The Molecular Investigation Of Plant Sulfated Tyrosine Peptide PSY1 In Plant Drought Stress Response

Drought is one of the most serious abiotic stresses in restrict of plant growth and development,as well as crop yield.To screen and investigate the plant drought responsive genes,and to find out their regulatory mechanisms is an important way to improve plant drought tolerance and further development of water-use-efficiency agriculture.Stomata are the micorpores for plants to communicate outside.Plants exchange gas and lose water through stomata,and some pathogens invade plants through stomata.As a stress phytohormone,ABA can induce stomatal closure.The N-terminus of Pseudomonas syringae DC3000 has 22 conserved amino acid sequences(flg22)which recognized by plants,and allowing plants to close the stomata.Studies have showed that ABA and pathogen-induced stomatal closure have many common functional components,such as ROS and NO,and some functional genes in the ABA signaling pathway also play important roles in stomatal immunity,such as ABI1,ABI2 and OST1.However,it remains unknown whether the functional genes that participate in stomatal immunity also can play a role in drought,and whether the two signal pathways have the same node in regulating stomatal movement.Recently,more and more studies have indicated that plant small peptides,as signal molecules,play an important role in regulating plant growth and coping with biotic and abiotic stresses.Among the candidate plant peptides which were up-regulated by flg22,the tyrosine sulfate peptide PSY1 was screened.Previous studies have shown that PSY1 can participate in plant growth and immune regulation through its receptor PSY1R.It has been reported that PSY1 can promote roots and hypocotyls elongation in Arabidopsis.Besides,in immunity,it can negatively regulate the resistance to PstDC3000.At present,there are no research about PSY1 on drought stress.In this paper,Arabidopsis thaliana was used to study the effect of PSY1 on plant drought stress response.Using the CRISPR/Cas9 gene editing technique,a valid functional null mutant of PSY1 was obtained;The results showed that in the ABA inhibited stomatal opening and ABA promoted stomatal closure,the mutant psyl was more sensitive to ABA than wild-type Col-0 in the both processes,and thus to decrease the water loss to enhance its drought-resistant ability.On the contrary,the PSY1 overexpression plants PSY1-OE-1 and PSY1-OE-2 had the opposite phenotypes to the loss-of-function mutants.The results indicated that PSY1 was involved in the ABA regulation of stomatal movements and plant drought response.As the receptor of PSY1,PSY1R may be involved in drought stress downstream of PSY1.T-DNA insertion to obtain effective mutan psy1r.psy1r showed ABA hyposensitivity in stomatal movements,and the psy1r lost water faster and with much lower survival rate in response to drought stress than wild type plants.While the overexpression plants PSY1R-OE-1 and PSY1R-OE-2 were with higer survival rate than wild type plant.DAB and NBT staining experiments showed that psy1r accumulated less ROS under ABA treatment.The results indicated that PSY1R was also involved in the regulation of stomatal movement and the drought response.