Genomic Basis of Specificity in Glucosinolate Hydrolysis

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Plants produce a vast catalog of secondary metabolites, partly generated by diverse structural modifications of common backbone structures. Glucosinolates, low-molecular-weight, sulfur rich thioglucosides, are a prime example of how a single molecular backbone can be modified to produce an amazing array of secondary metabolites. A single species, Arabidopsis thaliana, can derive 30 different glucosinolates from the methionine glucosinolate backbone that can be amplified to over 100 different compounds during glucosinolate hydrolysis. The biological activity of a glucosinolate is fully realized after degradation by the protein, myrosinase. This produces a series of different compounds such as isothiocyanates, nitriles, and epithionitriles that differentially impact human health. In Arabidopsis, a relative of many brassica vegetables, numerous genetic loci determine the hydrolytic path of glucosinolates. One locus, ESM1, previously defined only in genetic terms, will be cloned and characterized at the molecular level. Further, the biochemical impact of ESM1 on glucosinolate hydrolysis will be investigated. Glucosinolate structural modifications serve to control diverse biological activities that help the plant defend itself from insects, nematodes, fungi as well as containing the potential to greatly benefit human nutrition when modified in common Brassica crops. A key point in controlling glucosinolate biological activity is at the hydrolysis step. This step controls the production of compounds with dramatic differences in biological activity. For example, a given glucosinolate's isothiocyanate exhibits stronger cancer prevention activities and anti-insect/fungal activities than do the corresponding nitriles. Characterizing the Arabidopsis glucosinolate hydrolytic system could impact fields ranging from ecology to evolution to human nutrition. Additionally, the ESM1 locus may be useful in producing crops with altered insect and pathogen resistance as well as altered nutritional value for human consumption. Further, involving undergraduates and postdoctoral researchers in this project will expose them to a broad range of techniques and help to train them for their own future research.