Discovering Superior Haplotypes Of TaSAP Family Members Related With Abiotic Stress-tolerance In Wheat

Drought, salinity are the major abiotic stresses that restrict the food supply. Wheat (Triticum aestivum L.) is one of the most important cereal crops in the world. Exploring the wheat favorable gene resources and improving the stress tolerance are a fundamental approach for fighting to environmental stress. There are abundant allelic variations in wheat germplasm, identifying these alleles for stress tolerance will help us to understand the genetic mechanisms, and can develop function markers based on the sequence polymorphism, which provide the basis for marker assisted selection on stress tolerance. Stress-associated protein (SAP) gene family in plant mainly involved in the response to abiotic stress. The purpose of the present research is to identify TaSAP gene family member significant response to abiotic stresses in wheat by using expression pattern, clustering analysis and association mapping. Using TaSAP transgenic Arabidopsis thaliana and rice as the plant materials to verify the function of the gene. Screening the interaction proteins with yeast two hybridization, functional mechanism of TaSAPs was preliminarily revealed. The main results obtained in our study were as follows:1. Twenty-three candidate TaSAP gene family members were screened out by using Hidden Markov Model (HMM) tools.2. All 23 candidate TaSAP genes can be induced by diverse abiotic stresses, showed different expression patterns. Six members which significantly response to abiotic stresses were screened out by the expression patterns. TaSAP2 was located in chloroplastid. TaSAPS and TaSAP7 were located in nucleus, cytoplasm and cytomembrane. TaSAP3 and TaSAP 18 were also located in nucleus, cytoplasm and cytomembrane, but highly express in nucleus. Targeted PCR amplification of nullisomic-tetrasomic lines showed that TaSAP2 was located on homoeologous group 6, TaSAP3 and TaSAP5 on homoeologous group 5, TaSAP6 on homoeologous group 2, TaSAP7 on homoeologous group 7. TaSAP3 was taken out for the association analysis according to the previous researches and the clustering analysis.3. TaSAP3 sequences of 30 wheat accessions were analyzed. Total of 12 SNP (single nucleotide polymorphism) and 31 InDel (insertion-deletion) were identified in the sequence of 3.1 kb length. Two functional markers were developed based on an InDel site at-647 bp and a SNP site at-784 bp, named TaSAP3-647 and TaSAP3-784. Three haplotypes were detected among 262 wheat accessions based on the two markers. The TaSAP2 was mapped to a region flanked by SSR markers Xgwml86 (9.3 cM) andXgwml258 (7.7 cM) on chromosome 5A.4. Marker-trait association analysis on a natural population with 262 accessions showed that the two markers were significantly associated with thousand grain weight (TGW) and spike length. The haplotype Hap-3A-3 exhibited an increasing trend during the breeding process. Genotypes with Hap-3A-3 showed the highest TGW among the three haplotypes. The MCC (Chinese Wheat Mini Core Collection) was employed to verify the association mapping, the results agreed with the natural population. The distribution of Hap-3A-3 during the breeding process in ten wheat zones indicate that the application of Hap3 were expanded gradually.5. The TaSAP3 transgenic Arabidopsis thaliana showed obvious tolerance to osmotic stress. The roots and leaves of transgenic plants grew normally but the wild type and negative control lines grew slowly even withered. The cell membrane stabilities of the transgenic plants were higher than that of the wild type and negative control lines.