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  • 1.
    Ahad, Abdul
    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).
    Nick, Peter
    Actin is bundled in activation-tagged tobacco mutants that tolerate aluminum2007In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 225, no 2, p. 451-468Article in journal (Refereed)
    Abstract [en]

    A panel of aluminum-tolerant (AlRes) mutants was isolated by protoplast-based T-DNA activation tagging in the tobacco cultivar SR1. The mutants fell into two phenotypic classes: a minority of the mutants were fertile and developed similarly to the wild type (type I), the majority was male-sterile and grew as semi-dwarfs (type II). These traits, along with the aluminum tolerance, were inherited in a monogenic dominant manner. Both types of mutants were characterized by excessive bundling of actin microfilaments and by a strongly increased abundance of actin, a phenotype that could be partially phenocopied in the wild type by treatment with aluminum chloride. The actin bundles could be dissociated into finer strands by addition of exogenous auxin in both types of mutants. However, actin microfilaments and leaf expansion were sensitive to blockers of actin assembly in the wild type and in the mutants of type I, whereas they were more tolerant in the mutants of type II. The mutants of type II displayed a hypertrophic development of vasculature, manifest in form of supernumerary leaf veins and extended xylem layers in stems and petioles. Whereas mutants of type I were characterized by a normal, but aluminum-tolerant polar auxin-transport, auxin-transport was strongly promoted in the mutants of type II. The phenotype of these mutants is discussed in terms of reduced endocytosis leading, concomitantly with aluminum tolerance, to changes in polar auxin transport.

  • 2. Bailey, S
    et al.
    Walters, R G
    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).
    Horton, P
    Acclimation of Arabidopsis thaliana to the light environment: the existence of separate low light and high light responses2001In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 213, no 5, p. 794-801Article in journal (Refereed)
    Abstract [en]

    The capacity for photosynthetic acclimation in Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta was assessed during growth over a broad range of irradiance. Discontinuities in the response to growth irradiance were revealed for the light- and CO2-saturated rate of photosynthesis (P-max) and the ratio of chlorophyll a to chlorophyll b (Chl a/b). Three separate phases in the response of P-max and Chl a/b to growth light were evident, with increases at low and high irradiance ranges and a plateau at intermediate irradiance. By measuring all chlorophyll-containing components of the thylakoid membrane that contribute to Chl alb we reveal that distinct strategies for growth at low and high irradiance underlie the discontinuous response. These strategies include, in addition to changes in the major light-harvesting complexes of photosystem II (LHCII) , large shifts in the amounts of both reaction centres as well as significant changes in the levels of minor LHCII and LHCI components.

  • 3. 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.

  • 4. Contesto, Celine
    et al.
    Milesi, Sandrine
    Mantelin, Sophie
    Zancarini, Anouk
    Desbrosses, Guilhem
    Varoquaux, Fabrice
    Bellini, Catherine
    Kowalczyk, Mariusz
    Touraine, Bruno
    The auxin-signaling pathway is required for the lateral root response of Arabidopsis to the rhizobacterium Phyllobacterium brassicacearum2010In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 232, no 6, p. 1455-1470Article in journal (Refereed)
    Abstract [en]

    Plant root development is highly responsive both to changes in nitrate availability and beneficial microorganisms in the rhizosphere. We previously showed that Phyllobacterium brassicacearum STM196, a plant growth-promoting rhizobacteria strain isolated from rapeseed roots, alleviates the inhibition exerted by high nitrate supply on lateral root growth. Since soil-borne bacteria can produce IAA and since this plant hormone may be implicated in the high nitrate-dependent control of lateral root development, we investigated its role in the root development response of Arabidopsis thaliana to STM196. Inoculation with STM196 resulted in a 50% increase of lateral root growth in Arabidopsis wild-type seedlings. This effect was completely abolished in aux1 and axr1 mutants, altered in IAA transport and signaling, respectively, indicating that these pathways are required. The STM196 strain, however, appeared to be a very low IAA producer when compared with the high-IAA-producing Azospirillum brasilense sp245 strain and its low-IAA-producing ipdc mutant. Consistent with the hypothesis that STM196 does not release significant amounts of IAA to the host roots, inoculation with this strain failed to increase root IAA content. Inoculation with STM196 led to increased expression levels of several IAA biosynthesis genes in shoots, increased Trp concentration in shoots, and increased auxin-dependent GUS staining in the root apices of DR5::GUS transgenic plants. All together, our results suggest that STM196 inoculation triggers changes in IAA distribution and homeostasis independently from IAA release by the bacteria.

