RESUMEN
To explore the distribution and quantity of toxic epitopes in α-gliadins from Aegilops tauschii, a total of 133 complete α-gliadin coding sequences were obtained, including 69 pseudogenes with at least one premature stop codon and 64 genes with complete open reading frames (ORFs). Plenty of deletions and single amino acid substitutions were found in the 4 celiac disease (CD) toxic epitope domains through multiple alignments, in which the sequence of DQ2.5-glia-α2 demonstrated the most significant changes. Interestingly, 7 of the 59 α-gliadins were free of any kind of intact CD toxic epitopes, providing potential gene resources for low CD toxicity breeding of common wheat. Analysis of the neighbor-joining tree demonstrates that 2 of the totally 7 α-gliadins cluster within the homologues of Triticum (A genome), and the other 5 group with those of Aegilops Sitopsis (B genome). This result implies that the 7 α-gliadin genes may be originated from the ancestor species of Ae. tauschii, evolved by the homoploid hybrid of Triticum and Aegilops Sitopsis. The remaining 52 α-gliadins form a separate clade from other homologues of A and B genomes, suggesting a recent rapid gene expansion by gene duplication associated with the species adaptation.
Asunto(s)
Epítopos/química , Epítopos/genética , Gliadina/química , Gliadina/genética , Poaceae/genética , Triticum/inmunología , Secuencia de Aminoácidos , Enfermedad Celíaca/inmunología , Epítopos/inmunología , Variación Genética , Genoma de Planta , Gliadina/inmunología , Humanos , Datos de Secuencia Molecular , Filogenia , Poaceae/química , Poaceae/clasificación , Poaceae/inmunología , Dominios Proteicos , Alineación de Secuencia , Triticum/química , Triticum/genéticaRESUMEN
To clarify the effect of high molecular weight glutenin subunit (HMW-GS) from wild emmer wheat on flour quality, which has the same mobility as that from common wheat, the composition and molecular characterization of HMW-GS from wild emmer wheat accession TD-256, as well as its flour quality, were intensively analyzed. It is found that the mobilities of Glu-A1 and Glu-B1 subunits from TD-256 are consistent with those of bread wheat cv. 'XiaoYan 6'. Nevertheless, dough rheological properties of TD-256 reveal its poor flour quality. In the aspect of molecular structure from HMW-GS, only two conserved cysteine residues can be observed in the deduced protein sequence of 1Bx14* from TD-256, while most Glu-1Bx contain four conserved cysteine residues. In addition, as can be predicted from secondary structure, the quantity both of α-helixes and their amino acid residues of the subunits from TD-256 is fewer than those of common wheat. Though low molecular weight glutenin subunit (LMW-GS) and gliadin can also greatly influence flour quality, the protein structure of the HMW-GS revealed in this work can partly explain the poor flour quality of wild emmer accession TD-256.