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Guanyl nucleotide exchange factor Sql2 and Ras2 regulate filamentous growth in Ustilago maydis
Philip Müller1, Jörg D Katzenberger, Gabriel Loubradou
1Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany.
Eukaryotic Cell
|June 11, 2003
Summary
Sql2, a novel protein, regulates fungal development in Ustilago maydis by activating Ras2. This finding is crucial for understanding pathogenic development and cell morphology in this plant pathogen.
Area of Science:
- Mycology
- Molecular Biology
- Plant Pathology
Background:
- The cyclic AMP (cAMP) pathway is vital for cell morphology and pathogenesis in Ustilago maydis.
- Disruptions in the cAMP pathway, affecting Gpa3 or Uac1, lead to nonpathogenic filamentous growth or altered colony phenotypes.
Purpose of the Study:
- Identify suppressors of the glossy colony phenotype in Ustilago maydis.
- Investigate the role of the identified suppressor, sql2, in signaling pathways and pathogenic development.
Main Methods:
- Genetic screening to identify suppressor mutations.
- Gene cloning and characterization of sql2.
- Analysis of Ras protein function through dominant-active alleles.
- Phenotypic analysis of mutant strains (growth, morphology, pathogenesis).
Main Results:
- Sql2 was identified as a suppressor of the glossy colony phenotype.
- Sql2 overexpression induces filamentous growth, independent of exogenous cAMP.
- Ras2 activation leads to filamentous growth, while Ras1 affects pheromone expression.
- Sql2 appears to activate Ras2, playing a specific role in pathogenesis.
Conclusions:
- Sql2 acts downstream of the cAMP pathway, likely as an activator of the Ras2 protein.
- Ras1 and Ras2 have distinct functions in Ustilago maydis.
- Sql2 is specifically involved in the pathogenic development of Ustilago maydis.