β-Conglycinin, the 7S seed storage protein of soybean (Glycine max [L.] Merr.), is comprised mainly of three subunits, designated α, α′ and β. Expression of the gene encoding the β subunit is unique because its expression has been shown to be down-regulated by exogenously applied L-methionine in immature soybean cotyledon cultures in vitro. Arabidopsis thaliana strain carrying a mto1-1 mutation overaccumulates soluble methionine. By using this mutant, we analyzed the effects of methionine on expression of the β subunit gene in vivo. Reciprocal crosses were made between the mto1-1 mutant and a transgenic A. thaliana strain, designated SNTβ3, which carries a β-glucuronidase (GUS) reporter gene under the control of the promoter region of the β subunit gene. Analysis of GUS activity in F1 seeds indicated that the GUS activity was dramatically repressed when the mto1-1 mutant plants were used as female parents. We constructed a strain which carries both the transgene and mto1-1 mutation in the homozygous state. Analyses of the GUS activity in seeds of this double homozygous strain indicated that the GUS activity was repressed to 2.5% of control by introduction of the mto1-1 mutation. These results indicate that the β subunit gene promoter activity in seeds is down-regulated by maternal genotype and suggest that soluble methionine, or its mobile metabolite, is translocated from mother plants to repress β subunit gene expression in seeds.
No takes yet. Share an insight, caveat, or question.
Naito et al. (1994) studied this question.