  • 5. Delarue, M.
    et al.
    Santoni, V.
    Caboche, M.
    Bellini, C.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    cristal mutations in Arabidopsis confer a genetically heritable, recessive, hyperhydric phenotype1997In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 202, no 1, p. 51-61Article in journal (Refereed)
    Abstract [en]

    A new class of recessive Arabidopsis mutants, designated cristal (cii) has been isolated which display several abnormalities reminiscent of hyperhydric symptoms. These characteristics include translucent and wrinkled cotyledons and leaves, abnormal chloroplast organization, a reduced amount of chlorophyll, a reduced dry weight and a decreased number of palisade cells in the leaves accompanied by an increase of intercellular space, and therefore give a vitreous appearance to the aerial part. The phenotype is also dependent on the culture medium water potential. The cril gene was mapped on chromosome 4 close to the DHS1 marker.

  • 6. Heineke, D
    et al.
    Bykova, N
    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).
    Bauwe, H
    Metabolic response of potato plants to an antisense reduction of the P-protein of glycine decarboxylase2001In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 212, no 5-6, p. 880-887Article in journal (Refereed)
    Abstract [en]

    Potato (Solanum tuberosum L. cv. Desire) plants with reduced amounts of P-protein, one of the subunits of glycine decarboxylase (GDC), have been generated by introduction of an antisense transgene. Two transgenic lines, containing about 60-70% less P-protein in the leaves compared to wild-type potato, were analysed in more detail. The reduction in P-protein amount led to a decrease in the ability of leaf mitochondria to decarboxylate glycine. Photosynthetic and growth rates were reduced but the plants were viable under ambient air and produced tubers. Glycine concentrations within the leaves were elevated up to about 100-fold during illumination. Effects: on other amino acids and on sucrose and hexoses were minor. Nearly all of the glycine accumulated during the day was metabolised during the following night. The data suggest that the GDC operates far below substrate saturation under normal conditions thus allowing a flexible and fast response to changes in the environment.

  • 7. Hiltonen, T
    et al.
    Karlsson, Jan
    Palmqvist, K
    Clarke, A K
    Samuelsson, G
    Purification and characterisation of an intracellular carbonic anhydrase from the unicellular green alga Coccomyxa.1995In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 195, no 3, p. 345-51Article in journal (Refereed)
    Abstract [en]

    An intracellular carbonic anhydrase (CA; EC 4.2.1.1) was purified and characterised from the unicellular green alga Coccomyxa sp. Initial studies showed that cultured Coccomyxa cells contain an intracellular CA activity around 100 times higher than that measured in high-CO2-grown cells of Chlamydomonas reinhardtii CW 92. Purification of a protein extract containing the CA activity was carried out using ammonium-sulphate precipitation followed by anion-exchange chromatography. Proteins were then separated by native (non-dissociating) polyacrylamide gel electrophoresis, with each individual protein band excised and assayed for CA activity. Measurements revealed CA activity associated with two discrete protein bands with similar molecular masses of 80 +/- 5 kDa. Dissociation by denaturing polyacrylamide gel electrophoresis showed that both proteins contained a single polypeptide of 26 kDa, suggesting that each 80-kDa native protein was a homogeneous trimer. Isoelectric focusing of the 80-kDa proteins also produced a single protein band at a pH of 6.5. Inhibition studies on the purified CA extract showed that 50% inhibition of CA activity was obtained using 1 microM azetazolamide. Polyclonal antibodies against the 26-kDa CA were produced and shown to have a high specific binding to a single polypeptide in soluble protein extracts from Coccomyxa cells. The same antiserum, however, failed to cross-react with soluble proteins isolated from two different species of green algae, Chlamydomonas reinhardtii and Chlorella vulgaris. Correspondingly, antisera directed against pea chloroplastic CA, extracellular CA from C. reinhardtii and human CAII, showed no cross-hybridisation to the 26-kDa polypeptide in Coccomyxa.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 8.
    Hiltonen, Thomas
    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).
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    PALMQVIST, K
    CLARKE, AK
    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).
    PURIFICATION AND CHARACTERIZATION OF AN INTRACELLULAR CARBONIC-ANHYDRASE FROM THE UNICELLULAR GREEN-ALGA COCCOMYXA1995In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 195, no 3, p. 345-351Article in journal (Refereed)
    Abstract [en]

