledge towards making artificial systems. In this tribute, we summarize his research journey, which involved working on soft money' in several laboratories around the world for many years, as well as his research achievements. We also reflect upon his approach to life, science and student supervision, as we perceive it. Tom was not only a thoughtful scientist that inspired many to enter this field of research, but also a wonderful supervisor and friend, who is deeply missed (see footnote*).

  • 8. 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.

  • 9. Govindjee,
    et al.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Lars Olof
    Evolution of the Z-scheme of photosynthesis: a perspective2017In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 133, no 1-3, p. 5-15Article in journal (Refereed)
    Abstract [en]

    The concept of the Z-scheme of oxygenic photosynthesis is in all the textbooks. However, its evolution is not. We focus here mainly on some of the history of its biophysical aspects. We have arbitrarily divided here the 1941-2016 period into three sub-periods: (a) Origin of the concept of two light reactions: first hinted at, in 1941, by James Franck and Karl Herzfeld; described and explained, in 1945, by Eugene Rabinowitch; and a clear hypothesis, given in 1956 by Rabinowitch, of the then available cytochrome experiments: one light oxidizing it and another reducing it; (b) Experimental discovery of the two light reactions and two pigment systems and the Z-scheme of photosynthesis: Robert Emerson's discovery, in 1957, of enhancement in photosynthesis when two light beams (one in the far-red region, and the other of shorter wavelengths) are given together than when given separately; and the 1960 scheme of Robin Hill & Fay Bendall; and (c) Evolution of the many versions of the Z-Scheme: Louis Duysens and Jan Amesz's 1961 experiments on oxidation and reduction of cytochrome f by two different wavelengths of light, followed by the work of many others for more than 50 years.

  • 10. Haniewicz, Patrycja
    et al.
    De Sanctis, Daniele
    Büchel, Claudia
    Schröder, Wolfgang P
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Loi, Maria Cecilia
    Kieselbach, Thomas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bochtler, Matthias
    Piano, Dario
    Isolation of monomeric photosystem II that retains the subunit PsbS.2013In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 118, no 3, p. 199-207Article in journal (Refereed)
    Abstract [en]

    Photosystem II has been purified from a transplastomic strain of Nicotiana tabacum according to two different protocols. Using the procedure described in Piano et al. (Photosynth Res 106:221-226, 2010) it was possible to isolate highly active PSII composed of monomers and dimers but depleted in their PsbS protein content. A "milder" procedure than the protocol reported by Fey et al. (Biochim Biophys Acta 1777:1501-1509, 2008) led to almost exclusively monomeric PSII complexes which in part still bind the PsbS protein. This finding might support a role for PSII monomers in higher plants.

  • 11. 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.

  • 12. Igamberdiev, A U
    et al.
    Ivlev, A A
    Bykova, N V
    Threlkeld, C N
    Lea, P J
    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).
    Decarboxylation of glycine contributes to carbon isotope fractionation in photosynthetic organisms2001In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 67, no 3, p. 177-184Article in journal (Refereed)
    Abstract [en]

    Carbon isotope effects were investigated for the reaction catalyzed by the glycine decarboxylase complex (GDC; EC 2.1.2.10). Mitochondria isolated from leaves of pea (Pisum sativum L.) and spinach (Spinacia oleracea L.) were incubated with glycine, and the CO2 evolved was analyzed for the carbon isotope ratio (delta C-13). Within the range of parameters tested (temperature, pH, combination of cofactors NAD(+), ADP, pyridoxal 5-phosphate), carbon isotope shifts of CO2 relative to the C-1-carboxyl carbon of glycine varied from +14 parts per thousand to -7 parts per thousand. The maximum effect of cofactors was observed for NAD(+), the removal of which resulted in a strong C-12 enrichment of the CO2 evolved. This indicates the possibility of isotope effects with both positive and negative signs in the GDC reaction. The measurement of delta C-13 in the leaves of the GDC-deficient barley ( Hordeum vulgare L.) mutant (LaPr 87/30) plants indicated that photorespiratory carbon isotope fractionation, opposite in sign when compared to the carbon isotope effect during CO2 photoassimilation, takes place in vivo. Thus the key reaction of photorespiration catalyzed by GDC, together with the key reaction of CO2 fixation catalyzed by ribulose-1,5-bisphosphate carboxylase, both contribute to carbon isotope fractionation in photosynthesis.

