title: Isolation and characterization of a Rhizobium loti gene required for effective nodulation of Lotus pedunculatus.
abstract: A Rhizobium loti gene required for effective invasion of the host Lotus pedunculatus has been identified by transposon Tn5 mutagenesis. Cosmids that complemented a previously isolated mutation (239) at this invasion (inv) locus were identified by in planta complementation and used to construct a physical map of the gene region. The insertion site of Tn5 in PN239 was mapped to a 7.5-kb EcoRI fragment, which complemented the mutation when subcloned into pLAFR1. Further Tn5 mutagenesis of the 7.5-kb fragment was carried out in Escherichia coli using bacteriophage lambda 467, and the mutations homogenotized into R. loti NZP2037. Three additional Fix- mutations were isolated, and these were found to map adjacent to the position of the original mutation in strain PN239. All the other Tn5 insertions isolated in the 7.5-kb fragment gave a Fix+ phenotype on L. pedunculatus. Electron microscopic examination of the L. pedunculatus nodules induced by the isolated Fix- mutants showed that bacteria were either blocked in release from the infection threads or were unable to undergo normal bacteroid development. The inv locus as defined by the Tn5 insertions was sequenced, and a single open-reading frame (ORF) of 576 bp, corresponding to a polypeptide of 21.3 kDa, was identified. The position and orientation of this ORF were consistent with those of the isolated Tn5 Fix- insertions.
authors.affiliation: Department of Microbiology and Genetics, Massey University, Palmerston North, New Zealand.
authors.forename: L J
authors.initials: LJ
authors.lastname: Ward
authors.forename: E S
authors.initials: ES
authors.lastname: Rockman
authors.forename: P
authors.initials: P
authors.lastname: Ball
authors.forename: B D
authors.initials: BD
authors.lastname: Jarvis
authors.forename: D B
authors.initials: DB
authors.lastname: Scott
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009586:Nitrogen Fixation / Q000235:genetics*; D018521:Plant Physiological Phenomena; D010944:Plants / Q000382:microbiology / Q000648:ultrastructure; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C075172:invasion protein, Rhizobium loti