Exogenous GbHMGS1 Overexpression Improves the Contents of Three Terpenoids in Transgenic Populus

Abstract

Ginkgo biloba L. has attracted much attention due to its medicinal properties, particularly those of its terpenoid and flavonoid contents. However, the content and utilization efficiency of terpenoids remain low. The enzyme 3-hydroxy-3-methylglutaryl CoA synthase (HMGS) is a major rate-limiting factor, and RNA-seq has revealed that the mRNA expression of this enzyme is differentially expressed during terpenoid biosynthesis. Here, we investigated the function of the GbHMGS1 gene and its overexpression in Populus. We compared the metabolite contents of nontransgenic (CK) Populus with those of transgenic Populus lines through metabolomics analysis. Our results indicate that the GbHMGS1 protein is localized in the cytoplasm. Significant differences in chemical characteristics were found between the transgenic and CK plants, and a total of 31 differentially expressed metabolites were upregulated in the transgenic plants. We also found higher contents of lanosterol (triterpenoid), dehydroabietic acid (diterpenoid), and phytol (diterpenoid) in the transgenic Populus plants than in their CK counterparts. We thus speculate that GbHMGS1 might regulate plant-related product formation and increase metabolite contents. This study revealed the molecular mechanism governing metabolite synthesis and suggested that one triterpenoid and two diterpenoids with significant upregulation can be used as markers for the breeding of plants with specific terpenoid metabolism-related characteristics.