  • 13.
    Ishikawa, Yasuo
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Schröder, Wolfgang P
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Functional analysis of the PsbP-like protein (sll1418) in Synechocystis sp PCC 68032005In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 84, no 1-3, p. 257-262Article in journal (Refereed)
    Abstract [en]

    A recent proteomic analysis of the thylakoid lumen of Arabidopsis thaliana revealed the presence of several PsbP-like proteins, and a homologue to this gene family was detected in the genome of the cyanobacterium Synechocystis sp. PCC 6803 (Schubert M, Petersson UA, Haas BJ, Funk C, Schroder WP, Kieselbach T (2002) J Biol Chem 277, 8354-8365). Using a peptide-directed antibody against this cyanobacterial PsbP-like protein (sll1418) we could show that it was localized in the thylakoid membrane and associated with Photosystem II. While salt washes did not remove the PsbP-like protein from the thylakoid membrane, it was partially lost during the detergent-based isolation of PSII membrane fractions. In total cell extracts this protein is present in the same amount as the extrinsic PsbO protein. We did not see any significant functional difference between the wild-type and a PsbP-like insertion mutant.

  • 14. 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.

  • 15.
    Ivanov, Alexander G.
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Biology and The Biotron, University of Western Ontario, London, ON, Canada.
    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).
    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.
    Photosystem II reaction centre quenching: mechanisms and physiological role2008In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 98, no 1-3, p. 565-574Article in journal (Refereed)
    Abstract [en]

    Dissipation of excess absorbed light energy in eukaryotic photoautotrophs through zeaxanthin- and ΔpH-dependent 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.

  • 16.
    Kieselbach, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cheregi, Otilia
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Green, Beverley R.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Proteomic analysis of the phycobiliprotein antenna of the cryptophyte alga Guillardia theta cultured under different light intensities2018In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 135, no 1–3, p. 149-163Article in journal (Refereed)
    Abstract [en]

    Plants and algae have developed various light-harvesting mechanisms for optimal delivery of excitation energy to the photosystems. Cryptophyte algae have evolved a novel soluble light-harvesting antenna utilizing phycobilin pigments to complement the membrane-intrinsic Chl a/c-binding LHC antenna. This new antenna consists of the plastid-encoded β-subunit, a relic of the ancestral phycobilisome, and a novel nuclear-encoded α-subunit unique to cryptophytes. Together, these proteins form the active α1β·α2β-tetramer. In all cryptophyte algae investigated so far, the α-subunits have duplicated and diversified into a large gene family. Although there is transcriptional evidence for expression of all these genes, the X-ray structures determined to date suggest that only two of the α-subunit genes might be significantly expressed at the protein level. Using proteomics, we show that in phycoerythrin 545 (PE545) of Guillardia theta, the only cryptophyte with a sequenced genome, all 20 α-subunits are expressed when the algae grow under white light. The expression level of each protein depends on the intensity of the growth light, but there is no evidence for a specific light-dependent regulation of individual members of the α-subunit family under the growth conditions applied. GtcpeA10 seems to be a special member of the α-subunit family, because it consists of two similar N- and C-terminal domains, which likely are the result of a partial tandem gene duplication. The proteomics data of this study have been deposited to the ProteomeXchange Consortium and have the dataset identifiers PXD006301 and 10.6019/PXD006301.

  • 17.
    Kufryk, Galyna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hernández-Prieto, Miguel Angel
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kieselbach, Thomas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Miranda, Hélder
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vermaas, Wim
    Arizona State University School of Life Sciences and Center for Bioenergy and Photosynthesis, Tempe, USA.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Association of small CAB-like proteins (SCPs) of Synechocystis sp. PCC 6803 with Photosystem II2008In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 95, no 2/3, p. 135-145Article in journal (Refereed)
    Abstract [en]

    The cyanobacterial small CAB-like proteins (SCPs) are one-helix proteins with compelling similarity to the first and third transmembrane helix of proteins belonging to the CAB family of light-harvesting complex proteins in plants. The SCP proteins are transiently expressed at high light intensity and other stress conditions but their exact function remains largely unknown. Recently we showed association of ScpD with light-stressed, monomeric Photosystem II in Synechocystis sp. PCC 6803 (Yao et al. J Biol Chem 282:267-276, 2007). Here we show that ScpB associates with Photosystem II at normal growth conditions. Moreover, upon introduction of a construct into Synechocystis so that ScpB is expressed continuously under normal growth conditions, ScpE was detected under non-stressed conditions as well, and was copurified with tagged ScpB and Photosystem II. We also report on a one-helix protein, Slr1544, that is somewhat similar to the SCPs and whose gene is cotranscribed with that of ScpD; Slr1544 is another member of the extended light-harvesting-like (Lil) protein family, and we propose to name it LilA.

