NrcR, a new transcriptional regulator of rhizobium tropici ciat 899 involved in the legume root-nodule symbiosis
|Author||Cerro Sánchez, Pablo del
Rolla-Santos, Amanda Alves Paiva
Valderrama Fernández, Rocío
Gil Serrano, Antonio Miguel
Bellogín Izquierdo, Ramón Andrés
Gomes, Douglas Fabiano
Pérez Montaño, Francisco de Asís
Ollero Márquez, Francisco Javier
|Department||Universidad de Sevilla. Departamento de Microbiología
Universidad de Sevilla. Departamento de Química orgánica
|Published in||Plos One, 11 (4), e0154029-1-e0154029-19.|
|Abstract||The establishment of nitrogen-fixing rhizobium-legume symbioses requires a highly complex cascade of events. In this molecular dialogue the bacterial NodD transcriptional regulators in conjunction with plant inducers, ...
The establishment of nitrogen-fixing rhizobium-legume symbioses requires a highly complex cascade of events. In this molecular dialogue the bacterial NodD transcriptional regulators in conjunction with plant inducers, mostly flavonoids, are responsible for the biosynthesis and secretion of Nod factors which are key molecules for successful nodulation. Other transcriptional regulators related to the symbiotic process have been identified in rhizobial genomes, including negative regulators such as NolR. Rhizobium tropici CIAT 899 is an important symbiont of common bean (Phaseolus vulgaris L.), and its genome encompasses intriguing features such as five copies of nodD genes, as well as other possible transcriptional regulators including the NolR protein. Here we describe and characterize a new regulatory gene located in the non-symbiotic plasmid pRtrCIAT899c, that shows homology (46% identity) with the nolR gene located in the chromosome of CIAT 899. The mutation of this gene, named nrcR (nolR-like plasmid c Regulator), enhanced motility and exopolysaccharide production in comparison to the wild-type strain. Interestingly, the number and decoration of Nod Factors produced by this mutant were higher than those detected in the wildtype strain, especially under salinity stress. The nrcR mutant showed delayed nodulation and reduced competitiveness with P. vulgaris, and reduction in nodule number and shoot dry weight in both P. vulgaris and Leucaena leucocephala. Moreover, the mutant exhibited reduced capacity to induce the nodC gene in comparison to the wild-type CIAT 899. The finding of a new nod-gene regulator located in a non-symbiotic plasmid may reveal the existence of even more complex mechanisms of regulation of nodulation genes in R. tropici CIAT 899 that may be applicable to other rhizobial species.
|Cite||Cerro Sánchez, P.d., Rolla-Santos, A.A.P., Valderrama Fernández, R., Gil Serrano, A.M., Bellogín Izquierdo, R.A., Gomes, D.F.,...,Ollero Márquez, F.J. (2016). NrcR, a new transcriptional regulator of rhizobium tropici ciat 899 involved in the legume root-nodule symbiosis. Plos One, 11 (4), e0154029-1-e0154029-19.|