Activation of a Reserve Pool of Photosystem II in Chlamydomonas reinhardtii Counteracts Photoinhibition

Neale, Patrick J.; Melis, Anastasios

doi:10.1007/978-94-009-0511-5_322

Cited by 8 publications

(9 citation statements)

References 21 publications

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“…It is hypothesized (1) that the C-terminal portion of the REP27 protein is needed for the insertion of nascent D1 proteins in the D1-less PSII template, and (2) that TPR motifs are required for the "activation" of newly inserted and bound D1 proteins, which, in the case of the truncated REP27 transformants, remained inactive. Such an activation step was inferred earlier from biophysical studies Neale and Melis, 1990) and could involve a posttranslational modification and/or proper membrane deployment/folding of the nascent D1 protein during its assembly within the PSII template and subsequent maturation. Since the TPR-less strains had a low PSII photochemical charge separation efficiency and lack of photoautotrophic growth capacity, it appears that TPR domains are needed to ensure a full integration of nascent D1 proteins into the PSII reaction center template, leading to a functional PSII reaction center.…”

Section: Functional Role Of the Rep27 Tpr Motifs And C-terminal Domainmentioning

confidence: 70%

Mechanism of REP27 Protein Action in the D1 Protein Turnover and Photosystem II Repair from Photodamage

et al. 2009

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The function of the REP27 protein (GenBank accession no. EF127650) in the photosystem II (PSII) repair process was elucidated. REP27 is a nucleus-encoded and chloroplast-targeted protein containing two tetratricopeptide repeat (TPR) motifs, two putative transmembrane domains, and an extended carboxyl (C)-terminal region. Cell fractionation and western-blot analysis localized the REP27 protein in the Chlamydomonas reinhardtii chloroplast thylakoids. A folding model for REP27 suggested chloroplast stroma localization for amino-and C-terminal regions as well as the two TPRs. A REP27 gene knockout strain of Chlamydomonas, termed the rep27 mutant, was employed for complementation studies. The rep27 mutant was aberrant in the PSII-repair process and had substantially lower than wild-type levels of D1 protein. Truncated REP27 cDNA constructs were made for complementation of rep27, whereby TPR1, TPR2, TPR1+TPR2, or the C-terminal domains were deleted. rep27-complemented strains minus the TPR motifs showed elevated levels of D1 in thylakoids, comparable to those in the wild type, but the PSII photochemical efficiency of these strains was not restored, suggesting that the functionality of the PSII reaction center could not be recovered in the absence of the TPR motifs. It is suggested that TPR motifs play a role in the functional activation of the newly integrated D1 protein in the PSII reaction center. rep27-complemented strains missing the C-terminal domain showed low levels of D1 protein in thylakoids as well as low PSII photochemical efficiency, comparable to those in the rep27 mutant. Therefore, the C-terminal domain is needed for a de novo biosynthesis and/or assembly of D1 in the photodamaged PSII template. We conclude that REP27 plays a dual role in the regulation of D1 protein turnover by facilitating cotranslational biosynthesis insertion (C-terminal domain) and activation (TPR motifs) of the nascent D1 during the PSII repair process.

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Section: Functional Role Of the Rep27 Tpr Motifs And C-terminal Domainmentioning

confidence: 70%

Mechanism of REP27 Protein Action in the D1 Protein Turnover and Photosystem II Repair from Photodamage

et al. 2009

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“…We conclude that the transient increase in the PSII X population at the end of the light phase is likely due to a light-dependent process occurring in dividing cells. One possibility is that PSII X is related to the PSII repair cycle, as proposed by Neale and Melis (1990).…”

Section: Characterization Of Psii Heterogeneity During the Cell Cyclementioning

confidence: 99%

Characterization of Photosystem II Activity and Heterogeneity during the Cell Cycle of the Green AlgaScenedesmus quadricauda1

