Abstract
We showed that vernalization-induced bolting requires reduced glutathione (GSH) and then the γ-glutamylcysteine synthetase (γ-ECS) activity regulates GSH synthesis in Eustoma grandiflorum, but whether vernalization concomitantly regulates cysteine synthesis remains unclear. Thus we investigated the change in levels of γ-ECS substrate cysteine in the Arabidopsis cad2-1 mutant having an aberration of γ-ECS activity during vernalization. Vernalization increased the cysteine level in the mutant, whereas it reduced the level in the wild-type. This indicates that vernalization activates the cysteine synthesis concomitantly with the GSH-synthesis-rate-limiting γ-ECS. Increased levels of GSH in vernalized mutant were stoichiometrically equivalent to that of cysteine, being coupled with promotion of bolting. Considering suppression of cysteine synthesis and γ-ECS activity in reduced states, it is likely that the oxidative states brought by vernalization trigger the concomitant activation of cysteine and GSH syntheses for promotion of bolting.
