An IQGAP-related protein, encoded by AgCYK1, is required for septation in the filamentous fungus Ashbya gossypii.
In filamentous ascomycetes hyphae are compartmentalized by septation in which the cytoplasm of the compartments are interconnected via septal pores. Thus, septation in filamentous fungi is different from cytokinesis in yeast like fungi. We have identified an Ashbya gossypii orthologue of the Saccharomyces cerevisiae CYK1 gene which belongs to the IQGAP-protein family. In contrast to S. cerevisiae disruption of AgCYK1 yields viable mutant strains that exhibit wildtype-like polarized hyphal growth rates. In the Agcyk1 mutant cortical actin patches localize to growing hyphal tips like wildtype, however, mutant hyphae are totally devoid of actin rings at presumptive septal sites. Septation in wildtype results in the formation of chitin rings. Agcyk1 mutant hyphae are aseptate and do not accumulate chitin in their cell walls. Agcyk1 mutant strains are completely asporogenous indicating that septation is essential for the formation of sporangia in A. gossypii. AgCyk1p-GFP localizes to sites of future septation as a ring prior to chitin depositioning. Furthermore, decrease in Cyk1p-ring diameter was found to be a prerequisite for the accumulation of chitin and septum formation.
Wendland
Jürgen
J
Department of Microbiology, Friedrich-Schiller University, Winzerlaer Str. 10, Jena, Germany. juergen.wendland@uni-jena.de
Philippsen
Peter
P
D000199:Actins / Q000502:physiology*; D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D002473:Cell Wall / Q000502:physiology; D002686:Chitin / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000502:physiology; D005656:Fungal Proteins / Q000502:physiology*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009154:Mutation; D016366:Open Reading Frames; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D020703:ras GTPase-Activating Proteins
D000199:Actins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; C101203:IQ motif containing GTPase activating protein 1; D008164:Luminescent Proteins; D008840:Microfilament Proteins; D011993:Recombinant Fusion Proteins; D020703:ras GTPase-Activating Proteins; D002686:Chitin; D049452:Green Fluorescent Proteins