Biomechanics of Invasive Hyphal Growth

Abstract

Filamentous fungi penetrate diverse solid substrates, including plant and animal tissues, by a process called invasive hyphal growth. Extending hyphae overcome the resistance of their food sources by the secretion of lytic enzymes and the exertion of mechanical force. The forces utilized for invasive growth are derived from turgor pressure and are regulated through loosening of the apical cell wall of the hypha. This chapter explains how hyphae are pressurized and how they apply this pressure during invasive growth. Recent experimental work is discussed, including the use of miniature strain gauges and laser tweezers to measure the forces exerted by hyphae, and information on hyphal mechanics obtained by atomic force microscopy. Other topics in this chapter include current thinking on the role of secreted enzymes and the cytoskeleton in the invasive process, and the remarkable mechanism of leaf penetration by melanized appressoria.