Physiology and cytology of septation and branching in a temperature-sensitive colonial mutant (cot 1) of Neurospora crassa

Collinge, Annette J.; Fletcher, Margaret H.; Trinci, Anthony P. J.

doi:10.1016/s0007-1536(78)80012-6

Cited by 22 publications

(18 citation statements)

References 16 publications

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“…Further work in both yeasts as well as in animal cells has resulted in an emerging network, which includes the NDR kinase and its binding partner and activator MOB2, which are regulated through a Ste20 type kinase that interacts with a MO25-as well as a FURRY-like Kanai et al, 2005;Stegert et al, 2005;Hergovich et al, 2006). The founding member of the NDR family, the kinase COT1 of the filamentous fungus Neurospora crassa, is required for hyphal tip elongation (Collinge and Trinci, 1974;Collinge et al, 1978;Yarden et al, 1992), and the temperature-sensitive cot-1 mutant ceases hyphal elongation after being shifted to restrictive temperature. This is accompanied by a massive induction of new hyphal tip formation, creating the typical barbed-wired morphology of cot-1 cells.…”

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confidence: 99%

“…cot-1(1), pod-6(31-21), and cot-1(1); pod-6(31-21) mutants showed identical phenotypes at restrictive temperature. This provides further evidence of their involvement in a common genetic pathway and, possibly, of a physical interaction between the two proteins.The cot-1(1) mutation has been shown to result in increased cell-wall thickness at restrictive temperature (Collinge et al, 1978;Gorovits et al, 2000), suggesting a defect in cell-wall metabolism. We therefore tested chitin deposition by staining hyphae with Calcofluor White.…”

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confidence: 99%

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The STE20/Germinal Center Kinase POD6 Interacts with the NDR Kinase COT1 and Is Involved in Polar Tip Extension inNeurospora crassa

Seiler

Vogt

Ziv

et al. 2006

MBoC

104

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Members of the Ste20 and NDR protein kinase families are important for normal cell differentiation and morphogenesis in various organisms. We characterized POD6 (NCU02537.2), a novel member of the GCK family of Ste20 kinases that is essential for hyphal tip extension and coordinated branch formation in the filamentous fungus Neurospora crassa. pod-6 and the NDR kinase mutant cot-1 exhibit indistinguishable growth defects, characterized by cessation of cell elongation, hyperbranching, and altered cell-wall composition. We suggest that POD6 and COT1 act in the same genetic pathway, based on the fact that both pod-6 and cot-1 can be suppressed by 1) environmental stresses, 2) altering protein kinase A activity, and 3) common extragenic suppressors (ropy, as well as gul-1, which is characterized here as the ortholog of the budding and fission yeasts SSD1 and Sts5, respectively). Unlinked noncomplementation of cot-1/pod-6 alleles indicates a potential physical interaction between the two kinases, which is further supported by coimmunoprecipitation analyses, partial colocalization of both proteins in wild-type cells, and their common mislocalization in dynein/kinesin mutants. We conclude that POD6 acts together with COT1 and is essential for polar cell extension in a kinesin/dynein-dependent manner in N. crassa. INTRODUCTIONFactors that determine and modulate cell polarity have been the subject of extensive investigations in a variety of experimental organisms (Drubin and Nelson, 1996;Nelson, 2003), with the most progress having been made in the unicellular yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe (Bähler and Peter, 2000; Bretscher, 2000a, 2000b;Pruyne et al., 2004). The mechanisms by which polarity is established in filamentous fungi have remained largely obscure, but it is likely that the fundamental principles leading to the initial polarization of the cell are conserved among unicellular organisms (Bähler and Peter, 2000;Wendland, 2001), filamentous fungi (Galagan et al., 2003;Borkovich et al., 2004;Harris and Momany, 2004), and animals (Hall, 1998). But in contrast to baker's yeast, where growth becomes isotropic soon after bud emergence, the growth of filamentous fungi must stay highly polar to produce a tipgrowing hypha that can extend at astonishing rates of more than 1 m/s (Lopez-Franco et al., 1994;Seiler and Plamann, 2003;Harris et al., 2005). Thus, filamentous fungi present good model systems to study how this highly polar shape is maintained over long distances, the way in which new branch points are initiated and how their spatial relationship is regulated.In recent years, protein kinases of the NDR Ser/Thr protein kinase family have emerged as being important for normal cell differentiation and polar morphogenesis in various organisms, yet their specific functions are still elusive (Tamaskovic et al., 2003;Hergovich et al., 2006). In Drosophila melanogaster, the NDR kinases Tricornered and Warts are required for control of the extent and direction of cell proliferation as well as fo...

