Characterize The Function Of Candidate Overlapping Mirnas Response To Xanthomonas Oryzae Pv.Oryzae Infection And Nitrogen Starvation Stress In Rice

Nitrogen is one of essential mineral elements for plant growth and development. In order to increase yields of crop, excessive nitrogen fertilizer were used in the field. However, the excessive nitrogen fertilizer results in the deterioration of plant disease, and the unbalence of ecological environment. Bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae(Xoo) is a typical high-nitrogen disease, which shows positive correlation to nitrogen over application. A increasing number of studies have shown that mi RNAs involve in adaption to biotic and abiotic stresses in plants. Our previous results suggested that the disease resistance against Xoo infection can be improved in the susceptible rice specie under nitrogen deficiency stress. And our previous work had proofed 63 overlapping mi RNAs response to Xoo infection and nitrogen deficiency in rice. However, it is still little known that how these overlapping mi RNAs regulate the crosstalk between Xoo infection and nitrogen deficiency. In order to further dissect the underlying mechanism of mi RNAs response to Xoo infection and nitrogen deficiency, here we overexpressed 6 overlapping mi RNAs in rice respectively, and measured the resistance against Xoo, nitrogen use efficiency, nitrogen content in transgenic plants under normal nitrogen supplication and nitrogen deficiency stress conditions. The main results are listed as following: 1. Constract mi RNA overexpression binary vector and obtain the transgenic plants with certain overlapping mi RNA. The positive transgenic plant were screened by appropriate hygromycin stress and measured mi RNAs expression level by q RT-PCR. By far, these overexpression plants include mi R230 OX, mi R765 OX, mi R619 OX, mi R693 OX, mi R351 OX and mi R2118 b OX respectively.2. Compared with roots of WT which were inhibited under nitrogen deficiency condition, roots of mi R 351 OX showed little difference under different nitrogen supply conditions, while mi R2118, mi R230, mi R765 OX plants showed longer root length under nitrogen deficiency condition. Which indicates that mi R2118, mi R230, mi R765 and mi R351 may implicate in nitrogen uptaking and using by regulating root development in rice. Microscopic analysis of morphological phenotype of root demonstrated that the development of fibrous root in these OX plants were abnormal. The nitrogen content of mi R619 and mi R693 did not change compared to the wildtype, and the root length and fibrous root also shows no difference between different nitrogen condition, indicate that mi R619 and mi R693 are not involved in the regulation of root growth. 3. Under normal nitrogen supply, overexpression of mi R230 and mi R765 result in enhanced resistance against Xoo, while overexpression of mi R619, mi R693, mi R351 and mi R2118 b led to decreased reisistance against Xoo. Compared with WT plants, mi R2118 b OX greatly reduced the resistance against Xoo enhanced by nitrogen deficiency stress. All of these results suggested that these overlapping mi RNAs implicated in the regulation to adaption to Xoo infection.In conclusion, this study obstained 6 overlapping mi RNAs overexpression transgenic plants respectively. Analysis of the resistance against Xoo, root development under different nitrogen supply conditions suggested that these 6 overlapping mi RNAs implicate in the regulatory roles in the crosstalk between response to Xoo infection and nitrogen deficiency. This study will contribute to dissect the crosstalk mechanism between response to Xoo infection and nitrogen deficiency in rice. The following works is to check expression level of the relative genes and potential signal pathway under combined and individual stress.