Cloning And Functional Analysis Of Lipid Transfer Protein Gene TaLTP In Wheat

Wheat (Triticum aestivum L.) is a major grain crop for human and widely cultivated around the world. As a kind of plant, its growth and development can be impacted by adverse environments, such as drought, salinity, extreme temperature or other abiotic stress, which lead to a production reduction at different levels in wheat. To ensure a stable and high yield of wheat, an efficient approach is to discover and use key genes involved in tolerances to abiotic stresses. Lipid transfer protein (LTP) is a kind of small molecular protein, which is named for its ability to transfer lipid between cell membranes. It plays a key role in cuticle synthesis and adaptation to abiotic stresses. By homology-based cloning, we isolated TaLTP from a drought tolerant wheat cultivar Hanxuan 10. We charactered TaLTP-s gene by transgenic Arabidopsis, gene expression pattern and the association study between gene polymorphism and agronomic traits in wheat. The results provided a foundation for understanding the function of TaLTP. Our results are mainly as follows:1. A full-length cDNA sequence encoding a lipid transfer protein (TaLTP-s) was cloned from wheat, which length was 510 bp with a 339 bp open reading frame. The putative protein contained 112 amino acids with a N-terminal signal peptide within the first 25 amino acids. The TaLTP-s contained eight cysteine residues which were conserved in amino acid sequences. The result of subcellular localization exhibited that TaLTP-s located in the cell membrane and cytoplasm.2. TaLTP-s was detected in all tissues at flowering stage, including leaf, root, floret, anther, pistil and mature seeds of wheat. The highest expression level was identified from the floret, especially in the anther. TaLTP-s was up-regulated by ABA, PEG, NaCl and 4℃ treatments which indicated that TaLTP-s involved in different signal pathways responding to abiotic stresses.3. Arabidopsis thaliana overexpression TaLTP-s showed higher cell membrane stability and significantly enhanced survival under high-salinity conditions than the controls. Similarly, the transgenic TaLTP-s Arabidopsis lines developed more lateral roots over all controls, especially when treated with ABA or mannitol. These results provide a candidate gene for wheat improvement in response to salt and other abiotic stresses.4. The TaLTP-s (2.77 kb) sequences consisted of a promoter region and a coding region. TaLTP-s was located on chromosome 1A in wheat between markers WMC449 and WMC93, with 2.1 cM and 5.9 cM genetic distances by using the recombinant inbred lines (RIL) derived from a. cross of "Yanzhanl x Neixiang188".5. Three haplotypes were clustered by two sites of eight SNPs which were found in the promoter region of TaLTP-s. Using the dCAPS markers (SNP1 and SNP2) developed for TaLTP-s identified the genotypes of the natural population consisted of 262 accessions. Three kinds of haplotypes were significantly associated with plant height, length of the second internode which is below peduncle, and peduncle length. Hap I and HapⅢ of the TaLTP-s are considered as the haplotypes to increase the plant height. The SNP1-G was the superior allele to increase the spike number per plant and the SNP2-C was the allele to increase the plant height.