(408g) Transcriptomics- and Metabolomics-Driven Discovery of a Novel Indolic Secondary Metabolite Pathway in Arabidopsis Thaliana

Rajniak, J., Stanford University
Sattely, E., Stanford University

Plant secondary metabolism is an exceptionally rich source of both small molecules of therapeutic importance and enzyme catalysts with unique functions. However, owing largely to the complexities of their genomic and cellular organization, plants remain underutilized as a source of novel chemistries. Here, we describe the transcriptomics- and metabolomics-driven discovery of a novel secondary metabolite pathway in the model plant Arabidopsis thaliana. Starting with a single target gene in the cytochrome P450 family, we have systematically uncovered the biosynthesis of the novel metabolite indole-3-carbonyl nitrile (ICN), containing a unique alpha-keto nitrile moiety not previously seen in any plant or microbial species, from tryptophan. Conjugation of ICN with cysteine-containing peptides in vivo represents a new biosynthetic route towards thiazole and thiazoline ring-containing derivatives, similar to those produced by a number of bacterial nonribosomal peptide synthetases. Correlation analyses of publicly available transcriptomics data followed by metabolomic analysis of relevant homozygous knockout lines and in vitro biochemical assays enabled us to directly demonstrate the function of two new cytochrome P450 enzymes and an FADH-containing reductase, and thereby reconstitute essentially the entire ICN pathway. Our approach shows the power of an integrated “omics” strategy for the discovery of potentially useful biocatalysts and novel small molecular scaffolds.