Journal
BOTANY
Volume 95, Issue 12, Pages 1125-1140Publisher
CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS
DOI: 10.1139/cjb-2017-0066
Keywords
excitation pressure; green algae; light harvesting; photosynthesis; redox
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Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants program
- Canadian Foundation for Innovation
- Canada Research Chairs program
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Chlorella vulgaris acclimated to high light (HL) conditions exhibited a pale-green phenotype characterized by reduced chlorophyll and light harvesting polypeptide abundance compared with the dark green phenotype of the control, low-light-grown (LL) cultures. We hypothesized that if chloroplast redox status was the sole regulator of phenotype, exposure to darkness should cause reversion of the HL to LL phenotype. Surprisingly, HL cells transferred to darkness or dim light failed to green. Thus, phenotypic reversion is light-dependent with an optimal photon flux density (PFD) of 110 mu mol photons.m(-2).s(-1). HL cells shifted to this PFD exhibited increased chlorophyll and light harvesting polypeptide abundance, which were inhibited by 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone but not by 3-(3=, 4=-dichlorophenyl)-1,1-dimethylurea. Weconclude that photoacclimation of HL-grown cells to LL is governed by the redox state of the intersystem photosynthetic electron transport chain (PETC) at this PFD. At lower light levels, cells maintained the HL phenotype, despite an oxidized status of the PETC. Because 110 mu mol photons.m(-2).s(-1) was the optimal PFD for protochlorophyllide oxidoreductase accumulation, we suggest that stabilization of light-harvesting polypeptides by chlorophyll binding may also govern photoacclimation in C. vulgaris. The possible role of the metabolic balance between respiration and photosynthesis is also discussed.
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