Abstract To characterize the hormonal regulations in the transition between biotrophic and necrotrophic phases of Xanthomonas campestris pv. campestris (Xcc) infection, the endogenous phytohormone and reactive oxygen species (ROS) levels and glutathione (GSH) redox status of non-inoculated and Xcc-infected Brassica napus cv. Mosa leaves were measured at various points after inoculation. This time-course study revealed two distinct phases of the Xcc-infection, namely an early asymptomatic (biotrophic) phase that could be observed at 2 days post-inoculation (DPI) and a destructive necrotrophic phase that occurred at 7–24 DPI and was associated with V-shaped necrosis. The length of the V-shaped lesions increased significantly with the progression of infection, as did H2O2 accumulation and the expression of NADPH oxidase. Xcc-infections induced the gradual depression of the reduced/oxidized GSH/GSSG ratio with the progression of disease. Furthermore, Xcc inoculation reduced levels of salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), and cytokinin (CK) during the biotrophic phase (at 2 DPI); increased SA level (9.5 fold) and the expression of both SA synthesis-related genes (EDS1 and ICS1) and signaling-related genes (NPR1 and PR1) from the 2 to7 DPI. ABA and CK levels gradually increased during the necrotrophic phase. Interestingly, JA level was either reduced or not significantly affected during the necrotrophic phase of infection. Altogether, these results indicate that, in B. napus, changes in SA-mediated ROS production regulate the transition from the symptomless biotrophic phase of Xcc infection to the destructive necrotrophic phase.

中文翻译：

---

水杨酸信号在野油菜黄单胞菌生物营养-坏死性转变中的作用。油菜中油菜感染

摘要 表征油菜黄单胞菌 (Xanthomonas campestris pv.) 生物营养和坏死营养阶段之间的激素调节。油菜 (Xcc) 感染、内源性植物激素和活性氧 (ROS) 水平以及未接种和 Xcc 感染的甘蓝型油菜 cv. 的谷胱甘肽 (GSH) 氧化还原状态。接种后在不同点测量苔藓叶。该时间进程研究揭示了 Xcc 感染的两个不同阶段，即可以在接种后 2 天 (DPI) 观察到的早期无症状（生物营养）阶段和发生在 7-24 DPI 的破坏性坏死营养阶段，并且是与 V 形坏死有关。随着感染的进展，V形病变的长度显着增加，H2O2的积累和NADPH氧化酶的表达也是如此。随着疾病的进展，Xcc 感染诱导降低/氧化的 GSH/GSSG 比率逐渐降低。此外，在生物营养阶段（2 DPI），Xcc 接种降低了水杨酸 (SA)、茉莉酸 (JA)、脱落酸 (ABA) 和细胞分裂素 (CK) 的水平；从 2 到 7 DPI，SA 水平增加（9.5 倍）以及 SA 合成相关基因（EDS1 和 ICS1）和信号相关基因（NPR1 和 PR1）的表达。ABA 和 CK 水平在坏死营养阶段逐渐增加。有趣的是，在感染的坏死阶段，JA 水平要么降低，要么没有显着影响。总之，这些结果表明，在欧洲油菜中，SA 介导的 ROS 产生的变化调节了从 Xcc 感染的无症状生物营养阶段到破坏性坏死营养阶段的转变。