A novel role for catalase B in the maintenance of fungal cell-wall integrity during host invasion in the rice blast fungus Magnaporthe grisea.
A novel role for catalase B in the maintenance of fungal cell-wall integrity during host invasion in the rice blast fungus Magnaporthe grisea.
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DOI：
10.1094/mpmi-20-5-0568
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发表时间：
2007-04
期刊：
影响因子：
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通讯作者：
Pari Skamnioti;Catherine Henderson;Ziguo Zhang;Zena Robinson;S. Gurr
中科院分区：
文献类型：
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作者：
Pari Skamnioti;Catherine Henderson;Ziguo Zhang;Zena Robinson;S. Gurr
稻瘟病菌的无性孢子萌发产生一个特殊的黑化感染结构——附着胞，这是成功渗透植物的关键。为了研究稻瘟病菌是否会抵消H2O2的毒性爆发，我们检测了5个候选抗氧化基因的时间表达。其中，假设分泌的大亚基过氧化氢酶CATB基因在体内被上调600倍，与渗透一致，在体外被适度上调，以响应外源H2O2。靶向基因替换CATB导致病原菌适应度降低；catB突变体表现为色素沉着较淡，菌丝生长加快，但生物量较低，产孢较差，分生孢子和附着胞脆弱，黑化受损。catB突变体对大麦和水稻的致病性明显低于Guy 11， H2O2处理后其侵染力进一步降低。通过将CATB重新引入CATB突变体，恢复了野生型表型。我们没有发现证据支持CATB在渗透部位对宿主来源的H2O2解毒的作用。相反，我们证明了CATB在加强真菌壁方面发挥作用，这在强行进入宿主时起着特别重要的作用。
Asexual spores of the rice blast fungus germinate to produce a specialized and melanized infection structure, the appressorium, which is pivotal to successful plant penetration. To investigate whether Magnaporthe grisea counteracts the toxic burst of H2O2 localized beneath the site of attempted invasion, we examined the temporal expression of five candidate antioxidant genes. Of these, the putatively secreted large subunit catalase CATB gene was 600-fold up-regulated in vivo, coincident with penetration, and moderately up-regulated in vitro, in response to exogenous H2O2. Targeted gene replacement of CATB led to compromised pathogen fitness; the catB mutant displayed paler pigmentation and accelerated hyphal growth but lower biomass, poorer sporulation, fragile conidia and appressoria, and impaired melanization. The catB mutant was severely less pathogenic than Guy 11 on barley and rice, and its infectivity was further reduced on exposure to H2O2. The wild-type phenotype was restored by the reintroduction of CATB into the catB mutant We found no evidence to support a role for CATB in detoxification of the host-derived H2O2 at the site of penetration. Instead, we demonstrated that CATB plays a part in strengthening the fungal wall, a role of particular importance during forceful entry into the host.