title: Aspergillus nidulans RhoA is involved in polar growth, branching, and cell wall synthesis.
abstract: Growth of the filamentous fungus Aspergillus nidulans begins when the conidium breaks dormancy and grows isotropically. Eventually a germ tube emerges and the axis of growth remains fixed in the primary hypha while new growth axes are established basally to form secondary germ tubes and lateral branches. Rho1 is a Rho family GTPase that has been shown to be involved in polarity establishment and cell wall deposition in Saccharomyces cerevisiae. A gene predicted to encode a Rho1 homolog was cloned from A. nidulans and named rhoA. Strains carrying ectopic copies of the constitutively active rhoA(G14V) allele or the dominant rhoA(E40I) allele were created and characterized. The constitutively active rhoA(G14V) strain grew slowly relative to wild type and showed an abnormal clustered pattern of branch emergence. The rhoA(G14V) strain also labeled intensely with calcofluor, showed elevated levels of cell wall N-acetylglucosamine and had unusually thick cell walls. The dominant rhoA(E40I)strain was accelerated in the emergence of secondary and tertiary germ tubes, and lateral branches relative to wild type and showed lysis with prolonged incubation. The rhoA(E40I) strain also was hypersensitive to the cell wall disrupting agents calcofluor and caspofungin acetate and showed an increase in cell wall N-acetylglucosamine levels. Our results suggest that rhoA plays a role in polarity, proper branching pattern, and cell wall deposition.
authors.affiliation: Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Gretel M
authors.initials: GM
authors.lastname: Guest
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Lin
authors.forename: Michelle
authors.initials: M
authors.lastname: Momany
mesh_terms: D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000166:cytology / Q000254:growth & development* / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics; D016764:Cell Polarity / Q000235:genetics*; D002473:Cell Wall / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D025301:Hyphae / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D020742:rhoA GTP-Binding Protein / Q000502:physiology*
chemical_list: D020742:rhoA GTP-Binding Protein