    An intracellular carbonic anhydrase (CA; EC 4.2.1.1) was purified and characterised from the unicellular green alga Coccomyxa sp. Initial studies showed that cultured Coccomyxa cells contain an intracellular CA activity around 100 times higher than that measured in high-CO2-grown cells of Chlamydomonas reinhardtii CW 92. Purification of a protein extract containing the CA activity was carried out using ammonium-sulphate precipitation followed by anion-exchange chromatography. Proteins were then separated by native (non-dissociating) polyacrylamide gel electrophoresis, with each individual protein band excised and assayed for CA activity. Measurements revealed CA activity associated with two discrete protein bands with similar molecular masses of 80 +/- 5 kDa. Dissociation by denaturing polyacrylamide gel electrophoresis showed that both proteins contained a single polypeptide of 26 kDa, suggesting that each 80-kDa native protein was a homogeneous trimer. Isoelectric focusing of the 80-kDa proteins also produced a single protein band at a pH of 6.5. Inhibition studies on the purified CA extract showed that 50% inhibition of CA activity was obtained using 1 mu M azetazolamide. Polyclonal antibodies against the 26-kDa CA were produced and shown to have a high specific binding to a single polypeptide in soluble protein extracts from Coccomyxa. cells. The same antiserum, however, failed to cross-react with soluble proteins isolated from two different species of green algae, Chlamydomonas reinhardtii and Chlorella vulgaris. Correspondingly, antisera directed against pea chloroplastic CA, extracellular CA from C. reinhardtii and human CAII, showed no cross-hybridisation to the 26-kDa polypeptide in Coccomyxa. The 26-kDa protein was confirmed as being a CA by N-terminal sequencing of two internal polypeptide fragments and alignment of these sequences with that of previously identified CA proteins from several different species.

  • 9.
    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.

  • 10.
    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.

  • 11.
    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.

  • 12.
    HUSSDANELL, K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Sellstedt, Anita
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    FLOWERELLIS, A
    SJOSTROM, M
    AMMONIUM EFFECTS ON FUNCTION AND STRUCTURE OF NITROGEN-FIXING ROOT-NODULES OF ALNUS-INCANA (L) MOENCH1982In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 156, no 4, p. 332-340Article in journal (Refereed)
  • 13. 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.

  • 14. 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.

  • 15.
    Karlsson, Jan
    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).
    RAMAZANOV, Z
    Hiltonen, Thomas
    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).
    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).
    EFFECT OF VANADATE ON PHOTOSYNTHESIS AND THE ATP ADP RATIO IN LOW-CO2-ADAPTED CHLAMYDOMONAS-REINHARDTII CELLS1994In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 192, no 1, p. 46-51Article in journal (Refereed)
    Abstract [en]

    We have assessed the effect of vanadate as an inhibitor of plasma-membrane ATPase on photosynthesis and the ATP/ADP ratio in Chlamydomonas reinhardtii CW-92 (a mutant strain lacking a cell wall). This effect was compared in low-CO2-adapted cells grown in media bubbled with air containing 400 or 70 muL . L-1 CO2. Evidence is presented indicating that cells grown at 70 muL . L-1 CO2 have a higher rate of photosynthetic O2 evolution than cells grown at 400 muL . L-1 CO2, at limiting carbon concentrations. Extracellular and intracellular carbonic-anhydrase activities were, however, similar in cells grown in both of the low-carbon conditions. Vanadate inhibited, to a different extent, the HCO3--dependent O2 evolution in cells grown at 400 and 70 muL . L-1 CO2. At 400 muM vanadate, inhibition reached 70-75 % in cells grown at 400 muL . L-1 but only 50 % in those grown at 70 muL . L-1 CO2. The ATP/ADP ratios determined with and without vanadate at limiting concentrations of dissolved inorganic carbon indicated that more ATP was hydrolysed in algae grown at 70 muL . L-1 than in those grown at 400 muL . L-1 CO2. We conclude that the maximal capacity to accumulate dissolved inorganic carbon is inversely related to the CO2 concentration in the medium. Activation and - or synthesis of vanadate-sensitive ATPase may be the major explanation for the higher capacity for HCO3--dependent O2 evolution in cells grown under limited CO2 concentrations.

  • 16. 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.

  • 17. LEVERENZ, JW
    et al.
    FALK, S
    PILSTROM, CM
    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).
    THE EFFECTS OF PHOTOINHIBITION ON THE PHOTOSYNTHETIC LIGHT-RESPONSE CURVE OF GREEN PLANT-CELLS (CHLAMYDOMONAS-REINHARDTII)1990In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 182, no 2, p. 161-168Article in journal (Refereed)
  • 18. Matsubara, Shizue
    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).
    Druart, Nathalie
    Benedict, Catherine
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Janzik, Ingar
    Chavarrıa-Krauser, Andre
    Walter, Achim
    Schurr, Ulrich
    Nocturnal changes in leaf growth of Populus deltoides are controlled by cytoplasmic growth2006In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 223, no 6, p. 1315-1328Article in journal (Refereed)
    Abstract [en]

