The ubc2 gene of Ustilago maydis encodes a putative novel adaptor protein required for filamentous growth, pheromone response and virulence

• Published in: Molecular microbiology Vol. 41; no. 6; pp. 1365 - 1379
• Main Authors: Mayorga, María E., Gold, Scott E.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-09-2001; Blackwell Publishing Ltd
• Subjects: adaptor protein; Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Base Sequence; Cloning, Molecular; DNA Primers - genetics; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - physiology; Gene Deletion; Genes, Fungal; Genetic Complementation Test; Mitogen-Activated Protein Kinases - genetics; Molecular Sequence Data; Mutation, Missense; Phenotype; Pheromones - pharmacology; Plant Diseases - microbiology; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Temperature; ubc2 gene; Ustilago - genetics; Ustilago - growth & development; Ustilago - pathogenicity; Ustilago - physiology; Ustilago maydis; Virulence - genetics; Zea mays - microbiology
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1046/j.1365-2958.2001.02606.x

The Basidiomycete fungus Ustilago maydis causes corn smut disease and alternates between a budding haploid saprophyte and a filamentous dikaryotic pathogen. Previous work demonstrated that haploid adenylate cyclase (uac1) mutants display a constitutively filamentous phenotype. Suppressor mutants of a uac1 disruption strain, named ubc for Ustilagobypass of cyclase, no longer require cAMP for the budding morphology. The ubc2 gene was isolated by complementation and is required for filamentous growth. The deduced amino acid sequence encoded by ubc2 shows localized homology to Sterile Alpha Motif (SAM), Ras Association (RA) and Src homology 3 (SH3) protein–protein interaction domains. A K78E missense mutation within the SAM domain, revealed a genetic interaction between ubc2 and ubc4, a pheromone‐responsive MAP kinase kinase kinase. This indicates involvement of ubc2 in the pheromone‐responsive MAP kinase cascade and ubc2 is required for pheromone‐responsive morphogenesis. The ubc2 gene is a critical virulence factor. Thus, ubc2 encodes a putative novel adaptor protein that may act directly upstream of the pheromone‐responsive MAP kinase cascade in U. maydis.