Mechanisms of Hyphal Tip Growth: Tube Dwelling Amebae Revisited

Heath, I. Brent; Steinberg, Gero

doi:10.1006/fgbi.1999.1168

Cited by 55 publications

(48 citation statements)

References 145 publications

(164 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of these, only os-1 (nik-1) has been cloned; it is homologous with two-component histidine kinases, such as the Saccharomyces cerevisiae Sln1p osmosensor of the HOG pathway (Alex et al, 1996;Schumacher et al, 1997), important in osmotic regulation. The mutant grows as a protoplast in osmotically buffered media and exhibits amoeboidal movement, pointing to a role for the cytoskeleton during growth (Heath & Steinberg, 1999). The 'slime' mutant is a clear example of the ability of fungal organisms to grow in the absence of turgor, an example which supports the idea that amoeboidal growth can be an Fig.…”

Section: Discussionmentioning

confidence: 63%

See 1 more Smart Citation

Mass flow and pressure-driven hyphal extension in Neurospora crassa

Lew

2005

Microbiology

View full text Add to dashboard Cite

Mass flow of cytoplasm in Neurospora crassa trunk hyphae was directly confirmed by injecting oil droplets into the hyphae. The droplets move in a manner similar to cytoplasmic particles and vacuoles within the hyphae. The direction of mass flow is towards the growing hyphal tips at the colony edge. Based on flow velocities (about 5 μm s−1), hyphal radius and estimates of cytoplasm viscosity, the Reynolds number is about 10−4, indicating that mass flow is laminar. Therefore, the Poiseulle equation can be used to calculate the pressure gradient required for mass flow: 0·0005–0·1 bar cm−1 (depending on the values used for septal pore radius and cytoplasmic viscosity). These values are very small compared to the normal hydrostatic pressure of the hyphae (4–5 bar). Mass flow stops after respiratory inhibition with cyanide, or creation of an extracellular osmotic gradient. The flow is probably caused by internal osmotic gradients created by differential ion transport along the hyphae. Apical cytoplasm migrates at the same rate as tip extension, as do oil droplets injected near the tip. Thus, in addition to organelle positioning mediated by molecular motors, pressure-driven mass flow may be an integral part of hyphal extension.

show abstract

Section: Discussionmentioning

confidence: 63%

“…alternative mechanism of tip growth (Heath & Steinberg, 1999). Thus, turgor-driven growth is not obligatory, although it is probably the norm.…”

Section: Discussionmentioning

confidence: 99%

Mass flow and pressure-driven hyphal extension in Neurospora crassa

Lew

2005

Microbiology

View full text Add to dashboard Cite

show abstract

“…Hyphae grow by tip extension and then branch subapically to form a diffuse tree-like mycelium (Howard 1981;Gooday 1995;Heath & Steinberg 1999;Money 1997Money , 2008Steinberg 2006). As the colony continues to grow, hyphal fusions or anastomoses occur, producing a more reticulate, net-like structure.…”

Section: Introductionmentioning

confidence: 99%

Growth-induced mass flows in fungal networks

et al. 2010

View full text Add to dashboard Cite

Cord-forming fungi form extensive networks that continuously adapt to maintain an efficient transport system. As osmotically driven water uptake is often distal from the tips, and aqueous fluids are incompressible, we propose that growth induces mass flows across the mycelium, whether or not there are intrahyphal concentration gradients. We imaged the temporal evolution of networks formed by Phanerochaete velutina, and at each stage calculated the unique set of currents that account for the observed changes in cord volume, while minimizing the work required to overcome viscous drag. Predicted speeds were in reasonable agreement with experimental data, and the pressure gradients needed to produce these flows are small. Furthermore, cords that were predicted to carry fast-moving or large currents were significantly more likely to increase in size than cords with slow-moving or small currents. The incompressibility of the fluids within fungi means there is a rapid global response to local fluid movements. Hence velocity of fluid flow is a local signal that conveys quasi-global information about the role of a cord within the mycelium. We suggest that fluid incompressibility and the coupling of growth and mass flow are critical physical features that enable the development of efficient, adaptive biological transport networks.

