Diversity and distribution of puroindoline-D1 genes in Aegilops tauschii

Puroindoline-D1 genes are the key genes that decide kernel texture in bread wheat, but limited genetic resources have impeded the improvement of wheat quality. In this study, the puroindoline-D1 genes from 110 accessions of Aegilops tauschii Coss. (the D genomic ancestor of bread wheat) were isolated and sequenced to identify new alleles and discover their genetic diversities. Three new alleles: Pina-D1o, Pinb-D1dt and Pinb-D1it, were discovered, and they were only one nucleotide different to Pina-D1a, Pinb-D1a and Pinb-D1i, respectively. Two new puroindoline proteins were translated from the Pina-D1o and Pinb-D1dt. Pinb-D1it coded the same protein as Pinb-D1o, Pinb-D1m, Pinb-D1h, Pinb-D1n, AJ302108, Pinb-D1i and Pinb-d1it, which are common phenotypes found at the Pina-D1 and Pinb-D1 A. tauschii locus; Pina-D1h, Pina-D1f, Pina-D1e, Pina-D1d, Pina-D1c and AY608595 also coded the same amino acid at the Pina-D1 locus. Total eight Pina-D1 alleles, seven Pinb-D1 alleles and 20 haplotypes were found in these accessions. The synonymous mutations produced two kinds of synonymous haplotypes in our experiment. The first kind contained Pina-D1d/Pinb-D1i, Pina-D1c/Pinb-D1h, Pina-D1c/Pinb-D1i, Pina-D1d/pinb-D1h, Pina-D1j/pinb-D1i and Pina-D1e/Pinb-D1i, and the second kind contained Pina-D1a/Pinb-D1i and Pina-D1a/Pina-D1it. The eight synonymous haplotypes made up the majority of haplotypes, and covered also the majority of the geographical distribution. The large numbers of synonymous haplotypes and their wide distribution suggested that the puroindoline-D1 genes play important roles in A. tauschii survival. New puroindoline alleles and the haplotypes in A. tauschii will improve our understanding of puroindolines evolution and lead to increasing of wheat quality.