The tubulin cytoskeleton and its sites of nucleation in hyphal tips ofAllomyces macrogynus

Roberson, Robert W.; Vargas, Maria M.

doi:10.1007/bf01403685

Cited by 50 publications

(55 citation statements)

References 36 publications

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“…The conical microtubule organisation may facilitate the transport of cell elements to the top of the cell. A similar role of the microtubule cytoskeleton has been reported in other polarised systems, such as in chlorenchyma cells of flowering plants (Chuong et al 2006), bryophytes (Doonan et al 1988), fungal hyphae (Roberson and Vargas 1994), green algae (Holzinger et al 2002) and brown algae (Karyophyllis et al 1997, Katsaros et al 2006). However, actin has also been reported to participate in organelle movement (Grolig 1990, Higaki et al 2007, Blanchoin et al 2010 .…”

Section: Discussionmentioning

confidence: 90%

Cell structure and microtubule organisation during gametogenesis of Ulva mutabilis Føyn (Chlorophyta)

et al. 2017

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Cell structure and microtubule organisation during gametogenesis of the green alga Ulva mutabilis was studied using light microscopy, transmission electron microscopy (TEM) and tubulin immunofluorescence. Micro tubules in vegetative cells are organised in parallel bundles traversing the cortical cytoplasm. During gameto genesis, induced blade cells are transformed to gametangia, depending on the maturity of the algae and the removal of regulatory sporulation inhibitors. This differentiation is accompanied by formation of a conical cell projection (papilla) towards the exterior of the thallus. Microtubules form a clear, basket-like configuration converging towards the conical tip, but not reaching it. The conical microtubule structure stops below the tip, leaving a circular "opening". Parallel to the above, the cell wall of the tip is differentiated, forming a "cap". Nuclear divisions start at this stage, finally forming the nuclei of future gametes. Cytokinesis takes place by membrane furrowing and vesicle fusion, giving rise to 16 oval-shaped gametes. The conical microtubule organisation is gradually depoly merised, and a cortical, intensely fluorescing micro tubule bundle is formed in each gamete. At this stage, the cap at the conical cell wall projection is removed and the exit pore opens. The biflagellate gametes remain initially motionless, connected by thin cytoplasmic bridges. Finally, they are released to the environment upon additional removal of a swarming inhibitor accumulated in the growth medium during gametogenesis.

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Section: Discussionmentioning

confidence: 90%

Cell structure and microtubule organisation during gametogenesis of Ulva mutabilis Føyn (Chlorophyta)

et al. 2017

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“…Hyphae grow solely by apical extension, whereby cell surface expansion and cell wall deposition are confined to a discrete region at the hyphal tip (Gooday, 1971). This mode of growth is supported by extreme polarization of the cytoskeleton and endomembrane network, which permits the long-range transport of vesicles containing precursors required for apical extension to the tip region (Grove and Bracker, 1970;Bourett and Howard, 1991;Roberson and Vargas, 1994). Although hyphae are a defining feature of filamentous fungi, the molecular mechanisms underlying hyphal morphogenesis remain poorly understood.…”

Section: Introductionmentioning

confidence: 99%

MesA, a Novel Fungal Protein Required for the Stabilization of Polarity Axes inAspergillus nidulans

Pearson

Sharpless

et al. 2004

MBoC

113

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The Aspergillus nidulans proteome possesses a single formin, SepA, which is required for actin ring formation at septation sites and also plays a role in polarized morphogenesis. Previous observations imply that complex regulatory mechanisms control the function of SepA and ensure its correct localization within hyphal tip cells. To characterize these mechanisms, we undertook a screen for mutations that enhance sepA defects. Of the mutants recovered, mesA1 causes the most dramatic defect in polarity establishment when SepA function is compromised. In a wild-type background, mesA1 mutants undergo aberrant hyphal morphogenesis, whereas septum formation remains unaffected. Molecular characterization revealed that MesA is a novel fungal protein that contains predicted transmembrane domains and localizes to hyphal tips. We show that MesA promotes the localized assembly of actin cables at polarization sites by facilitating the stable recruitment of SepA. We also provide evidence that MesA may regulate the formation or distribution of sterol-rich membrane domains. Our results suggest that these domains may be part of novel mechanism that directs SepA to hyphal tips.

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“…pez-Franco & Bracker, 1996). In addition to vesicles (Girbardt, 1969 ;Grove & Bracker, 1970), other components have been detected in the Spk, including amorphous or granular material of undefined nature in the core region as well as components of the cytoskeleton and ribosomes (McClure et al, 1968 ;Turian, 1978 ;Bourett & Howard, 1991 ;Roberson & Vargas, 1994 ;Lo! pez-Franco & Bracker, 1996).…”

Section: Introductionmentioning

confidence: 99%

Dynein and dynactin deficiencies affect the formation and function of the Spitzenkörper and distort hyphal morphogenesis of Neurospora crassa

2000

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The impact of mutations affecting microtubule-associated motor proteins on the morphology and cytology of hyphae of Neurospora crassa was studied. Two ropy mutants, ro-1 and ro-3, deficient in dynein and dynactin, respectively, were examined by video-enhanced phase-contrast microscopy and image analysis. In contrast to the regular, hyphoid morphology of wildtype hyphae, the hyphae of the ropy mutants exhibited a great variety of distorted, non-hyphoid morphologies. The ropy hyphae were slow-growing and manifested frequent loss of growth directionality. Cytoplasmic appearance, including organelle distribution and movement, were ostensibly different in the ropy hyphae. The Spitzenko $ rper (Spk) of wild-type hyphae was readily seen by phase-contrast optics ; the Spk of both ro-1 and ro-3 was less prominent and sometimes undetectable. Only the fast-growing ropy hyphae displayed a Spk, and it was smaller and less phase-dark than the wild-type Spk. Growth rate in both wild-type and ropy mutants was directly correlated with the size of the Spk. Spk efficiency, measured in terms of cell area generated per Spk travelled distance, was lower in ropy mutants. Another salient difference between ropy mutants and wild-type hyphae was in Spk trajectory. Whereas the Spk of wild-type hyphae maintained a trajectory close to the cell growth axis, the Spk of ropy hyphae moved much more erratically. Sustained departures in the trajectory of the ropy Spk produced corresponding distortions in hyphal morphology. A causal correlation between Spk trajectory and cell shape was tested with the Fungus Simulator program. The characteristic morphologies of wild-type or ropy hyphae were reproduced by the Fungus Simulator, whose vesicle supply centre (VSC) was programmed to follow the corresponding Spk trajectories. This is evidence that the Spk controls hyphal morphology by operating as a VSC. These findings on dynein or dynactin deficiency support the notion that the microtubular cytoskeleton plays a major role in the formation and positioning of the Spk, with dramatic consequences on hyphal growth and morphogenesis.

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The tubulin cytoskeleton and its sites of nucleation in hyphal tips ofAllomyces macrogynus

Cited by 50 publications

References 36 publications

Cell structure and microtubule organisation during gametogenesis of Ulva mutabilis Føyn (Chlorophyta)

Cell structure and microtubule organisation during gametogenesis of Ulva mutabilis Føyn (Chlorophyta)

MesA, a Novel Fungal Protein Required for the Stabilization of Polarity Axes inAspergillus nidulans

Dynein and dynactin deficiencies affect the formation and function of the Spitzenkörper and distort hyphal morphogenesis of Neurospora crassa

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