  • 18.
    Kurepin, Leonid V.
    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). Univ Western Ontario Univ Western, Dept Biol, London, ON N6A 5B7, Canada; Univ Western Ontario Univ Western, Biotron Ctr Expt Climate Change Res, London, ON N6A 5B7, Canada.
    Ivanov, Alexander G.
    Zaman, Mohammad
    Pharis, Richard P.
    Allakhverdiev, Suleyman I.
    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, Norman P. A.
    Stress-related hormones and glycinebetaine interplay in protection of photosynthesis under abiotic stress conditions2015In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 126, no 2-3, p. 221-235Article, review/survey (Refereed)
    Abstract [en]

    Plants subjected to abiotic stresses such as extreme high and low temperatures, drought or salinity, often exhibit decreased vegetative growth and reduced reproductive capabilities. This is often associated with decreased photosynthesis via an increase in photoinhibition, and accompanied by rapid changes in endogenous levels of stress-related hormones such as abscisic acid (ABA), salicylic acid (SA) and ethylene. However, certain plant species and/or genotypes exhibit greater tolerance to abiotic stress because they are capable of accumulating endogenous levels of the zwitterionic osmolyte-glycinebetaine (GB). The accumulation of GB via natural production, exogenous application or genetic engineering, enhances plant osmoregulation and thus increases abiotic stress tolerance. The final steps of GB biosynthesis occur in chloroplasts where GB has been shown to play a key role in increasing the protection of soluble stromal and lumenal enzymes, lipids and proteins, of the photosynthetic apparatus. In addition, we suggest that the stress-induced GB biosynthesis pathway may well serve as an additional or alternative biochemical sink, one which consumes excess photosynthesis-generated electrons, thus protecting photosynthetic apparatus from overreduction. Glycinebetaine biosynthesis in chloroplasts is up-regulated by increases in endogenous ABA or SA levels. In this review, we propose and discuss a model describing the close interaction and synergistic physiological effects of GB and ABA in the process of cold acclimation of higher plants.

  • 19.
    Messinger, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Alia, A
    Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
    Govindjee,
    Department of Plant Biology, Department of Biochemistry, Center of Biophysics and Computational Biology, University of Illinois, Urbana, USA.
    Special educational issue on ‘Basics and application of biophysical techniques in photosynthesis and related processes’2009In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 101, no 2-3, p. 89-92Article in journal (Refereed)
  • 20.
    Oquist, Gunnar
    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).
    Campbell, D
    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).
    The cyanobacterium Synechococcus modulates Photosystem II function in response to excitation stress through D1 exchange1995In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 46, no 1-2, p. 151-158Article in journal (Refereed)
    Abstract [en]

    In this minireview we discuss effects of excitation stress on the molecular organization and function of PS II as induced by high light or low temperature in the cyanobacterium Synechococcus sp. PCC 7942. Synechococcus displays PS II plasticity by transiently replacing the constitutive D1 form (D1:1) with another form (D1:2) upon exposure to excitation stress. The cells thereby counteract photoinhibition by increasing D1 turn over and modulating PS II function. A comparison between the cyanobacterium Synechococcus and plants shows that in cyanobacteria, with their large phycobilisomes, resistance to photoinhibition is mainly through the dynamic properties ( D1 turnover and quenching) of the reaction centre. In contrast, plants use antenna quenching in the light-harvesting complex as an important means to protect the reaction center from excessive excitation.

