Wageningen University Plant Sciences, Laboratory of Phytopathology, PO Box 8025, 6700 EE Wageningen, the Netherlands.
Mol Plant Pathol. 2002 Jul 1;3(4):227-38. doi: 10.1046/j.1364-3703.2002.00114.x.
Summary There is evidence that the necrotrophic fungal pathogen Botrytis cinerea is exposed to oxidative processes within plant tissues. The pathogen itself also generates active oxygen species and H(2)O(2) as pathogenicity factors. Our aim was to study how the pathogen may defend itself against cellular damage caused by the accumulation of H(2)O(2) and the role of an extracellular catalase in its detoxification during the infection of tomato and bean plants by B. cinerea. Chloronaphthol staining followed by light microscopy showed that H(2)O(2) accumulates in the infection zone in tomato and bean leaves. An extracellular catalase gene (denominated Bccat2) was cloned from B. cinerea. Exposure of mycelium to H(2)O(2) in liquid culture resulted in increased Bccat2 mRNA levels in a concentration-dependent manner. Bccat2 mRNA was detected at early stages of tomato leaf infection, suggesting that B. cinerea experiences oxidative stress. Bccat2-deficient mutants were generated by transformation-mediated gene disruption. Mutants were more sensitive then the wild-type strain to H(2)O(2)in vitro, but they partly compensated for the absence of BcCAT2 by activating other protective mechanisms in the presence of H(2)O(2). Bccat2-deficient mutants did not display a consistent reduction of virulence on bean and tomato leaves. Cerium chloride staining of infected leaf tissue for ultrastructural studies showed that Bccat2-deficient mutants were exposed to H(2)O(2) comparably to the wild-type. The results suggest that B. cinerea is a robust pathogen adapted to growing in hostile oxidizing environments in host tissues.
有证据表明，坏死真菌病原体 Botrytis cinerea 会在植物组织中暴露于氧化过程中。病原体本身也会产生活性氧物质和 H(2)O(2)作为致病性因素。我们的目的是研究病原体如何抵御由 H(2)O(2)积累引起的细胞损伤，以及在番茄和豆类植物被 B. cinerea 感染期间，细胞外过氧化氢酶在其解毒中的作用。氯萘酚染色后通过显微镜观察表明，H(2)O(2)在番茄和豆类叶片的感染区积累。从 B. cinerea 中克隆出一种细胞外过氧化氢酶基因（命名为 Bccat2）。在液体培养中，将菌丝体暴露于 H(2)O(2)中，导致 Bccat2 mRNA 水平以浓度依赖的方式增加。在番茄叶片感染的早期阶段检测到 Bccat2 mRNA，表明 B. cinerea 经历氧化应激。通过转化介导的基因敲除生成 Bccat2 缺陷突变体。与野生型菌株相比，突变体在体外对 H(2)O(2)更敏感，但在存在 H(2)O(2)的情况下，它们通过激活其他保护机制，部分弥补了 BcCAT2 的缺失。Bccat2 缺陷突变体在感染豆科和番茄叶片时并没有表现出一致的毒力降低。对感染叶片组织进行超微结构研究的氯化铈染色表明，Bccat2 缺陷突变体与野生型暴露于 H(2)O(2)的程度相当。结果表明，B. cinerea 是一种适应在宿主组织中恶劣氧化环境中生长的强健病原体。
