Filamentous fungi grow by forming a network of branching filaments called hyphae. The hyphae are divided into compartments by so called septa that contain a central pore, which functions in transport and communication between the different compartments. Robert-Jan Bleichrodt from Utrecht University and the Kluyver Centre, together with colleagues from the University of Tokyo, recently published an article in Molecular Microbiology on the regulation of transport through these pores. They demonstrate that small organelles called Woronin bodies can plug the central pores and by doing so maintain differences in gene expression in neighbouring hyphae.
Robert-Jan Bleichrodt investigated flow of the cytoplasm and septal plugging in Aspergillus oryzae, a filamentous fungus commonly used in Chinese and Japanese cuisine to ferment soybeans. It was known that the fungus uses specialised Woronin body plugs, originating from peroxisomes, to close down pores in the transportation canals in case of damage, to prevent the fungus from bleeding.
Bleichrodt and his colleagues now found that this plug also reversibly closes the pores during normal growth, causing temporary restrictions of the flow. This allows the hyphae to specialise independently. Some branches only grow, but others are active enough to secrete enzymes. In the article, the researchers conclude that Woronin bodies maintain hyphal heterogeneity in a fungal mycelium by impeding cytoplasmic continuity.