    Growing leaves do not expand at a constantrate but exhibit pronounced diel growth rhythms.However, the mechanisms giving rise to distinct dielgrowth dynamics in different species are still largelyunknown. As a first step towards identifying genescontrolling rate and timing of leaf growth, we analysedthe transcriptomes of rapidly expanding and fully expandedleaves of Populus deltoides Bartr. ex. Marsh atpoints of high and low expansion at night. Tissues withwell defined temporal growth rates were harvested usingan online growth-monitoring system based on a digitalimage sequence processing method developed forquantitative mapping of dicot leaf growth. Unlike plantsstudied previously, leaf growth in P. deltoides wascharacterised by lack of a base-tip gradient across thelamina, and by maximal and minimal growth at duskand dawn, respectively. Microarray analysis revealedthat the nocturnal decline in growth coincided with aconcerted down-regulation of ribosomal protein genes,indicating deceleration of cytoplasmic growth. In asubsequent time-course experiment, Northern blottingand real-time RT-PCR confirmed that the ribosomalprotein gene RPL12 and a cell-cycle gene H2B weredown-regulated after midnight following a decrease incellular carbohydrate concentrations. Thus, we proposethat the spatio-temporal growth pattern in leaves ofP. deltoides primarily arises from cytoplasmic growthwhose activity increases from afternoon to midnight andthereafter decreases in this species.

  • 19. OGREN, E
    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).
    EFFECTS OF DROUGHT ON PHOTOSYNTHESIS, CHLOROPHYLL FLUORESCENCE AND PHOTOINHIBITION SUSCEPTIBILITY IN INTACT WILLOW LEAVES1985In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 166, no 3, p. 380-388Article 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).
    ANDERSON, JM
    MCCAFFERY, S
    CHOW, WS
    MECHANISTIC DIFFERENCES IN PHOTOINHIBITION OF SUN AND SHADE PLANTS1992In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 188, no 3, p. 422-431Article in journal (Refereed)
    Abstract [en]

    Leaf discs of the shade plant Tradescantia albiflora Kunth grown at 50 mumol . m-2 . s-1, and the facultative sun, shade plant Pisum sativum L. grown at 50 or 300 mumol . m-2 . s-1, were photoinhibited for 4 h in 1700 mumol photons m-2 . s-1 at 22-degrees-C. The effects of photoinhibition on the following parameters were studied: i) photosystem II (PSII) function; ii) amount of D1 protein in the PSII reaction centre; iii) dependence of photoinhibition and its recovery on chloroplast-encoded protein synthesis; and, iv) the sensitivity of photosynthesis to photoinhibition in the presence or absence of the carotenoid zeaxanthin. We show that: i) despite different sensitivities to photoinhibition, photoinhibition in all three plants occurred at the reaction centre of PSII; ii) there was no correlation between the extent of photoinhibition and the degradation of the D1 protein; iii) the susceptibility to photoinhibition by blockage of chloroplast-encoded protein synthesis was much less in shade plants than in plants acclimated to higher light; and iv) inhibition of zeaxanthin formation increased the sensitivity to photoinhibition in pea, but not in the shade plant Tradescantia. We suggest that there are mechanistic differences in photoinhibition of sun and shade plants. In sun plants, an active repair cycle of PSII replaces photoinhibited reaction centres with photochemically active ones, thereby conferring partial protection against photoinhibition. However, in shade plants, this repair cycle is less important for protection against photoinhibition; instead, photoinhibited PSII reaction centres may confer, as they accumulate, increased protection of the remaining connected, functional PSII centres by controlled, nonphotochemical dissipation of excess excitation energy.

  • 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
    ANDERSON, JM
    PHOTOINHIBITION OF PHOTOSYNTHESIS REPRESENTS A MECHANISM FOR THE LONG-TERM REGULATION OF PHOTOSYSTEM-II1992In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 186, no 3, p. 450-460Article in journal (Refereed)
    Abstract [en]

