Interaction between Starch Breakdown, Acetate Assimilation, and Photosynthetic Cyclic Electron Flow in Chlamydomonas reinhardtii

Johnson, Xenie; Alric, Jean

doi:10.1074/jbc.m112.370205

Cited by 114 publications

(96 citation statements)

References 44 publications

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“…The absorbance changes at 705 nm under PSII-inhibited conditions are proportional to the oxidation/reduction of PSI (Alric, 2010;Johnson and Alric, 2012). These P700 absorbance changes shown in Figure 5 are attributed to redox turnover at PSI due to CEF (Fig.…”

Section: Total Psi Turnover Rate Falls During N Deprivationmentioning

confidence: 99%

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

Juergens

Deshpande²,

Lucker

et al. 2014

Plant Physiology

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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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Section: Total Psi Turnover Rate Falls During N Deprivationmentioning

confidence: 99%

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

Juergens

Deshpande²,

Lucker

et al. 2014

Plant Physiology

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“…Chlamydomonas cells can grow phototrophically and can also metabolize acetate and related compounds to grow mixotrophically or heterotrophically. The relationship between these modes of growth is complex and involves partial suppression of photosynthesis and alterations in gene expression when acetate is present (Heifetz et al, 2000;Boyle and Morgan, 2009;Johnson and Alric, 2012;Roach et al, 2013;Chapman et al, 2015). However, very little is known about intracellular signaling pathways that sense carbon source and control carbon metabolism and utilization in Chlamydomonas.…”

Section: Introductionmentioning

confidence: 99%

Synergism between Inositol Polyphosphates and TOR Kinase Signaling in Nutrient Sensing, Growth Control, and Lipid Metabolism in Chlamydomonas

et al. 2016

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The networks that govern carbon metabolism and control intracellular carbon partitioning in photosynthetic cells are poorly understood. Target of Rapamycin (TOR) kinase is a conserved growth regulator that integrates nutrient signals and modulates cell growth in eukaryotes, though the TOR signaling pathway in plants and algae has yet to be completely elucidated. We screened the unicellular green alga Chlamydomonas reinhardtii using insertional mutagenesis to find mutants that conferred hypersensitivity to the TOR inhibitor rapamycin. We characterized one mutant, vip1-1, that is predicted to encode a conserved inositol hexakisphosphate kinase from the VIP family that pyrophosphorylates phytic acid (InsP 6 ) to produce the low abundance signaling molecules InsP 7 and InsP 8 . Unexpectedly, the rapamycin hypersensitive growth arrest of vip1-1 cells was dependent on the presence of external acetate, which normally has a growth-stimulatory effect on Chlamydomonas. vip1-1 mutants also constitutively overaccumulated triacylglycerols (TAGs) in a manner that was synergistic with other TAG inducing stimuli such as starvation. vip1-1 cells had reduced InsP 7 and InsP 8 , both of which are dynamically modulated in wild-type cells by TOR kinase activity and the presence of acetate. Our data uncover an interaction between the TOR kinase and inositol polyphosphate signaling systems that we propose governs carbon metabolism and intracellular pathways that lead to storage lipid accumulation.

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“…Importantly, as already pointed out in Refs. 29, 67, the observation that after a few minutes of illumination CEF reaches a steady state value implies that the "leak" of reducing power resulting from the CO 2 -reducing pathway, the implication of which has been discussed above, is compensated for by a constant influx of reducing power, which likely stems from starch and glucose catabolism (68). Now that we have demonstrated that the reoxidation of the pool of electron acceptors is sufficient to alleviate the unproductive buildup of charge-recombining PSI, we may reason that, similarly, the spontaneous consumption of reducing power is responsible for the alleviation of the acceptor side limitation after a prolonged incubation of anoxia in the dark.…”

mentioning

confidence: 99%

The Involvement of Hydrogen-producing and ATP-dependent NADPH-consuming Pathways in Setting the Redox Poise in the Chloroplast of Chlamydomonas reinhardtii in Anoxia

Clowez

Godaux

Cardol

et al. 2015

Journal of Biological Chemistry

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Background: Shift to anoxia promotes the over-reduction of photosystem I electron acceptors. Results: This over-reduction can be relieved by the activation of several pathways. Conclusion: The two mains pathways are the ATP-dependent CO 2 fixation pathway and the ATP-independent hydrogenase. Significance: We disentangle the role of the various NADPH-consuming pathways in setting the redox poise in the chloroplast of unicellular photosynthetic algae.

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Interaction between Starch Breakdown, Acetate Assimilation, and Photosynthetic Cyclic Electron Flow in Chlamydomonas reinhardtii

Cited by 114 publications

References 44 publications

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

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

Synergism between Inositol Polyphosphates and TOR Kinase Signaling in Nutrient Sensing, Growth Control, and Lipid Metabolism in Chlamydomonas

The Involvement of Hydrogen-producing and ATP-dependent NADPH-consuming Pathways in Setting the Redox Poise in the Chloroplast of Chlamydomonas reinhardtii in Anoxia

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