UPLC-MS/MS Profile Combined With RNA-Seq Reveals the Amino Acid Metabolism in Leaves Under Drought Stress.

leaves have a unique taste and incomparable nutritional value and hence are popular as a food item and traditional medicine in China. However, the studies on the metabolites in leaves are quite limited, especially for amino acids. Therefore, this study explored the amino acid component in leaves and also the accumulation mechanism under drought stress in two cultivars using the widely targeted metabolome combined with transcriptome analysis. A total of 56 amino acids and their derivatives were identified in leaves, including eight essential amino acids. The total amino acid content with most individual amino acids increased under progressive drought stress. More differentially accumulated amino acids (DAAs) and differentially expressed genes (DEGs) were found in FJ ( cv. 'Fengjiao') than in HJ ( cv. 'Hanjiao'). The orthogonal projections to latent structures discriminant analysis identified nine and seven indicator DAAs in FJ and HJ leaves, respectively. The weighted gene co-expression network analysis (WGCNA) showed that the green module was significantly correlated with most indicator DAAs and revealed the important role of , and 15 transcription factor genes in regulating the amino acid synthesis. Furthermore, the correlation analysis and redundancy analysis (RDA) identified four candidate synthesis genes (, , , and ) in amino acid biosynthesis pathway. This study provided useful information for the development of leaves in food and nutrition industry and also laid the foundations for future molecular breeding.