title: The RIM101/pacC homologue from the basidiomycete Ustilago maydis is functional in multiple pH-sensitive phenomena.
abstract: A homologue of the gene encoding the transcription factor Rim101 (PacC), involved in pH signal transduction in fungi, was identified in the pathogenic basidiomycete Ustilago maydis. The gene (RIM101) encodes a protein of 827 amino acid residues, which shows highest similarity to PacC proteins from Fusarium oxysporum and Aspergillus niger. The gene had the capacity to restore protease activity to rim101 mutants from Yarrowia lipolytica, confirming its homologous function, and was expressed at both acid and neutral pH. Null Deltarim101 mutants were not affected in the in vitro pH-induced dimorphic transition, their growth rate, resistance to hypertonic sorbitol or KCl stress, and pathogenicity. However, similar to pacC (rim101) mutants in other fungi, they displayed a pleiotropic phenotype with alterations in morphogenesis, impairment in protease secretion, and increased sensitivity to Na+ and Li+ ions. Other phenotypic characteristics not previously reported in fungal pacC (rim101) mutants (morphological changes, increased sensitivity to lytic enzymes, and augmented polysaccharide secretion) were also observed in U. maydis mutants. All these modifications were alleviated by transformation with the wild-type gene, confirming that all were the result of mutation in RIM101. These data indicate that the Pal/Rim pathway is functional in U. maydis (and probably in other basidiomycetes) and plays complex roles in pH-sensing phenomena, as occurs in ascomycetes and deuteromycetes.
authors.affiliation: Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del IPN Unidad Irapuato, Km. 9.6 Libramiento Norte, Carretera Irapuato-León, 36500 Irapuato, Gto., México.
authors.forename: Elva T
authors.initials: ET
authors.lastname: Aréchiga-Carvajal
authors.forename: José
authors.initials: J
authors.lastname: Ruiz-Herrera
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D014157:Transcription Factors; D014588:Ustilago / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity*; D014774:Virulence; D025062:Yarrowia / Q000235:genetics; D003313:Zea mays / Q000382:microbiology
chemical_list: D005656:Fungal Proteins; C092394:PacC protein, Aspergillus; D014157:Transcription Factors