title: Localization and function of ADP ribosylation factor A in Aspergillus nidulans.
abstract: Filamentous fungi undergo polarized hyphal growth throughout the majority of their life cycle. The Spitzenkörper is a structure unique to filamentous fungi that participates in hyphal growth and is composed largely of vesicles. An important class of proteins involved in vesicle assembly and trafficking are the ADP-ribosylation factors (Arfs). In Saccharomyces cerevisiae, Arf1p and Arf2p are involved in secretion. Aspergillus nidulans ArfA is a homolog of ScArf1p and ScArf2p with 75% of amino acid sequence similarity to each. ArfA::GFP localizes to cellular compartments consistent with Golgi equivalents. An N-terminal myristoylation motif is critical for localization of ArfA. Treatment with Brefeldin A, an inhibitor of Golgi transport, leads to ArfA::GFP diffusing through the cytosol and accumulating into a subcellular compartment further suggesting the ArfA localizes to and functions in the Golgi network. Costaining with FM4-64 revealed that ArfA::GFP likely localized to subcellular compartments participating in exocytosis. We were unable to recover arfA gene disruption strains indicating that the gene is essential in A. nidulans. The overexpression of ArfA protein partially suppresses the polarity defect phenotype of an N-myristoyltransferase mutant. Taken together, these results suggest that ArfA participates in hyphal growth through the secretory system.
authors.affiliation: Program for the Biology of Filamentous Fungi, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA.
authors.forename: Soo Chan
authors.initials: SC
authors.lastname: Lee
authors.forename: Brian D
authors.initials: BD
authors.lastname: Shaw
mesh_terms: D020727:ADP-Ribosylation Factors / Q000032:analysis*; D000595:Amino Acid Sequence; D019677:Artificial Gene Fusion; D001233:Aspergillus nidulans / Q000737:chemistry* / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D005089:Exocytosis; D017353:Gene Deletion; D018628:Gene Dosage; D020043:Genes, Essential; D017930:Genes, Reporter; D006056:Golgi Apparatus / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D025301:Hyphae / Q000737:chemistry / Q000166:cytology / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D020727:ADP-Ribosylation Factors