Inheritance and biochemical analysis of four electrophoretic variants of β-conglycinin from soybean.

Three genes which code for variant β-conglycinin subunits were identified. Alleles Cgy 1 (S) and Cgy 2 (S) were codominant with Cgy 1 and Cgy 2 and produced α' and α subunits, respectively, with reduced electrophoretic mobility. Allele Cgy 3 (D) increased the mobility of at least one polypeptide in the β subunit family and exhibited incomplete dominance. Gene loci Cgy 2/Cgy 2 (S) and Cgy 3 (D) /cgy 3 (D) were linked, whereas Cgy 1/Cgy 1 (S) / cgy 1 segregated independently of the others. Techniques developed for purification of normal β-conglycinin subunits were effective in purifying the altered subunits. Deglycosylated variant proteins from seeds containing the alleles Cgy 1 (S) , Cgy 2 (S) , or Cgy 3 (D) also has altered mobility relative to deglycosylated normal proteins. Therefore, the altered subunits contained changes in their amino acid sequences rather than in their carbohydrate moieties. This interpretation is consistent with the observed codominant or incompletely dominant mode of inheritance for these alleles and suggests that each contains an altered nucleotide sequence in the structural gene. A fourth variant, which exhibited doublet α' and a electrophoretic bands, was inherited in a recessive fashion. Deglycosylated subunit proteins from this variant were identical in electrophoretic mobility to those of the deglycosylated normal protein. This suggests that the doublet phenotype resulted from an alteration in the carbohydrate moiety of these subunits. The gene or genes which condition this variant presumably are required for normal post-translational modification of the subunit carbohydrates and as such may be useful for investigating these events.