Expression of Soybean Seed Storage Protein Genes in Transgenic Plants and Their Response to Sulfur Nutritional Conditions

Abstract

Summary β -Conglycinin, the 7S seed storage protein of soybean ( Glycine max [L.] Merr.), is comprised mainly of three subunits, designated α ' , ex and β . Among these subunits, expression of the β subunit is unique because its accumulation is enhanced under sulfate deficiency in vivo and repressed by exogenously applied L-methionine in cotyledon cultures of soybean. Transgenic Arabidopsis thaliana (L.) Heynh. strains carrying either intact gene encoding the β subunit, or β -glucuronidase fusion were constructed and the effects of sulfur nutritional conditions were analyzed. Expression of the transgene was enhanced under sulfate deficiency and repressed when the siliques of transgenic A. thaliana plants were cultured in the presence of L-methionine. The results indicate that response to sulfur nutritional conditions are conserved in transgenic A. thaliana . By using an A. thaliana mutant, designated mto1-1 , that overaccumulates free methionine, activity of the β subunit gene promoter was shown to be repressed in the seeds. These transgenic and mutant A. thaliana plants will be useful in analyzing the plants' response to nutritional conditions.