Identification, functional characterization and expression profiling of three triterpene synthases from the legume plant Vigna unguiculata

Abstract

Oxidosqualene cyclases (OSCs) are important regulatory enzymes involved in cyclization reactions of 2, 3-oxidosqualene to form triterpenes and sterols. This study presents the identification and characterization of three OSC genes, a β – amyrin synthase (VuβAS), a lupeol synthase (VuLUS) and a cycloartenol synthase (VuCAS) in Vigna unguiculata, an edible leguminous plant with high nutritional and nutraceutical value. Phylogenetic analysis showed that the VuβAS, VuLUS and VuCAS were clustered within the clades of previously characterized β – amyrin synthases, lupeol synthases and cycloartenol synthases. Heterologous expression in Saccharomyces cerevisiae and Gas Chromatography – Mass Spectrometry (GC – MS) analysis in different plant stages confirmed their specific functions. VuβAS showed higher expression in roots from early germinating seedlings to older plants (4-day to 28-day), while VuLUS expression levels were higher in the roots of older plants only (14-day to 28-day). VuCAS expression was increased in all the tissues of 4-day seedlings, with a peak in stem and leaves and a lower accumulation in radicles. These findings revealed the presence and function of OSC genes in V. unguiculata, and future research could lead to the discovery of promising biologically active compounds.