title: High temperature specifically affects the photoprotective responses of chlorophyll b-deficient wheat mutant lines.
abstract: The effects of high temperature on CO2assimilation rate, processes associated with photosynthetic electron and proton transport, as well as photoprotective responses, were studied in chlorophyll b-deficient mutant lines (ANK-32A and ANK-32B) and wild type (WT) of wheat (Triticum aestivum L.). Despite the low chlorophyll content and chlorophyll a-to-b ratio, the non-stressed mutant plants had the similar level of CO2assimilation and photosynthetic responses as WT. However, in ANK mutant plants exposed to prolonged high temperature episode (42 °C for ~10 h), we observed lower CO2assimilation compared to WT, especially when a high CO2supply was provided. In all heat-exposed plants, we found approximately the same level of PSII photoinhibition, but the decrease in content of photooxidizable PSI was higher in ANK mutant plants compared to WT. The PSI damage can be well explained by the level of overreduction of PSI acceptor side observed in plants exposed to high temperature, which was, in turn, the result of the insufficient transthylakoid proton gradient associated with low non-photochemical quenching and lack of ability to downregulate the linear electron transport to keep the reduction state of PSI acceptor side low enough. Compared to WT, the ANK mutant lines had lower capacity to drive the cyclic electron transport around PSI in moderate and high light; it confirms the protective role of cyclic electron transport for the protection of PSI against photoinhibition. Our results, however, also suggest that the inactivation of PSI in heat stress conditions can be the protective mechanism against photooxidative damage of chloroplast and cell structures.
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic. marian.brestic@uniag.sk.
authors.forename: Marian
authors.initials: M
authors.lastname: Brestic
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Zivcak
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.
authors.forename: Kristyna
authors.initials: K
authors.lastname: Kunderlikova
authors.affiliation: Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow, Russia, 127276.|Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, Russia, 142290.|Department of Plant Physiology, Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow, Russia, 119991.
authors.forename: Suleyman I
authors.initials: SI
authors.lastname: Allakhverdiev
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000172:deficiency / Q000378:metabolism*; D006358:Hot Temperature; D009154:Mutation; D010084:Oxidation-Reduction; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D014908:Triticum / Q000378:metabolism*
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; C037184:chlorophyll b
keywords: Chlorina mutants; Heat stress; Non-photochemical quenching; PSI photoinhibition; Photosynthetic electron transport; Wheat