SlMDAR Gene Response To Drought Stress In Tomato

Drought stress,which induces the accumulation of reactive oxygen species?ROS?,and affects the plant growth and development,is the most important abiotic stress factors restricting agricultural production.The chloroplast is one of the major sites for production of ROS in plant.The fast dissipation of chloroplast ROS is essential for protecting photosynthetic mechanism,and maintain plant photosynthetic ability.Ascorbate?AsA?is a key component for detoxifing ROS in chloroplast.Chloroplastic monodehyedroascorbate reductase?MDAR?is a pivotal enzyme in AsA regeneration.It reduces DHA to AsA,maintains the chloroplast AsA pool.In this study,the wild type?WT?and SlMDAR antisense transgenic tomato?Solanum lycopersicum?plants were used as test materials to analysis the the proportion of AsA in the AsA-Glu cycle,the relationship between the MDAR activity and and the chlorophyll fluorescence,photosynthesis,ROS accumulation,lipid peroxidation before and after drought stress,and the role of SlMDAR in response to plant drought stress.The main results were as follows:?1?The transgenic plants had lower mRNA and protein content than the WT.In addition,qRT-PCR showed that the expression of SlMDAR was obviously induced by PEG.?2?The MDAR enzyme activity,AsA,DHA and AsA/DHA were investigated before and after drought stress.The results showed that the transgenic plants showed lower MDAR activity and As A level than the WT.?3?Relative to the WT,the transgenic plants showed lower relative water content,higher MDA content and relative conductivity,and more serious membrane damage under drought stress,suggesting the inhibition of SlMDAR gene expression decreased the resistant of transgenic plants to drought stress.?4?The H₂O₂ and O₂– content was higher in the transgenic plants than in the WT,while little difference was found in the activities of APX and SOD,suggesting that the lower ROS scavenging ability in the transgenic plants may be associated with the lower AsA content.?5?After drought stress,the transgenic plants showed lower photosynthetic ability,higher F0,more serious PS? photoinhibition and higher D1 degradation rate.The above results suggest that inhibition of the expression of SlMDAR reduced the activity of MDAR enzyme and the regeneration ability of AsA,thus inhibited the elimination of ROS,increasing the oxidative damage to the photosynthetic system,and in the end reduced the resistance of the transgenic tomato to drought.