We attempted to characterize a soybean mutant lacking the 7S globulin (beta-conglycinin) subunits, alpha, alpha' and beta. The results of Southern and northern blot analyses indicated that the deficiency is not caused by a lack of, or structural defects in, the 7S globulin subunit genes, but rather arises at the mRNA level. Despite the independent inheritance of the two loci containing the alpha-and alpha'-subunit genes and the organization of the multi-gene families encoding these subunits and the beta-subunit, a single recessive gene controls the null trait of the mutant. This, taken together with the above results, leads to the assumption that the mutant gene encodes a common factor that regulates the 7S globulin subunit genes. Transient expression of glucuronidase from the promoters of the alpha'- and beta-subunit genes was detected in the mutant cotyledons. The results of gel mobility shift assays using the 5'-flanking regions of the alpha'- and beta-subunit genes failed to detect a deficiency of nuclear factors interacting with these regions. We propose that a seed-specific mechanism of expression of 7S globulin genes might be involved in chromatin organization, and that such an organization might not work normally in the mutant. The possibility that transcript stability is lowered in the mutant is not excluded.