Mycelium

About: Mycelium is a research topic. Over the lifetime, 8923 publications have been published within this topic receiving 170993 citations.

Host-induced gene silencing of cytochrome P450 lanosterol C14α-demethylase–encoding genes confers strong resistance to Fusarium species

Abstract: Head blight, which is caused by mycotoxin-producing fungi of the genus Fusarium, is an economically important crop disease. We assessed the potential of host-induced gene silencing targeting the fungal cytochrome P450 lanosterol C-14α-demethylase (CYP51) genes, which are essential for ergosterol biosynthesis, to restrict fungal infection. In axenic cultures of Fusarium graminearum, in vitro feeding of CYP3RNA, a 791-nt double-stranded (ds)RNA complementary to CYP51A, CYP51B, and CYP51C, resulted in growth inhibition [half-maximum growth inhibition (IC50) = 1.2 nM] as well as altered fungal morphology, similar to that observed after treatment with the azole fungicide tebuconazole, for which the CYP51 enzyme is a target. Expression of the same dsRNA in Arabidopsis and barley rendered susceptible plants highly resistant to fungal infection. Microscopic analysis revealed that mycelium formation on CYP3RNA-expressing leaves was restricted to the inoculation sites, and that inoculated barley caryopses were virtually free of fungal hyphae. This inhibition of fungal growth correlated with in planta production of siRNAs corresponding to the targeted CYP51 sequences, as well as highly efficient silencing of the fungal CYP51 genes. The high efficiency of fungal inhibition suggests that host-induced gene-silencing targeting of the CYP51 genes is an alternative to chemical treatments for the control of devastating fungal diseases.

A novel class of secreted hydrophobic proteins is involved in aerial hyphae formation in Streptomyces coelicolor by forming amyloid-like fibrils

Abstract: Streptomycetes exhibit a complex morphological differentiation. After a submerged mycelium has been formed, filaments grow into the air to septate into spores. A class of eight hydrophobic secreted proteins, ChpA-H, was shown to be instrumental in the development of Streptomyces coelicolor. Mature forms of ChpD-H are up to 63 amino acids in length, and those of ChpA-C are larger (+/-225 amino acids). ChpA-C contain two domains similar to ChpD-H, as well as a cell-wall sorting signal. The chp genes were expressed in submerged mycelium (chpE and chpH) as well as in aerial hyphae (chpA-H). Formation of aerial hyphae was strongly affected in a strain in which six chp genes were deleted (DeltachpABCDEH). A mixture of ChpD-H purified from cell walls of aerial hyphae complemented the DeltachpABCDEH strain extracellularly, and it accelerated development in the wild-type strain. The protein mixture was highly surface active, and it self-assembled into amyloid-like fibrils at the water-air interface. The fibrils resembled those of a surface layer of aerial hyphae. We thus conclude that the amyloid-like fibrils of ChpD-H lower the water surface tension to allow aerial growth and cover aerial structures, rendering them hydrophobic. ChpA-C possibly bind ChpD-H to the cell wall.

Fungal relationships and structural identity of their ectomycorrhizae

Abstract: Aproximately 5,000–6,000 fungal species form ectomyorrhizae (ECM), the symbiotic organs with roots of predominantly trees. The contributing fungi are not evenly distributed over the system of fungi. Within Basidiomycota exclusively Hymenomycetes and within Ascomycota exclusively Ascomycetes contribute to the symbiosis. Hymenomycetes play a big part, Ascomycetes a minor role; Zygomycetes only form exceptionally ECM. Responsible for ascomycetous ECM are mostly Pezizales with their hypogeous derivatives, whereas Boletales, Gomphales, Thelephorales, Amanitaceae, Cantharellaceae, Cortinariaceae, Russulaceae, and Tricholomataceae are the most important ectomycorrhizal relationships within Hymenomycetes. ECM, as transmitting organs between soil and roots, are transporting carbohydrates for growth of mycelium and fruitbodies from roots and have to satisfy the tree’s demand for water and nutrients. The latter task particularly influences the structure of ECM as nutrients are patchily distributed in the soil and saprotrophic as well as ectomycorrhizal fungi can act as strong competitors for nutrients. In focusing these requirements, ECM developed variously structured hyphal sheaths around the roots, the so-called mantles, and differently organized mycelium that emanates from the mantle, the so-called extramatrical mycelium. The mantles can be plectenchymatous consisting of loosely woven, differently arranged hyphae or they are densely packed, forming a pseudoparenchyma similar to the epidermis of leaves. The extramatrical mycelium grows either as simple scattered hyphae from the mantle into the soil or it can be united to undifferentiated rhizomorphs with a small reach or to highly organized root-like organs with vessel-like hyphae for efficient water and nutrient transport from distances of decimeters. Cystidia, sterile and variously shaped hyphal ends, possibly appropriate for preventing animal attack, in addition, can cover mantles and rhizomorphs. Although only a limited number of species could be considered, some general conclusions are possible.

In situ13CO2 pulse-labelling of upland grassland demonstrates a rapid pathway of carbon flux from arbuscular mycorrhizal mycelia to the soil

Abstract: Summary • The flux of pulse-derived 13C from upland pasture plants to the external mycelium of their arbuscular mycorrhizal (AM) symbionts was traced and quantified over a 7-d post-labelling period. • Mesh cores, which allowed in-growth of native AM mycelium but were impenetrable to roots, were inserted into unlimed and limed plots and the surrounding vegetation was exposed to 13CO2 at ambient CO2 concentrations. • Release of 13CO2 from cores colonized by AM mycelium peaked 9–14 h after labelling and declined within 24 h after severance of mycelial connections to roots. Between 5 and 8% of carbon lost by plants was respired by AM mycelium over the first 21 h after labelling. Liming increased the amount of carbon fixed by plants and subsequently allocated to fine roots and AM mycelium. • The results demonstrate for the first time under field conditions that AM mycelia provide a rapid and important pathway of carbon flux from plants to the soil and atmosphere.