Characterization of Seed Storage Proteins of Several Perennial Glycine Species

Perennial Glycine species, distant relatives of soybean, have been recognized as a potential source of new genetic diversity for soybean improvement. The subgenus Glycine includes around 30 perennial species, which are well-adapted to drought conditions and possess resistance to a number of soybean pathogens. In spite of the potential of the perennial Glycine species for soybean improvement, very little is known about their storage proteins and their relationship with cultivated soybean seed proteins. We have examined the seed protein composition of nine perennial Glycine species by one- and two-dimensional (1-D and 2-D) gel electrophoresis. The relationship between cultivated soybean and perennial soybean seed proteins was examined by immunoblot analyses using antibodies raised against G. max β-conglycinin, glycinin A3 subunit, lipoxygenase, leginsulin, Kunitz trypsin inhibitor, and Bowman-Birk protease inhibitor. Additionally, we have measured the trypsin and chymotrypsin inhibitor activities from cultivated soybean and perennial Glycine species and have found marked differences between them. Our 2-D gel and immunoblot analyses demonstrate significant differences in the protein composition and size heterogeneities of the 7S and 11S seed storage proteins of soybean and perennial Glycine species. Perennial Glycine species accumulated a 45 kDa protein that was not detected in G. max and G. soja. This unique 45 kDa protein was immunologically related to the A3 glycinin subunit of G. max. The results of our studies suggest that even though the seed proteins of wild perennial Glycine species and G. max are immunologically related, their genes have diverged from each other during the course of evolution.