  • 21.
    Oquist, Gunnar
    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).
    CHOW, WS
    ON THE RELATIONSHIP BETWEEN THE QUANTUM YIELD OF PHOTOSYSTEM-II ELECTRON-TRANSPORT, AS DETERMINED BY CHLOROPHYLL FLUORESCENCE AND THE QUANTUM YIELD OF CO2-DEPENDENT O-2 EVOLUTION1992In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 33, no 1, p. 51-62Article in journal (Refereed)
    Abstract [en]

    We tested the two empirical models of the relationship between chlorophyll fluorescence and photosynthesis, previously published by Weis E and Berry JA 1987 (Biochim Biophys Acta 894: 198-208) and Genty B et al. 1989 (Biochim Biophys Acta 990: 87-92). These were applied to data from different species representing different states of light acclimation, to species with C3 or C4 photosynthesis, and to wild-type and a chlorophyll b-less chlorina mutant of barley. Photosynthesis measured as CO2-saturated O2 evolution and modulated fluorescence were simultaneously monitored over a range of photon flux densities. The quantum yields of O2, evolution (OO2) were based on absorbed photons, and the fluorescence parameters for photochemical (q(p)) and non-photochemical (q(N)) quenching, as well as the ratio of variable fluorescence to maximum fluorescence during steady-state illumination (F(v)'/F(m)'), were determined. In accordance with the Weis and Berry model, most plants studied exhibited an approximately linear relationship between OO2/q(p) (i.e., the yield of O2 evolution by open Photosystem II reaction centres) and q(N) except for wild-type barley that showed a non-linear relationship. In contrast to the linear relationship reported by Genty et al. for q(p) X F(v)'/F(m)' (i.e., the quantum yield of Photosystem II electron transport) and OCO2, we found a non-linear relationship between qp x F(v)'/F(m)' and OO2 for all plants, except for the chlorina mutant of barley, which showed a largely linear relationship. The curvilinearity of wild-type barley deviated somewhat from that of other species tested. The non-linear part of the relationship was confined to low, limiting photon flux densities, whereas at higher light levels the relationship was linear. Photoinhibition did not change the overall shape of the relationship between q(p) x F(v)/F(m)' and OO2 except that the maximum values of the quantum yields of Photosystem II electron transport and photosynthetic O2 evolution decreased in proportion to the degree of photoinhibition. This implies that the quantum yield of Photosystem II electron transport under high light conditions may be similar for photoinhibited and non-inhibited plants. Based on our experimental results and theoretical analyses of photochemical and non-photochemical fluoresce quenching processes, we conclude that both models, although not universal for all plants, provide useful means for the prediction of photosynthesis from fluorescence parameters. However, we also discuss that conditions which alter one or more of the rate constants that determine the various fluorescence parameters, as well as differential light penetration in assays for oxygen evolution and fluorescence emission, may have direct effect on the relationships of the two models.

  • 22.
    Oquist, Gunnar
    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, G
    LIGHT AND TEMPERATURE-DEPENDENT INHIBITION OF PHOTOSYNTHESIS IN FROST-HARDENED AND UNHARDENED SEEDLINGS OF PINE1989In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 20, no 3, p. 261-277Article in journal (Refereed)
  • 23.
    Oquist, Gunnar
    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).
    OGREN, E
    EFFECTS OF WINTER STRESS ON PHOTOSYNTHETIC ELECTRON-TRANSPORT AND ENERGY-DISTRIBUTION BETWEEN THE 2 PHOTOSYSTEMS OF PINE AS ASSAYED BY CHLOROPHYLL FLUORESCENCE KINETICS1985In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 7, no 1, p. 19-30Article in journal (Refereed)
  • 24.
    Ottander, Christina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Department of Science and Mathematics Education.
    Hundal, T
    Andersson, B
    Huner, Npa
    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).
    Photosystem II reaction centres stay intact during low temperature photoinhibition1993In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 35, no 2, p. 191-200Article in journal (Refereed)
    Abstract [en]