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confidence: 99%

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confidence: 99%

The STE20/Germinal Center Kinase POD6 Interacts with the NDR Kinase COT1 and Is Involved in Polar Tip Extension inNeurospora crassa

Seiler

Vogt

Ziv

et al. 2006

MBoC

104

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“…A defect in the Neurospora crassa colonial temperature-sensitive 1 gene (cot-1) confers a defect in hyphal extension that results in colonial growth at 32°C and above but normal growth and morphology, similar to that of the wild type, at or below 28°C (8). The cot-1 gene encodes a Ser/Thr protein kinase (51), and the defect in a cot-1 mutant has been mapped to a single base change resulting in a His-to-Arg substitution at amino acid 351 within the catalytic domain of the kinase (17).…”

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Environmental Suppression of Neurospora crassa cot-1 Hyperbranching: a Link between COT1 Kinase and Stress Sensing

Gorovits

Yarden

2003

Eukaryot Cell

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cot-1 mutants belong to a class of Neurospora crassa colonial temperature-sensitive (cot) mutants that exhibit abnormal polar extension and branching patterns when grown at restrictive temperatures. cot-1 encodes a Ser/Thr protein kinase that is structurally related to the human myotonic dystrophy kinase which, when impaired, confers a disease that involves changes in cytoarchitecture and ion homeostasis. When grown under restrictive conditions, cot-1 cultures exhibited enhanced medium acidification rates, increased relative abundance of sodium, and increased intracellular glycerol content, indicating an ion homeostasis defect in a hyperbranching mutant. The application of ion transport blockers led to only mild suppression of the cot-1 phenotype. The presence of increased medium NaCl or sorbitol, H 2 O 2 , or ethanol levels significantly suppressed the cot-1 phenotype, restored ion homeostasis, and was accompanied by reduced levels of cyclic AMP-dependent protein kinase (PKA) activity. The cot-1 phenotype could also be partially suppressed by direct inhibition of PKA with KT-5720. A reduced availability of fermentable carbon sources also had a suppressive effect on the cot-1 phenotype. In contrast to the effect of extragenic ropy suppressors of cot-1, environmental stress-related suppression of cot-1 did not change COT1 polypeptide expression patterns in the mutant. We suggest that COT1 function is linked to environmental stress response signaling and that altering PKA activity bypasses the requirement for fully functional COT1.

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“…In N. crassa, cot-1, which encodes an NDR kinase (Yarden et al, 1992) has been recognised for many years at a genetic level as temperature sensitive cot-1 -alleles cause hyper-branching and a more compact "colonial" colony morphology (Collinge et al, 1978).…”

Section: Ndr Kinasesmentioning

confidence: 99%

Regulation of polarised growth in fungi

Sudbery

2008

Fungal Biology Reviews

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Polarised growth in fungi occurs through the delivery of secretory vesicles along tracks formed by cytoskeletal elements to specific sites on the cell surface where they dock with a multiprotein structure called the exocyst before fusing with the plasmamembrane. The budding yeast, Saccharomyces cerevisiae has provided a useful model to investigate the mechanisms involved and their control. Cortical markers, provided by bud site selection pathways during budding, the septin ring during cytokinesis or the stimulation of the pheromone response receptors during mating, act through upstream signalling pathways to localise Cdc24, the GEF for the rho family GTPase, Cdc42. Cdc42 in its GTP-bound activates a multiprotein protein complex called the polarisome which nucleates actin cables along which the secretory vesicles are transported to the cell surface. Hyphae can elongate at a rate orders of magnitude faster than the extension of a yeast bud, so understanding hyphal growth will require substantial modification of the yeast paradigm.The rapid rate of hyphal growth is driven by a structure called the Spitzenkörper, located just behind the growing tip and which is rich in secretory vesicles. It is thought that secretory vesicles are delivered to the apical region where they accumulate in the Spitzenkörper. The Spitzenkörper then acts as vesicle supply centre in which vesicles exit the Spitzenkörper in all directions, but because of its proximity, the tip receives a greater concentration of vesicles per unit area than subapical regions. There are no obvious equivalents to the bud site selection pathway to provide a spatial landmark for polarised growth in hyphae. However, an emerging model is the way that the site of polarised growth in the fission yeast, Schizosaccharomyces pombe, is marked by delivery of the kelch repeat protein, Tea1, along microtubules. The relationship of the Spitzenkörper to the polarisome and the mechanisms that promote its formation are key questions that form the focus of current research.3

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Physiology and cytology of septation and branching in a temperature-sensitive colonial mutant (cot 1) of Neurospora crassa

Cited by 22 publications

References 16 publications

The STE20/Germinal Center Kinase POD6 Interacts with the NDR Kinase COT1 and Is Involved in Polar Tip Extension inNeurospora crassa

The STE20/Germinal Center Kinase POD6 Interacts with the NDR Kinase COT1 and Is Involved in Polar Tip Extension inNeurospora crassa

Environmental Suppression of Neurospora crassa cot-1 Hyperbranching: a Link between COT1 Kinase and Stress Sensing

Regulation of polarised growth in fungi

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