Plasma Membrane-Adjacent Actin Filaments, but Not Microtubules, Are Essential for both Polarization and Hyphal Tip Morphogenesis in Saprolegnia ferax and Neurospora crassa

Heath, I. Brent; Gupta, Gagan D.; Bai, Shan

doi:10.1006/fgbi.2000.1203

Cited by 68 publications

(70 citation statements)

References 48 publications

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“…In dyn1 cells induced for hyphal formation failure in nuclear migration leads to anucleate hyphal tips that cease growth and thus establish a filamentation defect. (9). Efficient nuclear migration in S. cerevisiae is carried out by two partially redundant pathways centering on dynein and Kar9p (16).…”

Section: Discussionmentioning

confidence: 99%

Deletion of the Dynein Heavy-Chain Gene DYN1 Leads to Aberrant Nuclear Positioning and Defective Hyphal Development in Candida albicans

2004

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Cytoplasmic dynein is a microtubule-associated minus-end-directed motor protein. CaDYN1 encodes the single dynein heavy-chain gene of Candida albicans. The open reading frames of both alleles of CaDYN1 were completely deleted via a PCR-based approach. Cadyn1 mutants are viable but grow more slowly than the wild type. In vivo time-lapse microscopy was used to compare growth of wild-type (SC5314) and dyn1 mutant strains during yeast growth and after hyphal induction. During yeast-like growth, Cadyn1 strains formed chains of cells. Chromosomal TUB1-GFP and HHF1-GFP alleles were used both in wild-type and mutant strains to monitor the orientation of mitotic spindles and nuclear positioning in C. albicans. In vivo fluorescence time-lapse analyses with HHF1-GFP over several generations indicated defects in dyn1 cells in the realignment of spindles with the mother-daughter axis of yeast cells compared to that of the wild type. Mitosis in the dyn1 mutant, in contrast to that of wild-type yeast cells, was very frequently completed in the mother cells. Nevertheless, daughter nuclei were faithfully transported into the daughter cells, resulting in only a small number of multinucleate cells. Cadyn1 mutant strains responded to hypha-inducing media containing L-proline or serum with initial germ tube formation. Elongation of the hyphal tubes eventually came to a halt, and these tubes showed a defect in the tipward localization of nuclei. Using a heterozygous DYN1/dyn1 strain in which the remaining copy was controlled by the regulatable MAL2 promoter, we could switch between wild-type and mutant phenotypes depending on the carbon source, indicating that the observed mutant phenotypes were solely due to deletion of DYN1.Faithful segregation of nuclei is essential for the proliferation of the eukaryotic cell. Dynamic behavior of nuclei is required at several stages during the cell cycle for correct nuclear positioning, orientation of the mitotic spindle, and distribution of nuclei in the cytoplasm, particularly in filamentous fungi (18). Nuclear distribution has been studied in detail in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, as well as in the filamentous fungi Aspergillus nidulans and Neurospora crassa (30,31,32). The spindle pole body (SPB) plays a central role in nuclear dynamics, as it is the organizing center of cytoplasmic microtubules (MTs) that emanate from the SPB outer plaque (4, 5). These cytoplasmic MTs interact with the cell cortex in S. cerevisiae via a searchand-capture mechanism that results in the orientation of the mitotic spindle in the mother-bud axis, in the positioning of the nucleus at the bud neck, and in the translocation of the daughter nucleus into the bud. A set of proteins are involved in this process, including Kar9p, Bim1p, Bud6p, the formin Bni1p, and Myo2p (3,8,12,17,33,34). During anaphase, nuclear movement depends on the minus-end-directed microtubule motor protein Dyn1p (the S. cerevisiae dynein heavy-chain homolog), which provides the pulling force (1). Deletion of...