    Photoinhibition of photosynthesis was studied in intact barley leaves at 5 and 20-degrees-C, to reveal if Photosystem II becomes predisposed to photoinhibition at low temperature by 1) creation of excessive excitation of Photosystem II or, 2) inhibition of the repair process of Photosystem II. The light and temperature dependence of the reduction state of Q(A) was measured by modulated fluorescence. Photon flux densities giving 60% of Q(A) in a reduced state at steady-state photosynthesis (300 mu mol m-2 s-1 at 5-degrees-C and 1200 mumol m-2 s-1 at 20-degrees-C) resulted in a depression of the photochemical efficiency of Photosystem II (F(v)/F(m)) at both 5 and 20-degrees-C. Inhibition of F(v)/F(m) occurred with initially similar kinetics at the two temperatures. After 6 h, F(v)/F(m), was inhibited by 30% and had reached steady-state at 20-degrees-C. However, at 5-degrees-C, F(v)/F(m) continued to decrease and after 10 h, F(v)/F(m) was depressed to 55% of control. The light response of the reduction state of Q(A) did not change during photoinhibition at 20-degrees-C, whereas after photoinhibition at 5-degrees-C, the proportion of closed reaction centres at a given photon flux density was 10-20% lower than before photoinhibition. Changes in the D1-content were measured by immunoblotting and by the atrazine binding capacity during photoinhibition at high and low temperatures, with and without the addition of chloramphenicol to block chloroplast encoded protein synthesis. At 20-degrees-C, there was a close correlation between the amount of D1-protein and the photochemical efficiency of photosystem II, both in the presence or in the absence of an active repair cycle. At 5-degrees-C, an accumulation of inactive reaction centres occurred, since the photochemical efficiency of Photosystem II was much more depressed than the loss of D1-protein. Furthermore, at 5-degrees-C the repair cycle was largely inhibited as concluded from the finding that blockage of chloroplast encoded protein synthesis did not enhance the susceptibility to photoinihibition at 5-degrees-C. It is concluded that, the kinetics of the initial decrease of F(v)/F(m) was determined by the reduction state of the primary electron acceptor Q(A), at both temperatures. However, the further suppression of F(v)/F(m) at 5-degrees-C after several hours of photoinhibition implies that the inhibited repair cycle started to have an effect in determining the photochemical efficiency of Photosystem II.

  • 25. PALMQVIST, K
    et al.
    SUNDBLAD, LG
    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).
    SUNDBOM, E
    A CORRELATION BETWEEN CHANGES IN LUMINESCENCE DECAY KINETICS AND THE APPEARANCE OF A CO2-ACCUMULATING MECHANISM IN SCENEDESMUS OBLIQUUS1986In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 10, no 1-2, p. 113-123Article in journal (Refereed)
  • 26. Pham, Long Vo
    et al.
    Olmos, Julian David Janna
    Chernev, Petko
    Kargul, Joanna
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry - Ångström, Uppsala University, Uppsala, Sweden.
    Unequal misses during the flash-induced advancement of photosystem II: effects of the S state and acceptor side cycles2019In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 139, no 1-3, p. 93-106Article in journal (Refereed)
    Abstract [en]

    Photosynthetic water oxidation is catalyzed by the oxygen-evolving complex (OEC) in photosystem II (PSII). This process is energetically driven by light-induced charge separation in the reaction center of PSII, which leads to a stepwise accumulation of oxidizing equivalents in the OEC (S-i states, i=0-4) resulting in O-2 evolution after each fourth flash, and to the reduction of plastoquinone to plastoquinol on the acceptor side of PSII. However, the S-i-state advancement is not perfect, which according to the Kok model is described by miss-hits (misses). These may be caused by redox equilibria or kinetic limitations on the donor (OEC) or the acceptor side. In this study, we investigate the effects of individual S state transitions and of the quinone acceptor side on the miss parameter by analyzing the flash-induced oxygen evolution patterns and the S-2, S-3 and S-0 state lifetimes in thylakoid samples of the extremophilic red alga Cyanidioschyzon merolae. The data are analyzed employing a global fit analysis and the results are compared to the data obtained previously for spinach thylakoids. These two organisms were selected, because the redox potential of Q(A)/Q(A)(-) in PSII is significantly less negative in C. merolae (E-m=-104mV) than in spinach (E-m=-163mV). This significant difference in redox potential was expected to allow the disentanglement of acceptor and donor side effects on the miss parameter. Our data indicate that, at slightly acidic and neutral pH values, the E-m of Q(A)(-)/Q(A) plays only a minor role for the miss parameter. By contrast, the increased energy gap for the backward electron transfer from Q(A)(-) to Pheo slows down the charge recombination reaction with the S-3 and S-2 states considerably. In addition, our data support the concept that the S-2 S-3 transition is the least efficient step during the oxidation of water to molecular oxygen in the Kok cycle of PSII.

