Detection and characterization of a glutenin subunit with unusual high Mr at the Glu-A1 locus in hexaploid wheat.

A hexaploid wheat landrace collected from the Baluchistan province of Pakistan was found to possess a novel high-molecular-weight glutenin subunit (HMW-GS). The subunit has a very slow electrophoretic mobility as revealed by SDS-PAGE, and its molecular weight is comparable to that of the highest molecular weight glutenin subunit ("2.2" encoded in the D-genome) reported so far in hexaploid wheat varieties and landraces of Japanese origin. Evidence obtained from (PCR) gene amplification studies using the primers specific for Glu-1 loci proved that the gene coding for this novel subunit belongs to the Glu-A1 locus located on the long arm of chromosome 1A. Digestion of the amplified gene (PCR product) with restriction enzymes indicated that the novel gene differs from prevailing Glu-A1 alleles (null, 1 and 2(*)) by an extra DNA fragment of approximately 600 base pairs. The results also indicated that the novel subunit is most probably a derivative of subunit 2(*) that has very likely incorporated the 600-bp fragment following a process of unequal crossing over. The present findings were further substantiated by reserved phase high performance liquid chromatography (RP-HPLC) analysis.