A hallmark of the fungi is that their somatic cells form hyphae--long, polarized, tubular, walled cells, which grow by localized elongation at their tips. Hyphal tip growth is mediated by secretory vesicles and strategically arranged cytoskeletal elements concentrated in the hyphal apex and are assumed to provide the materials needed for localized gradients of new plasma membrane and cell wall as the cell continuously elongates at rates as high a 2 um/s. In the sepate (higher) fungi, secretory vesicles, microvesicles, cytoskeletal elements, and other small cell components are organized into a dynamic and visible phase-dark multicomponent complex called the Spitzenkorper (Rtip bodyS) located at the apical pole of growing cells. Coordination between the presence and behavior of the Spitzenkorper and patterns of cell growth clearly demonstrates that this apparatus plays a significant role in cell growth. Our goal is to contribute to a detailed understanding of the prec ise subcellular mechanisms responsible for hyphal tip growth because this process is the predominant mechanism by which fungi grow in nearly all environments. A useful approach for obtaining significant clues is to subject the cells to localized perturbations which manipulate the Spitzenkorper and other selected cell components. To this end, laser microbeam trapping and ablation have revealed refreshing and important new advances in the search for developmental mechanisms.
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