<i>Chlamydomonas</i>, a model system for studying the assembly and dynamics of photosynthetic complexes

Rochaix, Jean‐David

doi:10.1016/s0014-5793(02)03181-2

Cited by 96 publications

(74 citation statements)

References 35 publications

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“…However, at light intensities of Ͼ400 mol⅐m Ϫ2 ⅐s Ϫ1 , the NPQ of the mutant was significantly higher than that of the wild type. Further analysis revealed that the additional NPQ was not rapidly reversible, The plants shown in C were exposed to illumination (300 mol⅐m Ϫ2 ⅐s Ϫ1 ) for 2 days after 7 weeks of growth in low light (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) mol⅐m Ϫ2 ⅐s Ϫ1 ). indicating that the increased NPQ is due to a larger component of photoinhibitory quenching in the mutant.…”

Section: Resultsmentioning

confidence: 99%

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A chloroplast cyclophilin functions in the assembly and maintenance of photosystem II in Arabidopsis thaliana

Cho

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

154

144

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Photosynthetic light reactions rely on the proper function of large protein complexes (including photosystems I and II) that reside in the thylakoid membrane. Although their composition, structure, and function are known, the repertoire of assembly and maintenance factors is still being determined. Here we show that an immunophilin of the cyclophilin type, CYP38, plays a critical role in the assembly and maintenance of photosystem II (PSII) supercomplexes (SCs) in Arabidopsis. Mutant plants with the CYP38 gene interrupted by T-DNA insertion showed stunted growth and were hypersensitive to high light. Leaf chlorophyll fluorescence analysis and thylakoid membrane composition indicated that cyp38 mutant plants had defects in PSII SCs. Sucrose supplementation enabled the rescue of the mutant phenotype under low-light conditions, but failed to mitigate hypersensitivity to high-light stress. Protein radiolabeling assays showed that, although individual thylakoid proteins were synthesized equally in mutant and wild type, the assembly of the PSII SC was impaired in the mutant. In addition, the D1 and D2 components of the mutant PSII had a short half-life under high-light stress. The results provide evidence that CYP38 is necessary for the assembly and stabilization of PSII.thylakoid lumen ͉ immunophilin ͉ photosynthesis ͉ protein folding ͉ chaperone T he light reactions and attendant evolution of oxygen in photosynthesis are carried out by four multisubunit protein complexes residing in the chloroplast thylakoid membranes: photosystems I (PSI) and II (PSII), cytochrome b 6 f complex, and CF O -CF 1 complex (1-3). For a complete understanding of the photosynthetic process, it is essential to understand the biogenesis and maintenance of the participating complexes. Earlier studies on thylakoid protein supercomplex (SC) assembly, especially PSII, concentrated on the role of stromal factors, such as the translation and import machinery (4), because only a limited number of proteins were known to reside in the thylakoid lumen. However, recent proteomic findings suggest a population of 80-100 proteins in that compartment (5-7). The immunophilin family is one of the predominant groups identified.Immunophilins were originally discovered in their capacity as cellular receptors for immunosuppressive drugs: cyclosporin A and FK506 (8, 9). The receptors for cyclosporin A and FK506, named cyclophilins (CYPs) and FK506-binding proteins (FKBPs), respectively, were collectively designated as immunophilins. A common feature of most immunophilins is the associated peptidyl-prolyl cis-trans isomerase activity that catalyzes the cis-trans conversion of X-Pro peptide bonds, a rate-limiting step in protein folding (8). These proteins are now known to occur widely in organisms ranging from bacteria and fungi to animals and plants. Studies in animal and plant systems have uncovered diverse functions of immunophilins, such as protein foldases, chaperones, and scaffolding facilitators. They also possibly have unknown catalytic capabilities (10, ...

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Section: Resultsmentioning

confidence: 99%

“…Earlier work has shown that proteins functional in the translation and import of subunit proteins are required for the biogenesis of photosynthetic complexes (4,28). However, the proteins that function specifically in the assembly of the complexes have long been a mystery and are only now beginning to be identified (29)(30)(31).…”

Section: Resultsmentioning

confidence: 99%

A chloroplast cyclophilin functions in the assembly and maintenance of photosystem II in Arabidopsis thaliana

Cho

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

154

144

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“…The single-celled motile freshwater alga Chlamydomonas reinhardtii is a model system for studying photosynthesis, which is useful to complement and extend the understanding of photosynthetic eukaryotes when compared with Arabidopsis thaliana (Rochaix, 2002;Gutman and Niyogi, 2004). Chlamydomonas is a photoautotrophic organism in the wild and is exposed to a complex light environment that includes UV-B.…”

