Relationship Between Single Nucleotide Polymorphism (SNP) Of TaDREB1 Gene And Drought Tolerance In Wheat Germplasm

The function of TaDREB1 transcription factor, a product of TaDREB1 gene, is regulation the expression of obiotic stress-tolerant genes, such as drought-tolerant genes. Using the theory and methodology of molecular biology, to understand the molecular mechanism of crop drought tolerance and to discover novel drought-tolerant gene resources are not only important in theory but also valuable in practice for breeding drought-resistant and high yield variety and promoting the development of economizing water in agriculture. In this paper, 23 accessions including 20 hexaploid wheat cultivars with background of different drought resistance and 3 diploid species relative with common wheat were used to detect single nucleotide polymorphism (SNP) in TaDREB1 gene based on direct sequencing. The purpose was to analyze SNP of TaDREB1 in wheat germplasm and to reveal the relationship between drought tolerance and SNP in TaDREB1, and to serve for the application of excellently drought-resistant gene resources and the development of the SNP markers in wheat functional gene study. The results were as follows: 1. There are abundant SNPs in TaDREB1 gene among experimental accessions. A total of 209 SNPs and 2 InDels(insertion and deletion) were identified from 20 wheat genotypes ,on average of one SNP every 140bp and one InDel every 16540bp. 62 SNPs and 12 InDels were identified in 3 diploid genotypes, on average of one SNP every 80bp and one InDel every 413bp. An intron with 701bp was found between the sit of 302 and 303 of the TaDREB1 gene (Genbank accession: AF303376). 2. Two mutation hot blocks were found in the DNA sequence of TaDREB1. The first block was from the site 1156bp to 1181bp of AF303376, which had 43 SNPs distributed on 7 sites. The SNPs frequency in the first block was one SNP every 8bp and account for 20.6% of all the SNPs (209) in TaDREB1 gene. The second hot block, from the site 1200bp to 1230bp of AF303376, has 52 SNPs, which were distributed on 15 sites. The SNPs frequency was one SNP every 12bp and account for 24.9% of all the SNPs (209) in TaDREB1 gene. 3. Nucleotide diversity, the average diversity of every site in DNA sequence between individuals, presents the hereditary variation degree of a gene. Nucleotide diversity value(Л) of the TaDREB1 is 0.01211, indicating that the polymorphism is one SNP every 83 nucleotides between two homogenous chromosomes in 23 accessions. Nucleotide diversity value of hexaploid (Л=0.01029) is 47.03% of the value of diploid (Л=0.02188), which showes that the variety of TaDREB1 gene in diploid is larger than in hexaploid. This may be the result of artificial selection pressure put on the hexaploid wheat cultivars for a long time. 4. Analysis of haplotype revealed that most of drought-resistant genotypes had same haplotype structure, showing a correlation between SNP of TaDREB1 gene and drought-tolerant phenotype. Haplotype 1 and haplotype 3 are two drought-tolerant haplotypes. However, the confusion that some haplotypes include both drought-tolerant genotypes and non-drought-tolerant genotypes also imply the complexity of drought tolerance. 5. An analysis on the evolution of the wheat three genomes based on the SNP in TaDREB1 in diploid species showed that genome A and D was similar. Genome B diverges from A and D largely. The special 34 SNPs and 12 InDels in genome B were not identified in hexaploid wheat genotypes.This indicates that there was no copy of TaDREB1 gene in the genome B of hexaploid wheat.