title: Cytoplasmic dynamics of the general nuclear import machinery in apically growing syncytial cells.
abstract: Karyopherins are transporters involved in the bidirectional, selective and active transport of macromolecules through nuclear pores. Importin-β1 is the paradigm of karyopherins and, together with its cargo-adapter importin-α, mediates the general nuclear import pathway. Here we show the existence of different cellular pools of both importin-α and -β1 homologues, KapA and KapB, in the coenocytic ascomycete Aspergillus nidulans. Fluorescence analysis of haploid and diploid strains expressing KapB::GFP and/or KapA::mRFP showed patches of both karyopherins concurrently translocating long distances in apically-growing cells. Anterograde and retrograde movements allowed those patches to reach cell tips and distal regions with an average speed in the range of μm/s. This bidirectional traffic required microtubules as well as kinesin and dynein motors, since it is blocked by benomyl and also by the inactivation of the dynein/dynactin complex through nudA1 or nudK317 mutations. Deletion of Kinesin-3 motor UncA, required for the transport through detyrosinated microtubules, strongly inhibited KapA and KapB movement along hyphae. Overall, this is the first report describing the bidirectional dynamics of the main nuclear import system in coenocytic fungi. A functional link is proposed between two key cellular machines of the filamentous fungal cell: nuclear transport and the tip-growth apparatus.
authors.affiliation: Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain ; Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country, San Sebastian, Spain.
authors.forename: Oier
authors.initials: O
authors.lastname: Etxebeste
authors.affiliation: Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Villarino
authors.affiliation: Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain ; Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country, San Sebastian, Spain.
authors.forename: Ane
authors.initials: A
authors.lastname: Markina-Iñarrairaegui
authors.affiliation: Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain ; Department of Molecular Microbiology and Infection Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
authors.forename: Lidia
authors.initials: L
authors.lastname: Araújo-Bazán
authors.affiliation: Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Espeso
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D001233:Aspergillus nidulans / Q000235:genetics* / Q000502:physiology; D015153:Blotting, Western; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000502:physiology*; D005453:Fluorescence; D015726:Giant Cells / Q000502:physiology*; D042541:Intracellular Space / Q000378:metabolism; D028884:Karyopherins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000502:physiology; D009841:Oligonucleotides / Q000235:genetics
chemical_list: D028884:Karyopherins; D009841:Oligonucleotides