Association Analysis Of Dehydration Responsive Element Binding Gene And Its Expression Patterns Under Abiotic Stresses In Wheat

In our country, wheat (Triticum aestivum L.) is a staple food crop, also a crop consumes huge amount water resources. China is one of the water-poor countries in the global, identified as one of the world’s13water-poor countries. Per capita water resources are around the world average of quarter. Water shortage is one of the main factors restricting wheat production in China. So the wheat drought resistance has been paid more and more attentions. To improve the wheat drought resistance has become one of the key goals of breeding. The DREB (dehydration responsive element binding) transcription factor plays an important role in resisting adversity in plants, such as drought, high salt and low temperature by participating in abiotic stress related gene expression regulation. The researches on TaDREB gene mapping, association analysis and expression analysis, will be helpful to understand the gene variation and the relationship with agronomic characters and abiotic stress tolerance, and also be beneficial to wheat molecular marker assisted breeding.In the present research, the plant materials we used includ a natural population consisted of154historical wheat accessions, two wheat genetic populations, wheat wild relative species and a set of Chinese Spring nulli-tetrasomic lines. The nucleotide polymorphisms of TaDREB1and TaDREB4were detected by sequencing. Based on the nucleotide polymorphisms, the functional markers for two genes were developed and mapped, respectively. The relationship between genotypes of TaDREB1, TaDREB4and agronomic traits under different water regimes were identified by the correlation analysis. The purpose was to discover the favorable alleles and molecular markers for drought tolerance improvement in wheat. The main research results are as follows:1. Three kinds of TaDREB1sequences were identified from the genomes of20hexaploid wheat accessions with high genetic diversity, which were assigned on wheat genomes A, B and D, named as TaDREB1-A, TaDREB1-B and TaDREB1-D, respectively. Among them, there was no polymorphism in the genome sequences of TaDREB1-A and TaDREB1-D between wheat accessions, respectively, but three SNPs (single nucleotide polymorphisms) were detected from TaDREB1-B in the accessions.2. An unique sequence of TaDREB4was amplified from the genome of hexaploid wheat cultivar Hanxuan10. It was located on A genome. Six SNPs were detected from the20wheat accessions.3. Based on the SNPs in TaDREB1-B sequence between two parents, Hanxuan10and Lumai14for the DH population, Opata85and W7984for the RIL population, the functional markers were developed. Using the molecular linkage map of DH population, TaDREB1-B was mapped on chromosome3B, between SSR markers P2449-185and WMC231. The genetic distances from the left and right markers were19.2cM and16.0cM, respectively. By the linkage map of RIL population, the gene was also located on chromosome3B, between markers Xfbb117and Xgwm566, the genetic distances from markers were3.4cM and6.4cM in order.4. In accordance with the polymorphism in the genome sequence of TaDREB4gene between two parents of DH population, we developed a molecular marker. TaDREB4was located on chromosome1A with the flanking markers of CWM517and WMC20. The genetic distances were7.8cM and19.4cM.5. The genome sequences of TaDREB1in20wheat accessions were clustered into two kinds of haplotypes. Using the CAPS marker developed for TaDREBl detected the genotypes of the natural population, combined with2009-2011years of agronomic traits for the correlation analysis. There was no significant correlation between the gene alleles and agronomic characters.6. The genome sequences of TaDREB4in20wheat accessions were clustered into three kinds of haplotypes. Using the CAPS and AS-PCR markers developed for TaDREB4identified the genotypes of the natural population, combined with2009-2011years of agronomic characters for the correlation analysis. Three kinds of haplotypes were significantly associated with spike number per plant, grain number per spike, spikelet number per spike and grain plumpness, respectively. Among them, Hap Ⅱ was the hyplotype to increase the spike number per plant and grain plumpness, Hap Ⅲ was the favorable hyplotype for improving the grain number per spike.7. All of three types of TaDREB1gene in genomes A, B and D (TaDREB1-a, TaDREB1-b and TaDREB1-d) are responded to the abiotic stress, such as PEG (polyethylene glycol), NaCl, ABA and cold stresses. Under different stress conditions, it was varied that the expression peaks, their intensity and time points of TaDREB1in the leaf and root of wheat seedlings. In which, the expression of TaDREB1-a and TaDREB1-b in leaf were upregulated by the stress treatments of PEG, NaCl and ABA, but TaDREB1-d was downregulated. Under low temperature stress, all three types of TaDREB1represented an upregulation. Three types in seedling root were all represented upregulation, too.