Acclimation of Chlamydomonas reinhardtii to different growth irradiances.
We report on the changes the photosynthetic apparatus of Chlamydomonas reinhardtii undergoes upon acclimation to different light intensity. When grown in high light, cells had a faster growth rate and higher biomass production compared with low and control light conditions. However, cells acclimated to low light intensity are indeed able to produce more biomass per photon available as compared with high light-acclimated cells, which dissipate as heat a large part of light absorbed, thus reducing their photosynthetic efficiency. This dissipative state is strictly dependent on the accumulation of LhcSR3, a protein related to light-harvesting complexes, responsible for nonphotochemical quenching in microalgae. Other changes induced in the composition of the photosynthetic apparatus upon high light acclimation consist of an increase of carotenoid content on a chlorophyll basis, particularly zeaxanthin, and a major down-regulation of light absorption capacity by decreasing the chlorophyll content per cell. Surprisingly, the antenna size of both photosystem I and II is not modulated by acclimation; rather, the regulation affects the PSI/PSII ratio. Major effects of the acclimation to low light consist of increased activity of state 1 and 2 transitions and increased contributions of cyclic electron flow.
Dipartimento di Biotecnologie, Università di Verona, Ca'Vignal 1, Strada le Grazie 15, I-37134 Verona, Italy.
Giulia
G
Bonente
Sara
S
Pippa
Stefania
S
Castellano
Roberto
R
Bassi
Matteo
M
Ballottari
D000222:Adaptation, Physiological / Q000528:radiation effects*; D016825:Chlamydomonas reinhardtii / Q000254:growth & development / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects*; D003624:Darkness; D004307:Dose-Response Relationship, Radiation; D004579:Electron Transport / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects*; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism
D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological