Molecular characterization of a β-conglycinin deficient soybean

The soybean seed storage protein β-conglycinin has a low amino acid score, shows lower functional gelling properties compared with glycinin and contains a major allergen. The wild soybean (Glycine soja Sieb et Zucc.) QT2 lacks all the subunits of β-conglycinin, and this deficiency is controlled by a single dominant gene Scg-1 (suppressor of β-conglycinin). Scg-1 was introduced into a soybean cultivar Fukuyutaka from QT2 and this near-isogenic line was designated as QY7-25. Segregation analyses of the progeny derived from a cross between QY7-25 and the wild type did not show any significant changes caused by Scg-1 in the germination ratio and seed weight. Low amounts of mRNAs for the α ’, α and β subunits of β-conglycinin were detected by RT-PCR in QY7-25. We revealed that an α subunit mRNA expressed from a region which replaced with mutant line in the near-isogenic line QY7-25 by single nucleotide polymorphisms analysis. In addition, an abnormal splicing event in a cDNA clone for the β subunit isolated from immature seed of QY7-25 was observed. Southern analysis using the coding region of α ’ subunit gene as a probe revealed a polymorphism between QY7-25 and wild type and this genotypes co-segregate with the deficiency of β-conglycinin subunits. These results suggest that the β-conglycinin deficiency might be controlled by a claster region of β-conglycinin subunit genes. In the present study, no agronomical disadvantage in QY7-25 was observed, confirming that Scg-1 is a valuable gene for soybean breeding.