Identification and characterization of the peroxin 1 gene MoPEX1 required for infection-related morphogenesis and pathogenicity in Magnaporthe oryzae

Peroxisomes are required for pathogenicity in many phytopathogenic fungi, but the relationships between fungal pathogenicity and peroxisomal function are not fully understood. Here, we report the identification of a T-DNA insertional mutant C445 of Magnaporthe oryzae, which is defective in pathogenicity. Analysis of the mutation confirmed an insertion into the gene MoPEX1, which encodes a putative homologue to peroxin 1. Targeted gene deletion mutants of MoPEX1 were nonpathogenic and were impaired in vegetative growth, conidiation, and appressorium formation. ΔMopex1 mutants formed abnormal, less pigmented, and nonfunctional appressoria, but they were unable to penetrate plant cuticle. The ΔMopex1 mutants were defective in the utilization of fatty acids (e.g., olive oil and Tween-20). Moreover, deletion of MoPEX1 significantly impaired the mobilization and degradation of lipid droplets during appressorium development. Interestingly, deletion of MoPEX1 blocked the import of peroxisomal matrix proteins. Analysis of an M. oryzae strain expressing GFP-MoPEX1 and RFP-PTS1 fusions revealed that MoPex1 localizes to peroxisomes. Yeast two hybrid experiments showed that MoPex1 physically interacts with MoPex6, a peroxisomal matrix protein important for fungal morphogenesis and pathogenicity. Taken together, we conclude that MoPEX1 plays important roles in peroxisomal function and is required for infection-related morphogenesis and pathogenicity in M. oryzae.