PFP1, a gene encoding an Epc-N domain-containing protein, is essential for pathogenicity of the barley pathogen Rhynchosporium commune.

Scald caused by Rhynchosporium commune is an important foliar disease of barley. Insertion mutagenesis of R. commune generated a nonpathogenic fungal mutant which carries the inserted plasmid in the upstream region of a gene named PFP1. 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 in R. commune with an essential role in the epigenetic control of fungal pathogenicity. Targeted PFP1 disruption also yielded nonpathogenic mutants which showed wild-type-like growth ex 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-level PFP1 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 of PFP1 expression.

Isolation of a novel barley cDNA encoding a nuclear protein involved in stress response and leaf senescence.

In order to isolate genes involved in the early acclimation of winter barley (Hordeum vulgare L. cv. Trixi) to a combined cold and light stress of 2 degrees C and 600 micromol m(-2) s(-1) restriction fragment differential display-polymerase chain reaction was performed. Impact of the cold-treatment on the leaves was characterized by measuring chlorophyll content and photosystem II efficiency. By this approach several cDNAs of genes that quickly and transiently up-regulated during early stages of the stress were identified. One of these genes (HvFP1) includes sequence motifs representing a heavy metal associated domain (HMA), nuclear localization signals (NLS) and a farnesylation motif. This gene is also induced at drought stress, during leaf senescence and after exposure to abscisic acid. Analysis of its spatial expression patterns in barley plants either grown at 21 or 2 degrees C showed that in contrast to the situation in leaves transcript level of this gene is high not only in cold-treated plants but also in controls kept at 21 degrees C in plant compartments enriched in meristematic tissues. The nuclear localization of the protein was confirmed by confocal laser scanning microscopy of epidermal onion cells after particle bombardment with chimeric HVFP1-GFP constructs. Using a construct with a modified farnesylation motif yielded a different pattern of nuclear distribution of the chimeric protein.