Analysis of secondary metabolites and genes related to the pathogenicity of the rice blast fungus Pyricularia oryzae

Abstract

Pyricularia oryzae causes rice blast disease and is one of the most significant plant pathogens worldwide. The rice blast fungus can produce a variety of phytotoxic secondary metabolites and has been found to be essential for host invasion. Two isolates, virulent isolate RBR55003 and non-virulent isolate CCO56003 were selected which based on their abilities to cause blast symptoms on rice leaves. Pyriculol and picolinic acid were detected in culture filtrate of both isolates during the exponential growth phase. Expression of genes involved in fungal pathogenicity and plant defense were analyzed. The expression of MoPks19 gene in isolate RBR55003 was higher than avirulent isolate CCO56003, indicating that MoPks19 may play a role in the pathogenesis of RBR55003. The expression of the OsWRKY30 gene that plays an important role in the regulation of a defense-related gene in rice was higher in CCO56003 inoculated than in RBR55003 inoculated rice sample, indicating the increased resistance of rice plants occurring in rice after non-virulent isolate infection, while the expression of the OsCPS4 gene involved in phytoalexin synthesis in rice was not different after isolate infections. Gene expression analysis revealed different responses according to plant-pathogen relationships.