José Manuel Palacios, E. Giraud, L. Tighilt, Tomás Ruiz-Argüeso, B. F. S. De Sousa, Juan Imperial, Luis Rey, Farida Boulila, Ministerio de Ciencia, Innovación y Universidades (España), Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Ministry of Higher Education and Scientific Research (Algeria), Tighilt, L [0000-0002-9220-6959], Boulila, F [0000-0002-1968-7610], De Sousa, B F S [0000-0003-4125-6611], Giraud, E [0000-0002-4190-1732], Ruiz-Argüeso, T [0000-0001-9118-3065], Palacios, J M [0000-0002-2541-8812], Imperial, J [0000-0002-5002-6458], Rey, L [0000-0003-3477-6942], Tighilt, L, Boulila, F, De Sousa, B F S, Giraud, E, Ruiz-Argüeso, T, Palacios, J M, Imperial, J, and Rey, L
Centro de Biotecnología y Genómica de Plantas (CBGP), Many bacteria of the genus Bradyrhizobium are capable of inducing nodules in legumes. In this work, the importance of a type VI secretion system (T6SS) in a symbiotic strain of the genus Bradyrhizobium is described. T6SS of Bradyrhizobium sp. LmicA16 (A16) is necessary for efficient nodulation with Lupinus micranthus and Lupinus angustifolius. A mutant in the gene vgrG, coding for a component of the T6SS nanostructure, induced less nodules and smaller plants than the wild-type (wt) strain and was less competitive when co-inoculated with the wt strain. A16 T6SS genes are organized in a 26-kb DNA region in two divergent gene clusters of nine genes each. One of these genes codes for a protein (Tsb1) of unknown function but containing a methyltransferase domain. A tsb1 mutant showed an intermediate symbiotic phenotype regarding vgrG mutant and higher mucoidity than the wt strain in free-living conditions. T6SS promoter fusions to the lacZ reporter indicate expression in nodules but not in free-living cells grown in different media and conditions. The analysis of nodule structure revealed that the level of nodule colonization was significantly reduced in the mutants with respect to the wt strain., This research was funded by the Ministerio de Ciencia, Innovación y Universidades, Spain (RTI2018-094985-B-100). BFSS is supported by a scholarship from CNPq Conselho Nacional de Desenvolvimento Científico e Tecnológico-GDE-204842/2018–2. L.T. is supported by scholarships from the National Exceptional Program (PNE), Ministry of Higher Education and Scientific research of Algeria and from the Erasmus + Program project 2019–1-ES01-KA107-063778. EG is supported by the ANR grants “SymEffectors” and “ET-Nod” (ANR-16-CE20-0013 and ANR-20-CE20-0012, respectively)., 12 Pág.