Abstract
GTPases of the Rho family are important molecular switches that regulate many basic cellular processes. The function of the Rho2 and Rho5 proteins from Saccharomyces cerevisiae and of their homologs in other species is poorly understood. Here, we report on the analysis of the AgRho2 and AgRho5 proteins of the filamentous fungus Ashbya gossypii. In contrast to S. cerevisiae mutants of both encoding genes displayed a strong morphological phenotype. The Agrho2 mutants showed defects in tip-branching, while Agrho5 mutants had a significantly decreased growth rate and failed to maintain their growth axis. In addition, the Agrho5 mutants had highly defective actin rings at septation sites. We also found that a deletion mutant of a putative GDP-GTP-exchange factor (GEF) that was homologous to a Rac-GEF from other species phenocopied the Agrho5 mutant, suggesting that both proteins act in the same pathway, but the AgRho5 protein has acquired functions that are fulfilled by Rac-proteins in other species.
Highlights
The family of small GTP-binding proteins of the Rho-type is composed of important regulators of the actin cytoskeleton in most eukaryotic organisms
Wild-type A. gossypii typically switches from a lateral branching pattern to a tip-branching pattern, which is the dichotomous division of one growing hyphae into two new hypha, at a growth speed above 80 mm/h [33]
We performed an analysis of two uncharacterized Rho-type GTPases of the filamentous fungus A. gossypii
Summary
The family of small GTP-binding proteins of the Rho-type is composed of important regulators of the actin cytoskeleton in most eukaryotic organisms. A recent survey that is based on datasets containing many complete genome sequences suggests that generally six groups of paralogs exist in fungi [1]. While some fungi contain additional Rho paralogs that seem to have been acquired by horizontal gene transfer (e.g. Aspergillus fumigatus and Neurospora crassa), some species within the above named groups carry additional copies which most probably stem from duplication events. This is, for example, the case for Rho in Ashbya gossypii (see below) and Schizzosaccharomyces pombe [1]. Within the currently available fungal genome datasets, Schizzosaccharomyces pombe seems to be the only fungal model organism that does not possess a Rac-homolog [1]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
