Fig. 1

Chemical structures of basidiomycete monomeric and dimeric hepta- and octaketides. Clade VIII non-reducing polyketide synthases (NR-PKSs) comprise orsellinic acid (3) synthases, including ArmB [24] and others. Clade XII NR-PKSs are known from Cortinarius species [22], lack an N-terminal SAT domain and are associated with the synthesis of bi- and tricyclic polyketides such as 6-hydroxymusizin (2) and atrochrysone (1). In basidiomycetes, 1 and 2, and their derivatives, often occur in dimeric form, as shown for phlegmacin (known from C. odorifer [36]), rufoolivacin (known from C. rufoolivaceus [36]) and flavomannin (known from Tricholoma flavovirens [40])