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Eukaryotic Cell, July 2007, p. 1097-1107, Vol. 6, No. 7
1535-9778/07/$08.00+0     doi:10.1128/EC.00050-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Localization of RHO-4 Indicates Differential Regulation of Conidial versus Vegetative Septation in the Filamentous Fungus Neurospora crassa ^,

Carolyn G. Rasmussen and N. Louise Glass^*

Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, California 94720-3102

Received 21 February 2007/ Accepted 4 May 2007

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.

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* Corresponding author. Mailing address: Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, CA 94720-3102. Phone: (510) 643-2399. Fax: (510) 642-4995. E-mail: Lglass{at}nature.berkeley.edu

Published ahead of print on 11 May 2007.

Supplemental material for this article may be found at http://ec.asm.org/.

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Eukaryotic Cell, July 2007, p. 1097-1107, Vol. 6, No. 7
1535-9778/07/$08.00+0     doi:10.1128/EC.00050-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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