NADPH Oxidases Are Required for Appressorium-Mediated Penetration in Colletotrichum scovillei-Pepper Fruit Pathosystem

초록

NADPH oxidase (Nox) complexes are known to play es-sential roles in differentiation and proliferation of many filamentous fungi. However, the functions of Noxs have not been elucidated in Colletotrichum species. There-fore, we set out to characterize the roles of Nox enzymes and their regulators in Colletotrichum scovillei, which causes serious anthracnose disease on pepper fruits in temperate and subtropical and temperate region. In this study, we generated targeted deletion mutants for CsNox1, CsNox2, CsNoxR, and CsNoxD via homolo-gous recombination. All deletion mutants were normal in mycelial growth, conidiation, conidial germination, and appressorium formation, suggesting that CsNox1, CsNox2, CsNoxR, and CsNoxD are not involved in those developmental processes. Notably, conidia of ACsnox2 and ACsnoxr, other than ACsnox1 and ACsnoxd, failed to cause anthracnose on intact pepper fruits. However, they still caused normal disease on wounded pepper fruits, suggesting that Csnox2 and CsnoxR are essential for penetration-related morphogenesis in C. scovillei. Further observation proved that ACsnox2 and ACsnoxr were unable to form penetration peg, while they fully developed appressoria, revealing that defect of anthracnose development by ACsnox2 and ACsnoxr resulted from failure in penetration peg formation. Our results suggest that CsNox2 and CsNoxR are critical for ap-pressorium-mediated penetration in C. scovillei-pepper fruit pathosystem, which provides insight into under-standing roles of Nox genes in anthracnose disease de-velopment.

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