Exogenous Trehalose Reduces The Generation Of Reactive Oxygen Species Under Heat Stress

Wheat is the second grain crop in total production in the world, whose caryopsis is one of people’s staple food. Its yield directly affects people’s living standards and the speed of the national economy. However, due to the global climate change, wheat often encounters high temperature stress, which can result in damage to the photosynthetic mechanism, reducing leaf photosynthesis, blocking organic matter accumulation and eventually leading to a substantial decline in production. Many studies have shown that the non-reducing disaccharide, trehalose, can improve the biological tolerance under stress conditions.In this paper, we investigated the effects of exogenous trehalose on antioxidant metabolism, cell membrane stability, photosynthetic rate and the D1 protein of wheat seedlings under high temperature stress, we expect to provide a theoretical basis for the resilience field production operations by exploring the protective metabolism of trehalose for the photosynthetic apparatus.The main results are as follows:1 Compared with the content of the superoxide anion (O2·-) and hydrogen peroxide (H2O2) of the wheat seedlings under normal temperature, the content of O2·- and H2O2 in the wheat seedlings under heat stress increased. Exogenous trehalose reduced the generation of H2O2 under heat stress. For malondialdehyde (MDA), the MDA content in trehalose pretreated wheat seedlings was lower than that in the control in the recovery phase. So trehalose maintained the ability of scavenging reactive oxygen species of wheat seedling under heat stress. At the same time, it reduced the accumulation of free radicals under heat stress, alleviated the destruction for the biofilm system and decreased the membrane lipid peroxidation. It showed that trehalose played a protective role for cell membrane of wheat seedling under heat stress.2 Compared to the wheat seedlings with trehalose pre-treatment at normal temperature, the SOD activity was improved under heat stress. The activities of CAT and APX of wheat seedlings with trehalose pre-treatment significantly increased under heat stress, and they effectively improved the ability of wheat seedlings to remove reactive oxygen species under stress conditions. During the recovery period, exogenous trehalose pretreatment increased the POD and APX activity. The relative expressions of manganese-superoxide dismutase (Mn-SOD), copper-zinc superoxide dismutase (Cu-SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) of wheat seedlings were improved by exogenous trehalose under heat stress and recovery period,. In particular, the POD gene expression significantly increased and was 10.2 times compared to that in the control wheat seedlings in the recovery period.3 In addition, trehalose pretreatment increased the content of ASA and GSH in the wheat seedlings under heat stress. In the recovery pried, ASA content of wheat seedlings with trehalose pretreatment is higher than the control in all treatments; the GSH content is higher than control at 12h the recovery pried.The pretreatment of trehalose before heat stress effectively reduced the injury to the Dl protein. After the stress thereby wheat maintained a good photosynthetic rate. After recovery of 24h from the heat stress the photosynthetic rate of wheat seedling with trehalose pretreatment reached the maximum, and increased 23.3% compared with that in the control of wheat seedling. It could be summed up that exogenous trehalose increased the potential and efficiency of photosynthesis of wheat seedling under heat stress.In short, the results in this study showed that:On one hand, exogenous trehalose could increase SOD, APX activity and ASA, GSH content of wheat seedling leaves to strengthen the ability of removing ROS under heat stress, while reducing the MDA content to enhance lipid membrane stability. The damage to the D1 protein reduced, photosynthetic rate would be maintained on a high level. On the other hand, exogenous trehalose could directly protect D1 protein under stress to maintain the function of photosynthetic apparatus. Finally, exogenously-supplied trehalose realized the protection for photosynthetic apparatus and enhanced the accumulation of photosynthetic products, so as to provide a guarantee for weakening the decline in production of wheat under stress conditions.