Imazaki Iori, Kurahashi Makoto, Iida Yuichiro, Tsuge Takashi
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
Mol Microbiol. 2007 Feb;63(3):737-53. doi: 10.1111/j.1365-2958.2006.05554.x.
The filamentous fungus Fusarium oxysporum is a soil-borne parasite that causes vascular wilts in a wide variety of crops by directly penetrating roots and colonizing the vascular tissue. In previous work, we generated the non-pathogenic mutant B137 of the melon wilt pathogen F. oxysporum f. sp. melonis by using restriction enzyme-mediated integration (REMI) mutagenesis. Molecular characterization of B137 revealed that this mutant has a single-copy plasmid insertion in a gene, designated FOW2, which encodes a putative transcription regulator belonging to the Zn(II)2Cys6 family. The REMI mutant B137 and other FOW2-targeted mutants completely lost pathogenicity, but were not impaired in vegetative growth and conidiation in cultures. Microscopic observation of infection behaviours of green fluorescent protein (GFP)-marked wild-type and mutant strains revealed that the mutants were defective in their abilities to invade roots and colonize plant tissues. FOW2 is conserved in F. oxysporum pathogens that infect different plants. The FOW2-targeted mutants of the tomato wilt pathogen F. oxysporum f. sp. lycopersici also lost pathogenicity. Nuclear localization of Fow2 was verified using strains expressing Fow2-GFP and GFP-Fow2 fusion proteins. These data strongly suggest that FOW2 encodes a transcription regulator controlling the plant infection capability of F. oxysporum pathogens.
丝状真菌尖孢镰刀菌是一种土传寄生虫，通过直接穿透根部并定殖于维管组织，在多种作物中引起维管束萎蔫病。在之前的研究中，我们利用限制性内切酶介导整合（REMI）诱变技术，获得了甜瓜枯萎病病原菌尖孢镰刀菌甜瓜专化型的非致病突变体B137。对B137的分子特征分析表明，该突变体在一个名为FOW2的基因中有单拷贝质粒插入，该基因编码一种属于Zn(II)2Cys6家族的假定转录调节因子。REMI突变体B137和其他靶向FOW2的突变体完全丧失了致病性，但在培养物中的营养生长和分生孢子形成未受影响。对绿色荧光蛋白（GFP）标记的野生型和突变体菌株感染行为的显微镜观察表明，突变体在侵入根部和定殖于植物组织的能力方面存在缺陷。FOW2在感染不同植物的尖孢镰刀菌病原菌中是保守的。番茄枯萎病病原菌尖孢镰刀菌番茄专化型的靶向FOW2突变体也丧失了致病性。利用表达Fow2-GFP和GFP-Fow2融合蛋白的菌株验证了Fow2的核定位。这些数据强烈表明，FOW2编码一种控制尖孢镰刀菌病原菌植物感染能力的转录调节因子。
