Transcriptome and metabonomics revealed Eucommia ulmoides UDP-glucose pyrophosphorylase gene UGP1 improved carbohydrate accumulation and flavonoid metabolism in transgenic tobaccos

UDP-glucose pyrophosphorylase is ubiquitously present in animals, plants and bacteria and plays essential role in biosynthesis of UDP-glucose which is a fundamentally important molecule in biology. In this paper, we cloned an E. ulmoides UGP1 gene and alignment of the EuUGP1 protein showed it belonged to A-type UGPase (UGPase-A) with characteristics of cytoplasm-localization. Further study showed the EuUGP1 introduction improved UGPase activity and UDP-Glc content in transgenic tobaccos, which subsequently acted as the donor for synthesis of glucose, sucrose, and cellulose, etc. Actually, the EuUGP1-overexpression increased the contents of glucose, cellulose, sucrose and soluble sugar in transgenic tobaccos. Transcriptome data showed that the differentially expressed genes (DEGs) were mainly enriched in metabolic pathway and secondary metabolic pathway, especially the genes related to glycosyltransferase activity (e.g. UGT) being significantly up-regulated. Further, metabolomic data showed that the differentially accumulated metabolites (DAMs) were also mainly enriched in metabolic pathway, secondary metabolic pathway and flavonoid metabolic pathway, and the content of secondary metabolites in transgenic tobaccos was significantly higher than that in wild-type plants. Among these metabolites, the flavonoids and their derivatives including glycosides metabolites accounted for 34% compared with other secondary metabolites, which suggesting EuUGP1 could significantly regulate the UDP-Glc accumulation and the latter provided free glucoside for flavonoid glycosides synthesis. These findings provide a theoretical basis for further study of the function of E. ulmoides EuUGP1 gene.