  • 27.
    Selstam, Eva
    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).
    Brain, Anthony P R
    Williams, W Patrick
    The relationship between different spectral forms of the protochlorophyllide oxidoreductase complex and the structural organisation of prolamellar bodies isolated from Zea mays2011In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 108, no 1, p. 47-59Article in journal (Refereed)
    Abstract [en]

    Incubation of prolamellar bodies (PLB) in high-salt media leads to changes in PLB structure and properties of their protochlorophyllide oxidoreductase-protochlorophyllide (POR-PChlide) complex. The paracrystalline organisation typical of PLB is disrupted and NADPH dissociates from photoconvertible POR-PChlide, with absorption maxima at 640 and 650 nm (POR-PChlide ( 640/650 )), and a non-photoconvertible form, with absorption maxima at 635 nm (POR-PChlide ( 635 )), is formed. These effects are strongly dependent on the valence of the cation of the perturbing salt, indicating that they involve surface double layers effects. They are also influenced by the nature of the anion and by high concentrations of non-electrolytes, suggesting the involvement of surface hydration effects. The structural changes are largely, if not entirely, independent of the presence of excess NADPH. Changes to the POR-PChlide complex, however, are strongly inhibited by excess NADPH suggesting that the two sets of changes may not be causally linked. As long as the disruption is not too great, the structural changes seen on incubation of PLB in high salt media lacking excess NADPH are reversed on removal of the high salt perturbation. This reversal is independent of the presence or absence of added NADPH. Reformation of photoconvertible POR-PChlide, however, requires the presence of NADPH. The reformation of paracrystalline PLB in the absence of NADPH strongly indicates that preservation of PLB structure, in isolated PLB preparations at least, is independent of the presence or absence of POR-PChlide ( 650 ).

  • 28.
    Shevela, Dmitriy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ort, Donald R.
    Department of Plant Biology, University of Illinois, Urbana, IL, 61801, USA .
    Book Review: Agu Laisk, Ladislav Nedbal, and Govindjee (eds): Photosynthesis in silico. Understanding complexity from molecules to ecosystems.2010In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 103, no 2, p. 139-140Article, book review (Refereed)
  • 29.
    Shevela, Dmitriy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Max Planck Institute for Chemical Energy Conversion, Mülheim, Germany.
    Nöring, Birgit
    Max Planck Institute for Chemical Energy Conversion, Mülheim, Germany.
    Koroidov, Sergey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shutova, Tatyana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    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).
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Max Planck Institute for Chemical Energy Conversion, Mülheim, Germany.
    Efficiency of photosynthetic water oxidation at ambient and depleted levels of inorganic carbon2013In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 117, no 1-3, p. 401-412Article in journal (Refereed)
    Abstract [en]

    Over 40 years ago, Joliot et al. (Photochem Photobiol 10:309-329, 1969) designed and employed an elegant and highly sensitive electrochemical technique capable of measuring O2 evolved by photosystem II (PSII) in response to trains of single turn-over light flashes. The measurement and analysis of flash-induced oxygen evolution patterns (FIOPs) has since proven to be a powerful method for probing the turnover efficiency of PSII. Stemler et al. (Proc Natl Acad Sci USA 71(12):4679-4683, 1974), in Govindjee's lab, were the first to study the effect of "bicarbonate" on FIOPs by adding the competitive inhibitor acetate. Here, we extend this earlier work by performing FIOPs experiments at various, strictly controlled inorganic carbon (Ci) levels without addition of any inhibitors. For this, we placed a Joliot-type bare platinum electrode inside a N2-filled glove-box (containing 10-20 ppm CO2) and reduced the Ci concentration simply by washing the samples in Ci-depleted media. FIOPs of spinach thylakoids were recorded either at 20-times reduced levels of Ci or at ambient Ci conditions (390 ppm CO2). Numerical analysis of the FIOPs within an extended Kok model reveals that under Ci-depleted conditions the miss probability is discernibly larger (by 2-3 %) than at ambient conditions, and that the addition of 5 mM HCO3 (-) to the Ci-depleted thylakoids largely restores the original miss parameter. Since a "mild" Ci-depletion procedure was employed, we discuss our data with respect to a possible function of free or weakly bound HCO3 (-) at the water-splitting side of PSII.