    The obligate shade plant, Tradescantia albiflora Kunth grown at 50-mu-mol photons.m-2 s-1 and Pisum sativum L. acclimated to two photon fluence rates, 50 and 300-mu-mol.m-2.s-1, were exposed to photoinhibitory light conditions of 1700-mu-mol.m-2.s-1 for 4 h at 22-degrees-C. Photosynthesis was assayed by measurement of CO2- saturated O2 evolution, and photosystem II (PSII) was assayed using modulated chlorophyll fluorescence and flash-yield determinations of functional reaction centres. Tradescantia was most sensitive to photoinhibition, while pea grown at 300-mu-mol.m-2.s-1 was most resistant, with pea grown at 50-mu-mol.m-2.s-1 showing an intermediate sensitivity. A very good correlation was found between the decrease of functional PSII reaction centres and both the inhibition of photosynthesis and PSII photochemistry. Photoinhibition caused a decline in the maximum quantum yield for PSII electron transport as determined by the product of photochemical quenching (q(p)) and the yield of open PSII reaction centres as given by the steady-state fluorescence ratio, F'(v)F'(m), according to Genty et al. (1989, Biochim. Biophys. Acta 990, 81-92). The decrease in the quantum yield for PSII electron transport was fully accounted for by a decrease in F'(v)F'(m), since q(p) at a given photon fluence rate was similar for photoinhibited and noninhibited plants. Under light-saturating conditions, the quantum yield of PSII electron transport was similar in photoinhibited and noninhibited plants. The data give support for the view that photoinhibition of the reaction centres of PSII represents a stable, long-term, down-regulation of photochemistry, which occurs in plants under sustained high-light conditions, and replaces part of the regulation usually exerted by the transthylakoid DELTA-pH gradient. Furthermore, by investigating the susceptibility of differently light-acclimated sun and shade species to photoinhibition in relation to q(p), i.e. the fraction of open-to-closed PSII reaction centres, we also show that irrespective of light acclimation, plants become susceptible to photoinhibition when the majority of their PSII reaction centres are still open (i.e. primary quinone acceptor oxidized). Photoinhibition appears to be an unavoidable consequence of PSII function when light causes sustained closure of more than 40% of PSII reaction centres.

  • 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).
    HUNER, NPA
    COLD-HARDENING-INDUCED RESISTANCE TO PHOTOINHIBITION OF PHOTOSYNTHESIS IN WINTER RYE IS DEPENDENT UPON AN INCREASED CAPACITY FOR PHOTOSYNTHESIS1993In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 189, no 1, p. 150-156Article in journal (Refereed)
    Abstract [en]

    Analyses of chlorophyll fluorescence and photosynthetic oxygen evolution were conducted to understand why cold-hardened winter rye (Secale cereale L.) is more resistant to photoinhibition of photosynthesis than is non-hardened winter rye. Under similar light and temperature conditions, leaves of cold-hardened rye were able to keep a larger fraction of the PS II reaction centres in an open configuration, i.e. a higher ratio of oxidized to reduced Q(A) (the primary, stable quinone acceptor of PSII), than leaves of non-hardened rye. Three fold-higher photon fluence rates were required for cold-hardened leaves than for non-hardened leaves in order to establish the same proportion of oxidized to reduced Q(A). This ability of cold-hardened rye fully accounted for its higher resistance to photoinhibition; under similar redox states of Q(A) cold-hardened and non-hardened leaves of winter rye exhibited similar sensitivities to photoinhibition. Under given light and temperature conditions, it was the higher capacity for light-saturated photosynthesis in cold-hardened than in non-hardened leaves, which was responsible for maintaining a higher proportion of oxidized to reduced Q(A). This higher capacity for photosynthesis of cold-hardened leaves also explained the increased resistance of photosynthesis to photoinhibition upon cold-hardening.

  • 23.
    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.
    Campbell, D
    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).
    Seasonal-changes in photosystem-II organiszation and pigment composition in Pinus-Sylvestris1995In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 197, no 1, p. 176-183Article in journal (Refereed)
    Abstract [en]

    Conifers of the boreal zone encounter considerable combined stress of low temperature and high light during winter, when photosynthetic consumption of excitation energy is blocked. In the evergreen Pinus sylvestris L. these stresses coincided with major seasonal changes in photosystem II (PSII) organisation and pigment composition. The earliest changes occurred in September, before any freezing stress, with initial losses of chlorophyll, the D1-protein of the PSTI reaction centre and of PSII light-harvesting-complex (LHC Il) proteins. In October there was a transient increase in F-o, resulting from detachment of the light-harvesting antennae as reaction centres lost D1. The D1-protein content eventually decreased to 90%, reaching a minimum by December, but PSII photochemical efficiency [variable fluorescence (F-v)/maximum fluorescence (F-m)] did not reach the winter minimum until mid-February. The carotenoid composition varied seasonally with a twofold increase in lutein and the carotenoids of the xanthophyll cycle during winter, while the epoxidation state of the xanthophylls decreased from 0.9 to 0.1 from October to January. The loss of chlorophyll was complete by October and during winter much of the remaining chlorophyll was reorganised in aggregates of specific polypeptide composition, which apparently efficiently quench excitation energy through non-radiative dissipation. The timing of the autumn and winter changes indicated that xanthophyll de-epoxidation correlates with winter quenching of chlorophyll fluorescence while the drop in photochemical efficiency relates more to loss of D1-protein. In April and May recovery of the photochemistry of PSII, protein synthesis, pigment rearrangements and zeaxanthin epoxidation occurred concomitantly. Indoor recovery of photosynthesis in winter-stressed branches under favourable conditions was completed within 3 d, with rapid increases in F-o, the epoxidation state of the xanthophylls and in light-harvesting polypeptides, followed by recovery of D1-protein content and F-v/F-m, all without net increase in chlorophyll. The fall and winter reorganisation allow Pinus sylvestris is to maintain a large stock of chlorophyll in a quenched, photoprotected state, allowing rapid recovery of photosynthesis in spring.

