title: Characterization of Nops, nodulation outer proteins, secreted via the type III secretion system of NGR234.
abstract: The nitrogen-fixing symbiotic bacterium Rhizobium species NGR234 secretes, via a type III secretion system (TTSS), proteins called Nops (nodulation outer proteins). Abolition of TTSS-dependent protein secretion has either no effect or leads to a change in the number of nodules on selected plants. More dramatically, Nops impair nodule development on Crotalaria juncea roots, resulting in the formation of nonfixing pseudonodules. A double mutation of nopX and nopL, which code for two previously identified secreted proteins, leads to a phenotype on Pachyrhizus tuberosus differing from that of a mutant in which the TTSS is not functional. Use of antibodies and a modification of the purification protocol revealed that NGR234 secretes additional proteins in a TTSS-dependent manner. One of them was identified as NopA, a small 7-kDa protein. Single mutations in nopX and nopL were also generated to assess the involvement of each Nop in protein secretion and nodule formation. Mutation of nopX had little effect on NopL and NopA secretion but greatly affected the interaction of NGR234 with many plant hosts tested. NopL was not necessary for the secretion of any Nops but was required for efficient nodulation of some plant species. NopL may thus act as an effector protein whose recognition is dependent upon the hosts' genetic background.
authors.affiliation: Laboratoire de Biologie Moléculaire des Plantes Supérieures, University of Geneva, 1 chemin de l'Impératrice, CH1292 Chambésy-Geneva, Switzerland.
authors.forename: Corinne
authors.initials: C
authors.lastname: Marie
authors.forename: William J
authors.initials: WJ
authors.lastname: Deakin
authors.forename: Virginie
authors.initials: V
authors.lastname: Viprey
authors.forename: Joanna
authors.initials: J
authors.lastname: Kopciñska
authors.forename: Wladyslaw
authors.initials: W
authors.lastname: Golinowski
authors.forename: Hari B
authors.initials: HB
authors.lastname: Krishnan
authors.forename: Xavier
authors.initials: X
authors.lastname: Perret
authors.forename: William J
authors.initials: WJ
authors.lastname: Broughton
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D012231:Rhizobium / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers