Short-chain dehydrogenase/reductase; part of the core atranone cluster (CAC) which products are predicted to catalyze most or all steps of mycotoxin atranone synthesis, starting from geranylgeranyl pyrophosphate (GGPP) (PubMed:25015739). The initial cyclization of GGPP to dolabellane is probably performed by the terpene cyclase ATR13 (PubMed:25015739). The Baeyer-Villiger oxidation near the end of the atranone synthesis, which converts atranones D and E to atranones F and G is predicted to be catalyzed by the monooxygenase ATR8 (PubMed:25015739). Of the CAC's other predicted gene products, the reducing PKS ATR6 might synthesize a polyketide chain (PubMed:25015739). This polyketide is probably transferred onto the atranone backbone by the polyketide transferase ATR5 (By similarity). Other predicted CAC products include 4 oxygenases (ATR2, ATR3, ATR4, and ATR14), 3 short-chain reductases (ATR7, ATR9, and ATR10), and a methyltransferase (ATR12) (PubMed:25015739). These may all be involved in the various steps of atranone biosynthesis, although their specific roles must await experimental determination (PubMed:25015739). Mycotoxin biosynthesis. Belongs to the short-chain dehydrogenases/reductases (SDR) family.