One hundred years of the Spitzenkörper: A story in three acts

The production and growth of long filamentous cells, i.e., hyphae, via apical extension is a hallmark of most fungi. This polarized growth requires a robust secretory system to deliver materials, such as membrane components, proteins, and cell wall precursors, to the growing tip. Central to this process is the formation of the Spitzenkörper (SPK), a structure located at the hyphal apex. The SPK is most observed in species from the Basidiomycota and Ascomycota, as well as in some members of the Blastocladiomycota and the Zoopagomycota. It is composed of a dynamic assembly of secretory vesicles, cytoskeletal elements, and signaling proteins. This review explores the current understanding of SPK structure and function and outlines future directions for advancing research in this area.