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Section: Discussionmentioning

confidence: 99%

Deletion of the Dynein Heavy-Chain Gene DYN1 Leads to Aberrant Nuclear Positioning and Defective Hyphal Development in Candida albicans

2004

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“…Protein Sac6 cooperates with Scp1p (calponin/transgelin) in the organization and maintenance of the actin cytoskeleton. Since the actin cytoskeleton is both necessary and sufficient for cell polarization and polarized hyphal growth in filamentous fungi (Heath et al, 2000), the aberrant polar growth and septation associated with the mutant might mainly arise from diminished AMBP and Sac6.…”

Section: Proteins Involved In Polaritymentioning

confidence: 99%

Comparative proteomic analysis of an Aspergillus fumigatus mutant deficient in glucosidase I (AfCwh41)

et al. 2009

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a-Glucosidase I regulates trimming of the terminal a-1,2-glucose residue in the N-glycan processing pathway, which plays an important role in quality control systems in mammalian cells. Previously, we identified the gene encoding a-glucosidase I in the opportunistic human fungal pathogen Aspergillus fumigatus, namely Afcwh41. Deletion of the Afcwh41 gene results in a severe reduction of conidia formation, a temperature-sensitive deficiency of cell wall integrity, and abnormalities of polar growth and septation. An upregulation of the genes encoding Rho-type GTPases was also observed, which suggests activation of the cell wall integrity pathway in the mutant. Using 2D gel analysis, we revealed that the proteins involved in protein assembly, ubiquitin-mediated degradation and actin organization are altered in the DAfcwh41 mutant. Evidence was obtained for a defect in the polarized localization of the actin cytoskeleton in the mutant. Our results suggest that blocking of the glucose trimming in A. fumigatus might induce accumulation of misfolded proteins in the endoplasmic reticulum; these misfolded proteins are probably required for cell wall synthesis and thus activate the cell wall integrity pathway, which then causes the abnormal polarity associated with the DAfcwh41 mutant.

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“…In C. albicans the ability to initiate hyphal growth is associated with its virulence (27). Polarized growth in ascomycetous fungi is dependent on the actin cytoskeleton, whereas microtubules are not required to initiate hyphal extensions (19,52). Rho protein modules are central regulators for the organization of the actin cytoskeleton (12).…”

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confidence: 99%

Polarized Hyphal Growth in Candida albicans Requires the Wiskott-Aldrich Syndrome Protein Homolog Wal1p

Walther

Wendland

2004

Eukaryot Cell

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The yeast-to-hypha transition is a key feature in the cell biology of the dimorphic human fungal pathogen Candida albicans. Reorganization of the actin cytoskeleton is required for this dimorphic switch in Candida. We show that C. albicans WAL1 mutants with both copies of the Wiskott-Aldrich syndrome protein (WASP) homolog deleted do not form hyphae under all inducing conditions tested. Growth of the wild-type and wal1 mutant strains was monitored by in vivo time-lapse microscopy both during yeast-like growth and under hypha-inducing conditions. Isotropic bud growth produced round wal1 cells and unusual mother cell growth. Defects in the organization of the actin cytoskeleton resulted in the random localization of actin patches. Furthermore, wal1 cells exhibited defects in the endocytosis of the lipophilic dye FM4-64, contained increased numbers of vacuoles compared to the wild type, and showed defects in bud site selection. Under hypha-inducing conditions wal1 cells were able to initiate polarized morphogenesis, which, however, resulted in the formation of pseudohyphal cells. Green fluorescent protein (GFP)-tagged Wal1p showed patch-like localization in emerging daughter cells during the yeast growth phase and at the hyphal tips under hypha-inducing conditions. Wal1p-GFP localization largely overlapped with that of actin. Our results demonstrate that Wal1p is required for the organization of the actin cytoskeleton and hyphal morphogenesis in C. albicans as well as for endocytosis and vacuole morphology.

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Plasma Membrane-Adjacent Actin Filaments, but Not Microtubules, Are Essential for both Polarization and Hyphal Tip Morphogenesis in Saprolegnia ferax and Neurospora crassa

Cited by 68 publications

References 48 publications

Deletion of the Dynein Heavy-Chain Gene DYN1 Leads to Aberrant Nuclear Positioning and Defective Hyphal Development in Candida albicans

Deletion of the Dynein Heavy-Chain Gene DYN1 Leads to Aberrant Nuclear Positioning and Defective Hyphal Development in Candida albicans

Comparative proteomic analysis of an Aspergillus fumigatus mutant deficient in glucosidase I (AfCwh41)

Polarized Hyphal Growth in Candida albicans Requires the Wiskott-Aldrich Syndrome Protein Homolog Wal1p

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