Electroporated protoplasts express seed specific gene promoters

The soybean 7S seed storage protein, β-conglycinin, is comprised of three major subunits, α', α, and β. Chimeric genes having β-conglycinin α' and β subunit promoters and the β-glucuronidase gene coding sequence were constructed and electroporated into protoplasts prepared from three cultured cell lines and from tobacco mesophyll cells. The β-conglycinin promoters were active in all protoplasts examined, and their activities were 10-60% of that of the cauliflower mosaic virus 35S promoter. In electroporated protoplasts isolated from tobacco suspension cultures the time course of expression and the pattern of cell cycle dependency of the β-conglycinin promoters were similar to those of the 35S promoter. The responses to exogenously added L-methionine and abscisic acid, which are known to have differential effects on the expression of β-conglycinin promoters in cultured soybean cotyledons, were essentially the same among the promoters used. The results indicate that β-conglycinin promoters are expressed in electroporated protoplasts, but their regulation is relaxed.