Endocytic recycling underlies the polarized hyphal mode of life

An idiosyncratic feature of filamentous fungi is that their vegetative phase consists of tube-shaped cells (hyphae) that grow exclusively by apical extension. Therefore polarized growth is a distinctive feature of hyphal organisms, and the one that underlies their capacity to colonize substrates or, in the case of pathogenic species, to invade tissues. To sustain the strikingly fast rates of growth, the secretory pathway must efficiently deliver to the apex both the lipids accounting for the extension in plasma membrane surface and the enzymes that synthesize the cell wall in the hyphal tip dome. Our studies with one of these physiologically crucial cell-wall modifying enzymes demonstrated that its polarized localization to the apical dome is mediated by endocytic recycling, which streamlines the delivery of this type of cargoes to their site of action to facilitate rapid apical extension.