Function Analyses Of The Late Embryogenesis-Abundant Protein From Jatropha Curcasand Function Analyses Of AtMSH6 And AtMSH7 In Meiotic Recombination

Part OneThe late embryogenesis-abundant protein (LEA protein), originally identified in terrestrial plants, is a family of hydrophilic proteins that accumulate in late stages of embryogenesis in seeds from dehydration. Known as its indispensable role in abiotic stress tolerance of stabilizing the cellular structure and preventing membrane infusion, especially in drought tolerance, LEA protein has been placed great value on its potential in stress tolerance improvement. In this study, expression of JcLEA in Jatropha curcas was induced by drought and salt stress. Subcellular localization analyses revealed that JcLEA was localized in nucleus and cytoplasm. The phylogenetic tree of LEA proteins showed that the JcLEA protein belonged to the Group 5 protein, which has not been fully studied. In these study, two transgenic lines (25-29 and 25-33) showed relatively higher expression level of JcLEA was chose for further analyses, including imposing drought and salt stress in the medium and soil to test the physiological indexes.Under the drought treatment by PEG on the medium, the transgenic lines and wild type plants showed an impacted growth condition, but the transgenic lines grew better and their root lengths were much longer. Under drought treatment in soil, the survival rate of transgenic was 1.5 times that of wild type. After rewatering, the survival rates of the transgenic lines increased slightly, while the wildtype plants could not recover. Relative water content of all the plants decreased under the drought stress, but that of transgenic lines decreased less and increased after rewatering and the wild type could not recover after rewatering and its relative water content decreased continually. The electrolyte leakage of all the plants increased, indicating the impact of membrane to a variable extent, while the electrolyte leakage of transgenic lines was lower than that of wild type plants, even after rewatering. The glucose content of all the plants improved to respond to the drought stress, but the glucose content of transgenic lines was higher than that of wild type.The transgenic lines showed better growth condition and longer root lengths under the 50 mM,100 mM and 150 mM NaCl treatment in the medium. Imposed NaCl stress in soil, the transgenic lines showed higher survival rate, execially under 100 mM,150 mM and 200 mM NaCl treatment. Under different concentrations of NaCl treatment, the relatively water content of transgenic lines decreased less than that of wild type plants. The transgenic lines exhibited lower electrolyte leakage and accumulated more glucose to regulate cell osmotic potential. Besides, the transgenic can maintain Na+/K+homeostasis better compared with the wild type plants.This study was focused on the group the JcLEA belonged to, the expression characteristics, protein subcellular localization and its function. These analyses indicated that JcLEA was localized to nucleus and cytoplasm and belonged to the group 5 LEA protein and JcLEA contributed to tolerance to drought and salt stress of plants, shows its potential in the study of transgenic crop breeding. This study not only provides a potential genes for the anti-drought and anti-salt engineering in crop breeding, but also serves as a reference for the study on the group 5 LEA protein.Meiosis is the highly conserved and crucial step for sexual reproduction. The pairing, synapsis, recombination and segregation are the key events in meiosis. With the development of experiment methods and the utilization of mutants from model organisms, such as yeast, Arabidopsis and maize, the functions and regulation mechanisms of genes participating in this critical process have been elucidated. MSH derives its name from MutS homologue protein, which has been identified to have 7 members (MSH1-7) in eukaryotes, MSH6 participates in the nuclear mismatch repair and showed the highest expression level among MSH genes in male meiocytes. MSH7 has only been identified in plants and shows closer relationship with MSH6 compared with other MSH members. MSH7 has also been called MSH6-2. There have been reports on the function of MSH4 and MSH5, while there are no reports on the function of MSH6 and MSH7 in meiosis. In this study, we utilized the Arabidopsis Atmsh6 and Atmsh.7 salkline T-DNA mutants and the fluorescent tetrad lines to analyze the effect of AtMSH6 and AtMSH7 mutations on the meiotic recombination frequency. In order to study in which specific process the AtMSH6 and AtMSH7 will function in the meiotic recombination, I crossed the mutants of AtMSH6 and AtMSH7 with the mutants of key genes in meiotic recombination to construct double and triple mutants, then crossed these mutants with the fluorescent tetrad lines to construct the multiple mutants. This study indicated that the mutation of MSH6 on chromosome 3 could cause an increased meiotic recombination frequency of 9.5% compared with the wild type and the difference was significant. The meiotic recombination frequency on chromosome 3 of the msh6 mutant was 26.07% and that of the heterozygous plants was 23.81%. The msh7-1 mutant showed a improved meiotic recombination frequency of 11.26% compared with the wild type and heterozygous plants, but the difference was not significant, as in this case with the interference level between them. This result needs further confirmation. This study was focused on the meiotic recombination frequency of msh6 and msh7-1 single mutants and constructs the materials. This study can serve as a reference for the study on the function of MSH members, AtMSH6 and AtMSH7, in meiotic recombination.