Hyphae in Hypha: Large-Scale Tubular and Tubular-Lamellar Endomembrane Fungal Systems

Fungi and oomycetes have four large intracellular membrane systems consisting of tubes, lamellae, or a combination thereof. Such elongated membrane structures can extend for tens of micrometers in hyphal cells, branching and connecting into bundles and networks. These systems are represented by tubular vacuoles, elongated mitochondria, endoplasmic reticulum, and macroinvaginations of the plasma membrane. They are most developed in xylotrophic and mycorrhiza-forming basidiomycetes. This review examines three membrane systems, excluding the macroinvagination system. It proposes that, at least in apical hyphae, tubular vacuoles, elongated mitochondria, and the endoplasmic reticulum form a single intrahyphal complex with shared physiological functions. The main function is the transport of dissolved substances, independent of intrahyphal mass flow. In basidiomycetes, such a complex plays an important role, ensuring the independence of resource exchange or accumulation with the host plant or dead wood from the growth rate of apical hyphae and variable turgor gradients within them.