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Philosophical Transactions of the Royal Society B: Biological Sciences logoLink to Philosophical Transactions of the Royal Society B: Biological Sciences
. 1997 Dec 29;352(1364):1963–1974. doi: 10.1098/rstb.1997.0182

Aggregation and collapse of fungal wall vesicles in hyphal tips: a model for the origin of the Spitzenkörper

C M Regalado, B D Sleeman, K Ritz
PMCID: PMC1692166

Abstract

The intracellular origins of polarity and branch initiation in fungi centre upon a localization in the supply of fungal wall constituents to specific regions on the hyphal wall. Polarity is achieved and maintained by accumulating secretory vesicles, prior to incorporation into the wall, in the form of an apical body or Spitzenkörper. However, neither the mechanisms leading to this accumulation nor the initiation of branching, are as yet understood. We propose a mechanism, based on experimental evidence, which considers the mechanical properties of the cytoskeleton in order to explain these phenomena. Cytoskeletal viscoelastic forces are hypothesized to be responsible for biasing vesicles in their motion, and a mathematical model is derived to take these considerations into account. We find that, as a natural consequence of the assumed interactions between vesicles and cytoskeleton, wall vesicles aggregate in a localized region close to the tip apex. These results are used to interpret the origin of the Spitzenkörper. The model also shows that an aggregation peak can collapse and give rise to two new centres of aggregation coexisting near the tip. We interpret this as a mechanism for apical branching, in agreement with published observations. We also investigate the consequences and presumptive role of vesicle–cytoskeleton interactions in the migration of satellite Spitzenkörper. The results of this work strongly suggest that the formation of the Spitzenkörper and the series of dynamical events leading to hyphal branching arise as a consequence of the bias in vesicle motion resulting from interactions with the cytoskeleton.

Keywords: Fungal Wall Vesicles Spitzenkörper Hyphal Tips Vesicle–Cytoskeletons Interactions

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Selected References

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