Molecular Plant-Microbe Interactions (Jun 2004)

NolR Regulates Diverse Symbiotic Signals of Sinorhizobium fredii HH103

  • JoséMaría Vinardell,
  • Francisco Javier Ollero,
  • Ángeles Hidalgo,
  • Francisco Javier López-Baena,
  • Carlos Medina,
  • Kalojan Ivanov-Vangelov,
  • Maribel Parada,
  • Nuria Madinabeitia,
  • María del Rosario Espuny,
  • Ramón Andrés Bellogín,
  • María Camacho,
  • Dulce-Nombre Rodríguez-Navarro,
  • María Eugenia Soria-Díaz,
  • Antonio M. Gil-Serrano,
  • José Enrique Ruiz-Sainz

DOI
https://doi.org/10.1094/MPMI.2004.17.6.676
Journal volume & issue
Vol. 17, no. 6
pp. 676 – 685

Abstract

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We have investigated in Sinorhizobium fredii HH103-1 (=HH103 Strr) the influence of the nolR gene on the production of three different bacterial symbiotic signals: Nod factors, signal responsive (SR) proteins, and exopolysac-charide (EPS). The presence of multiple copies of nolR (in plasmid pMUS675) repressed the transcription of all the flavonoid-inducible genes analyzed: nodA, nodD1, nolO, nolX, noeL, rhcJ, hesB, and y4pF. Inactivation of nolR (mutant SVQ517) or its overexpression (presence of pMUS675) altered the amount of Nod factors detected. Mutant SVQ517 produced Nod factors carrying N-methyl residues at the nonreducing N-acetyl-glucosamine, which never have been detected in S. fredii HH103. Plasmid pMUS675 increased the amounts of EPS produced by HH103-1 and SVQ517. The flavonoid genistein repressed EPS production of HH103-1 and SVQ517 but the presence of pMUS675 reduced this repression. The presence of plasmid pMUS675 clearly decreased the secretion of SR proteins. Inactivation, or overexpression, of nolR decreased the capacity of HH103 to nodulate Glycine max. However, HH103-1 and SVQ517 carrying plasmid pMUS675 showed enhanced nodulation capacity with Vigna unguiculata. The nolR gene was positively identified in all S. fredii strains investigated, S. xinjiangense CCBAU110, and S. saheli USDA4102. Apparently, S. teranga USDA4101 does not contain this gene.

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