  • 24. PALMQVIST, K
    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).
    BADGER, MR
    PHOTOBIONT-RELATED DIFFERENCES IN CARBON ACQUISITION AMONG GREEN-ALGAL LICHENS1994In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 195, no 1, p. 70-79Article in journal (Refereed)
    Abstract [en]

    The photosynthetic properties of a range of lichens (eight species) containing green algal primary photobionts of either the genus Coccomyxa, Dictyochloropsis or Trebouxia were examined with the aim of obtaining a better understanding for the different CO2 acquisition strategies of lichenized green algae. Fast transients of light/dark-dependent CO2 uptake and release were measured in order to screen for the presence or absence of a photosynthetic CO2-concentrating mechanism (CCM) within the photobiont. It was found that lichens with Trebouxia photobionts (four species) were able to accumulate a small pool of inorganic carbon (DIC; 70-140 nmol per mg chlorophyll (Chl)), in the light, which theoretically may result in, at least, a two- to threefold increase in the stromal CO2 concentration, as compared to that in equilibrium with ambient air. The other lichens (four species), which were tripartite associations between a fungus, a cyanobacterium (Nostoc) and a green alga (Coccomyxa or Dictyochloropsis) accumulated a much smaller pool of DIC (10-30 nmol.(mg Chl)(-1)). This pool is most probably associated with the previously documented CCM of Nostoc, inferred from the finding that free-living cells of Coccomyxa did not show any signs of DIC accumulation. In addition, the kinetics of fast CO2 exchange for free-living Nostoc were similar to those of intact tripartite lichens, especially in their responses to the CCM and the carbonic anhydrase (CA) inhibitor ethoxyzolamide. Trebouxia lichens had a higher photosynthetic capacity at low and limiting external CO2 concentrations, with an initial slope of the CO2-response curve of 2.6-3.9 mu mol.(mg Chl)-1.h(-1).Pa-1, compared to the tripartite lichens which had an initial slope of 0.5-1.1 mu mol.(mg Chl)(-1).h(-1).Pa-1, suggesting that the presence of a CCM in the photobiont affects the photosynthetic performance of the whole lichen. Regardless of these indications for the presence or absence of a CCM, ethoxyzolamide inhibited the steady-state rate of photosynthesis at low CO2 in all lichens, indicating a role of CA in the photosynthetic process within all of the photobionts. Measurements of CA activity in photobiont-enriched homogenates of the lichens showed that Coccomyxa had by far the highest activity, while the other photobionts displayed only traces or no activity at all. As the CCM is apparently absent in Coccomyxa, it is speculated that this alga compensates for this absence with high internal CA activity, which may function to reduce the CO2-diffusion resistance through the cell.

  • 25. SANDBERG, G
    et al.
    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).
    SITBON, F
    OLSSON, O
    PRESENCE OF INDOLE-3-ACETIC-ACID IN CHLOROPLASTS OF NICOTIANA-TABACUM AND PINUS-SYLVESTRIS1990In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 180, no 4, p. 562-568Article in journal (Refereed)
  • 26. Santoni, V.
    et al.
    Bellini, C.
    Caboche, M.
    Use of two-dimensional protein pattern analysis for the characterization of Arabidopsis thaliana mutants.1994In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 192, no 4, p. 557-566Article in journal (Refereed)
    Abstract [en]

    Total proteins extracted from wild-type plants of Arabidopsis thaliana Heyhn, an etiolated mutant, a de-etiolated mutant and a mutant affected in cotyledon morphology, were analyzed by two-dimensional gel electrophoresis. Computer analysis of two-dimensional gels allowed the characterization of the mutants by a set of proteins showing a differential expression when compared with the wild-type plant grown under the same conditions. The overlap between comparisons of the different mutants with the wild-type allowed the identification of groups of polypeptides which, since their expression is altered in several mutants, might be involved in certain physiological functions. For example, this approach showed a possible involvement of actin in the elongation process. The simultaneous analysis of the two-dimensional protein patterns of different mutants seems, therefore, to be a promising approach to characterize proteins involved in various physiological functions.

