prhJ and hrpG, two new components of the plant signal‐dependent regulatory cascade controlled by PrhA in Ralstonia solanacearum

Brito, Belén; Marenda, Marc S.; Barberis, Patrick; Boucher, Christian; Genin, Stéphane

doi:10.1046/j.1365-2958.1999.01165.x

Cited by 100 publications

(119 citation statements)

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“…hrpG is activated by plant cell contact through the PrhARIJ cascade (Aldon et al, 2000). In addition, HrpGcontrolled functions can also be activated via HrpG post-transcriptional modification, as well as via activation of hrpB transcription by an unidentified environmental metabolic signal(s) perceived in minimal culture medium (Genin et al, 1992;Brito et al, 1999;Plener et al, 2010). Beside HrpG, the sensor histidine kinase VsrA controls many other virulence functions (Schell et al, 1994;Huang et al, 1995;Schneider et al, 2009;Meng et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…Intracellular infection was restored by adding a T3SS À mutation, indicating that the T3SS blocks intracellular infection, in addition to nodulation (Marchetti et al, 2010). T3SS reactivation within ITs in prhI and p 112 hrpG mutants is likely due to both the post-transcriptional activation of HrpG (Brito et al, 1999) and the transcriptional activation of hrpB (Genin et al, 1992;Plener et al, 2010) by a metabolic signal present in the IT apoplastic fluid (Figure 3a). Rhizobia were shown to use T3SS to promote or impair symbiosis upon secretion of type three effectors that often have homologs in pathogenic bacteria (Deakin and Broughton, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…By contrast, we observed a strong impact of the mutations on nodulation itself. The prhI and p 112 hrpG mutations were indeed found to greatly improve the nodulation kinetics of a chimeric Ralstonia bearing a T3SS À (hrcV or hrcS) mutation allowing the induction of 4-5 times more nodules at 21 days post inoculation (dpi) (Genin et al, 1992;Brito et al, 1999;Plener et al, 2010) likely occurs in the IT apoplastic medium. No link between the sensor histidine kinase VsrA and HrpG has been evidenced so far.…”

Section: Adaptive Mutations Involved In Intracellular Infection Acquimentioning

confidence: 99%

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Experimental evolution of nodule intracellular infection in legume symbionts

et al. 2013

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Soil bacteria known as rhizobia are able to establish an endosymbiosis with legumes that takes place in neoformed nodules in which intracellularly hosted bacteria fix nitrogen. Intracellular accommodation that facilitates nutrient exchange between the two partners and protects bacteria from plant defense reactions has been a major evolutionary step towards mutualism. Yet the forces that drove the selection of the late event of intracellular infection during rhizobium evolution are unknown. To address this question, we took advantage of the previous conversion of the plant pathogen Ralstonia solanacearum into a legume-nodulating bacterium that infected nodules only extracellularly. We experimentally evolved this draft rhizobium into intracellular endosymbionts using serial cycles of legume-bacterium cocultures. The three derived lineages rapidly gained intracellular infection capacity, revealing that the legume is a highly selective environment for the evolution of this trait. From genome resequencing, we identified in each lineage a mutation responsible for the extracellular-intracellular transition. All three mutations target virulence regulators, strongly suggesting that several virulence-associated functions interfere with intracellular infection. We provide evidence that the adaptive mutations were selected for their positive effect on nodulation. Moreover, we showed that inactivation of the type three secretion system of R. solanacearum that initially allowed the ancestral draft rhizobium to nodulate, was also required to permit intracellular infection, suggesting a similar checkpoint for bacterial invasion at the early nodulation/root infection and late nodule cell entry levels. We discuss our findings with respect to the spread and maintenance of intracellular infection in rhizobial lineages during evolutionary times.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Adaptive Mutations Involved In Intracellular Infection Acquimentioning

confidence: 99%

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Experimental evolution of nodule intracellular infection in legume symbionts

et al. 2013

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“…The signals are transferred to hrpB expression via the signal cascade PrhA-PrhR/PrhI-PrhJ-HrpG (Aldon et al 2000;Brito et al 1999Brito et al & 2002. By co-cultivating OE1-1 carrying the lacZ reporter gene with Arabidopsis thaliana in liquid medium, we were able to investigate the regulation of pathogenicity gene expression, including hrp genes, at early stages of the infection process of OE1-1.…”

Section: Global Regulation Of Genes In the Hrp Regulon At Early Stagementioning

confidence: 99%

“…cascade integrated by PrhJ, HrpG, and HrpB regulators (Aldon et al 2000;Brito et al 1999Brito et al & 2002.…”

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confidence: 99%