| Bacterial terminal differentiation is a process of co evolution between plants and rhizobia,induced by the NCR of the host root nodule,and this process requires the participation of BacA protein from rhizobia.BacA protein is an ABC transporter protein involved in the transport of NCR peptides,and can protect plants from NCR damage.In the early stage of our laboratory,we obtained the interaction between BacA protein and Typ A protein of rhizobia through bacterial double hybridization experiments.It is speculated that Typ A protein may be related to bacterial differentiation.In this paper,we mainly studied the effect of typA gene on symbiotic nitrogen fixation of soybean by taking the Chinese rhizobium fredii HH103 typA gene as the rescarch object.The research results are as follows:1.The results of growth curve showed that the deletion of typA gene would lead to the prolongation of the delay period,and there was no significant difference in the later period,and there was no significant effect on the spontaneous growth of rhizobium HH103;The results of stress resistance test showed that the mutant strain added 3mol/L HCI,Na Cl O and 10% SDS had a larger zone of inhibition,and the deletion of typA gene would reduce the stress resistance of HH103.The symbiotic phenotype results showed that the mutant had or strengthened or weakened the symbiotic nitrogen fixation ability,which was related to the symbiotic matching of soybean.2.The experimental results of real-time fluorescence quantitative detection show that the expression of typA gene was relatively high in the early stage of symbiosis,and the delction of typA gene would reduce the expression of sbm A gene.Typ A and Sbm A could interact in the symbiosis stage of soybean and HH103.The results of bacterial double hybridization showed that there was interaction betwecn the full length of Typ A and the full length of Sbm A under the condition of autogenesis of HH103.There was interaction betwecn the full length of Typ A and the truncated proteins S2 and S3 of Sbm A.There was also interaction between the 7653 R Typ A protein and the Sbm A protein of HH103.Under the conditions of autogenesis and symbiosis,there is interaction between Typ A and Sbm A proteins.Sbm A(BacA)protein is necessary for the terminal differentiation of IRLC leguminous plants,and can resist the injury of NCR peptides secreted by plants;The non-IRLC leguminous plant soybean does not secrete NCR or secretes less.It is worth studying whether the Sbm A protein of rhizobia HH103 has an effect on the bacteroid differentiation of soybean symbiotic nitrogen fixation.3.The results of flow cytomctry showed that NCR067 could enhance the proliferation of rhizobia and increase the proportion of diploid,but the optimal proliferation concentration of different strains of rhizobia was different;The deletion of typA gene will strengthen the proliferation ability of rhizobia,but the deletion of bac A gene has no significant effect.The plate results showed that the induced expression of NCR083 would significantly reduce the number of colonies and increasc the diametcr of colonies;The deletion of typA gene made the number of colonies of HH103 inducible strain smaller and the diameter of colonies larger,while the result of 7653 R inducible strain was opposite.The results of biofilm detection of inducible strains showed that NCR083 could promote the increase of biofilm area,and the deletion of typA gene led to a significant increase of biofilm area of HH103 inducible strains,which was contrary to the results of 7653 R inducible strains.The typA genes of HH103,7653 R and 1021 all participate in the NCR responsc. |
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