Tip Growth in Filamentous Fungi: A Road Trip to the Apex

Fungal hyphae extend by apical growth. This process involves the polarized traffic of secretory vesicles to the Spitzenkörper (SPK) and their subsequent distribution to specific domains of the plasma membrane, where they fuse to provide all the enzymes and material needed for cell wall expansion. Endocytic recycling and localized translation of specific mRNAs play an important role in hyphal apical growth. The traffic of vesicular carriers from synthesis sites to their destinations is coordinated by the combined action of coats, tethers, Rab GTPases, motors, and SNAREs in a mechanism that is just beginning to be understood. Only recently has it been confirmed that the different-sized vesicles present at the SPK contain distinct cell wall biosynthetic activities and are distributed in a stratified manner.