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Seminaire invité

Oxidation of P700 ensures robust photosynthesis

Du 12/02/2019 au 12/02/2019
Ginga Shimakawa (CEA Saclay, I2BC)

​Conférencier :  Ginga Shimakawa (CEA Saclay, I2BC) invité par Adrien Burlacot (BIAM/LB3M)


Photosynthesis is one of the most important biological activities on the earth and produces the chemical energy from the sunlight to synthesize sugars. In the light reaction of photosynthesis, light energy causes charge separation of the reaction center chlorophylls in photosystem (PS) I and II to drive photosynthetic electron transport from PSII to PSI on the thylakoid membrane, resulting in the production of NADPH and ATP for the CO2 assimilation. On the other hand, light also has potential to generate reactive oxygen species in PSII and PSI and cause the oxidative damage to photosynthetic cells. Nevertheless, a variety of oxygenic photoautotrophs, including cyanobacteria, algae, and plants, can manage their photosynthetic machineries successfully under the natural sunlight. In this presentation, I would like to talk about how photoautotrophs safely utilize light energy for photosynthesis without any photo-oxidative damages to PSI. The reaction center chlorophyll in PSI, P700, is flexibly kept in an oxidized state in response to excess light to tune the light utilization and dissipate the excess photo-excitation energy as the heat. Oxidation of P700 is the common strategy for photoautotrophs to alleviate the photo-oxidative damages to PSI, which is co-operatively regulated by a number of molecular mechanisms. Whereas on the electron donor side of PSI the regulatory mechanisms suppress the electron transport to keep P700 oxidized, on the acceptor sides the alternative electron sinks dissipate excess electrons to support P700 oxidation. The strategies to keep P700 oxidized are diverse among a variety of photoautotrophs, which might be evolutionarily optimized for their ecological niche.

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