PFP1 , a Gene Encoding an Epc-N Domain-Containing Protein, Is Essential for Pathogenicity of the Barley Pathogen Rhynchosporium commune

Scald caused byRhynchosporium commune is an important foliar disease of barley. Insertion mutagenesis ofR. commune generated a nonpathogenic fungal mutant which carries the inserted plasmid in the upstream region of a gene namedPFP1 . The characteristic feature of the gene product is an Epc-N domain. This motif is also found in homologous proteins shown to be components of histone acetyltransferase (HAT) complexes of fungi and animals. Therefore, PFP1 is suggested to be the subunit of a HAT complex inR. commune with an essential role in the epigenetic control of fungal pathogenicity. TargetedPFP1 disruption also yielded nonpathogenic mutants which showed wild-type-like growthex planta , except for the occurrence of hyphal swellings. Complementation of the deletion mutants with the wild-type gene reestablished pathogenicity and suppressed the hyphal swellings. However, despite wild-type-levelPFP1 expression, the complementation mutants did not reach wild-type-level virulence. This indicates that the function of the protein complex and, thus, fungal virulence are influenced by a position-affected long-range control ofPFP1 expression.