Biochemical genetics of glucosinolate modification in Arabidopsis and Brassica

Fine mapping of the glucosinolate biosynthesis gene OHP, which regulates th e conversion of 3-methylsulphinylpropyl to 3-hydroxypropyl glucosinolate, i n an Arabidopsis thaliana Columbia x Landsberg erecta RI line population po sitioned the gene within 54 kb of DNA on chromosome IV. Sequence data ident ified a family of genes encoding 2-oxoglutarate-dependent dioxygenases in t his region. A probe based on these genes co-segregated with ALK in Brassica oleracea, a gene regulating the synthesis of alkenyl glucosinolates. The r eactions catalysed by the OHP and ALK enzymes utilise similar substrates an d may have a common mechanism. Thus, these dioxygenases are prime candidate s for controlling the side chain modification of glucosinolates.