Genotypic variation in sulphur assimilation and metabolism of onion (Allium cepa L.). II: Characterisation of ATP sulphurylase activity

► Differential activity of enzymes in the sulphur assimilation pathway at the bulbing (high S demanding) stage. ► APR activity highest in S-deprived leaves, ATPS activity highest in S-sufficient leaves. ► ATPS isoform abundance varies according the S-supply. ► ATPS may undergo post-translational modification.