A Wiskott–Aldrich syndrome protein is involved in endocytosis in <i>Aspergillus nidulans</i>

Endocytosis is vital for hyphal tip growth in filamentous fungi and is involved in the tip localization of various membrane proteins. To investigate the function of a Wiskott–Aldrich syndrome protein (WASP) in endocytosis of filamentous fungi, we identified a WASP ortholog-encoding gene, <i>wspA</i>, in <i>Aspergillus nidulans</i> and characterized it. The <i>wspA</i> product, WspA, localized to the tips of germ tubes during germination and actin rings in the subapical regions of mature hyphae. <i>wspA</i> is essential for the growth and functioned in the polarity establishment and maintenance during germination of conidia. We also investigated its function in endocytosis and revealed that endocytosis of SynA, a synaptobrevin ortholog that is known to be endocytosed at the subapical regions of hyphal tips in <i>A</i>. <i>nidulans</i>, did not occur when <i>wspA</i> expression was repressed. These results suggest that WspA plays roles in endocytosis at hyphal tips and polarity establishment during germination. Colocalization of a WASP ortholog and actin filament in the hyphal tips of <i>Aspergillus nidulans</i>.