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Projekt
The role of small GTPases for exocyst localization and regulation of polar growth in Ustilago maydis (P6)
Antragsteller
Professor Dr. Michael Bölker
Fachliche Zuordnung
Zell- und Entwicklungsbiologie der Pflanzen
Förderung
Förderung von 2010 bis 2019
Projektkennung
Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 140043741
Dimorphic switching is a characteristic aspect of many pathogenic fungi. During its life cycle, the phytopathogenic fungus Ustilago maydis undergoes a morphogenetic transition between budding and filamentous growth. This switch is controlled by the multiallelic b mating-type locus, which encodes a pair of homeodomain transcription factors, named bE and bW. While many genes have been identified that are regulated by this master control locus, the molecular mechanism by which the b mating-type genes induce filamentous growth is still unknown. We are studying the function of the Rho family GTP binding protein Rac1, which acts as molecular switch during filamentous growth. We discovered that b-induced filament formation involves stimulation of the activity of the Rac1-specific Rho-GEF Cdc24. Rho-GEF dependent recruitment of active Rac1 into a Bem1-scaffolded ternary complex triggers destruction of Cdc24 and thus constitutes a negative feedback loop. We will analyze the role of this autoregulation for establishment and maintenance of hyphal tip growth. Furthermore, the dynamic localization of active Rac1 during filament formation and the role of Rac1 recycling by the guanine nucleotide dissociation inhibitor Rdi1 will be studied. In addition, we will analyze whether Ras1, which interacts with Cdc24, stimulates the GEF activity of Cdc24 and thus may participate in dimorphic switching.
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