Molecular analyses of a glucosinolate polymorphism in barbarea vulgaris

The capacity of plants to defend themselves against phytophages heavily depends on the quantity and quality of secondary metabolites. For crucifers the most well-known defense compounds are glucosinolates. In Dutch Barbarea vulgaris populations, we have found different frequencies of two naturally occurring chemotypes: one produces mainly 2- phenylethylglucosinolate (gluconasturtiin) whereas the other produces mainly the hydroxylated form, S-2-OH-2- phenylethylglucosinolate (glucobarbarin). Due to this single 2-hydroxyaltion, the glucosinolates and their hydrolysis products may have a different toxicity. We found that the heritability of this polymorphism is determined by a single gene with a dominant allele for glucobarbarin and a recessive allele for gluconasturtiin. Based on a similar 2- hydroxylation enzyme found in A. thaliana, we hypothesize that the hydroxylation of gluconasturtiin is performed by a 2-oxoacid dependent dioxygenase (2ODD). We use degenerate primers based on that 2ODD in A. thaliana, and homologues of that gene in other plants, to identify the enzyme responsible for differences in glucosinolates in B. vulgaris.