Identification And Analysis Of Differentical Genes Responding To Copper In The Medicago Lupulina Root Symbiosis

Due to the ability at nitrogen fixation of legumes-rhizobia symbiosis, it can be used to improve the soil structure and enhance soil fertility,so the legumes-rhizobia symbiosis increases nitrogen cumulation and maintains nutrient cycling in some metal contaminated soils. Nowadays, research about legume plants is mainly focused on plant growth, cell structure, photosynthesis, enzyme system, cell division, uptake of nutrient elements and so on responding to copper,but little research about mechanism of legumes-rhizobia symbiosis has been done.Becase of the strong resistance of medicago lupulina, many researches show that it plays a very important role in phytoremediation at mine tailings. In this dissertation, we mainly focus on the genes screened and identified from medicago lupulina-rhizobia symbiotic system under the different level of copper concentration to get symbiotic genes which can be used in phytoremediation. The research will provide the theoretical foundation for mechanism of legumes-rhizobia responding to Copper and reference to the subsequent study about ecological rehabilitation at Copper mine tailings.The main results are summarized as follows:1. The influence of heavy metal Copper on physiological and biochemical characteristics: the result shows that the Copper have inhibitory effect on the plant growth with the increase of Copper concentration;Under low copper concentration(≤50mg/kg)is advantageous to nodulation and nitrogen fixation, but they are inhibited under high copper concentration(≥100mg/kg).2. 42 genes which are related to symbiotic and the expression level is different obviously responding to Copper are selected. According to detect the expression level of 42 genes responding to diffrent Copper concentration, the result shows the 42 genes expression level are influenced in different degrees and the expression level are not consistent responding to different copper concentration3.10 target genes are selected to continue our research. The spatio-temporal expression analysis reveal that transcription of the genes about photosynthesis(except plastocyanin) and metabolism can be detected at early stage of nodulation; the defense genes play a very important role at the mid-late stage;the genes about plastocyanin have a high transcription at middle stage or all the stage of nodule development;the genes about the transcription factors are mainly expressed at entire time of nodulation or low expressed at middle stage of nodulation.When adding Copper, we find that the expression of 42 genes(except CU14068) are suppressed.4.The spatial expression of 10 genes show that 10 genes are expressed differently at roots,stems,leaves and nodule. At the same time we find that CU16249、CK18747、CU3361、CU11648 genes are specially expressed at nodule and root and indicate they are specific for nodulation.