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

• Published in: Photosynthesis research 2012-09, Vol.113 (1-3), p.191-206
• Main Authors: Ivanov, A. G, Rosso, D, Savitch, L. V, Stachula, P, Rosembert, M, Oquist, G, Hurry, V, Hüner, N. P. A
• Format: Article
• Language: English
• Subjects: Acclimatization - drug effects; Acclimatization - radiation effects; Adaptation; Alternative electron flows; Arabidopsis - drug effects; Arabidopsis - physiology; Arabidopsis - radiation effects; Arabidopsis thaliana; Biochemistry; Biomedical and Life Sciences; Botany; carbon; Carbon Dioxide - metabolism; Cold; Cold acclimation; Cold Temperature; Densitometry; electron transfer; Electron transport; Electron Transport - drug effects; Electron Transport - radiation effects; Electrons; Fluorescence; genes; Glyceraldehyde - pharmacology; Immunoblotting; leaves; Life Sciences; Light; Oxidation-Reduction - drug effects; Oxidation-Reduction - radiation effects; oxygen; Photochemical Processes - radiation effects; Photochemistry; Photons; Photoprotection; photorespiration; Photosynthesis; Photosystem I; Photosystem I Protein Complex - metabolism; Photosystem II; Photosystem II Protein Complex - metabolism; Plant Genetics and Genomics; Plant Leaves - drug effects; Plant Leaves - metabolism; Plant Leaves - radiation effects; Plant Physiology; Plant Sciences; PTOX; Regular Paper; Stress, Physiological - drug effects; Stress, Physiological - radiation effects; Temperature; Time Factors; Xanthophylls - metabolism
• ISSN: 0166-8595; 1573-5079; 1573-5079
• DOI: 10.1007/s11120-012-9769-y

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