Exogenously-Supplied Trehalose Provides Better Protection for D1 Protein in Winter Wheat under Heat Stress

Abstract

Photosystem II (PSII) is sensitive to heat stress which can overproduce reactive oxygen species (ROS). To investigate the underlying mechanism of exogenously-supplied trehalose to improve photosynthesis and heat tolerance, in this study, we initially determined the antioxidants to get rid of ROS and examined the effects of trehalose pretreatment on D1 protein. Our results show that heat (40°C) stress decreased PSII activity and D1 protein content. However, trehalose pretreatment enhanced PSII activity and the content of D1 protein during heat stress. In the presence of streptomycin, an inhibitor of D1 protein synthesis, the maximal photochemical efficiency of PSII (Fv/Fm) in trehalose pretreated seedlings was enhanced. Hydrogen peroxide content and malondialdehyde content in trehalose pretreated seedlings were less than those in control plants under heat conditions. Consistently, the ratio of reduced ascorbate to dehydroascorbic acid, the activities of catalase (CAT) and ascorbate peroxidase (APX) and the gene expressions of antioxidant enzymes including superoxide dismutase, CAT, peroxidase and APX were increased in trehalose pretreated plants compared to control seedlings. These results suggest that exogenously applied trehalose may play a key role in the recovery of decreased synthesis of D1 protein and protect it from heat-induced photoinhibition in wheat (Triticum aestivum L.) by decreasing the production of ROS and reducing membrane lipid peroxidation via the change of antioxidants including APX, CAT and reduced ascorbate and by increasing gene transcript level of related antioxidant enzymes during heat stress.