The role of +TIPs in directional tip expansion

Abstract

Aspergillus nidulans is an ideal model to study nuclear migration and intracellular transport by dynein and kinesin owing to its long neuron-like hyphae, conserved transport mechanisms, and powerful genetics. In this organism, as in other filamentous fungi, microtubules have been implicated in patterning cell shape through polarized tip growth - the hallmark mode of growth that generates the elongated hyphae. Exactly how microtubules regulate tip growth is incompletely understood and remains a fascinating question for various cell types, such as pollen tubes and root hairs. Zeng et al. (2014) describe important new findings in A. nidulans regarding the role of EBA, the master regulator of microtubule plus end-tracking proteins, in specifying microtubule dynamics required for directional tip growth at the hyphal tip.

Figure 1. A model for +TIPs in A. nidulans hyphal tip

(1) CLIPA, ALPA, and KIPA depend on EBA for plus end-tracking on microtubules polymerizing towards the hyphal apex. (2) CLIPA functioning at sites other than the plus ends. (3) EBA and CLIPA promoting microtubule turnover at the hyphal tip cortex.