[Characterization of low-molecular-weighT i-type glutenin subunit genes from diploid wheat in relation to the gene family structure]

Abstract

The low-molecular-weight (LMW) glutenin subunits are important for aspects of wheat quality and dough processing, and the LMW-i type glutenin is one of the typical glutenins. However, a detailed description of the DNA structure and encoded polypeptides of the LMW-i type glutenin subunit gene family is still lacking. In this study, two LMW-i type glutenin subunit genes, i.e., LMW-Eb from Triticum boeoticum and LMW-Em from T. monococcum, were obtained from genomic DNA, respectively. The LMW-Eb is a novel gene and the LMW-Em has the identical sequence with a known gene. To comprehensively understand the LMW-i type glutenin subunit gene family structure, all known LMW-i type glutenin subunit genes were comparatively analyzed. Detailed comparison of these genes revealed a high-level of single nucleotide polymorphisms (SNP). In these LMW glutenin subunits, the percentage of glutamine and proline were approximately 38.27 and 12.77%, respectively. They started directly from the repetitive domain with ISQQQ- after the signal sequence, which the N-terminal regions were absent. In addition, there are three consensus repeat motifs (i.e. PPFSQQQQ, PPISQQQQ and PPYSQQQQ) in the repetitive domains of these LMW glutenin subunits. The C-terminal I domain is the most conserved region, while the domains of C-terminal II and III are more variable. The eight cysteine residues are highly conserved. These genes could be clustered into two major groups, among which one group could be further divided into five subgroups. Furthermore, to date, all known LMW-i type glutenin subunit genes are located on chromosome 1A, whereas no LMW-i type glutenin subunit gene is obtained from the B and D genomes in wheat.