NolR regulates diverse symbiotic signals of Sinorhizobium fredii HH103.
We have investigated in Sinorhizobium fredii HH103-1 (=HH103 Str(r)) the influence of the nolR gene on the production of three different bacterial symbiotic signals: Nod factors, signal responsive (SR) proteins, and exopolysaccharide (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.
Vinardell
José María
JM
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes 6, C.P. 41012, Sevilla, Spain. jvinar@us.es
Ollero
Francisco Javier
FJ
Hidalgo
Angeles
A
López-Baena
Francisco Javier
FJ
Medina
Carlos
C
Ivanov-Vangelov
Kalojan
K
Parada
Maribel
M
Madinabeitia
Nuria
N
Espuny
María del Rosario
Mdel R
Bellogín
Ramón Andrés
RA
Camacho
María
M
Rodríguez-Navarro
Dulce-Nombre
DN
Soria-Díaz
María Eugenia
ME
Gil-Serrano
Antonio M
AM
Ruiz-Sainz
José Enrique
JE
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D017124:Conserved Sequence; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008070:Lipopolysaccharides / Q000096:biosynthesis; D008969:Molecular Sequence Data; D009154:Mutation; D010944:Plants / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D012231:Rhizobium / Q000235:genetics; D015398:Signal Transduction; D042181:Sinorhizobium fredii / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D013559:Symbiosis
D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D011135:Polysaccharides, Bacterial; D012097:Repressor Proteins; C023023:lipid-linked oligosaccharides