title: The pH signalling transcription factor PacC controls virulence in the plant pathogen Fusarium oxysporum.
abstract: Gene expression in fungi by ambient pH is regulated via a conserved signalling cascade whose terminal component is the zinc finger transcription factor PacC/Rim1p. We have identified a pacC orthologue in the vascular wilt pathogen Fusarium oxysporum that binds the consensus 5'-GCCAAG-3' sequence and is proteolytically processed in a similar way to PacC from Aspergillus nidulans. pacC transcript levels were elevated in F. oxysporum grown in alkaline conditions and almost undetectable at extreme acidic growth conditions. PacC+/- loss-of-function mutants displayed an acidity-mimicking phenotype resulting in poor growth at alkaline pH, increased acid protease activity and higher transcript levels of acid-expressed polygalacturonase genes. Reintroduction of a functional pacC copy into a pacC+/- mutant restored the wild-type phenotype. Conversely, F. oxysporum merodiploids carrying a dominant activating pacCc allele had increased pacC transcript and protein levels and displayed an alkalinity-mimicking phenotype with reduced acid phosphatase and increased alkaline protease activities. PacC+/- mutants were more virulent than the wild-type strain in root infection assays with tomato plants, whereas pacCc strains were significantly reduced in virulence. We propose that F. oxysporum PacC acts as a negative regulator of virulence to plants, possibly by preventing transcription of acid-expressed genes important for infection.
authors.affiliation: Departamento de Genética, Universidad de Córdoba, Campus Universitario de Rabanales Edif. C5, 14071 Córdoba, Spain.
authors.forename: Zaira
authors.initials: Z
authors.lastname: Caracuel
authors.forename: M Isabel G
authors.initials: MI
authors.lastname: Roncero
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Espeso
authors.forename: Clara I
authors.initials: CI
authors.lastname: González-Verdejo
authors.forename: Fe I
authors.initials: FI
authors.lastname: García-Maceira
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Pietro
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018551:Solanum lycopersicum / Q000378:metabolism / Q000382:microbiology; D008969:Molecular Sequence Data; D010641:Phenotype; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D016335:Zinc Fingers
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; C092394:PacC protein, Aspergillus; D014157:Transcription Factors; D037521:Virulence Factors