O-methyltransferase; part of the gene cluster that mediates the biosynthesis of aurasperone B, a dimeric gamma-naphthopyrone (PubMed:31067027). The first step in the biosynthesis of aurasperone B is the production of gamma-naphthopyrone precursor YWA1 by the non-reducing polyketide synthase albA, via condensation of one acetyl-CoA starter unit with 6 malonyl-CoA units (PubMed:31067027). YWA1 is then methylated by aunE at position C-6 to yield foncesin which is further methylated at position C-8 by aunD to produce fonsecin B (Probable). A key enzyme in the biosynthetic pathway is the cytochrome P450 monooxygenase aunB which catalyzes the oxidative dimerization of fonsecin B to aurasperone B (PubMed:31067027). AunB also catalyzes the oxidative dimerization of rubrofusarin B into aurasperone A (PubMed:31067027). Secondary metabolite biosynthesis. Leads to the accumulatio of aurasperone B and fonsecin B. Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family.