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Distinct roles for the different Lhcb isoforms in light harvesting regulation

Du 18/05/2017 au 18/05/2017
Aurélie Crépin (SBVME/LGBP)

Conférencier : Aurélie Crépin (SBVME/LGBP)

Light harvesting in photosynthesis relies on "antenna" systems composed of chlorophyll-binding proteins. In the green line, this role is occupied by the LHC proteins. The LHCII trimers are the major antenna of photosystem II (PSII) and represent a large family of proteins highly conserved from green algae (Lhcbm isoforms) to plants (Lhcb1-3 isoforms) that have a crucial function in both light harvesting and its regulation.
We investigated these roles on detergent-purified photosystems from Arabidopsis thaliana, with a focus on state transitions, an excitation-balance mechanism involving a movement of LHCII trimers from one photosystem to the other. We showed that phosphorylated (P-) Lhcb2 is specifically involved in the binding of LHCII to PSI on the PsaH side, as well as probably on other sites, while P-Lhcb1 is mostly retained on PSII. In the case of Lhcb3, its specific localization in the less phosphorylated M-trimer of PSII seems to point to a role in state transitions limitation and photosystem dynamic; an involvement in high light regulation was also suggested in previous studies.
Altogether, these results contribute to the increasing evidence pointing out to distinct roles of the different Lhcb isoforms in light harvesting regulation, and raise the question of their evolution and their role in the modification of the regulation mechanisms between green algae and plants.

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