| Title: | "Ubc2, an ortholog of the yeast Ste50p adaptor, possesses a basidiomycete-specific carboxy terminal extension essential for pathogenicity independent of pheromone response" |
| Author(s): | Klosterman SJ; Martinez-Espinoza AD; Andrews DL; Seay JR; Gold SE; |
| Address: | "Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA" |
| Journal Title: | Mol Plant Microbe Interact |
| ISSN/ISBN: | 0894-0282 (Print) 0894-0282 (Linking) |
| Abstract: | "Proteins involved in the mitogen-activated protein (MAP) kinase pathway controlling mating, morphogenesis, and pathogenicity have been identified previously in the fungus Ustilago maydis. One of these, the Ubc2 adaptor protein, possesses a basidiomycete-specific structure. In addition to containing sterile alpha motif (SAM) and ras association (RA) domains typical of Ste50-like adaptor proteins found in the fungal phylum Ascomycota, Ubc2 also contains two C-terminal SH3 domains. Yeast two-hybrid assays indicated that Ubc2 interacts with the MAP kinase-kinase kinase Ubc4 via the SAM domains at each of their respective N-termini. Site-directed mutagenesis of ubc2 and complementation analyses revealed that the SAM and RA domains of Ubc2 are essential for filamentous growth. These data support a role for the ascomycete-like N-terminus of Ubc2 in regulating pheromone-responsive mating and morphogenesis analogous to the role of Ste50p in Saccharomyces cerevisiae. In contrast, C-terminal deletion mutants were fully capable of filamentous growth and mating. However, surprisingly, these strains were nonpathogenic. Further, directed mutagenesis of the C-terminus revealed that both SH3 domains are required for pathogenicity. These results suggest that the Basidiomycota have retained the mating and morphogenetic functions of Ste50-type proteins in the N-terminal half of their Ubc2-type adaptors but, additionally, have integrated C-terminal SH3 domains that are critical for additional signal transduction mechanisms, including those that lead to pathogenesis" |
| Keywords: | "Adaptor Proteins, Signal Transducing/chemistry/metabolism Conserved Sequence Fungal Proteins/*chemistry/*metabolism Genes, Mating Type, Fungal Genetic Complementation Test MAP Kinase Kinase Kinases/metabolism Mitogen-Activated Protein Kinases/*chemistry/*;" |
| Notes: | "MedlineKlosterman, Steven J Martinez-Espinoza, Alfredo D Andrews, David L Seay, Jeffrey R Gold, Scott E eng Research Support, U.S. Gov't, Non-P.H.S. 2007/12/07 Mol Plant Microbe Interact. 2008 Jan; 21(1):110-21. doi: 10.1094/MPMI-21-1-0110" |
