Abstract
Cystathionine γ-synthase (CGS) catalyzes the key step of methionine (Met) biosynthesis. It has been revealed that the stability of CGS mRNA is feedback-regulated by S-adenosylmethionine, a direct metabolite of Met, and that the CGS exon 1 region is necessary and sufficient for this regulation.
To identify the factors that are involved in the regulation, transgenic plants carrying a CGS exon 1:GFP chimeric gene under the control of CaMV 35S promoter were mutagenized. Four mutant candidates were isolated that showed elevated levels of GFP fluorescence. Endogenous CGS mRNA levels were also increased in two of the candidates (#53 and #57). #57 showed less response to Met treatment in transfection experiments. Together with the fact that the stability of CGS mRNA was increased in #57 suggests that #57 carries a genetic lesion in the CGS regulation.
