THE TIGHT-ADHESION PROTEIN TadG OF BRADYRHIZOBIUM JAPONICUM IS INVOLVED IN ADHESION AND INFECTIVITY ON SOYBEAN ROOTS

ANÍBAL R. LODEIRO; ELÍAS J. MONGIARDINI; GUSTAVO PARISI; JULIETA PÉREZ GIMÉNEZ

Perth

Congreso; Rhizosphere 3 International Conference; 2011

RHIZOSPHERE 3 International Steering Committee-University of Western Australia

Aims and Background Adhesion of Bradyrhizobium japonicum to soybean roots is required for rhizosphere colonization and root infection, and is mediated by bacterial adhesins. Among them are Tad (tight adhesion) proteins, which were studied in other bacteria but not in rhizobia. We addressed a bioinformatic and molecular study of tadG in B. japonicum USDA 110.  Methods  Evolutionary analysis was done with PHYLIP. Three-dimensional models were constructed with SOPMA, PredictProtein, JUFO, MODELLER, and ITASSER. tadG was deleted in USDA 110 by replacement with a kanamycin-resistance cassette. Adhesion and infectivity were studied as described (1).  Results  The ORF blr3941 encodes TadG, which is implicated in the processing and transporting of Flp pili. TadG has N-terminal and C-terminal domains separated by a 15-aminoacid transmembrane region. The C-terminal domain is homologous to integrin α1β1 family, and contains a von Willebrand fold, which is related with cell adhesion and recognition. B. japonicum USDA 110 and the blr3941 deletion mutant adhered to roots in clusters of 4-7 cells but adhesion of mutant was 50% lower. Accordingly, mutant infectivity diminished by 67%.  Conclusion  The ORF blr3941 encodes TadG, which is involved in B. japonicum adhesion and infectivity on soybean roots.  References  1. Mongiardini E.J. et al. (2008) FEMS Microbiol Ecol 65:279-88.