Abstract
Peroxisomes are ubiquitous eukaryotic organelles that play critical roles in the infection processes of many plant pathogenic fungi. Peroxisome biogenesis depends on peroxins encoded by PEX genes. Pex8 is a fungus-specific peroxin present only in yeasts and filamentous fungi. In this study, we investigated the function of CoPEX8 in the cucumber anthracnose fungus Colletotrichum orbiculare using targeted gene deletion. Fluorescence microscopy using red fluorescent protein fused to peroxisomal targeting signal 1 (PTS1) showed that matrix protein import was abolished in the ΔCopex8 mutant. Compared with the wild-type strain, the ΔCopex8 mutant lacked detectable peroxisomes and exhibited severe defects in melanin production, fatty acid utilization, cell wall integrity, osmotic stress tolerance, and reactive oxygen species (ROS) scavenging. Deletion of CoPEX8 also reduced conidiation and impaired appressorium formation. Pathogenicity assays on cucumber leaves revealed that lesions produced by the ΔCopex8 mutant were significantly smaller than those caused by the wild-type strain. These results demonstrate that CoPEX8 is indispensable for peroxisome biogenesis and is essential for both development and virulence of C. orbiculare.