Soybean Receptor-Like Kinase GmRLK Mediated Bacteria-Plant Protein Interaction Module And Evaluation Of Symbiotic Nitrogen Fixation Efficiency

The early recognition process between leguminous plants and rhizobia is crucial for the initiation of the entire symbiotic nitrogen fixation process,and research on the early signal exchange of their symbiosis has been highly concerned.Previous research in Our laboratory found an interaction between the effector protein Nop P in the Mesorhizobium huakuii 7653 R and the receptor-like kinase NIP43 in Astragalus sinicus.Based on this result,our study transferred the research material to soybean plants,and the results obtained in this study are as follows:Firstly,we found a soybean receptor-like kinase homologous to NIP43,named Gm RLK,interacted directly with the Bradyrhizobium japonicum USDA6 effector protein Nop P.Through pot experiments,it was found that overexpressing Gm RLK significantly reduced nitrogen fixation activity in plants compared to the control.This indicates that Gm RLK is involved in the recognition process of soybean USDA6 effector protein Nop P,and this protein has a negative regulatory effect on the entire symbiotic process.Secondly,we found an interaction between the Nop P and Gm RLK effector proteins of Bradyrhizobium japonicum USDA6 in the interaction experiment.Through bioinformatics analysis,it was found that the Nop P in Bradyrhizobium is highly conserved.Subsequently,through pot experiments,it was found that there was a significant difference in nitrogen fixation activity between plants inoculated with USDA6 and USDA110.At the same time,it was found that the deletion of the nop P gene of the two types of rhizobia significantly reduced the nitrogen fixation activity of the symbionts,and this degree of reduction was more significant in USDA6.This indicates that the Nop P protein in Bradyrhizobium plays an important role in symbiotic recognition and matching of nodulation and nitrogen fixation efficiency.Thirdly,we found a soybean pathogenesis-related protein with strong interaction with Gm RLK through yeast hybridization,named Gm PRX-1.Through a series of interaction experiments,it was confirmed that there was a direct interaction between Gm PRX-1 and Gm RLK,and the key interaction regions were the PAN domain of Gm RLK and the 100 –154 amino acid segments of Gm PRX-1.Through pot experiments,it was found that overexpressing Gm PRX-1 had significantly larger root nodules and increased nitrogen fixation activity compared to the control,while the related phenotypes of interfering Gmprx-1 plants were completely opposite to the former.This indicates that Gm PRX-1 may participate in the symbiotic process between soybean and rhizobia by regulating the development of root nodule cells.This study reveals the molecular modules interconnected by "EffectorproteinReceptor-like kinases-Immune defense related proteins" through direct evidence,and for the first time reveals the positive regulatory role of plant innate immune defense related proteins in the symbiotic nodulation process between soybean and rhizobia,providing new directions and potential genetic resources for the breeding of high-efficiency nitrogen fixing soybean varieties.