Abstract
Cystathionine γ-synthase (CGS) of Arabidopsis catalyzes the key step of methionine biosynthesis. Expression of the CGS gene is negatively feedback-regulated at the step of mRNA stability in response to S-adenosyl-L-methyonine (SAM). The exon 1-coding region of CGS is necessary and sufficient for this regulation. The regulation was reproduced in the in vitro translation system of wheat germ extract. Studies using the wheat germ extract revealed that, prior to the CGS mRNA degradation, translational pausing was induced in response to SAM application. In this study, we developed an in vitro translation system from Arabidopsis callus cultures. A reporter assay analysis using the Arabidopsis cell extract system showed CGS exon 1-mediated downregulation of reporter activity in response to SAM. Also SAM-dependent translational pausing and mRNA degradation were reproduced in this system. Furthermore we optimized conditions to detect the response to SAM.
