Novel LMW glutenin subunit genes from wild emmer wheat (Triticum turgidum ssp. dicoccoides) in relation to Glu-3 evolution

Four low-molecular-weight-isoleucine (LMW-i)-type and one novel chimeric (between LMW-i and LMW-methionine (m) types) low-molecular-weight glutenin subunit (LMW-GS) genes were characterized from wild emmer wheat ( Triticum dicoccoides ), designated as emmer - 1 to emmer - 5 . All five LMW-GS genes possessed the same primary structure shared by other published LMW-GSs. The three genes emmer - 1 , emmer - 3 , and emmer - 5 are similar, with the exception that emmer-3 and emmer-5 lost a few repeat motifs compared to emmer-1. Gene duplication and insertions/deletions of repeat motifs mediated through unequal crossing over may be responsible for the generation of these three Glu - 3 alleles. Although the first residue of mature peptide of emmer-4 is isoleucine, it is not typical LMW-i-type LMW-GS. Phylogenetic analysis indicated that emmer-4 is located in the LMW-m subgroup, suggesting a closer relationship with LMW-m-type gene Y14104 of T. durum . Sequence alignment indicated that the emmer - 4 is likely a chimeric gene generated by illegitimate recombination between LMW-i and LMW-m type. Unequal crossing over and illegitimate recombination are effective mechanisms for enriching both copy numbers and variations of LMW-GSs.