The Absence of the N-acyl-homoserine-lactone Autoinducer Synthase Genes traI and ngrI Increases the Copy Number of the Symbiotic Plasmid in Sinorhizobium fredii NGR234

• Published in: Frontiers in microbiology Vol. 7; p. 1858
• Main Authors: Grote, Jessica, Krysciak, Dagmar, Petersen, Katrin, Güllert, Simon, Schmeisser, Christel, Förstner, Konrad U, Krishnan, Hari B, Schwalbe, Harald, Kubatova, Nina, Streit, Wolfgang R
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 18-11-2016
• Subjects: Microbiology; Plant Symbioses; Plasmid copy number; quorum sensing (QS); RNA sequencing (RNA-Seq); Sinorhizobium fredii; plant symbioses; Sinorhizobium fredii; quorum sensing (QS); RNA sequencing (RNA-Seq); plasmid copy number
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2016.01858

Plant-released flavonoids induce the transcription of symbiotic genes in rhizobia and one of the first bacterial responses is the synthesis of so called Nod factors. They are responsible for the initial root hair curling during onset of root nodule development. This signal exchange is believed to be essential for initiating the plant symbiosis with rhizobia affiliated with the
. Here, we provide evidence that in the broad host range strain
NGR234 the complete lack of quorum sensing molecules results in an elevated copy number of its symbiotic plasmid (pNGR234
). This in turn triggers the expression of symbiotic genes and the production of Nod factors in the absence of plant signals. Therefore, increasing the copy number of specific plasmids could be a widespread mechanism of specialized bacterial populations to bridge gaps in signaling cascades.