Three genes designated AtST5a, AtST5b and AtST5c from Arabidopsis thaliana , were characterized at the biochemical and molecular levels. They were found to code for desulfoglucosinolate sulfotransferases. Amino acid alignment of the three deduced amino acid sequences showed that they share 70-95% amino acid identity and 81-95% similarity. The results of enzymology studies showed that the three enzymes exhibit strict requirement for the thioglucose moiety of the desulfoglucosinolate substrate and for 3 ' -phosphoadenosine 5 ' -phosphosulfate as sulfate donor. The recombinant AtST5b and AtST5c enzymes exhibit broad substrate specificity with preference for 3-methylthiobutyl- and 2-phenylethyl desulfoglucosinolates. In contrast, the recombinant AtST5a enzyme is more specific and accepts only 3-methylthiobutyl desulfoglucosinolate to a significant level.  Promoter sequences of the AtST5a, 5b and 5c genes ( Pro5a, Pro5b and Pro5c ) were cloned into Ý-glucuronidase-containing vectors and transformed into Arabidopsis thaliana