Functional Analysis Of A Salt-stress Response Gene TaTIP2;2 Of Wheat

The salt tolerance is a multi-gene controlled trait, and the genes involved functions in diverse bio-processes, such as cell defense, metabolism, ionic homeostasis, and transporting, which weaves a complicated regulatory network. Therefore, to study the functions of these salt-responsive genes will help us to further understand the mechanisms by which plants tolerant high salinity and to promote the molecular breeding of crops.As one of the most widely distributed and planted crops in the world, common wheat (Triticum asetivum) is a very important object of study. A new somatic hybrid introgression line Shanrong No.3 (SR3) has been generated in our lab via asymmetric somatic hybridization of common wheat cv. Jinan 177 with wheat grass (Thinopyrum ponticum), a salt and drought tolerant grass relative to wheat. SR3 had a significantly higher yield and salt-resistance than its parent JN177. Cytological and molecular analysis showed that some chromosome fragments, nuclear/non-nuclear DNAs and even functional genes from donor Th. ponticum were introgressed into this line. It is different from other salt-enduring materials which have single genetic background, the salt tolerance of SR3 is controlled by major salt tolerance genes and some other microgenes.In this study, we cloned TaTIP2;2 from the SR3 cDNA salt library, and made a series of functional study, the main research and results are as follows.According to the information of NCBI, we cloned TaTIP2;2 from the genome of SR3. Then the cDNA of TaTIP2;2 was amplified from a salt-cDNA library of SR3. We can find that the genomic sequence of TaTIP2;2 comprises three exons and two introns. The PCR-based analysis of genomic DNA of wheat aneuploid lines showed that this gene was located on the long arm of chromosome 7B.TaTIP2;2 was constitutively expressed in both the roots and leaves of wheat seedlings grown under non-stressed conditions. It was substantially down-regulated by the imposition of salinity and drought, but there is no change under the ABA-stressed. Subcellular localization result figured that it was in the endomembrane system, especially in the tonoplast and ER membrane.The heterologous over-expression of TaTIP2;2 in Arabidopsis increased sensitivity to salinity stress and mannitol stress of the transgenic lines. These results suggest that TaTIP2;2 plays a role in the plant's response to abiotic stress.To further understand the the machanism of TaTIP2;2, real-time PCR was performed to trace the expression patterns of salt-responsive marker genes in the wildtype and TaTIP2;2 transgenic Arabidopsis. The result showed that the transcription of ABI1, ABI2 and ABF3 was not affected by the overexpression of TaTIP2;2, whereas the expression of SOS pathway genes was markably restricted in transgenic lines, and the transcription levels of DREB2A, CBF3 and P5CS1 were also slightly down-regulated. Based on these results, we suggest that TaTIP2;2 involve in the ABA-independend pathway.