Woronin body

A Woronin body (named after the Russian botanist Mikhail Stepanovich Woronin) is an organelle found near the septae that divide hyphal compartments in filamentous Ascomycota. It is formed by budding from conventional peroxisomes. Woronin bodies are present in the fungal class Pezizomycotina, which includes species such as Neurospora crassa, Aspergillus fumigatus, and various plant pathogenic fungi, like Zymoseptoria tritici.

Transmission electron microscopy (TEM) reveals Woronin bodies as structures with a dense, proteinaceous core surrounded by a tightly bound unit membrane. The membrane-bound structure contains a dense core made of a protein called HEX-1, which self-assembles into a hexagonal crystal and forms a 3D protein lattice. The size of Woronin bodies range from 100 nm to over 1 μm, consistently exceeding the diameter of the septal pore.

In most species, Woronin bodies are positioned on both sides of the septum and are connected to the pore via a mesh-like tether. Evidence for this tether was strengthened by laser tweezer experiments, which demonstrated that Woronin bodies, when displaced from the septum, return to their original position upon release.

One established function of Woronin bodies is the plugging of the septal pores after hyphal wounding, which restricts the loss of cytoplasm to the sites of injury. This plug is reinforced as new material is deposited over the septal plate and on the cytoplasmic side of the Woronin body, consolidating it into a permanent seal. The plugging process occurs rapidly within the mycelium near the site of significant damage.

Woronin bodies can also regulate pore opening and closure, which aids in the control of hyphal heterogeneity. This dynamic function enables the fungus to adapt to changing environmental conditions while maintaining cellular homeostasis by selectively regulating the flow of materials between hyphal compartments.