  • 30. Siggel, Ulrich
    et al.
    Schmitt, Franz-Josef
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gernot Renger (1937-2013): his life, Max-Volmer Laboratory, and photosynthesis research2016In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 129, no 2, p. 109-127Article in journal (Refereed)
    Abstract [en]

    Gernot Renger (October 23, 1937-January 12, 2013), one of the leading biophysicists in the field of photosynthesis research, studied and worked at the Max-Volmer-Institute (MVI) of the Technische Universitat Berlin, Germany, for more than 50 years, and thus witnessed the rise and decline of photosynthesis research at this institute, which at its prime was one of the leading centers in this field. We present a tribute to Gernot Renger's work and life in the context of the history of photosynthesis research of that period, with special focus on the MVI. Gernot will be remembered for his thought-provoking questions and his boundless enthusiasm for science.

  • 31.
    Storm, Patrik
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Hernandez-Prieto, Miguel Angel
    Umeå University, Faculty of Science and Technology, Chemistry.
    Eggink, Laura
    Hoober, J. Kenneth
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Chemistry.
    The small CAB-like proteins of Synechocystis sp. PCC 6803 bind chlorophyll: In vitro pigment reconstitution studies on one-helix light-harvesting-like proteins.2008In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 98, no 1/3, p. 479-488Article in journal (Refereed)
    Abstract [en]

    The large family of light-harvesting-like proteins contains members with one to four membrane spanning helices with significant homology to the chlorophyll a/b-binding antenna proteins of plants. From structural as well as evolutionary perspective, it is likely that the members of this family bind chlorophylls and carotenoids. However, undisputable evidence is still lacking. The cyanobacterial small CAB-like proteins (SCPs) are one-helix proteins with compelling similarity to the first and third transmembrane helix of LHCII (LHCIIb) including the chlorophyll-binding motifs. They have been proposed to act as chlorophyll-carrier proteins. Here, we analyze the in vivo absorption spectra of single scp deletion mutants in Synechocystis sp. PCC 6803 and compare the in vitro pigment binding ability of the SCP pairs ScpC/D and ScpB/E with the one of LHCII and a synthetic peptide containing the chlorophyll-binding motif (Eggink LL, Hoober JK (2000) J Biol Chem 275:9087–9090). We demonstrate that deletion of scpB alters the pigmentation in the cyanobacterial cell. Furthermore, we are able to show that chlorophylls and carotenoids interact in vitro with the pairs of ScpC/D and ScpB/E, demonstrated by fluorescence resonance energy transfer and circular dichroism.

  • 32. SUNDBLAD, LG
    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).
    WIGGE, B
    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).
    LUMINESCENCE DECAY KINETICS IN RELATION TO QUENCHING AND STIMULATION OF DARK FLUORESCENCE FROM HIGH AND LOW CO2 ADAPTED CELLS OF SCENEDESMUS-OBLIQUUS AND CHLAMYDOMONAS-REINHARDTII1990In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 23, no 3, p. 269-282Article in journal (Refereed)
  • 33.
    Tibiletti, Tania
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. SC Synchrotron SOLEIL, AILES beamline, L’Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, France.
    Rehman, Ateeq Ur
    Vass, Imre
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The stress-induced SCP/HLIP family of small light-harvesting-like proteins (ScpABCDE) protects Photosystem II from photoinhibitory damages in the cyanobacterium Synechocystis sp. PCC 68032018In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 135, no 1–3, p. 103-114Article in journal (Refereed)
    Abstract [en]

    Small CAB-like proteins (SCPs) are single-helix light-harvesting-like proteins found in all organisms performing oxygenic photosynthesis. We investigated the effect of growth in moderate salt stress on these stress-induced proteins in the cyanobacterium Synechocystis sp. PCC 6803 depleted of Photosystem I (PSI), which expresses SCPs constitutively, and compared these cells with a PSI-less/ScpABCDE mutant. SCPs, by stabilizing chlorophyll-binding proteins and Photosystem II (PSII) assembly, protect PSII from photoinhibitory damages, and in their absence electrons accumulate and will lead to ROS formation. The presence of 0.2 M NaCl in the growth medium increased the respiratory activity and other PSII electron sinks in the PSI-less/ScpABCDE strain. We postulate that this salt-induced effect consumes the excess of PSII-generated electrons, reduces the pressure of the electron transport chain, and thereby prevents 1O2 production.

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