An order of fungi in the phylum BASIDIOMYCOTA having macroscopic basidiocarps. The members are characterized by their saprophytic activities as decomposers, particularly in the degradation of CELLULOSE and LIGNIN. A large number of species in the order have been used medicinally. (From Alexopoulos, Introductory Mycology, 4th ed, pp504-68)

The intergenic DNA segments that are between the ribosomal RNA genes (internal transcribed spacers) and between the tandemly repeated units of rDNA (external transcribed spacers and nontranscribed spacers).