Septum development in filamentous ascomycetes

Filamentous ascomycetes form multinucleated hyphae that are compartmentalized by septa. In this review, the central events in the dynamics and regulation of septum assembly of two ascomycetous model organisms (Aspergillus nidulans and Neurospora crassa) are discussed. It has been shown that septum formation has different stages that start with the accumulation of signals after the completion of mitosis, followed by the assembly of a “septal actomyosin tangle” prior to plasma membrane invagination, the formation and constriction of a contractile actomyosin ring that coincides with plasma membrane invagination and finishing with construction of the septum wall and supporting plasma membrane. The role of actin, actin-binding proteins, landmark proteins, septins, and chitin synthases in each stage of septation is compared between the two model organisms. Although the main mechanisms seem to be conserved, the timing of the different proteins regulating the initiation of septum development, the determination of the septation site (i.e. cell division plane) and the constriction of the contractile actomyosin ring (CAR) differs from one organism to the other.

► The most relevant information on septum formation in filamentous fungi is compiled.
► A reliable chronology of events during septum formation is provided.
► Septum formation is compared in two important model ascomycete fungi.