The Cytoskeleton in Filamentous Fungi

This chapter focuses on the microtubule and actin cytoskeletons of filamentous fungi, including the motor proteins that are integral to cytoskeletal function. Relevant results from yeasts are discussed to provide background and context. The emphasis is on more recent data from live-cell imaging as well as genetic and molecular genetic studies. It has been shown that both the microtubule and the actin cytoskeletons play roles in polarized growth of hyphae, and how these cytoskeletal elements function to support hyphal growth and organelle distribution in elongated hyphae is a topic of great interest. Dynein in filamentous fungi also participates in organizing the microtubule network by regulating microtubule dynamics and by providing force for transporting microtubules. In filamentous fungi, the actin cytoskeleton and its myosin motors are important for the delivery of cell membrane and cell wall components to the growing hyphal tip and to the septum. Myosins are a diverse superfamily of actin motor proteins that play various cellular roles. In filamentous fungi such as A. nidulans and N. crassa, four families of myosins have been found, including myosin-I, myosin-II, myosin-V, and the fungus-specific chitin synthases with myosin motor domains. Hyphal growth in filamentous fungi needs both microtubule and actin cytoskeletons, and thus, it would be important to understand how these two systems interact to coordinate vesicle transport towards the hyphal tip.