Differential localization patterns of septins during growth of the human fungal pathogen Aspergillus fumigatus reveal novel functions

Septins, a conserved family of GTPases, are heteropolymeric filament-forming proteins that associate with the cell membrane and cytoskeleton and serve essential functions in cell division and morphogenesis. Their roles in fungal cell wall chitin deposition, septation, cytokinesis, and sporulation have been well established and they have recently been implicated in tissue invasion and virulence in Candida albicans. Septins have never been investigated in the human pathogenic fungus, Aspergillus fumigatus, which is a leading cause of death in immunocompromised patients. Here we localize all the five septins (AspA–E) from A. fumigatus for the first time, and show that each of the five septins exhibit varied patterns of distribution. Interestingly AspE, which is unique to filamentous fungi, and AspD, belonging to the CDC10 class of septins, localized prominently to tubular structures which were dependent on actin and microtubule networks. Localization of AspD and AspE has never been reported in filamentous fungi. Taken together these results suggest that septins in A. fumigatus might have unique functions in morphogenesis and pathogenicity.

Research highlights
► All five septins from Aspergillus fumigatus were localized during its growth.
► Filamentous fungal-specific septin, AspE, showed unique tubular localization pattern.
► AspE shifted to Microtubule Organising Centers in presence of microtubule inhibitors.
► Septin AspD, belonging to CDC10 class, showed ring-like and tubular localization.
► AspD localization was dependent on actin and microtubules.