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

Mol Microbiol. 2007 Dec;66(6):1579-96. doi: 10.1111/j.1365-2958.2007.06021.x. Epub 2007 Nov 13.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aspergillus nidulans / genetics
  • Aspergillus nidulans / growth & development*
  • Aspergillus nidulans / metabolism
  • Cytoskeleton / metabolism
  • 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
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Morphogenesis*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • cdc42 GTP-Binding Protein / genetics
  • cdc42 GTP-Binding Protein / metabolism
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism


  • Fungal Proteins
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • cdc42 GTP-Binding Protein
  • rac1 GTP-Binding Protein

Associated data

  • GENBANK/AAF24513
  • GENBANK/AAF24514