From function to shape - the role of a Formin in tip-branching and hyphal formation in Ashbya gossypii.
Andreas Kaufmann, Michael Koehli, Pierre Philippe Laissue, Peter Philippsen, Hans-Peter Schmitz
Applied Microbiology, Biozentrum University of Basel, Klingelbergstrasse 5, Basel, 4056, Switzerland
Evolutionary sequence comparison suggests that filamentous growth was the ancestral growth form of the phyllum ascomycetes (Liu and Hall PNAS March 30, 2004 vol. 101 no. 13 4507-4512). Using the filamentous ascomycete Ashbya gossypii which is a close relative of Saccharomyces cerevisiae we show that actin based vesicle transport is absolutely essential for filamentous growth. This process is regulated by a Formin homology protein homologous to Bni1p and by Rho-type GTPases as we proof by deletion analysis, 2-hybrid data, site-directed mutagenesis and localization of GFP-fusions. We found that these factors are also involved in the process of tip-branching, a unique characteristic of some filamentous growing cells and not present in Saccharomyces cerevisiae. During tip-branching a new site of polarity is not established but an existing axis of polarity splits into two new axes and polar growth continues.
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