Abstract
Arabidopsis cystathionine γ-synthase (CGS) catalyzes the key step in methionine biosynthesis. Expression of the CGS gene is feedback-regulated at the step of mRNA stability, and S-adenosylmethionine (SAM), the direct metabolite of methionine acts as the effector. We have demonstrated that a short amino acid sequence, termed the MTO1 region, encoded by the exon 1 of CGS itself is important for this regulation, but other factor has not been discovered. In order to identify such a factor, we screened by expression of reporter gene and isolated cms1-1 mutant, in which CGS mRNA stability is increased. Accumulation of SAM was higher in cms1-1 than that in wild type. Map-based cloning and sequence analysis identified a nonsense mutation in the gene encoding a protein which has two regions. One region contains MATH domain which is thought to be involved in multimerization. The other has no characteristic domain.
