Study On The Function Of CBF Pathway Antifreeze Gene And The Function Of Arabidopsis Thaliana MSH2 / 3 Gene During Meiosis And Recombination

Temperature is an important influence in the process of plant growth. Low temperature also affects the crop production. With the development of genetic engineering technology, improving the plant tolerance to cold by transgenic technology has been an important research topic and a hot sopt.CBF pathway is a main cold response pathway in plants. CBF transcription factor can activate several downstream genes to improve the cold tolerance of plants. The main genes are called COR genes. And an upstream transcription factor ICE also plays an important role in activating CBF. Overexpression of these genes can all significantly improve the plant resistance to cold.Being a plant with high cold-tolerance, The CBF pathway genes in Shepherd’s purse have already been researched much. Under chilling temperature CbICE53 activates the transcription of CbCBF. The tobaccos overexpressing CbICE53 and CbCBF can both gain great resistence under chilling and freezing treatments. But overexpressing CbCBF may lead to delay in plant growth, while the cold-induced RD29A and CbCOR15bP promotor can solve this problem. CbRCI35, a peroxidase gene, may also be involved in plant cold acclimation dealing with the accumulation of reactive oxygen.Our research combines CbCBF, CbICE53, CbCOR15bP, CbRCI35 to reconstruct vectors by isocaudomers. After transferring the three reconstructive vectors, CbCOR15bP::CbICE53,CbCOR15bP::CbICE53+pCaMV35S::CbCBF,CbCOR15bP:. CbICE53+ pCaMV35S::CbCBF+pCaMV35S::CbRCI35, into tobacco, we observed the morphologis of the transgenic plants and analysed the electrolyte leakage and relative water content, two physiological indexes indicating cold-tolerance. The results show that in transgenic plants, the electrolyte leakage and relative water content are significantly different with the wildtype and empty vector transgenic plants, showing a much greater cold tolerance. This also show that constructing co-transformation vectors by isocaudomers can be a more effective and efficient method in genetic engineering combining several different functional genes, showing a certain practical significance in genetic breeding and crop agriculture..ivieiosis is a Key process in sexuai reproduction in euKaryoies. During meiosis the chromosomes replicate once and the cell di s twice, ensuring the integrity and stability of the chromosomes. Chromosome rearrangements and recombination lead to species diversity. Pairing, synapsis, and recombination are three important processes in plant meiosis. But the detailed molecular mechanisms still need more research.Meiosis recombination is a very complex but crucial process. According to double-strand break model, after the formation of double-strand breaks in chromosomes, the DNA repair complexes functions using the homologous sequence as a template. The 3’ single-stand end then invases into the homologous chromosome and form Holliday junction intermediates. At last crossover and non-crossover are formed. MSH genes play a role in meiosis recombination and mismatch repair by forming different heterodimers.In this study, we analysed the mutant of AtMSH2 and AtMSH3, which is called Atmsh2-2（SALK₀02708） and Atmsh3-1（SALK₀98944C） from the aspects of morphological observation, gene expression patterns, multi-genes mutants construction and recombination frequency analysis. The results show that the mutant of AtMSH2 and AtMSH3 neither affects the growth of the plants. The Alexander staining shows normal quantity and vitality of the pollens. Tissue specific mRNA expression results show AtMSH2 and AtMSH3 both highly express in reproductive tissues such as flowers and siliques. As to the expression of MSH family genes in the mutants, the AtMSH6 is not affected in both Atmsh2-2 and Atmsh3-1. But AtMSH3 and AtMSH7 are down regulated in Atmsh2-2, while AtMSH2 and AtMSH7 are down regulated in Atmsh3-1. The more detailed mechanisms of these four mismatch repair genes still need more research. We crossed the Atmsh2-2 and Atmsh3-1 with other meiosis related genes’mutants such as AtMSH4, AtMUS81 and AtPTD to construct double mutants, establishing a foundation for further research. At last, using the fluorescent tetrad visual assay, we analysed the meiosis recombination frequency and fertility of Atmsh3-1 and wildtype, finding no significant difference and indicating that the mutant of AtMSH3 doesn’t affect the recombination frequency during meiosis.Overall, our research studied the function of AtMSH2 and AtMSH3 on meiosis recombination and mismatch repair, and prepared more materials for follow-up researches.