Woronin bodies, their impact on stress resistance and virulence of the pathogenic mould Aspergillus fumigatus and their anchoring at the septal pore of filamentous Ascomycota

Abstract

Hyphae of filamentous Ascomycota consist of compartments that are connected via septal pores. To avoid a dramatic loss of cellular content after wounding, fungi developed mechanisms to occlude their septal pores. In most Pezizomycotina, so-called Woronin bodies are anchored in proximity to the pore. This is a prominent example for precise spatial positioning of organelles, but so far the underlying molecular organization has remained largely unknown. Using the pathogenic mould Aspergillus fumigatus, we provide evidence that Woronin bodies are important for stress resistance and virulence. Furthermore the molecular machinery anchoring them at the septum is described. Namely, we have identified Lah as the tethering protein and provide evidence that the Woronin body protein HexA binds to the septal pore in a Lah-dependent manner. Moreover, we demonstrate that a striking poly-histidine motif targets HexA to the septal cell wall. Thus, the axis HexA-Lah is an excellent candidate for the tether linking Woronin bodies to the septum. This model applies to A.fumigatus, but most likely also to the vast majority of the Pezizomycotina. Our findings shed light on the evolution of Woronin body anchoring and provide a basis for the development of novel strategies to combat fungal pathogens like A.fumigatus.