Regine Vedel

Publications (2)8.86 Total impact

• Article: PecS and PecT coregulate the synthesis of HrpN and pectate lyases, two virulence determinants in Erwinia chrysanthemi 3937.

  William Nasser, Sylvie Reverchon, Regine Vedel, Martine Boccara
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  ABSTRACT: Erwinia chrysanthemi strain 3937 is a necrotrophic bacterial plant pathogen. Pectinolytic enzymes and, in particular, pectate lyases play a key role in soft rot symptoms; however, the efficient colonization of plants by E. chrysanthemi requires additional factors. These factors include HrpN (harpin), a heat-stable, glycine-rich hydrophilic protein, which is secreted by the type III secretion system. We investigated the expression of hrpN in E. chrysanthemi 3937 in various environmental conditions and different regulatory backgrounds. Using lacZ fusions, hrpN expression was markedly influenced by the carbon source, osmolarity, growth phase, and growth substrate. hrpN was repressed when pectinolysis started and negatively regulated by the repressors of pectate lyase synthesis, PecS and PecT. Primer extension data and in vitro DNA-protein interaction experiments support a model whereby PecS represses hrpN expression by binding to the hrpN regulatory region and inhibiting transcript elongation. The results suggest coordinated regulation of HrpN and pectate lyases by PecS and PecT. A putative model of the synthesis of these two virulence factors in E. chrysanthemi during pathogenesis is presented.
  Molecular Plant-Microbe Interactions 12/2005; 18(11):1205-14. · 4.43 Impact Factor
• Article: hrp genes of Erwinia chrysanthemi 3937 are important virulence factors.

  Ching-Hong Yang, Marina Gavilanes-Ruiz, Yasushi Okinaka, Regine Vedel, Isabelle Berthuy, Martine Boccara, Jason Wei-Ta Chen, Nicole T Perna, Noel T Keen
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  ABSTRACT: We developed improved virulence assays for Erwinia chrysanthemi 3937 on African violet varieties and devised a new method for the construction of precise bacterial gene knockouts. These methods were tested by constructing mutations in genes suspected to be involved with plant interactions. The virulence of the hrpG and hrcC mutant strains (both gene products presumed to be involved in protein secretion) was greatly reduced on leaves of semitolerant African violet varieties. An hrpN mutant strain produced delayed symptoms on African violet leaves and an hrpN delta pel (delta pel = five major pectate lyase genes deleted) double mutant was nonpathogenic. The hrcC and hrpG mutants did not produce a rapid hypersensitive response (HR) in tobacco, unlike the wild-type bacterium, and the hrpN mutant gave a reduced HR. The results, therefore, establish the importance of hrp genes in the virulence of E. chrysanthemi and their ability to elicit HR on nonhosts. The data also suggest that other effector proteins secreted by the Hrp system are required for full virulence and HR elicitation.
  Molecular Plant-Microbe Interactions 06/2002; 15(5):472-80. · 4.43 Impact Factor