Metabolomic association analysis reveals defense related secondary metabolic reprogramming in callus of Scutellaria baicalensis Georgi induced by endophytic Pseudomonas sp. 2B

Interactions between plants and endophyte can influence the secondary metabolism in host plants. Scutellaria baicalensis Georgi, is widely used as traditional Chinese medicine and cultivated extensively in China. Until now, the influence of endophytes on secondary metabolism of S. baicalensis is still unclear. To address this issue, non-targeted metabolomics tool was performed to explore the global secondary metabolic changes in S. baicalensis with a dual culture of callus and endophytic Pseudomonas sp. 2B. Further, the activity of polyphenol oxidase (PPO) and the expression patterns of key genes in flavonoid biosynthesis pathway were detected. Through the analysis of non-targeted metabolomics, a total of 1814 differential metabolites were found and the identified differential metabolites were mainly belonged to flavonoids, anthraquinones, lignin and phenylethanoids. The target quantitative analysis revealed that the contents of baicalin and wogonoside decreased in callus of S. baicalensis co-cultured with Pseudomonas sp. 2B, but the accumulations of baicalein, wogonin and chrysin were promoted. The activity of PPO was also increased in this process. Furthermore, there was a significant decrease in flavone synthase (sbFNS II-2) and chalcone synthase (sbCHS2) transcripts in dual culture of endophyte-callus. The expression of cinnamic acid–specific coenzyme A ligase (sbCLL7) and the UDP-glucuronate baicalein 7-O-glucuronosyltransferase (sbUBGAT) transcripts were promoted. The results demonstrated that endophytic Pseudomonas sp. 2B could reprogram defense related secondary metabolism in S. baicalensis and had a potential application value in biocontrol for cultivation of S. baicalensis.