Abstract
Cystathionine γ-synthase(CGS) catalyzes the key step of methionine biosynthesis in plants. CGS1<I/> gene encodes CGS in Arabidopsis thaliana. Expression of CGS1<I/> is feedback regulated at the step of mRNA degradation in response to S<I/>-adenosyl-L-methionin. A short amino acid sequence named the MTO1 region that is encoded by the exon 1 of CGS1 itself is important for this regulation as a cis-acting element.
To identify trans-acting factors involved in the CGS1<I/> regulation, we conducted a genetic screen for mutations affecting the regulation, by monitoring expression of two different reporter genes fused in flame to CGS1<I/> exon 1, respectively. This screen was designed to enable us to isolate temperature-sensitive mutants, considering the possibility that general factors involved in translation or mRNA decay have a role in the CGS1<I/> regulation. Four mutants have been isolated from this screen, and analysis of the mutants is under way.
