Sorting Nexins(SNXs)Regulate ABA Mediated Stomatal Movements And Drought Stress Responses In Arabidopsis

Drought is one of the most severe environmental stress factors and has caused a 13.7%loss on average in the worldwide cereal production over recent decades.Therefore,it is necessary to develop improved crop varieties with enhanced drought tolerance.A comprehensive understanding of the molecular mechanisms underlying drought responses is required for classical breeding or genetic modification of crop species for enhanced drought tolerance.To date,hundreds of genes have been identified that control key processes in the plant responses to drought stress,such as stress signal perception,signal transduction and amplification,and adaptation.Sorting nexins(SNXs)are conserved eukaryotic proteins that associate with three types of vacuolar protein sorting(VPS)proteins to form the retromer complex and function in vesicular trafficking and contain a characteristic phoxhomology(PX)domain.There are many reports about involvement of SNXs in vesicular transport.For exemple,AtSNX2b,identified as the trans-Golgi network,prevacuolar compartment and endosomes,is involved in vesicular trafficking from endosomes to the vacuole.However,the role of AtSNXs in drought stress response remains to be elucidated.In this study,T-DNA insertion mutants snx2a,snx2b,and snx2a snx2b in Arabidopsis thaliana were characterized to dissect the role of AtSNXs in plant drought stress and explore the primary molecular mechanism.Based on our findings,we showed that the mutants snx2a,snx2b and snx2a snx2b were more tolerant to drought stress than the wild type in terms of whole-plant drought assay and the rate of water loss from detached leaves.The stomatal movement experiment showed that the mutants were more sensitive to ABA inhibited stomatal opening and ABA promoted stomatal closure compared to the wild type,and the double mutant was more sensitive than the single mutants.In addition,the guard cells of mutants were hypersensitive to ABA inhibited inward K+currents and ABA-activated slow anion currents than those of wild type.The DAB and NBT staining experiments showed that the mutants had much higher ROS levels than the wild type.In summary,SNXs are involved in the ABA regulation of stomatal movements,ion channel activities and thus regulate drought stress in plant.Further mechanism exploration is still ongoing.