The tail domain of the Aspergillus fumigatus class V myosin MyoE orchestrates septal localization and hyphal growth

Abstract

Myosins are critical motor proteins that contribute to the secretory pathway, polarized growth, and cytokinesis. The globular tail domains of class Vmyosins have been shown to be important for cargo binding and actin cable organization. Additionally, phosphorylation plays a role in class Vmyosin cargo choice. Our previous studies on the class V myosin MyoE in the fungal pathogen Aspergillus fumigatus confirmed its requirement for normal morphology and virulence. However, the domains and molecular mechanisms governing the functions of MyoE remain unknown. Here, by analyzing tail mutants, we demonstrate that the tail is required for radial growth, conidiation, septation frequency and MyoE's location at the septum. Furthermore, MyoE is phosphorylated at multiple residues in vivo; however, alanine substitution mutants revealed that no single phosphorylated residuewas critical. Importantly, in the absence of the phosphatase calcineurin, an additional residue was phosphorylated in its tail domain. Mutation of this tail residue led to mislocalization of MyoE from the septa. This work reveals the importance of the MyoE tail domain and its phosphorylation/dephosphorylation in the growth and morphology of A. fumigatus.