Abstract:

Drought is one of the major elements affecting the yield of wheat, one of the most important crops in arid and semi-arid areaes. Mining pivotal drought-resistant genes and probing their polymorphisms are a feasible approach to decipher crops’ drought resistance. The genes involved in drought resistance are classified into two classifications, functional genes and regulatory genes, based on their functions responding to water deficient. Much attention has been paid to regulatory genes because of their crucial roles in drought resistance. AtMyb2 regulates the expression of dehydration-responsive genes rd22 and AtADH1 in plants. Recent studies indicate that TaMyb2 is involved in response to water stress in common wheat, but whether its polymorphisms associated with drought resistance is still unclear. To probe the polymorphisms of TaMyb2 gene and uncover their functions in drought resistance, a total of fifty-six accessions, including thirty-nine common wheat cultivars with different drought resistance, five species with A genome including three T. urartu, one T. monococcum and one T. boeoticum, four Aegilops. speltoides, six Ae. tauschii and two tetraploid wheat species, were selected to perform the research. The PCR amplification showed that TaMyb2 was detectable in all accessions except A genome species. Based on the genomic sequences, TaMyb2 was classified into 3 types named as TaMyb2-Ⅰ, TaMyb2-Ⅱ and TaMyb2-Ⅲ, respectively. The full-length sequence of TaMyb-Ⅱ geneomic DNA was 1 606 bp. Twenty-six SNPs (single nucleotide polymorphism) and eight InDels (insertion-deletion) were identified in 77 088 bp nucleotide acid sequence of forty-eight accessions, and the frequencies of SNP and InDel were 1/2 965 bp and 1/9 636 bp, respectively. The frequency of SNP in coding region (π=0.00055) of TaMyb-Ⅱ was lower than that in noncoding region (π=0.00185), the ratio of Ka/Ks was 0.32 which seemed to suggest TaMyb2-Ⅱ suffered artificial selection pressure and was very conservative. Phylogenetic analysis demonstrated that the relationship between Ae. tauschii and common wheat was much closer than that between Ae. speltoides and common wheat. Eighteen haplotypes were detected in forty-eight accessions, in which haplotype 2, 3, 5, 6, 8 and 9 were common wheat cultivars with drought resistance, which indicated that these haplotypes might relate to the drought resistance of common wheat.

Key words: TaMyb2-Ⅱ, Single nucleotide polymorphism, Common wheat, Relative, Drought resistance