Cloning and characterization of special HMW glutenin subunit genes from Aegilops longissima L. and their potential for wheat quality improvement.

Identification and cloning of new glutenin genes from wheat-related species can provide candidate gene resources for quality improvement of wheat. In this study, ten special high-molecular-weight glutenin subunits (HMW-GS), including five x-type (1Sl2x, 1Sl16x, 1Sl17x, 1Sl23x, and 1Sl25x) and five y-type (1Sl2y, 1Sl6y1, 1Sl16y, 1Sl17y, and 1Sl23y) from Aegilops longissima L. (SlSl, 2n = 2x = 14) were identified, and their complete encoding genes were cloned by allelic-specific polymerase chain reaction (AS-PCR). The deduced amino acid (aa) residues of the x-type subunit genes ranged from 821 aa (2469 bp) to 941 aa (2829 bp), while those of the y-type subunit genes varied from 749 aa (2250 bp) to 771 aa (2361 bp). These special HMW-GS had a longer central repetitive domain with more glutamine repeats and glutamine residues compared to the previously characterized HMW-GS in common wheat, which provided a structural basis for superior gluten quality formation. The authenticity of the four cloned genes were verified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). Abundant single-nucleotide polymorphism (SNP) and insertion/deletion (InDel) variations among these genes were identified, which would benefit for developing specific molecular markers used for wheat gluten quality improvement. Phylogenetic analysis revealed that the 1Sl-encoded HMW-GS had close relationships with those from bread wheat, which were divergent from Triticum species at 2.10-10.00 million years ago. Our results indicate that the 1Sl genome contains superior candidate glutenin genes that have potential application values for the improvement of wheat bread making quality.