title: Queuosine biosynthesis is required for sinorhizobium meliloti-induced cytoskeletal modifications on HeLa Cells and symbiosis with Medicago truncatula.
abstract: Rhizobia are symbiotic soil bacteria able to intracellularly colonize legume nodule cells and form nitrogen-fixing symbiosomes therein. How the plant cell cytoskeleton reorganizes in response to rhizobium colonization has remained poorly understood especially because of the lack of an in vitro infection assay. Here, we report on the use of the heterologous HeLa cell model to experimentally tackle this question. We observed that the model rhizobium Sinorhizobium meliloti, and other rhizobia as well, were able to trigger a major reorganization of actin cytoskeleton of cultured HeLa cells in vitro. Cell deformation was associated with an inhibition of the three major small RhoGTPases Cdc42, RhoA and Rac1. Bacterial entry, cytoskeleton rearrangements and modulation of RhoGTPase activity required an intact S. meliloti biosynthetic pathway for queuosine, a hypermodifed nucleoside regulating protein translation through tRNA, and possibly mRNA, modification. We showed that an intact bacterial queuosine biosynthetic pathway was also required for effective nitrogen-fixing symbiosis of S. meliloti with its host plant Medicago truncatula, thus indicating that one or several key symbiotic functions of S. meliloti are under queuosine control. We discuss whether the symbiotic defect of que mutants may originate, at least in part, from an altered capacity to modify plant cell actin cytoskeleton.
authors: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France.
authors: Marta
authors: M
authors: Marchetti
authors: Delphine
authors: D
authors: Capela
authors: Renaud
authors: R
authors: Poincloux
authors: Nacer
authors: N
authors: Benmeradi
authors: Marie-Christine
authors: MC
authors: Auriac
authors: Aurélie
authors: A
authors: Le Ru
authors: Isabelle
authors: I
authors: Maridonneau-Parini
authors: Jacques
authors: J
authors: Batut
authors: Catherine
authors: C
authors: Masson-Boivin
mesh_terms: D053898:Biosynthetic Pathways; D003599:Cytoskeleton / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D046913:Medicago truncatula / Q000382:microbiology*; D009154:Mutation; D009704:Nucleoside Q / Q000096:biosynthesis* / Q000235:genetics; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000378:metabolism*; D013559:Symbiosis; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D009704:Nucleoside Q; D020558:GTP Phosphohydrolases; D020741:rho GTP-Binding Proteins