title: Colonization of Phaseolus vulgaris nodules by Agrobacterium-like strains.
abstract: Non-nodulating Agrobacterium-like strains identified among root nodule isolates of common bean were labeled with gusA, a reporter gene encoding beta-glucuronidase (GUS). Bean plants were then co-inoculated with an infective Rhizobium strain and labeled transconjugants of Agrobacterium-like strains. Blue staining of nodules showed that Agrobacterium-like strains were able to colonize these symbiotic organs. Isolation and characterization by restriction fragment length polymorphism analysis of PCR-amplified 16S rRNA genes revealed a mixed population of Rhizobium and Agrobacterium-like strains in all nodules showing GUS activity. PCR amplification of the nifH gene and nodulation tests did not show any evidence of acquisition of symbiotic gene by lateral transfer from Rhizobium to Agrobacterium-like strains. Moreover, these strains were able to invade mature nodules. Based on sequencing of the 16S rRNA gene, one of these Agrobacterium-like strains showed 99.4% sequence similarity with Agrobacterium bv. 1 reference strains and 99% similarity with an Agrobacterium bv. 1 strain isolated from Acacia mollisima in Senegal. Agrobacterium tumefaciens C58 and the disarmed variant AT123 did not show any ability to colonize nodules. Co-inoculation of bean seeds with Agrobacterium and Rhizobium strains did not enhance nodulation and plant yield under controlled conditions.
authors.affiliation: Laboratoire des Interactions Legumineuses-Microorganismes, Institut National de Recherche Scientifique et Technique, Bp 95, 2050 Hammam-Lif, Tunisie. ridhamhamdi@yahoo.fr
authors.forename: Ridha
authors.initials: R
authors.lastname: Mhamdi
authors.forename: Moncef
authors.initials: M
authors.lastname: Mrabet
authors.forename: Gisèle
authors.initials: G
authors.lastname: Laguerre
authors.forename: Ravi
authors.initials: R
authors.lastname: Tiwari
authors.forename: Mohamed Elarbi
authors.initials: ME
authors.lastname: Aouani
mesh_terms: D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D010088:Oxidoreductases / Q000235:genetics; D027805:Phaseolus / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012231:Rhizobium / Q000145:classification* / Q000235:genetics / Q000254:growth & development*; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase; D005966:Glucuronidase