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.
Highlights
Ginkgo biloba L. is an ancient plant, the only extant species of the Ginkgoaceae family, and it is considered a “living fossil” [1]
The biosynthesis pathway of terpenoids mainly consists of three stages: (i) generation of the isopentenyl diphosphate (IPP) and its double-bond dimethylallyl diphosphate (DMAPP C5) precursors; (ii) formation of farnesyl diphosphate (FPP), geranyl diphosphate (GPP), geranylgeranyl diphosphate (GGPP), and other direct precursors; and (iii) generation and modification of terpenes
By scanning and overlapping the total ion chromatograms (TICs) of different samples, we found that the experimental instrument has good stability and data acquisition performance, which indicated that the test results were reliable (Figure S1)
Summary
Ginkgo biloba L. (ginkgo) is an ancient plant, the only extant species of the Ginkgoaceae family, and it is considered a “living fossil” [1]. Several particularities or differences have been described in gymnosperms compared to angiosperms that are relevant in the field and add new layers of complexity into the study of terpenoid biosynthesis. This is the case for the enzyme HDR (responsible for the synthesis of IPP and DMAPP in the last step of the MEP pathway) in Ginko bilboa. To generally improve accumulation of terpenoid end-products, the pool of the universal building blocks IPP and DMAPP plays a key role whereas for increasing specific compounds, specific terpene synthases (and mostly at the branching points of the pathways) are required [12]
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