et al. 1999

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The photosynthetic activity of the green alga Scenedesmus quadricauda was investigated during synchronous growth in light/dark cycles. The rate of O 2 evolution increased 2-fold during the first 3 to 4 h of the light period, remained high for the next 3 to 4 h, and then declined during the last half of the light period. During cell division, which occurred at the beginning of the dark period, the ability of the cells to evolve O 2 was at a minimum. To determine if photosystem II (PSII) controls the photosynthetic capacity of the cells during the cell cycle we measured PSII activity and heterogeneity. Measurements of electron-transport activity revealed two populations of PSII, active centers that contribute to carbon reduction and inactive centers that do not. Measurements of PSII antenna sizes also revealed two populations, PSII ␣ and PSII ␤ , which differ from one another by their antenna size. During the early light period the photosynthetic capacity of the cells doubled, the O 2 -evolving capacity of PSII was nearly constant, the proportion of PSII ␤ centers decreased to nearly zero, and the proportion of inactive PSII centers remained constant. During the period of minimum photosynthetic activity 30% of the PSII centers were insensitive to the inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea, which may be related to reorganization of the thylakoid membrane. We conclude from these results that PSII does not limit the photosynthetic activity of the cells during the first half of the light period. However, the decline in photosynthetic activity observed during the last half of the light period can be accounted for by limited PSII activity.The photosynthetic activity of synchronously grown cells of algae is strongly modulated during the cell cycle. In algal cells synchronized by light/dark periods, the rate of photosynthesis can vary more than 2-fold. The photosynthetic activity reaches a maximum during the early phase of the light period, persists for a few hours, and then steadily declines until the end of the light period, which coincides with the onset of cell division (Sorokin, 1957;Sorokin and Mayers, 1957). Respiratory activity exhibits a similar periodic modulation during the cell cycle (Sorokin and Mayers, 1957). Despite decades of research, the factors that control the photosynthetic activity of a cell during its development have not been identified. Some studies indicate that a component of the electron-transport apparatus of the thylakoid membrane may be rate limiting during the cell cycle (Senger and Bishop, 1967, 1969;Schor et al., 1970;Senger, 1970; Frickel-Faulstich and Senger, 1974; Hesse et al., 1976 Hesse et al., , 1977Mende et al., 1981), whereas other studies point to a limitation in the C-reduction cycle (Walther and Edmunds, 1973;Myers and Graham, 1975). These observations raise the possibility that the site of control may change during the cell cycle.Several studies reveal cell-cycle-dependent modifications of the photosynthetic machinery of the thylakoid membrane that could impose l...

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“…The F. to Fi rise has been previously attributed to PSII units with a reduced antenna size (PSII, centers) (15), and more recently to PSII units lacking the ability to reduce QB (non-QB reducing PSII) (9,10,17 The photon yield of oxygen evolution appears to be more sensitive than the photochemical efficiency of PSII in Fedeficient plants; this contrasts with data obtained from healthy plants subjected to high-light stress, in which a close correlation between QY and photochemical efficiency of PSII has often been found (6,11,18). The response of QY and photochemical efficiency of PSII to Fe stress is similar to responses induced by water stress (5),S02 fumigation (1), and cold stress (2, 7), which have been suggested to arise from an impaired electron transport beyond the PSII-reaction center complex (2).…”

Section: K Psi Chl Fluorescencementioning

confidence: 99%

Chlorophyll Fluorescence and Photon Yield of Oxygen Evolution in Iron-Deficient Sugar Beet (Beta vulgaris L.) Leaves

Morales¹,

Abadı́a²,

Abadı́a³

1991

Plant Physiol.

125

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The response of sugar beet (Beta vulgaris L.) leaves to iron deficiency can be described as consisting of two phases. In the first phase, leaves may lose a large part of their chlorophyll while maintaining a roughly constant efficiency of photosystem 11 photochemistry; ratios of variable to maximum fluorescence decreased by only 6%, and photon yields of oxygen evolution decreased by 30% when chlorophyll decreased by 70%. In the second phase, when chlorophyll decreased below a threshold level, iron deficiency caused major decreases in the efficiency of photosystem 11 photochemistry and in the photon yield of oxygen evolution. These decreases in photosystem 11 photochemical efficiency were found both in plants dark-adapted for 30 minutes and in plants dark-adapted overnight, indicating that photochemical efficiency cannot be repaired in that time scale. Decreases in photosystem 11 photochemical efficiency and in the photon yield of oxygen evolution were similar when measurements were made (a) with light absorbed by carotenoids and chlorophylls and (b) with light absorbed only by chlorophylls. Leaves of irondeficient plants exhibited a room temperature fluorescence induction curve with a characteristic intermediate peak I that increases with deficiency symptoms.

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Activation of a Reserve Pool of Photosystem II in Chlamydomonas reinhardtii Counteracts Photoinhibition

Cited by 8 publications

References 21 publications

Mechanism of REP27 Protein Action in the D1 Protein Turnover and Photosystem II Repair from Photodamage

Mechanism of REP27 Protein Action in the D1 Protein Turnover and Photosystem II Repair from Photodamage

Characterization of Photosystem II Activity and Heterogeneity during the Cell Cycle of the Green AlgaScenedesmus quadricauda1

Chlorophyll Fluorescence and Photon Yield of Oxygen Evolution in Iron-Deficient Sugar Beet (Beta vulgaris L.) Leaves

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