Section: Introductionmentioning

confidence: 99%

UV-B Perception and Acclimation in Chlamydomonas reinhardtii

et al. 2016

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Plants perceive UV-B, an intrinsic component of sunlight, via a signaling pathway that is mediated by the photoreceptor UV RESISTANCE LOCUS8 (UVR8) and induces UV-B acclimation. To test whether similar UV-B perception mechanisms exist in the evolutionarily distant green alga Chlamydomonas reinhardtii, we identified Chlamydomonas orthologs of UVR8 and the key signaling factor CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Cr-UVR8 shares sequence and structural similarity to Arabidopsis thaliana UVR8, has conserved tryptophan residues for UV-B photoreception, monomerizes upon UV-B exposure, and interacts with Cr-COP1 in a UV-B-dependent manner. Moreover, Cr-UVR8 can interact with At-COP1 and complement the Arabidopsis uvr8 mutant, demonstrating that it is a functional UV-B photoreceptor. Chlamydomonas shows apparent UV-B acclimation in colony survival and photosynthetic efficiency assays. UV-B exposure, at low levels that induce acclimation, led to broad changes in the Chlamydomonas transcriptome, including in genes related to photosynthesis. Impaired UV-B-induced activation in the Cr-COP1 mutant hit1 indicates that UVR8-COP1 signaling induces transcriptome changes in response to UV-B. Also, hit1 mutants are impaired in UV-B acclimation. Chlamydomonas UV-B acclimation preserved the photosystem II core proteins D1 and D2 under UV-B stress, which mitigated UV-B-induced photoinhibition. These findings highlight the early evolution of UVR8 photoreceptor signaling in the green lineage to induce UV-B acclimation and protection.

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“…Among these, microalgal oil and biomass production has shown promise (Chisti, 2007;Ohlrogge et al, 2009;Williams and Laurens, 2010;Atabani et al, 2012) because of the photoautotrophic growth of algae and their ability to reach high cell densities and accumulate high dry weight percentages of triacylglycerol (TAG) and their potential for much higher productivity per hectare than terrestrial biofuel crops (Hu et al, 2008;Wijffels and Barbosa, 2010). The unicellular green alga Chlamydomonas reinhardtii is among the most widely studied models of photosynthesis (Rochaix, 2002) and other cellular processes, including lipid accumulation by algae under stress . Its advantages for studying photosynthetic mechanisms and regulation include the ability to grow both photo-and heterotrophically so that photosynthetic down-regulation and photosynthetically impaired mutants can be isolated (Dent et al, 2001) and a fully sequenced genome, collections of mutants, and the ease with which its growth, physiology, and photosynthetic rates can be measured.…”

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confidence: 99%

The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii

Deshpande²,

et al. 2014

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The accumulation of carbon storage compounds by many unicellular algae after nutrient deprivation occurs despite declines in their photosynthetic apparatus. To understand the regulation and roles of photosynthesis during this potentially bioenergetically valuable process, we analyzed photosynthetic structure and function after nitrogen deprivation in the model alga Chlamydomonas reinhardtii. Transcriptomic, proteomic, metabolite, and lipid profiling and microscopic time course data were combined with multiple measures of photosynthetic function. Levels of transcripts and proteins of photosystems I and II and most antenna genes fell with differing trajectories; thylakoid membrane lipid levels decreased, while their proportions remained similar and thylakoid membrane organization appeared to be preserved. Cellular chlorophyll (Chl) content decreased more than 2-fold within 24 h, and we conclude from transcript protein and 13 C labeling rates that Chl synthesis was down-regulated both pre-and posttranslationally and that Chl levels fell because of a rapid cessation in synthesis and dilution by cellular growth rather than because of degradation. Photosynthetically driven oxygen production and the efficiency of photosystem II as well as P700 + reduction and electrochromic shift kinetics all decreased over the time course, without evidence of substantial energy overflow. The results also indicate that linear electron flow fell approximately 15% more than cyclic flow over the first 24 h. Comparing Calvin-Benson cycle transcript and enzyme levels with changes in photosynthetic 13 CO 2 incorporation rates also pointed to a coordinated multilevel down-regulation of photosynthetic fluxes during starch synthesis before the induction of high triacylglycerol accumulation rates.

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Chlamydomonas, a model system for studying the assembly and dynamics of photosynthetic complexes

Cited by 96 publications

References 35 publications

A chloroplast cyclophilin functions in the assembly and maintenance of photosystem II in Arabidopsis thaliana

A chloroplast cyclophilin functions in the assembly and maintenance of photosystem II in Arabidopsis thaliana

UV-B Perception and Acclimation in Chlamydomonas reinhardtii

The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii

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