转反义SlMDAR番茄植株对干旱胁迫的响应OA

Monodehydroascorbate reductase(MDAR)is a key enzyme for ascorbic acid(AsA)regeneration in tomato chloroplasts.In this study,wild-type(WT)tomatoes and tomato lines transformed with antisense SlMDAR were used as materials.Through molecular identification and analysis of phenotypes and physiology under drought stress,the functional mechanism of SlMDAR in tomato drought resistance was systematically explored.The results showed that SlMDAR had been successfully integrated into the tomato genome,and its transcriptional and translational levels were effectively inhibited by more than 50％.Treatment with 25％polyethylene glycol(PEG)could induce the expression of SlMDAR,indicating that this gene is involved in the response to drought stress.Un-der drought conditions,the antisense lines exhibited more severe wilting and growth inhibition,with their relative water content being only 85％-94％of that of the wild type.Compared with the wild type,the MDAR enzyme activ-ity of the antisense lines decreased by 35.0％-40.6％,and the AsA content decreased by 54.4％-67.4％.These changes led to a 50.0％-62.0％increase in reactive oxygen species(ROS)accumulation and a more than 50％in-crease in the degree of cell membrane damage in the antisense lines.After drought treatment,the photosynthetic ca-pacity of all tested plants generally decreased.However,the rates of change in net photosynthetic rate and the de-gree of Photosystem Ⅱ(PS Ⅱ)photoinhibition of the transgenic plants were both 1.3 times those of the wild type.In conclusion,SlMDAR positively regulates tomato drought tolerance by regulating the AsA regeneration system,maintaining ROS homeostasis,and protecting photosynthetic machinery.