title: Photosystem II photoinactivation, repair, and protection in marine centric diatoms.
abstract: Diatoms are important contributors to aquatic primary production, and can dominate phytoplankton communities under variable light regimes. We grew two marine diatoms, the small Thalassiosira pseudonana and the large Coscinodiscus radiatus, across a range of temperatures and treated them with a light challenge to understand their exploitation of variable light environments. In the smaller T. pseudonana, photosystem II (PSII) photoinactivation outran the clearance of PSII protein subunits, particularly in cells grown at sub- or supraoptimal temperatures. In turn the absorption cross section serving PSII photochemistry was down-regulated in T. pseudonana through induction of a sustained phase of nonphotochemical quenching that relaxed only slowly over 30 min of subsequent low-light incubation. In contrast, in the larger diatom C. radiatus, PSII subunit turnover was sufficient to counteract a lower intrinsic susceptibility to photoinactivation, and C. radiatus thus did not need to induce sustained nonphotochemical quenching under the high-light treatment. T. pseudonana thus incurs an opportunity cost of sustained photosynthetic down-regulation after the end of an upward light shift, whereas the larger C. radiatus can maintain a balanced PSII repair cycle under comparable conditions.
authors: Biology, Mount Allison University, Sackville, New Brunswick, Canada E4L 1G7.
authors: Hongyan
authors: H
authors: Wu
authors: Suzanne
authors: S
authors: Roy
authors: Meriem
authors: M
authors: Alami
authors: Beverley R
authors: BR
authors: Green
authors: Douglas A
authors: DA
authors: Campbell
mesh_terms: D000042:Absorption; D046508:Culture Techniques / Q000379:methods; D017377:Diatoms / Q000737:chemistry / Q000502:physiology / Q000528:radiation effects*; D008027:Light; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D021122:Protein Subunits / Q000737:chemistry; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors; D024341:Xanthophylls / Q000737:chemistry
chemical_list: D045332:Photosystem II Protein Complex; D021122:Protein Subunits; D024341:Xanthophylls; C422369:photosystem II, psbA subunit; C033808:diadinoxanthin; C103105:diatoxanthin