Abstract
Cystathionine γ-synthase (CGS) is a key enzyme in methionine biosynthesis. CGS is encoded by a nuclear gene and is translocated to chloroplasts. We have reported that the exon 1 coding region of CGS acted to destabilize its own mRNA in response to methionine application. A region within the exon 1 has highly conserved amino acid sequence (the conserved region) and a short stretch of amino acid sequence termed MTO1 region is necessary for this regulation. To identify the region necessary for chloroplast translocation and its relationship to the MTO1 region, various deletion mutants of CGS exon 1 fused to GFP were delivered to Arabidopsis leaves and the localization of GFP was analyzed. The results indicated that the conserved region and its adjacent regions were involved in the translocation. Translocation to chloroplast and down-regulatation of mRNA stability were independent of each other.
