Critical evaluation of the VSC model for tip growth
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The vesicle supply centre (VSC) model (Bartnicki-Garcia et al., 1989) for hyphal tip growth is powerful because it can model diverse developmental morphologies and predicts cellular organization based in current cell biology. It predicts that tip growth results from the random distribution of cell surface synthesizing vesicles from a point in the tip, the VSC, which determines their pattern of impact and fusion at the plasma membrane. We derive equations for tip-high gradients of vesicle fusions, generated by mechanisms not related to a supply centre, which create typical hyphal morphologies. These equations direct the conceptual basis for tip growth to vesicle fusion gradients, presumably mediated by a putative membrane skeleton associated with the plasma membrane. We also show that the organization and behaviour of motile organelles in growing hyphal tips of the oomycete,Saprolegnia ferax, argue against the presence of an apparatus capable of generating the distribution of vesicles postulated by the VSC model. We conclude that the VSC model is unlikely to describe the mechanistic basis of tip growth inS. ferax, and therefore, at best, it is not universally applicable.
Key Wordsmathematical model Saprolegnia ferax tip growth VSC model
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- Bartnicki-Garcia, S. 1990. Role of vesicles in apical growth and a new mathematical model of hyphal morphogenesis. In: Tip growth in plant and fungal cells. (ed. by Heath, I. B.), pp. 211–232. Academic Press, San Diego.Google Scholar
- Bray, D. 1992. Cell Movements Garland Publishing, Inc., New York.Google Scholar
- Heath, I. B. 1987. Preservation of a labile cortical array of actin filaments in growing hyphal tips of the fungusSaprolegnia ferax. Eur. J. Cell Biol.44: 10–16.Google Scholar
- Heath, I. B. and Kaminskyj, S. G. W. 1989. The organization of tip-growth related organelles and microtubules revealed by quantitative analysis of freeze-substituted oomycete hyphae. J. Cell Sci.93: 41–52.Google Scholar
- Heath, I. B. 1995. Integration and regulation of hyphal tip growth. Can. J. Bot.73 (Suppl. 1): S131-S139.Google Scholar
- Lodish, H. Baltimore, D., Berk, A., Zipursky, S. L., Matsudaira, P. and Darnell, J. 1995. Molecular Cell Biology, 3rd ed. Scientific American Books Inc. New York.Google Scholar
- Wessels, J. G. H. 1990. Role of cell wall architecture in fungal tip growth generation. In Tip growth in plant and fungal cells. (ed. by Heath, I. B.), pp. 1–29. Academic Press, San Diego.Google Scholar