The exceptionality of stress response in Magnaporthe oryzae: a set of “salt stress-induced” genes unique to the rice blast fungus

The ability of pathogens to signal perception and adaptation to environmental changes is an important prerequisite for successful colonization of the host organism. Filamentous phytopathogenic fungi, for example, have to cope with rapid changes in the environment during invasive growth in planta. Consequently, they have evolved a range of specific factors contributing to environmental adaptation facilitating host invasion. In addition to conserved pathways, including genes participating in stress response, unique/individual genes within the pathogens might represent determinants of pathogenicity. Therefore, identification of unique genes could provide a set of excellent candidates for novel and specific fungicide targets. One of the environmental changes during host invasion comprises the accumulation of osmolytes, which are present in varying concentrations inside the plant. Transcriptional profiling of the rice blast fungus Magnaporthe oryzae undergoing osmotic stress revealed interesting results. We identified a set of 239 genes which were regulated significantly by salt stress. Among these “salt stress-regulated” genes, 176 (75%) of the upregulated and all of the downregulated genes were found to have no homologues in yeast when interrogation against the yeast protein database was performed. Functional annotation analysis by InterProScan and clustering of genes based on gene ontology (GO) enrichment analysis was conducted to annotate each of the “salt stress-regulated” genes and to identify functional categories of biological processes associated with environmental stress response. Finally, we present a set of “salt stress-regulated” genes suggested as unique in the rice blast fungus.