Nasser William, Reverchon Sylvie, Vedel Regine, Boccara Martine
Unité de Microbiologie et Génétique UMR CNRS-INSA-UCBL 5122 Domaine Scientifique de la Doua, Université Claude Bernard Lyon I Bâtiment A Lwoff, Villeurbanne, France.
Mol Plant Microbe Interact. 2005 Nov;18(11):1205-14. doi: 10.1094/MPMI-18-1205.
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.
菊欧文氏菌3937菌株是一种坏死型细菌性植物病原体。果胶分解酶，尤其是果胶酸裂解酶在软腐症状中起关键作用；然而，菊欧文氏菌在植物中的有效定殖还需要其他因素。这些因素包括HrpN（harpin），一种热稳定、富含甘氨酸的亲水性蛋白质，它由III型分泌系统分泌。我们研究了在各种环境条件和不同调控背景下菊欧文氏菌3937中hrpN的表达。使用lacZ融合技术，hrpN的表达受到碳源、渗透压、生长阶段和生长底物的显著影响。当果胶分解开始时，hrpN受到抑制，并受到果胶酸裂解酶合成阻遏物PecS和PecT的负调控。引物延伸数据和体外DNA-蛋白质相互作用实验支持了一个模型，即PecS通过与hrpN调控区域结合并抑制转录延伸来抑制hrpN的表达。结果表明PecS和PecT对HrpN和果胶酸裂解酶进行协同调控。本文提出了菊欧文氏菌在发病过程中这两种毒力因子合成的一个假定模型。
