Role of MAPK Signaling Pathways in Regulating the Hydrophobin Cryparin in the Chestnut Blight Fungus .

We assessed the regulation of cryparin, a class II hydrophobin, using three representative mitogen-activated protein kinase (MAPK) pathways in . Mutation of the gene, an ortholog of yeast in the cell wall integrity (CWI) pathway, resulted in a dramatic decrease in cryparin production. Similarly, a mutant of the gene, a MAP kinase kinase kinase gene in the CWI pathway, showed decreased cryparin production. Additionally, mutation of the 1 gene, an ortholog of yeast , showed decreased cryparin production. However, mutation of the 2 gene, an ortholog of yeast Kss1/Fus3, showed increased cryparin production. The easy-wet phenotype and accumulation of the cryparin transcript in corresponding mutants were consistent with the cryparin production results. analysis of the promoter region of the cryparin gene revealed the presence of binding motifs related to downstream transcription factors of CWI, HOG1, and pheromone responsive pathways including MADS-box- and Ste12-binding domains. Real-time reverse transcriptase PCR analyses indicated that both , an ortholog of yeast in the CWI pathway, and , an ortholog of yeast in the mating pathway, showed significantly reduced transcription levels in the mutant strains showing lower cryparin production in . However, the transcription of , an ortholog of yeast , did not correlate with that of the mutant strains showing downregulation of cryparin. These results indicate that three representative MAPK pathways played a role in regulating cryparin production. However, regulation varied depending on the MAPK pathways: the CWI and HOG1 pathways were stimulatory, whereas the pheromone-responsive MAPK was repressive.