Abstract
The first step of the sulfate assimilation pathway is catalyzed by ATP sulfurylase (ATPS). Four ATPS genes exist in Arabidopsis thaliana genome. ATPS activity has been detected in chloroplasts and in cytosol in Arabidopsis; however, all of the isoforms appear to encode a transit peptide for chloroplast targeting. Thus, the origin of the cytosolic form of ATPS is still uncertain. In this study, to clarify the physiological role of each ATPS isoform in Arabidopsis, we carried out gene expression analysis of the isoforms and functional analysis of atps mutants. The gene expression was detected by real-time quantitative PCR analysis. ATPS4 showed a specific pattern, in which the expression is low at two-week-old leaf, but is high at six-week-old leaf and silique. We isolated T-DNA inserted mutants of ATPS2 and ATPS3. The accumulation of cysteine and glutathione decreased about 80% in the obtained mutants compared to wild-type plant.
