Identification of candidate genes governing key metabolic pathways in fenugreek (Trigonella spp.) through integrated...

Fenugreek (Trigonella spp.) is one of the oldest known medicinal plants, containing a plethora of metabolites which confer multiple health promoting properties to the plant. Two species of fenugreek, colloquially referred to as methi (Trigonella foenum-graecum L.) and Kasuri methi (Trigonella corniculata L.), share a widely similar spectra of metabolites. However, there are not many studies which report on the metabolic differences between the species. In the present study, to identify the molecular basis of metabolic diversity, we performed transcriptome profiling across four tissues (root, stem, leaf and flower) of the two fenugreek species. Through the transcriptome, we identified putative genes encoding important enzymes which widely shape the metabolome of an organism such as the Cytochrome P450 (CYPs), Uridine diphosphate-dependent glycosyltransferases (UGTs) and the Oxidosqualene cyclases (OSCs). A total of 60 CYP, 33 UGT and 3 OSC genes were identified, which is the first report on characterization of members of these gene families in Trigonella. GC-MS (Gas Chromatography-Mass Spectrometry) based leaf metabolite profiling revealed significant inter-specific differences in both the composition and abundance of sugar alcohols. D-pinitol, a cyclic sugar alcohol (cyclitol) with anti-diabetic activity, was identified as a predominant sugar alcohol in both species. Genes encoding D-pinitol biosynthetic enzymes were significantly (adjusted p-value < 0.05) upregulated in Kasuri methi leaves relative to methi, consistent with observed differences in leaf D-pinitol accumulation. Collectively, this study establishes the transcriptomic and metabolic framework underlying interspecific diversity in fenugreek, identifies candidate genes for the biosynthesis of therapeutically relevant metabolites and provides a transcriptomic resource for functional genomic studies in Trigonella.