  • 27. Santoni, V.
    et al.
    Delarue, M.
    Caboche, M.
    Bellini, C.
    A comparison or two-dimensional electrophoresis data with phenotypical traits in Arabidopsis leads to the identification of a mutant (cri1) that accumulates cytokinins1997In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 202, no 1, p. 62-69Article in journal (Refereed)
    Abstract [en]

    Total proteins extracted from developmental mutants of Arabidopsis thaliana (L.) Heyhn, and from wild-type plants cultivated in the presence of various hormones were analyzed by two-dimensional (2-D) gel electrophoresis. Computer analysis of 2-D gels followed by a statistical treatment of data allowed us to build a phenogram that describes the biochemical distances between the different genotypes. Analysis of the 2-D electrophoresis data allowed us to discriminate mutants in agreement with phenotypical and physiological traits. This biochemical analysis helped us to develop a working hypothesis which led us to show that one developmental mutant (cril) overaccumulates cytokinins.

  • 28. Savitch, L V
    et al.
    Barker-Astrom, J
    Ivanov, A G
    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, N P A
    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).
    Cold acclimation of Arabidopsis thaliana results in incomplete recovery of photosynthetic capacity, associated with an increased reduction of the chloroplast stroma2001In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 214, no 2, p. 295-303Article in journal (Refereed)
    Abstract [en]

    The effects of short-term cold stress and long-term cold acclimation on the light reactions of photosynthesis were examined in vivo to assess their contributions to photosynthetic acclimation to low temperature in Arabidopsis thaliana (L.) Heynh.. All photosynthetic measurements were made at the temperature of exposure: 23 degreesC for non-acclimated plants and 5 degreesC for cold-stressed and cold-acclimated plants. Three-day cold-stress treatments at 5 degreesC inhibited light-saturated rates of CO2 assimilation and O-2 evolution by approximately 75%. The 3-day exposure to 5 degreesC also increased the proportion of reduced QA by 50%, decreased the yield of PSII electron transport by 65% and decreased PSI activity by 31%. In contrast, long-term cold acclimation resulted in a strong but incomplete recovery of light-saturated photosynthesis at 5 degreesC. The rates of light-saturated CO2 and O-2 gas exchange and the in vivo yield of PSII activity under light-saturating conditions were only 35-40% lower, and the relative redox state of QA only 20% lower, at 5 degreesC after cold acclimation than in controls at 23 degreesC. PSI activity showed full recovery during long-term cold acclimation. Neither short-term cold stress nor long-term cold acclimation of Arabidopsis was associated with a limitation in ATP, and both treatments resulted in an increase in the ATP/NADPH ratio. This increase in ATP/NADPH was associated with an inhibition of PSI cyclic electron transport but there was no apparent change in the Mehler reaction activity in either cold-stressed or cold-acclimated leaves. Cold acclimation also resulted in an increase in the reduction state of the stroma, as indicated by an increased total activity and activation state of NADP-dependent malate dehydrogenase, and increased light-dependent activities of the major regulatory enzymes of the oxidative pentose-phosphate pathway. We suggest that the photosynthetic capacity during cold stress as well as cold acclimation is altered by limitations at the level of consumption of reducing power in carbon metabolism.

  • 29.
    Schmid, M.
    et al.
    Lehrstuhl für Botanik, Technische Universität München, Germany..
    Simpson, D.
    Kalousek, F.
    Gietl, C.
    A cysteine endopeptidase with a C-terminal KDEL motif isolated from castor bean endosperm is a marker enzyme for the ricinosome, a putative lytic compartment1998In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 206, no 3, p. 466-475Article in journal (Refereed)
  • 30.
    Sellstedt, Anita
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    ACETYLENE-REDUCTION, H-2 EVOLUTION AND N-14(2) FIXATION IN THE ALNUS-INCANA-FRANKIA SYMBIOSIS1986In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 167, no 3, p. 382-386Article in journal (Refereed)
  • 31.
    Sellstedt, Anita
    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).
    HUSSDANELL, K
    BIOMASS PRODUCTION AND NITROGEN-UTILIZATION BY ALNUS-INCANA WHEN GROWN ON N-2 OR NH4+ MADE AVAILABLE AT THE SAME RATE1986In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 167, no 3, p. 387-394Article in journal (Refereed)
  • 32. Siedlecka, A
    et al.
    Ciereszko, I
    Mellerowicz, E
    Martz, F
    Chen, J
    Kleczkowski, Leszek A
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The small subunit ADP-glucose pyrophosphorylase (ApS) promoter mediates okadaic acid-sensitive uidA expression in starch-synthesizing tissues and cells in Arabidopsis2003In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 217, no 2, p. 184-192Article in journal (Refereed)
    Abstract [en]

