The preprotein translocase YajC Mediates Biofilm Formation and Symbiotic nitrogen-fixation in Mesorhizobium huakuii

ABSTRACT: In bacteria, the auxiliary complex SecDF–YajC participates in the Sec system, facilitating post-translational translocation of pre-proteins across the membrane through the SecYEG channel. Although YajC homologs are strongly conserved in rhizobial strains and may play important roles in many processes, the functions and mechanisms by which they are involved in the interaction between rhizobia and host legumes are unknown. By constructing M. huakuii yajC mutant, we observed an increase in the strain growth rate but a reduction in both the biomass and average thickness of the biofilm in yajC gene mutant compared to the wild type. Deletion of yajC gene results in severe suppression of competitive ability in the plant rhizosphere, alongside a substantial reduction in root hair curling and infection thread initiation during the early infection stages. The yajC-deficient mutant formed more numerous but smaller root nodules, with a 77% decrease in nitrogen-fixing capacity. Scanning electron microscopy analysis revealed that yajC mutant bacteroids displayed alongside clear hallmarks of cellular deformation, dissociation, and premature senescence. From nodule bacteroid proteomic analysis, we further identified 210 differentially expressed proteins, including 32 transport-related proteins and 10 associated with nitrogen fixation. Altogether, our findings reveal the importance of YajC-mediated transport and biofilm formation in rhizobial infection and nodule development during M. huakuii-Astragalus sinicus symbiosis.

ORGANISM(S): Mesorhizobium Huakuii

SUBMITTER: Guojun Cheng  

PROVIDER: PXD084460 | iProX | Sat Sep 19 00:00:00 BST 2026

REPOSITORIES: iProX