Implications of alternative electron sinks in increased resistance of PSII and PSI photochemistry to high light stress in cold-acclimated Arabidopsis thaliana

摘要: Exposure of control (non-hardened) Arabidopsis leaves to high light stress at 5 °C resulted in a decrease both photosystem II (PSII) (45 %) and Photosystem I (PSI) (35 photochemical efficiencies compared non-treated plants. In contrast, cold-acclimated (CA) exhibited only 35 22 % PSII PSI photochemistry, respectively, under the same conditions. This was accompanied by an accelerated rate P700+ re-reduction, indicating up-regulation PSI-dependent cyclic electron transport (CET). Interestingly, expression NDH-H gene relative abundance Ndh-H polypeptide, representing NDH-complex, decreased as result exposure low temperatures. indicates that NDH-dependent CET pathway cannot be involved overall stimulation CA plants is due ferredoxin–plastoquinone reductase, antimycin A-sensitive pathway. The lower NDH complex also implies activity chlororespiratory plants, although level other well-characterized component chlororespiration, plastid terminal oxidase (PTOX), up-regulated suggests increased PTOX-mediated alternative flow oxygen exposed Indeed, estimated proportion O2-dependent linear not utilized carbon assimilation directed photorespiration twofold higher Arabidopsis. possible involvement pathways inducing greater resistance discussed.