| Rice is the most important crop in the world. At present, the cultivated land in China is decreasing day by day. Various chemical fertilizers especially nitrogen fertilizer were applied into the field in order to satisfy people's demand for food. As we all know nitrogen is the most important nutrient element for crop production. However, the substantial inputs of nitrogen fertilizer have taken negative effects such as the increased production cost and environment pollution. Obviously, the conventional breeding methods can't keep up with the increasing food demand of the people. It will play a very important role in rice production and even the entire agricultural development in our country by using transformation method to obtain the new rice variety of high efficiency of nitrogen absorption and untilization. In addition, abiotic stress, such as drought, salt, and low temperature, frequently influences rice growth, development. It becomes more and more urgent to study the genes related to abiotic stress to improve rice tolerance to these abiotic stresses. In this study genes including nitrogen-induced genes, ammonium transpoter(AMT) and nitrate transporter (NRT) were over-expressed in rice plants, the phenotype and metabolic level of transgenic plants were analyzed by molecular biology and physiology methods in order to obtain the transgenic rice plant with the higher efficiency of nitrogen absorption and untilization. The C3HC4-type zinc finger proteins were studied by informatics and the expression level of OsRHCs were analyzed under various stresses. Finally some OsRHCs related to abiotic stress were found. The main results are as follows:1. The sequence information of genes including nitrogen-induced genes, ammonium transpoter(AMT) and nitrate transporter (NRT) were obtained from NCBI database using bioinformatic methods. And the genes were isolated by PCR amplification or cloned from cDNA library in our lab. The pCAMBIA1301S vector which contained 35S promoter were used to overexpress the target gene by an Agrobacterium tumefaciens-mediated transformation method. The copy numbers and expression level of transformed genes in transgenic plants were also checked by Southern and Northern blot respectively. In order to find the differences between the transgenic plants and wild-type plants, the overexpressed transgenic plants with one or two copies were studied in hydroponic culture condition and in field.2. The ammonium transporter (AMT) family contains ten members(OsAMT1;1, OsAMT1;2, OsAMT1;3, OsAMT2;1, OsAMT2;2, OsAMT2;3, OsAMT3;1, OsAMT3;2, OsAMT3;3, OsAMT4;1) in rice (Oryza sativa). Here we systemically examined 27 rice tissues or organs of whole-life time by Real-PCR method. The results showed that OsAMT1;1, OsAMT1;2,OsAMT2;1,OsAMT4;1 were widely expressed in 27 tissues or organs, while other six genes were specifically expressed in some tissues or organs, such as root, panicle, endosperm and so on.3. Expression levels of OsAMT genes with nitrogen deprivation or different nitrogen forms treatments by Real-PCR method. The results showed that among the ten OsAMT genes, the expression levels of five genes (OsAMT1;3,OsAMT2;1, OsAMT2;3, OsAMT3;1, OsAMT3;2 and OsAMT4;1) did not change under the N deprivation both in root and shoot under nitrogen deprivation,and the expression level of the other five genes were up-or down-regulated at different time point. In addition, all genes except OsAMT1;1 were influenced by different nitrogen forms. The results suggested that most ammonium transporters were affected by at least one nitrogen form and could quickly respond to the nitrogen deprivation condition at the transcriptional level to adapt the complicated environment.4.OsAMT2;1 and OsAMT2;3 were overexpressed respectively in rice Zhonghua 11 (Oryza sativa L. ssp japonica) by an Agrobacterium tumefaciens-mediated transformation method. The results showed that overexpression of OsAMT2;1 in rice results in enhanced ammonium uptake but impaired growth under normal nitrogen condition, the tiller number and fresh weight of transgenic plants were about 30% lower than that of control (Zhonghua 11) and the free ammonium in root of transgenic plants were more than 10% higher than that of control(Zhonghua 11), respectively. Similarly, overexpression of OsAMT2;3 in transgenic rice decreases the ammonium uptake and impaired growth. 15N-labeled ammonium uptake experiment was also proven that approximately 10-15% decrease in root uptake capacity for N-labeled ammonium.5. Here, we report the identification and characterization of 29 typical OsRHC genes in rice, describing the gene structure, cis-elements, genome localization, phylogenetic relationship of each member and gene expression. We have used Real-time PCR to perform a characterization of the hormone-regulated and abiotic stress-regulated OsRHC genes. These results help us to understand the function of OsRHC genes for plants' growth and development and the responses to abiotic stress...
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