Characterization of a Gy4 glycinin gene from soybean Glycine max cv. Forrest

The glycinin gene family encoding the glycinin subunits in soybean plants is composed of at least five gene members. A genomic clone S312 containing the Gy4 gene from a genomic library of cv. Forrest was isolated and partially characterized. The organization of this gene was found to be similar to that of a null allele from cv. Raiden, but different from the Gy4 gene from cv. Dare. The complete nucleotide sequence of this gene has been determined. It is 2599 bp long consisting of four exons and three introns. Comparing the DNA sequences between this gene and the gene from Dare and a null allele from Raiden, the difference found in the coding region was 5-GCAGTGCAAG-3 (nt 824 to 833) in the former case versus 5-TGGAGTTGCAATT-3 (nt 1314 to 1326) in the latter case in the exon 2 domain, resulting in three amino acid differences and one amino acid absence. Some other differences were also found in the non-coding region. The coding sequence and 5-flanking region of the Gy4 gene, when compared with that of other legumin genes as well as group 1 glycinin subunit genes, revealed some interesting features: (1) a transposable element-like sequence was found in the hypervariable region (HVR) of the exon 3 domain, which was lacking in the legumin and the glycinin group 1 genes; (2) in the 5-flanking region from nt –145 to –1, two high-homology sequences were found: one from nt –141 to nt –132, the other from nt –118 to nt –92 which includes the legumin box and the RY repeat element.