The Physiological And Molecular Mechanisms Of Sophora Davidii Seedling Under Drought Stress

Sophora davidii has a strong adaptation to drought and is widely distributed in the karst region of Guizhou,China.Studies on the drought resistance of Sophora davidii have focused on seed germination,seedling growth,morphology,physiology,biochemistry and cloning of drought-related genes at the molecular level,while little research has been reported on transcriptomics and metabolomics.Therefore,in this experiment,drought treatments were applied to potted seedlings of S.davidii,and the four treatments of control（CK）,mild drought（LD）,moderate drought（MD）and severe drought（SD）were maintained together for 12 days to measure morphological and physiological and biochemical parameters,and to screen key drought tolerance genes and characteristic metabolites by transcriptomics and metabolomics.The main results were as follows.1.The results of the morphological study on S.davidii showed that:compared to the control,growth rate decreased under mild and moderate drought stress and increased under moderate drought stress,indicating that appropriate drought stress promoted the growth of S.davidii plant height;leaf length,leaf width,leaf area and leaf perimeter decreased under all three drought stress treatments,and significantly decreased under severe drought stress,indicating that S.davidii adapted to drought stress by reducing leaf morphological indicators.2.The results of physiological and biochemical studies on S.davidii showed that the relative leaf water content increased and then decreased with increasing drought stress,and was significantly lower than the rest of the groups under severe drought stress,but still maintained a high water content,indicating that white spurge has a strong water retention capacity;the contents of ascorbate peroxidase（APX）activity,chlorophyll a（Chl a）,chlorophyll b（Chl b）,total chlorophyll（Total Chl）,carotenoid（Car）,soluble sugar（SS）,proline（Pro）,malondialdehyde（MDA）and hydrogen peroxide（H₂O₂）increased significantly with increasing drought stress,while catalase（CAT）,superoxide dismutase（SOD）,peroxidase（POD）activities and soluble protein（SP）content decreased significantly with increasing drought stress.The content of auxin（IAA）,cytokinin（CTK）,salicylic acid（SA）,abscisic acid（ABA）,gibberellin（GA）and brassinosteroid（BR）increased significantly with increasing drought stress,while jasmonic acid（JA）and ethylene（ETH）increased significantly with increasing drought stress,suggesting that S.davidii responds to drought stress by altering hormone levels.3.Transcriptome analysis of S.davidii showed that a total of 2163 differentially expressed genes（DEGs）were detected in the 3 groups LD/CK,MD/CK and SD/CK with 318,734 and 1779 DEGs,respectively.KEGG enrichment analysis identified phytohormone signaling（PYL,PP2C,ABF,JAZ,JAR1,ARR-A,SAUR,AUX1,TIR1,GH3,ETR and ERF）,starch and sucrose metabolism（AMY,E3.2.1.2,INV and E2.4.1.13）,arginine and proline metabolism（ALDH18A1,ALDH and PRODH）,glutathione metabolism（GPX and GST）and carotenoid biosynthesis（NCED）five pathways and their genes are significantly affected by drought stress and may play a key regulatory role in the response of S.davidii to drought stress.4.The results of metabolomic analysis of S.davidii showed that a total of 549differential metabolites（DEMs）were identified,with 100,168 and 281 DEMs screened in the LD/CK,MD/CK and SD/CK groups,respectively,and 57 common DEMs in the three groups.KEGG annotation results identified three key metabolic pathways:carotenoid biosynthesis,glutathione metabolism,and arginine and proline metabolism,in which three key metabolites,abscisic acid,oxidized glutathione and ornithine,were identified,suggesting that these three metabolites play a key role in the response of S.davidii to drought stress.