Genomics and Metabolomics: A Strategy for Elucidation of Metabolic Pathways in Medicinal Plants

Abstract

Medicinal plants are storehouse of numerous phytochemicals which are structurally and functionally divergent group of molecules. The biosynthesis of these molecules is channelized through complex network of metabolic pathways, which are evolved in response to various biotic and abiotic stress factors. As the concentration of these metabolites in the field grown plants is abysmally low and do not meet the demand, metabolic pathway analysis, and subsequent engineering for augmented in vitro production of these phytochemicals, is an alternative proposition to sustain the growth of phyto-pharmaceutical industries. Broadly, integration of metabolite profiling with genomic techniques including transcriptome analysis could lead to identify the rate limiting step(s) in the pathway and subsequently the gene(s) of interest. However, there is no single step technology available for the detection of all phytochemicals synthesized by a plant and hence combination of analytical techniques, both qualitative and quantitative, such as GC-MS, LC-MS, CE-MS, FT-IR, NMR, etc., are required. Similarly, as the complexity of phytochemicals increases, there is proportionate increase in the biochemical steps such as, derivatization/cyclization and modification of the molecules, making the whole pathway elucidation more cumbersome and difficult. Interestingly, the application of elicitation techniques along with specific metabolite inhibitors including enzyme inhibitor studies coupled with gene expression analysis is added techniques, in pathway analysis. In plant cell culture studies, elicitors have shown to trigger significant changes in metabolite production and corresponding gene expression, leading to annotation of genes(s) involved in the metabolite biosynthesis. Therefore, an integrated analysis of metabolic pathway including metabolic flux, gene expression, enzyme activity, elicitors, and transcriptome studies will be strategic for sustained in vitro production of phytochemicals, in future.