Molecular characterization of a deletion mutation affecting the alpha'-subunit of beta-conglycinin of soybean.

A naturally occurring variety of soybean Glycine max cv. Keburi, which lacks the alpha'-subunits of the 7S seed storage protein (beta-conglycinin), was recently described by Kitamura and Kaizuma. Keburi beta-conglycinins contain a normal complement of alpha-, beta-, and gamma-subunits that accumulate in a temporally and spatially regulated manner comparable to that of the standard cultivar Provar. Poly(A)+ RNA isolated from mid-to-late maturation stage Keburi seeds was translated in vitro, yielding products equivalent to those of Provar poly(A)+ RNA except that Keburi mRNA did not produce the pre-alpha'-subunit polypeptide. The basis of the Keburi phenotype was determined by examining genomic DNA using Southern blot hybridization. Restriction fragments isolated from a cloned 11.5 kb EcoRI fragment of genomic DNA containing a normal alpha'-subunit gene (Gmg 17.1) were used as hybridization probes. Sequences far upstream of the alpha'-subunit gene were present in both Provar and Keburi cultivars. However, hybridization reactions with probes from within the gene demonstrated that a deletion had occurred in Keburi DNA beginning immediately 5' to the alpha'-subunit gene represented on this 11.5 kb fragment. The deletion extends through most of the coding sequences, producing the Keburi phenotype.