Abstract
Cystathionine γ-synthase (CGS) catalyzes the key step of methionine biosynthesis in plants. Expression of the AtCGS1 gene, which encodes CGS in Arabidopsis thaliana, is feedback-regulated at the step of mRNA degradation by S-adenosyl-L-methionine (SAM), a metabolite of methionine. SAM induces translation arrest in the middle of AtCGS1 exon 1, which is followed by mRNA degradation. A fourteen amino acid sequence, termed the MTO1 region, encoded within AtCGS1 exon 1 is responsible for this regulation, and is widely conserved in plants.
In order to assess if this CGS regulation mechanism is generally conserved among plants, we isolated cDNA segments that correspond to AtCGS1 exon 1 from various model plants, and analyzed by transfection and wheat germ in vitro translation experiments. These segments were shown to suppress reporter gene activity in response to SAM. This result suggests that post-transcriptional regulation of CGS by SAM is conserved among plant species.
