Xanthomonas campestris pv. campestris (Xcc) bacterium is a seed-transmitted vascular pathogen causing black rot disease on cultivated and wild Brassicaceae. Xcc enters the plant tissues preferentially via hydathodes which are organs localized at leaf margins. In order to decipher both physiological and virulence strategies deployed by Xcc during early stages of infection, the transcriptomic profile of Xcc was analyzed three days after entry into cauliflower hydathodes. Despite the absence of visible plant tissue alterations and a bacterial biotrophic lifestyle, 18% of Xcc genes undergo a transcriptional reprogramming, including a striking repression of chemotaxis and motility functions. Xcc full repertoire of virulence factors was not yet activated but the expression of the 95-gene HrpG regulon, including genes coding for the type three secretion machinery important for suppression of plant immunity, was induced. The expression of genes involved in metabolic adaptations such as catabolism of plant compounds, transport functions, sulfur and phosphate metabolism was upregulated while limited stress responses were observed three days post infection. These transcriptomic observations give information about the nutritional and stress status of bacteria during the early biotrophic infection stages and help to decipher the adaptive strategy of Xcc to the hydathode environment.

中文翻译：

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花椰菜杂藻内的黄单胞菌转录组揭示了细菌感染力的策略和在感染初期的生理适应性

Xanthomonas campestris pv。campestris（Xcc）细菌是种子传播的血管病原体，在栽培的和野生的十字花科上引起黑腐病。Xcc优先通过hydrathodes进入植物组织，hydrathodes是位于叶缘的器官。为了破译Xcc在感染早期阶段所采用的生理和毒力策略，在进入花椰菜hydrathodes后三天对Xcc的转录组谱进行了分析。尽管没有可见的植物组织改变和细菌生物营养的生活方式，但仍有18％的Xcc基因经历了转录重编程，包括对趋化性和运动功能的显着抑制。Xcc完整的毒力因子库尚未激活，但95个基因的HrpG regulon的表达 诱导了包括编码对抑制植物免疫重要的三型分泌机制的基因。参与代谢适应的基因表达如植物化合物的分解代谢，转运功能，硫和磷酸盐代谢被上调，而感染后三天观察到有限的应激反应。这些转录组学观察结果提供了有关细菌在营养富营养化早期阶段的营养和应激状态的信息，并有助于破译Xcc对氢化物环境的适应性策略。硫和磷酸盐的代谢被上调，而感染后三天观察到有限的应激反应。这些转录组学观察结果提供了有关细菌在营养富营养化早期阶段的营养和应激状态的信息，并有助于破译Xcc对氢化物环境的适应性策略。硫和磷酸盐的代谢被上调，而感染后三天观察到有限的应激反应。这些转录组学观察结果提供了有关细菌在营养富营养化早期阶段的营养和应激状态的信息，并有助于破译Xcc对氢化物环境的适应性策略。