Suppression of soybean β-conglycinin genes by a dominant gene, Scg-1

beta-Conglycinin (7S globulin) is a predominant seed storage protein found in soybean [Glycine max (L.) Merr]. A spontaneous mutant lacking the beta-conglycinin subunits, alpha', alpha and beta, has been identified among Japanese wild soybean genetic resources. Although a multigene family encodes the subunits and is distributed in different linkage groups, a single dominant gene, Scg-1 (a suppressor of beta-conglycinin), controls the mutant trait. This report characterized the genetic and molecular basis of Scg-1. The null trait was caused not by either structural defects or changes in the beta-conglycinin subunit genes, but by a lack of transcription of the genes, indicating that Scg-1 suppresses expression of all the structural genes. Linkage analysis revealed that the Scg-1 locus was located in the same chromosomal region as the alpha and beta subunit genes, which are tightly linked to each other. Furthermore, the methylation of the chromosomal region containing the Scg-1 and alpha and beta subunit loci was observed, suggesting that the deficiency is associated with the silencing of multicopy genes. Scg-1 had no obvious effect on the plant growth, so it will be a useful gene source for manipulation of the protein composition in soybean seeds.