The Cytoskeleton and Polarized Growth of Filamentous Fungi

Abstract

Polarized growth is the mechanism by which filamentous fungi extend their hyphae. Microtubules (MT) and filamentous actin (F-actin), in combination with their corresponding motor proteins, kinesin, dynein and myosin, play important roles in this process. Actin has an essential role for tip elongation and septation. It is required for vesicle secretion and cell wall extension, and possibly - together with the MT cytoskeleton - for the localization of so-called cell end marker or landmark proteins, which control growth directionality. The exact contribution of the MT cytoskeleton on polarized growth is less clear. Genetic, biochemical and cell biological approaches in Aspergillus nidulans and other fungi led to a modified view of many MT-related aspects within the past few years. There is increasing evidence that MT cables, which are visualized by immunostaining or GFP-tubulin fusion proteins, consist of several MTs and their dynamics appears to be different in fast-growing hyphal tips as compared with young germlings.