Regulation of hyphal morphogenesis by cdc42 and rac1 homologues in Aspergillus nidulans

The ability of filamentous fungi to form hyphae requires the establishment and maintenance of a stable polarity axis. Based on studies in yeasts and animals, the GTPases Cdc42 and Rac1 are presumed to play a central role in organizing the morphogenetic machinery to enable axis formation and stabiliz...

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Bibliographic Details
Published in:Molecular microbiology 2007-12, Vol.66 (6), p.1579-1596
Main Authors: Virag, Aleksandra, Lee, Maurice P, Si, Haoyu, Harris, Steven D
Format: Article
Language:English
Subjects:
Aspergillus nidulans
Aspergillus nidulans - genetics
Aspergillus nidulans - growth & development
Aspergillus nidulans - metabolism
Biological and medical sciences
cdc42 GTP-Binding Protein - genetics
cdc42 GTP-Binding Protein - metabolism
Cytoskeleton - metabolism
Fundamental and applied biological sciences. Psychology
Fungal Proteins - genetics
Fungal Proteins - metabolism
Gene Expression Regulation, Fungal
Green Fluorescent Proteins - genetics
Green Fluorescent Proteins - metabolism
Hyphae - genetics
Hyphae - growth & development
Hyphae - metabolism
Microbiology
Microscopy, Fluorescence
Miscellaneous
Molecular Sequence Data
Morphogenesis
Mycology
rac1 GTP-Binding Protein - genetics
rac1 GTP-Binding Protein - metabolism
Recombinant Fusion Proteins - genetics
Recombinant Fusion Proteins - metabolism
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Summary:The ability of filamentous fungi to form hyphae requires the establishment and maintenance of a stable polarity axis. Based on studies in yeasts and animals, the GTPases Cdc42 and Rac1 are presumed to play a central role in organizing the morphogenetic machinery to enable axis formation and stabilization. Here, we report that Cdc42 (ModA) and Rac1 (RacA) share an overlapping function required for polarity establishment in Aspergillus nidulans. Nevertheless, Cdc42 appears to have a more important role in hyphal morphogenesis in that it alone is required for the timely formation of lateral branches. In addition, we provide genetic evidence suggesting that the polarisome components SepA and SpaA function downstream of Cdc42 in a pathway that may regulate microfilament formation. Finally, we show that microtubules become essential for the establishment of hyphal polarity when the function of either Cdc42 or SepA is compromised. Our results are consistent with the action of parallel Cdc42 and microtubule-based pathways in regulating the formation of a stable axis of hyphal polarity in A. nidulans.
ISSN:0950-382X
1365-2958
DOI:10.1111/j.1365-2958.2007.06021.x