Abstract
Cysteine synthase (CSase) forms cysteine from sulfide and O-acetylserine. In the genome of Arabidopsis, there are nine CSase-like genes (Bsas). Judging from gene expression levels and Km values, it is seemed that Bsas1;1, 2;1 and 2;2 are major CSase and Bsas3;1 is β-cyanoalanine synthase (CASase), which forms β-cyanoalanine from cysteine and cyanide, rather than CSase. In this study, to elucidate the specific role of each Bsas, T-DNA knockout mutants were isolated and analyzed for their gene expressions, enzyme activities and metabolite profiles. In all mutants, expressions of target Bsas genes were repressed, but expression levels of other Bsas were not significantly changed. In bsas1;1, CSase activity was decreased to 54% of wild-type and cysteine content was decreased. In bsas3;1, CASase activity was decreased to 36% of wild-type. These results suggested that Bsas1;1 and Bsas3;1 play the most important role for cysteine biosynthesis and β-cyanoalanine synthesis, respectively.
