Abstract
Serine acetyltransferase (Serat) catalyzes the formation of O-acetylserine (OAS) from L-serine and acetyl-CoA, leading to synthesis of cysteine. In the genome of Arabidopsis, there are five Serat genes (Serat1;1, 2;1, 2;2, 3;1, 3;2). Until now, we have isolated T-DNA knockout mutants in each Serat gene. The results from gene expression analysis and metabolite profiles on these mutants suggested that each Serat gene has distinct role for cysteine biosynthesis. To investigate their roles further, we crossed those mutants to obtain double knockout mutants (serat1;1serat2;1, serat1;1serat2;2, serat2;1serat2;2). Serat1;1, 2;1, 2;2, which are thought to be major isoforms, are localized in cytosol, plastids, mitochondria respectively. In serat2;1serat2;2 mutants, expression levels of Serat3;2 was increased and OAS, Cys and GSH contents were remarkably decreased. Such result was not observed in serat2;1 or serat2;2 single mutants, implying that Serat2;1 and Serat2;2 complemented their function each other. We are currently analyzing the other two mutants.
