EXPRESSION OF A SOYBEAN (GLYCINE-MAX [L] MERR) SEED STORAGE PROTEIN GENE IN TRANSGENIC ARABIDOPSIS-THALIANA AND ITS RESPONSE TO NUTRITIONAL STRESS AND TO ABSCISIC-ACID MUTATIONS

Among the three subunits of beta-conglycinin, the 7S seed storage protein of soybean (Glycine max [L.] Merr.), expression of the beta subunit gene is unique. Accumulation of the beta subunit is enhanced in sulfate-deficient soybean plants, and its mRNA levels increase when abscisic acid (ABA) is added to the in vitro cotyledon culture medium. Transgenic Arabidopsis thaliana lines carrying a gene encoding the beta subunit was constructed and grown under sulfate deficiency. Accumulation of both beta subunit mRNA and protein were enhanced in developing A. thaliana seeds. Accumulation of one of the A. thaliana seed storage protein mRNAs was also enhanced by sulfate deficiency, although the response was weaker than that observed for the soybean beta subunit mRNA. When the aba1-1 or abi3-1 mutations were crossed into the transgenic A. thaliana line, accumulation of the beta subunit was significantly reduced, whereas accumulation of the A. thaliana seed storage protein was not greatly affected. These results indicate that soybean and A. thaliana share a common mechanism for response to sulfate deficiency and to ABA, although the sensitivity is different between the species. The transgenic A. thaliana carrying the beta subunit gene of beta-conglycinin will be a goad system to analyze these responses.