title: LHCSR3 affects de-coupling and re-coupling of LHCII to PSII during state transitions in Chlamydomonas reinhardtii.
abstract: Photosynthetic organisms have to tolerate rapid changes in light intensity, which is facilitated by non-photochemical quenching (NPQ) and involves modification of energy transfer from light-harvesting complexes (LHC) to the photosystem reaction centres. NPQ includes dissipating excess light energy to heat (qE) and the reversible coupling of LHCII to photosystems (state transitions/qT), which are considered separate NPQ mechanisms. In the model alga Chlamydomonas reinhardtii the LHCSR3 protein has a well characterised role in qE. Here, it is shown in the npq4 mutant, deficient in LHCSR3, that energy coupling to photosystem II (PSII) more akin to qT is also disrupted, but no major differences in LHC phosphorylation or LHC compositions were found in comparison to wild-type cells. The qT of wild-type cells possessed two kinetically distinguishable phases, with LHCSR3 participating in the more rapid (<2 min) phase. This LHCSR3-mediated qT was sensitive to physiological levels of H2O2, which accelerated qE induction, revealing a way that may help C. reinhardtii tolerate a sudden increase in light intensity. Overall, a clear mechanistic overlap between qE and qT is shown.
authors.affiliation: Institute of Botany, Leopold-Franzens-Universität-Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Roach
authors.affiliation: Institute of Botany, Leopold-Franzens-Universität-Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria.|Institute of Ecological Phytochemistry, Department of Plant Life and Environmental Science, Hankyong National University, Anseong 456-749, Gyeonggi-do, Republic of Korea.
authors.forename: Chae Sun
authors.initials: CS
authors.lastname: Na
mesh_terms: D020418:Algal Proteins / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000378:metabolism* / Q000528:radiation effects*; D004734:Energy Metabolism; D006358:Hot Temperature; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D011485:Protein Binding
chemical_list: D020418:Algal Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex