A wheat stay-green mutant, tasg1, was previously generated via mutation breeding of HS2, a common wheat cultivar (Triticum aestivum L.). Compared with wild-type (WT) plants, tasg1 exhibited delayed senescence indicated by the slower degradation of chlorophyll. In this study, the stability of proteins in thylakoid membranes was evaluated in tasg1 under drought stress compared with WT plants in the field as well as in seedlings in the laboratory. Drought stress was imposed by controlling irrigation and sheltering the plants from rain in the field, and by polyethylene glycol (PEG)-6000 in the laboratory. The results indicated that tasg1 plants could maintain higher Hill activity, actual efficiency (ΦPSII), maximal photochemical efficiency of PSII (Fv/Fm), and Ca2+-ATPase and Mg2+-ATPase activities than the WT plants under drought stress. Furthermore, the abundance of some polypeptides in thylakoid membranes of tasg1 was greater than that in the WT under drought stress. Expression levels of TaLhcb4 and TaLhcb6 were higher in tasg1 compared with the WT. Under drought stress, the accumulation of superoxide radical (O2·–) and hydrogen peroxide (H2O2) was lower in tasg1 compared with the WT not only at the senescence stage but also at the seedling stages. These results suggest greater functional stability of thylakoid membrane proteins in tasg1 compared with the WT, and the higher antioxidant competence of tasg1 may play an important role in the enhanced drought tolerance of tasg1.

We investigated the drought resistance of a wheat (Triticum aestivum L.) stay-green mutant tasg1 and its wild-type (WT) in field experiments conducted for two years. Drought stress was imposed by controlling irrigation and sheltering the plants from rain. Compared with the WT, tasg1 exhibited a distinct delayed senescence under both normal and drought stress conditions, as indicated by slower degradation of chlorophyll and decrease in net photosynthetic rate than in WT. At the same time, tasg1 mutants maintained more integrated chloroplasts and thylakoid ultrastructure than did WT plants under drought stress. Lower malondialdehyde content and higher antioxidative enzyme activities in tasg1, compared to WT, may be involved in the stay-green phenotype and drought resistance of tasg1.Additional key words: antioxidative defense system, chlorophyll degradation, chloroplast and thylakoid ultrastructures, drought stress, photosynthesis.

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Ubiquitin (Ub) is regarded as a stress protein involved in many stress responses. In this paper, sense and antisense transgenic tobacco plants, as well as the wild type and vector control, were used to study the role of Ub in salt tolerance of plants. In sense Ta-Ub2 transgenic tobacco plants, there was higher expression of Ub protein conjugates than in the wild type and vector control, but the reverse trend was observed in antisense Nt-Ub1 transgenic plants. The germination rate of tobacco seed, growth status and photosynthesis of the tobacco plants suggested that over-expressing Ub promoted the growth of transgenic tobacco plants and enhanced their salt tolerance, but the opposite effect was seen in plants with repressed Ub expression. Changes in antioxidant capacity may be one of the mechanisms underlying Ub-regulated salt tolerance. Furthermore, improved tolerance to a combination of stresses was also observed in the sense transgenic tobacco plants. These findings imply that Ub is involved in the tolerance of plants to abiotic stress.

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