Key genes for ergothioneine biosynthesis and stress adaptation in Schizophyllum commune

Ergothioneine (EGT) is an antioxidant synthesized by fungi and bacteria, yet its biosynthesis and physiological roles, particularly in fungal growth, development, and stress resistance, are poorly understood. This study investigates the EGT biosynthetic pathway in Schizophyllum commune 20R-7-F01, a subseafloor fungus isolated from ∼2 km sediment beneath the seafloor. Gene knockout mutants (ΔScegt1a and ΔScegt2a-d) were generated to clarify the pathway and examine its role in stress responses. Six genes, Scegt1a, Scegt1b, Scegt2a, Scegt2b, Scegt2c, and Scegt2d, are essential for EGT production. ScEgt1a catalyzes the conversion of histidine and S-adenosyl-L-methionine (SAM) to hercynine (HER). ScEgt1a/ScEgt1b subsequently facilitate the reaction of HER with cysteine to form hercynyl-cysteine sulfoxide (Cys-HER), a precursor to EGT by the ScEgt2 family of enzymes. EGT is vital for fruiting body development, oxidative stress resistance (H₂O₂), and survival in anaerobic conditions. EGT-deficient mutants grow better at high temperatures (40 °C), indicating a differential regulatory role of EGT under extreme environments.