title: pH response transcription factor PacC controls salt stress tolerance and expression of the P-Type Na+ -ATPase Ena1 in Fusarium oxysporum.
abstract: Fungi possess efficient mechanisms of pH and ion homeostasis, allowing them to grow over a wide range of environmental conditions. In this study, we addressed the role of the pH response transcription factor PacC in salt tolerance of the vascular wilt pathogen Fusarium oxysporum. Loss-of-function pacC(+/-) mutants showed increased sensitivity to Li(+) and Na(+) and accumulated higher levels of these cations than the wild type. In contrast, strains expressing a dominant activating pacC(c) allele were more salt tolerant and had lower intracellular Li(+) and Na(+) concentrations. Although the kinetics of Li(+) influx were not altered by mutations in pacC, we found that Li(+) efflux at an alkaline, but not at an acidic, ambient pH was significantly reduced in pacC(+/-) loss-of-function mutants. To explore the presence of a PacC-dependent efflux mechanism in F. oxysporum, we cloned ena1 encoding an orthologue of the yeast P-type Na(+)-ATPase ENA1. Northern analysis revealed that efficient transcriptional activation of ena1 in F. oxysporum required the presence of high Na(+) concentrations and alkaline ambient pH and was dependent on PacC function. We propose a model in which PacC controls ion homeostasis in F. oxysporum at a high pH by activating expression of ena1 coordinately with a second Na(+)-responsive signaling pathway.
authors.affiliation: Departamento de Genética, Universidad de Córdoba, Córdoba, Spain.
authors.forename: Zaira
authors.initials: Z
authors.lastname: Caracuel
authors.forename: Carlos
authors.initials: C
authors.lastname: Casanova
authors.forename: M Isabel G
authors.initials: MI
authors.lastname: Roncero
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Pietro
authors.forename: José
authors.initials: J
authors.lastname: Ramos
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D027682:Cation Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D017124:Conserved Sequence; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008094:Lithium / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D027682:Cation Transport Proteins; D005656:Fungal Proteins; C092394:PacC protein, Aspergillus; D014157:Transcription Factors; D008094:Lithium; D012964:Sodium; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase