Metabolome and transcriptome association analysis revealed key genes and metabolic pathways involved in cadmium response in Gynostemma pentaphyllum

Gynostemma pentaphyllum an important medicinal herb, has a high Cd absorption ability, and it is excessive Cd contamination in the production of medicine and tea. Hence, it is crucial to investigate the response mechanism of G. pentaphyllum under Cd stress and further develop varieties with low Cd accumulation and high tolerance. In this study, physiological response analysis, transcriptome and metabolome were performed on G. pentaphyllum seedlings exposed to Cd stress. The results showed that G. pentaphyllum seedlings could significantly enhance antioxidant enzymes activities (POD, CAT and APX), proline and polysaccharide content to subject to Cd stress. Transcriptome analysis identified 4921 differentially expressed genes responding to Cd stress, mainly involving secondary metabolites, carbohydrate metabolism, amino acid metabolism, lipid metabolism, and signal transduction pathway among which some XTH, EXP and GST genes were key genes to respond to Cd stress. Metabolome analysis identified 126 differentially expressed metabolites in six pathways, including citric acid, flavonoid (diosmetin-7-O-rutinoside, diosmetin-7-O-galactoside and 6-C-methyl kaempferol-3-glucoside) and amino acids (L-isoleucine and L-arginine) metabolites, which were accumulation under Cd stress. Multi-omics integrative analysis unraveled that the phenylpropanoid biosynthesis, starch, and sucrose metabolism, alpha-linolenic acid metabolism, and ABC transporter pathway in response to Cd stress in G. pentaphyllum are significantly enriched at the gene and metabolic levels among which MYB, MYB_related, ERF, GRAS, bZIP, WRKY and bHLH may regulate the changes of these key pathway to impact these metabolites accumulation, contribute to G. pentaphyllum resistance to Cd stress. In conclusion, the genetic regulatory network sheds light on Cd tolerance mechanisms in G. pentaphyllum.