Peroxisomes are present ubiquitously and make important contributions to cellular metabolism in eukaryotes. They play crucial roles in pathogenicity of plant fungal pathogens. The peroxisomal matrix proteins and peroxisomal membrane proteins (PMPs) are synthesized in the cytosol and imported post-translationally. Although the peroxisomal import machineries are generally conserved, some species-specific features were found in different types of organisms. In phytopathogenic fungi, the pathways of the matrix proteins have been elucidated, while the import machinery of PMPs remains obscure. Here, we report that MoPEX19, an ortholog of ScPEX19, was required for PMPs import and peroxisomal maintenance, and played crucial roles in metabolism and pathogenicity of the rice blast fungus Magnaporthe oryzae. MoPEX19 was expressed in a low level and Mopex19p was distributed in the cytoplasm and newly formed peroxisomes. MoPEX19 deletion led to mislocalization of peroxisomal membrane proteins (PMPs), as well peroxisomal matrix proteins. Peroxisomal structures were totally absent in Δmopex19 mutants and woronin bodies also vanished. Δmopex19 exhibited metabolic deficiency typical in peroxisomal disorders and also abnormality in glyoxylate cycle which was undetected in the known mopex mutants. The Δmopex19 mutants performed multiple disorders in fungal development and pathogenicity-related morphogenesis, and lost completely the pathogenicity on its hosts. These data demonstrate that MoPEX19 plays crucial roles in maintenance of peroxisomal and peroxisome-derived structures and makes more contributions to fungal development and pathogenicity than the known MoPEX genes in the rice blast fungus.

Peroxisomes participate in various important metabolisms and are required in pathogenicity of fungal plant pathogens. Peroxisomal matrix proteins are imported from cytoplasm into peroxisomes through peroxisomal targeting signal 1 (PTS1) or peroxisomal targeting signal 2 (PTS2) import pathway. PEX5 and PEX7 genes participate in the two pathways respectively. The involvement of PEX7 mediated PTS2 import pathway in fungal pathogenicity has been documented, while that of PTS1 remains unclear. Through null mutant analysis of MoPEX5, the PEX5 homolog in Magnaporthe oryzae, we report the crucial roles of PTS1 pathway in the development and host infection in the rice blast fungus, and compared with those of PTS2. We found that MoPEX5 disruption specifically blocked the PTS1 pathway. Δmopex5 was unable to use lipids as sole carbon source and lost pathogenicity completely. Similar as Δmopex7, Δmopex5 exhibited significant reduction in lipid utilization and mobilization, appressorial turgor genesis and H2O2 resistance. Additionally, Δmopex5 presented some distinct defects which were undetected in Δmopex7 in vegetative growth, conidial morphogenesis, appressorial morphogenesis and melanization. The results indicated that the PTS1 peroxisomal import pathway, in addition to PTS2, is required for fungal development and pathogenicity of the rice blast fungus, and also, as a main peroxisomal import pathway, played a more predominant role than PTS2.

Peroxisomes are ubiquitous organelles in eukaryotic cells that fulfil a variety of biochemical functions. The biogenesis of peroxisomes requires a variety of proteins, named peroxins, which are encoded by PEX genes. Pex14/17 is a putative recently identified peroxin, specifically present in filamentous fungal species. Its function in peroxisomal biogenesis is still obscure and its roles in fungal pathogenicity have not yet been documented. Here, we demonstrate the contributions of Pex14/17 in the rice blast fungus Magnaporthe oryzae (Mopex14/17) to peroxisomal biogenesis and fungal pathogenicity by targeting gene replacement strategies. Mopex14/17 has properties of both Pex14 and Pex17 with regard to its protein sequence. Mopex14/17 is distributed at the peroxisomal membrane and is essential for efficient peroxisomal targeting of proteins containing peroxisomal targeting signal 1. MoPEX19 deletion leads to the cytoplasmic distribution of Mopex14/17, indicating that the peroxisomal import of Pex14/17 is dependent on Pex19. The knockout mutants of MoPEX14/17 show reduced fatty acid utilization, reactive oxygen species (ROS) degradation and cell wall integrity. Moreover, Δmopex14/17 mutants show delayed conidial generation and appressorial formation, and a reduction in appressorial turgor accumulation and penetration ability in host plants. These defects result in a significant reduction in the virulence of the mutant. These data indicate that MoPEX14/17 plays a crucial role in peroxisome biogenesis and contributes to fungal development and pathogenicity.