Genetic Improvement of Seed Storage Proteins Using Three Variant Alleles of 7S Globulin Subunits in Soybean (Glycine max L.)

Abstract

Genetrcally fixed "7S-low lines" were developed from a cross Keburi × F1 (Oodate No. 1 × Mo-shi-dou Gong 503) in soybean. Seven S-low lines are characterized by the lack of the α'-subunit of 7S globulin and a marked decrease of both the α- and β-subunits of 7S globulin due to the simultaneous incorporation of α'-null, α-low and β-low alleles. The 7S-low lines and ordinary varieties were examined for their respective contents of 7 S and 11S globulins, total protein contents, development of protein bodies and amino acid composition in the mature seeds. The contents of 7S globulin in the 7S-low lines were only half of those in the ordlnary varieties, whereas the contents of 11S globulin in the lines were about 14% higher than those in the ordinary varieties. The marked modifications in the protein compositlon of the seeds did not adversely affect the total protein contents as well as de-velopment and morphology of the protein bodies. A high negative correlation was found be-tween the 7S and 11S globulin contents (r= -0.84, P{r=0}0.001), and the calculated absolute value of the slope of the regression line was slightly larger than 1.0 (a=-1.5). These results suggest that 11S globulin may compensate for the decrease in 7S globulin to maintain the production of total seed protein in the 7S-low lines. The mean value of the sulfur-containing amino acid contents in the seeds of four representative 7S-low lines was about 20% higher than that of four ordinary varieties.