Functional Characterization of Sesquiterpene Synthase in Mongolian Medicine Syringa Oblata During Heartwood Formation

Abstract

Lilac (Syringa oblata) is a famous horticultural plant, and its aromatic heartwood is widely used in Traditional Mongolian Medicine for the treatment of angina. However, limited research on the dynamic changes and aromatic substances formation mechanisms during heartwood formation hampers the analysis and utilization of its medicinal components. In this study, through volatile metabolome analysis, it was revealed that sesquiterpenes are the main metabolites responsible for the aroma formation in heartwood, with cadinane and eremophilane types account for the largest proportion. SoSTPS1-5, showing significantly increased expression during heartwood formation, was chosen for further study. Molecular docking simulations predicted the multiplicity of amino acid binding sites and verified its ability to catalyze the formation of eremophilane, copaene, cadinane, germacrane, and elemane-type sesquiterpenes from FPP. Co-expression and promoter analysis suggested a potential transcriptional regulatory network primarily involving WRKY factors. Furthermore, it was confirmed that abiotic and biotic stress inducers such as Ag+, Fo, especially MeJA can activate the expression of SoSTPS1-5 and promote sesquiterpene accumulation. Taken together, this study reveals the basis of medicinal substances and the potential mechanism of sesquiterpene accumulation in lilac heartwood, laying the foundation for future studies on the biosynthesis and utilization of its medicinal components.

Keywords: Syringa oblata, Metabolome and transcriptome, Sesquiterpene biosynthesis, Environmental stress, Transcriptional regulation