show abstract

“…In general, polarized fungal growth occurs via the restriction of the delivery of new membrane and cell wall components to hyphal tips (Wendland, 2001;Momany, 2002). The actin cytoskeleton and microtubules play an important role in this targeted delivery of vesicles to sites of growth (Heath and Steinberg, 1999). The tendency of hyphae to grow in a stable direction for considerable distances is a property common to all filamentous fungi.…”

Section: Introductionmentioning

confidence: 99%

A Ras-like GTPase Is Involved in Hyphal Growth Guidance in the Filamentous FungusAshbya gossypii

Bauer

Knechtle

Wendland

et al. 2004

MBoC

View full text Add to dashboard Cite

Characteristic features of morphogenesis in filamentous fungi are sustained polar growth at tips of hyphae and frequent initiation of novel growth sites (branches) along the extending hyphae. We have begun to study regulation of this process on the molecular level by using the model fungus Ashbya gossypii. We found that the A. gossypii Ras-like GTPase Rsr1p/Bud1p localizes to the tip region and that it is involved in apical polarization of the actin cytoskeleton, a determinant of growth direction. In the absence of RSR1/BUD1, hyphal growth was severely slowed down due to frequent phases of pausing of growth at the hyphal tip. During pausing events a hyphal tip marker, encoded by the polarisome component AgSPA2, disappeared from the tip as was shown by in vivo time-lapse fluorescence microscopy of green fluorescent protein-labeled AgSpa2p. Reoccurrence of AgSpa2p was required for the resumption of hyphal growth. In the Agrsr1/bud1⌬ deletion mutant, resumption of growth occurred at the hyphal tip in a frequently uncoordinated manner to the previous axis of polarity. Additionally, hyphal filaments in the mutant developed aberrant branching sites by mislocalizing AgSpa2p thus distorting hyphal morphology. These results define AgRsr1p/Bud1p as a key regulator of hyphal growth guidance. INTRODUCTIONPolarized cell growth in both unicellular and multicellular organisms is a prerequisite for cellular and organ morphogenesis (Harold, 1995). Hyphal tip extensions of filamentous fungi, neuronal outgrowth in vertebrates, and extension of pollen tubes in plants are extreme examples of polarized cell growth. In the case of filamentous fungi, this leads to the production of long tubular cells, the hyphae. In general, polarized fungal growth occurs via the restriction of the delivery of new membrane and cell wall components to hyphal tips (Wendland, 2001;Momany, 2002). The actin cytoskeleton and microtubules play an important role in this targeted delivery of vesicles to sites of growth (Heath and Steinberg, 1999). The tendency of hyphae to grow in a stable direction for considerable distances is a property common to all filamentous fungi. This phenomenon requires growth guidance and the maintenance of growth direction similarly as found in neuronal cells (Luo, 2000;Dickson, 2001). As hyphae elongate at the tips, the growing tip is the prime place where growth guidance should be executed.Although much research has been done to understand the ability of hyphae to change their growth direction in response to external stimuli such as electrical fields, calcium concentration, and nutrient gradients, the internal determinants of growth guidance largely remain unknown (Gow, 1994). An interesting class of mutants of the ascomycete Neurospora crassa, the ropy mutants, revealed distorted hyphal morphologies and frequent loss of growth directionality that were correlated with sustained misalignments of the Spitzenkorper (vesicle supply center) at the hyphal tip (Riquelme et al., 2000). N. crassa ropy mutants were found to encode component...

show abstract

Mechanisms of Hyphal Tip Growth: Tube Dwelling Amebae Revisited

Cited by 55 publications

References 145 publications

Mass flow and pressure-driven hyphal extension in Neurospora crassa

Mass flow and pressure-driven hyphal extension in Neurospora crassa

Growth-induced mass flows in fungal networks

A Ras-like GTPase Is Involved in Hyphal Growth Guidance in the Filamentous FungusAshbya gossypii

Contact Info

Product

Resources

About