Structure and diversity of 13S globulin zero-repeat subunit, the trypsin-resistant storage protein of common buckwheat (Fagopyrum esculentum M.) seeds

摘要

The zero-repeat subunit of 13S globulin, which lacks tandem repeat inserts, is trypsin-resistant and suggested to show higher allergenicity than the other subunits in common buckwheat (Fagopyrum esculentum Moench). To evaluate allelic variations and find novel alleles, the diversity of the zero-repeat genes was examined for two Japanese elite cultivars and 15 Pakistani landraces. The results demonstrated that two new alleles GIbNAI and GIbNCI, plus three additional new alleles GIbNA2, GIbNA3, and GIbND, were identified besides the already-known GIbNA, GIbNB, and GIbNC alleles. In the Pakistani landraces, Glb:VA was the most dominant allele (0.60-0.88 of allele frequency) in all except one landrace, where GIbNB was the most dominant allele (0.50 of allele frequency). Similar to GIbNC, the alleles GIbNA2 and GIbNA3 had extra similar to 200 bp MITE-like sequences around the stop codon. Secondary structure predictions of a sense strand demonstrated that the extra similar to 200 bp sequences of GIbNC, GIbNA2, and GIbNA3 can form rigid hairpin structures with free energies of -78.95, -67.06, and -29.90 kcal/mol, respectively. These structures may affect proper transcription and/or translation. In the GIbNV homozygous line, no transcript of a zero-repeat gene was detected, suggesting the material would be useful for developing hypoallergenic buckwheat.