title: Localization of RHO-4 indicates differential regulation of conidial versus vegetative septation in the filamentous fungus Neurospora crassa.
abstract: Rho-4 mutants of the filamentous fungus Neurospora crassa lack septa and asexual spores (conidia) and grow slowly. In this report, localization of green fluorescent protein-tagged RHO-4 is used to elucidate the differences in factors controlling RHO-4 localization during vegetative growth versus asexual development. RHO-4 forms a ring at incipient vegetative septation sites that constricts with the formation of the septum toward the septal pore; RHO-4 persists around the septal pore after septum completion. During the formation of conidia, RHO-4 localizes to the primary septum but subsequently is relocalized to the cytoplasm after the placement of the secondary septum. Cytoplasmic localization and inactivation of RHO-4 are mediated by a direct physical interaction with RDI-1, a RHO guanosine nucleotide dissociation inhibitor. Inappropriate activation of the cyclic AMP-dependent protein kinase A pathway during vegetative growth causes mislocalization of RHO-4 away from septa to the cytoplasm, a process which was dependent upon RDI-1. An adenylate cyclase cr-1 mutant partially suppresses the aconidial defect of rho-4 mutants but only rarely suppresses the vegetative septation defect, indicating that conidial septation is negatively regulated by CR-1. These data highlight the differences in the regulation of septation during conidiation versus vegetative septation in filamentous fungi.
authors.affiliation: Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, CA 94720-3102, USA.
authors.forename: Carolyn G
authors.initials: CG
authors.lastname: Rasmussen
authors.forename: N Louise
authors.initials: NL
authors.lastname: Glass
mesh_terms: D000199:Actins / Q000378:metabolism; D001483:Base Sequence; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003572:Cytochalasins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D025301:Hyphae / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000166:cytology / Q000502:physiology; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013172:Spores, Fungal / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000199:Actins; D003572:Cytochalasins; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; C031218:cytochalasin A; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins