Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, Rosario, Argentina.
PLoS One. 2012;7(7):e40051. doi: 10.1371/journal.pone.0040051. Epub 2012 Jul 6.
Xanthomonas axonopodis pv. citri (Xac) is the phytopathogen responsible for citrus canker, one of the most devastating citrus diseases in the world. A broad range of pathogens is recognized by plants through so-called pathogen-associated molecular patterns (PAMPs), which are highly conserved fragments of pathogenic molecules. In plant pathogenic bacteria, lipopolisaccharyde (LPS) is considered a virulence factor and it is being recognized as a PAMP. The study of the participation of Xac LPS in citrus canker establishment could help to understand the molecular bases of this disease. In the present work we investigated the role of Xac LPS in bacterial virulence and in basal defense during the interaction with host and non host plants. We analyzed physiological features of Xac mutants in LPS biosynthesis genes (wzt and rfb303) and the effect of these mutations on the interaction with orange and tobacco plants. Xac mutants showed an increased sensitivity to external stresses and differences in bacterial motilities, in vivo and in vitro adhesion and biofilm formation. Changes in the expression levels of the LPS biosynthesis genes were observed in a medium that mimics the plant environment. Xacwzt exhibited reduced virulence in host plants compared to Xac wild-type and Xacrfb303. However, both mutant strains produced a lower increase in the expression levels of host plant defense-related genes respect to the parental strain. In addition, Xac LPS mutants were not able to generate HR during the incompatible interaction with tobacco plants. Our findings indicate that the structural modifications of Xac LPS impinge on other physiological attributes and lead to a reduction in bacterial virulence. On the other hand, Xac LPS has a role in the activation of basal defense in host and non host plants.
黄单胞菌属柑橘致病变种（Xac）是引起柑橘溃疡病的病原体，这是世界上最具破坏性的柑橘病害之一。植物通过所谓的病原体相关分子模式（PAMPs）识别出广泛的病原体，这些模式是致病分子的高度保守片段。在植物病原细菌中，脂多糖（LPS）被认为是一种毒力因子，并且被认为是一种 PAMP。研究 Xac LPS 在柑橘溃疡病建立过程中的参与作用有助于了解该疾病的分子基础。在本工作中，我们研究了 Xac LPS 在与宿主和非宿主植物相互作用过程中细菌毒力和基础防御中的作用。我们分析了 LPS 生物合成基因（wzt 和 rfb303）突变体的生理特征，以及这些突变对与橙子和烟草植物相互作用的影响。Xac 突变体对外部应激的敏感性增加，并且在体内和体外的运动性、粘附和生物膜形成方面存在差异。在模拟植物环境的培养基中观察到 LPS 生物合成基因表达水平的变化。与 Xac 野生型和 Xacrfb303 相比，Xacwzt 在宿主植物中的毒力降低。然而，与亲本菌株相比，两种突变株诱导宿主植物防御相关基因表达水平的增加都较低。此外，Xac LPS 突变体在与烟草植物的非亲和相互作用中无法引发 HR。我们的研究结果表明，Xac LPS 的结构修饰会影响其他生理特性，并导致细菌毒力降低。另一方面，Xac LPS 在宿主和非宿主植物中激活基础防御方面发挥作用。
