127 Noble Research Center, Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
Mol Plant Pathol. 2007 Jan;8(1):83-92. doi: 10.1111/j.1364-3703.2006.00372.x.
SUMMARY The phytotoxin coronatine (COR) contributes to the virulence of Pseudomonas syringae pv. tomato (Pst) strain DC3000 on Arabidopsis thaliana and tomato. However, little is known regarding the role of COR in the virulence of DC3000 on cultivated Brassica spp. In this study, the role of COR and its precursors, coronafacic acid (CFA) and coronamic acid (CMA), were examined in the virulence of Pst DC3000 on collard and turnip, two important edible brassicas. Pst DC3000 and three well-defined COR(-) biosynthetic mutants of DC3000 exhibited substantial differences in the timing and phenotype of disease lesions on collard and turnip. When examined 3 days post-inoculation (dpi), collard inoculated with DC3000 exhibited visible anthocyanin production and lesions were chlorotic and water-soaked. On turnip, chlorotic and necrotic lesions were evident on DC3000-inoculated leaves 5 dpi. The bacterial population dynamics on plants inoculated with DC3000 and the COR(-) mutants indicated that COR was essential for DC3000 to maintain high populations in turnip, but not collard. Real-time quantitative PCR revealed that the jasmonic acid pathway responsive genes, LOX2 and CORI1, were expressed in both hosts inoculated with Pst DC3000. PR1, a marker associated with the salicylic acid pathway, was expressed in collard and turnip inoculated with the CFA(-) CMA(-) mutant DB29, but not DC3000. Further comparison of PR1 and LOX2 expression indicated that CFA plays a subtle role in modulating defence in turnip. This is the first study to investigate the role of COR in the interaction of Pst DC3000 and cultivated brassicas using genetically and biochemically defined COR(-) mutants.
植物毒素冠菌素（COR）有助于丁香假单胞菌 pv.番茄（Pst）菌株 DC3000 对拟南芥和番茄的毒力。然而，关于 COR 在 DC3000 对栽培芸薹属植物的毒力中的作用知之甚少。在这项研究中，研究了 COR 及其前体冠芳酸（CFA）和冠氨酸（CMA）在 Pst DC3000 对羽衣甘蓝和萝卜（两种重要的食用芸薹属植物）的毒力中的作用。Pst DC3000 和三个明确的 COR(-)生物合成突变体 DC3000 在羽衣甘蓝和萝卜上的发病症状的时间和表型上表现出显著差异。接种后 3 天（dpi）检查时，用 DC3000 接种的羽衣甘蓝表现出明显的花青素产生，病斑呈褪绿和水渍状。在萝卜上，接种 DC3000 的叶片在 5 dpi 时出现明显的黄化和坏死病斑。用 DC3000 和 COR(-)突变体接种的植物上的细菌种群动态表明，COR 对于 DC3000 在萝卜中维持高种群是必不可少的，但在羽衣甘蓝中则不是。实时定量 PCR 显示，茉莉酸途径响应基因 LOX2 和 CORI1 在接种 Pst DC3000 的两种宿主中均有表达。与水杨酸途径相关的标记物 PR1 在接种 CFA(-) CMA(-)突变体 DB29 的羽衣甘蓝和萝卜中表达，但在 DC3000 中则没有。进一步比较 PR1 和 LOX2 的表达表明，CFA 在调节萝卜防御中起着微妙的作用。这是首次使用遗传和生化定义的 COR(-)突变体研究 COR 在 Pst DC3000 与栽培芸薹属植物相互作用中的作用。
