Molecular characterization and marker development for hexaploid wheat-specific HMW glutenin subunit 1By18 gene

Abstract

Wheat grain high molecular weight glutenin subunits (HMW-GS) are the major determinants of dough elasticity and viscosity, and thus of breadmaking quality. Most known HMW-GS genes in bread wheat have been already cloned except for very few such as 1By18 and 1By19. In this study, HMW-GS 1By18 gene was isolated from bread wheat for the first time. In the past, this subunit has been considered to have positive effect on gluten quality. Molecular characterization of the 1By18 subunit gene showed that its complete coding nucleotide sequence was 2163 bp long, being highly identical to 1By8, with only three single nucleotide polymorphisms (SNPs) at sites 231, 233 and 1976 of the coding sequence. The deduced amino acid sequence of 1By18 exhibited two substitutions compared to 1By8. The deduced protein was further verified by expression in E. coli and LC–MS/MS analysis. Phylogenetic analysis showed that 1By18 was more closely related to 1By8, 1By9 and 1By16 than to 1By15 and 1By20. Molecular phylogenetic analysis indicated that the Glu-B1i allele emerged after the formation of modern hexaploid wheat. Two sets of SNP-based AS-PCR markers for 1By18 gene were developed and validated on 110 bread wheat varieties with different Glu-Bly alleles, and five recombinant inbred lines. Both markers could effectively distinguish 1By18 from the other genes at the Glu-B1 locus, thus making them valuable for marker-assisted selection in wheat quality improvement programs.