    Transgenic plants of Arabidopsis thaliana Heynh., transformed with a bacterial beta-glucuronidase (GUS) gene under the control of the promoter of the small subunit (ApS) of ADP-glucose pyrophosphorylase (AGPase), exhibited GUS staining in leaves (including stomata), stems, roots and flowers. Cross-sections of stems revealed GUS staining in protoxylem parenchyma, primary phloem and cortex. In young roots, the staining was found in the root tips, including the root cap, and in vascular tissue, while the older root-hypocotyl axis showed prominent staining in the secondary phloem and paratracheary parenchyma of secondary xylem. The GUS staining co-localized with ApS protein, as found by tissue printing using antibodies against ApS. Starch was found only in cell and tissue types exhibiting GUS staining and ApS labelling, but not in all of them. For example, starch was lacking in the xylem parenchyma and secondary phloem of the root-hypocotyl axis. Sucrose potently activated ApS gene expression in leaves of wild-type (wt) plants, and in transgenic seedlings grown on sucrose medium where GUS activity was quantified with 4-methylumbelliferyl-beta-glucuronide as substrate. Okadaic acid, an inhibitor of protein phosphatases 1 and 2A, completely blocked expression of ApS in mature leaves of wt plants and prevented GUS staining in root tips and flowers of the transgenic plants, suggesting a similar signal transduction mechanism for ApS expression in various tissues. The data support the key role of AGPase in starch synthesis, but they also underlie the ubiquitous importance of the ApS gene for AGPase function in all organs/tissues of Arabidopsis.

  • 33. SITBON, F
    et al.
    EDLUND, A
    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).
    OLSSON, O
    SANDBERG, G
    COMPARTMENTATION OF INDOLE-3-ACETIC-ACID METABOLISM IN PROTOPLASTS ISOLATED FROM LEAVES OF WILD-TYPE AND IAA-OVERPRODUCING TRANSGENIC TOBACCO PLANTS1993In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 191, no 2, p. 274-279Article in journal (Refereed)
    Abstract [en]

    Cellular compartmentation of indole-3-acetamide (IAM), indole-3-acetic acid (IAA), and [N-15(1)]IAA synthesised from [N-15(1)]tryptophan was monitored in protoplasts isolated from sterile wild-type tobacco SR1 plants, and in IAA-overproducing plants expressing the Agrobacterium tumefaciens T-DNA IAA genes iaaM and iaaH. Indole-3-acetamide was located exclusively in the cytosol of both iaaM and iaaM/iaaH protoplasts, being 75% lower than in iaaM protoplasts, presumably because of conversion into IAA by action of the iaaH-encoded hydrolase. The free-IAA level, however, was raised only 8% in iaaM/iaaH compared to iaaM protoplasts, whereas the level of IAA-conjugates was increased more than fivefold. For both genotypes, the location of IAA conjugates was restricted to the cytosol, while one-third of the free-IAA pool was present in chloroplasts. Transcription of the iaaM gene was increased by fusion to the strong cautiflower mosaic virus (CaMV) 35S promoter. Compared with the wildtype, this led to an 18-fold higher conversion of [N-15(1)]tryptophan to [N-15(1)]IAA, a three- to fourfold increase in free IAA, and a tenfold higher level of IAA conjugates in 35S-iaaM/iaaH protoplasts. Also in these genotypes, IAA conjugates were exclusively cytosolic. There was no major difference between transgenic and wildtype protoplasts in the proportion of chloroplastic to total cellular IAA, although the chloroplastic IAA and [N-15(1)]IAA pools in the transformant were threefold and eightfold higher, respectively. Since the IAM pool in transgenic plants is exclusively cytosolic, these findings suggest that the increased chloroplastic [N-15(1)]IAA pool in 35S-iaaM/iaaH protoplasts is synthesised in the cytosol but rapidly transported into the chloroplast. Furthermore, the presence of IAA in the chloroplast together with the exclusively cytosolic location of IAA conjugates, suggests the presence of two differentially subcellular pools of IAA. The first is located in the cytosol and mainly regulated by non-decarboxylative catabolism and conjugation (Sandberg et al. 1990, Planta 180, 562-568), whereas the second is located in the chloroplast and is seemingly not directly regulated inside the organelle by either of these two processes. The cytosolic IAA control mechanisms, however, also affect the chloroplastic pool size due to the rapid transport of IAA between the two compartments.

  • 34. Szal, Bożena
    et al.
    Jastrzębska, Agata
    Kulka, Marek
    Leśniak, Karolina
    Podgórska, Anna
    Pärnik, Tiit
    Ivanova, Hiie
    Keerberg, Olav
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Rychter, Anna M
    Influence of mitochondrial genome rearrangement on cucumber leaf carbon and nitrogen metabolism2010In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 232, no 6, p. 1371-1382Article in journal (Refereed)
    Abstract [en]

    The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no effect on photosynthetic CO(2) assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions. In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity is needed for synthesis of carbon skeletons required as the acceptors for NH(4) (+) assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and accumulation of Glu.

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