Study On The Melocular Mechanism Of Bacterioid Differentiation Mediated By Molecular Chaperones Protein HtpG Of Mesorhizobium Huakuii

The previous research in our laboratory showed the lipid transporter of astragalus sinicus AsE246 played an important role in the lipid transport of root nodules.The HtpG proteins of Mesorhizobium Huakuii and AsDJL1 proteins of astragalus sinicus could also interact with AsE246.In addition,the gene mutation lead to abnormal bacteroids differentiation and the lipid abundance in root nodules,also lead to abnormal nitrogen fixation function.How does HtpG enter plant cells as a molecularchaperones protein? How does it affect lipid transport and bacteroids differentiation? For these problems,we assume that: the molecular chaperones protein HtpG may enter plant cells through the outer membrane vesicles(OMVs),and regulate lipid transport and bacteroids differentiation in root nodules by forming complexes with AsE246 and AsDJL1 proteins.The main results of this work were as follows.(1)Proteomic analysis was conducted on the 7653 R OMVs extracted from Mesorhizobium Huakuii under free living and simulated symbiosis conditions under different temperature inducing.HtpG proteins were identified both in proteomic from free living and simulated symbiosis conditions,and there was a significant content difference in two proteomic Therefore,HtpG may play a role in symbiotic process;(2)By lipid binding experiments,it was confirmed that the HtpG protein can promote the lipid binding activity of AsE246.It proves that the acting mechanism of HtpG is to enter plant cells through the OMVs pathway,and then interact with AsE246 protein to promote lipid transporting from plant cell to the symbiotic membrane,thereby promoting bacterial differentiation and root nodule development.By lipid binding experiments,the AsDJL1 protein was found that it can also enhance the lipid transport effect of AsE246.Therefore,we can speculated that: the three proteins,HtpG,AsDJL1,and AsE246,may form an interactive complex to enhance the lipid transport of AsE246 and promote the bacteroids differentiation.(3)The GST pull down demonstrated that: AsE246,HtpG,and AsDJL1 can form interactive complexes in vitro,but the yeast three hybrid experiment have not detected the interaction of AsE246,HtpG,and AsDJL1.Above results indicate that: during the symbiotic process,the HtpG protein may enters plant cells through the OMVs pathway and promotes lipid transport to the symbiosis membrane by interaction with the AsE246,and than promoting bacteroids differentiation and nodule development.These results will give some data to progress of the molecular mechanism of symbiotic interaction between rhizobia and leguminous,and also give some help for further research of rhizobia OMVs in the symbiotic process between rhizobia and host plants.