Drew Klein Abstract:
The adept synthesis of antimicrobial small molecules is central to plant innate immunity. In the case of plants that we consume as food, these natural compounds are significant for human nutrition, too. Cruciferous vegetables, such as broccoli, mustards, and turnip, produce a bouquet of sulfur-containing molecules that restrict fungal pathogens and also possess drug-like activities in humans. Knowledge of the enzymes that assemble these natural compounds — termed the biosynthetic pathway — is crucial to understand their biological functions. Furthermore, elucidating a complete biosynthetic pathway would open the door to engineering plant metabolism for applications in sustainable agriculture and human health.
Here I describe recent studies that discover and characterize enzymes involved in the synthesis of plant antibiotics known as phytoalexins. These investigations employ a combination of mass spectrometry-based metabolite profiling, comparative genomics, gene expression analysis, and enzyme biochemistry. Since my last talk at the Carnegie Plant Biology retreat, we had completed an entire pathway of Brassica phytoalexin biosynthesis. A set of ten enzymes is sufficient to engineer this pathway into a foreign plant, and future work will examine the valuable traits conferred by over 30 chemically diverse derivatives that are produced in cruciferous plants. The biochemical and genetic basis of phytoalexin biosynthesis elucidated here provides insights into the evolution and future engineering of the complex chemical communication among plants and their associated microbes.