Repression of cystathionine γ-synthase in Arabidopsis thaliana produces partial methionine auxotrophy and developmental abnormalities

Cystathionine γ-synthase (CGS), a key enzyme in methionine biosynthesis, was repressed in transgenic Arabidopsis thaliana by antisense expression of CGS RNA. CGS activity was reduced by 5-9-fold in the antisense plants resulting in severe growth stunting, morphological abnormalities and an inability to flower. Feeding the plants methionine (Met) or Met metabolites reversed the morphological effects of CGS repression. There was little change in the content of free Met and S-methylmethionine despite the need for exogenously applied Met for growth. The overall amino acid content was significantly increased. The CGS antisense transgene is inherited as a single recessive locus.