Reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of fusarielins F, G and H, decaketide compounds with 5 methylations and a decaline core that act as mycoestrogens as they stimulate growth of MCF-7 breast cancer cells (PubMed:22252016, PubMed:27983606). The initial compound in the pathway is produced by the reducing polyketide synthase FSL1. FSL1 lacks an active enoyl reductase (ER) domain and biosynthesis of fusarielins relies on the trans-acting enoyl reductase FSL5, before it is released through hydrolysis catalyzed by the thioesterase FSL2 (PubMed:22252016, PubMed:27983606). Fusarielins F, G, and H have a C11=C12 cis double bond and is fully reduced between C10 and C11 and between C12 and C13. FSL3 can be involved in the formation of the C11=C12 cis double bond by moving a hypothetical C10=C11 or C12=C13 trans double bond to form prefusarielin (PubMed:27983606). Prefusarielin is oxygenated at C15 and C16 by the cytochrome P450 monooxygenase FSL4, resulting in fusarielin F, which subsequently is epoxidized into fusarielin G by the same enzyme (PubMed:27983606). The final step in the pathway is a reduction of the carboxylic acid moiety to yield fusarielin H via a still undetermined mechanism (PubMed:27983606). Binds 1 phosphopantetheine covalently. Secondary metabolite biosynthesis. Expressed during sexual development (PubMed:16278459). Is not expressed during infection of wheat plants (PubMed:23290226). Expression is positively regulated by the fusarielin biosynthesis cluster-specific transcription factor FSL7, probably via its binding at the 5'-CGGNNNCCG-3' motif present in the promoter of all the cluster genes (PubMed:22252016). Multidomain protein; including a ketosynthase (KS) that catalyzes repeated decarboxylative condensation to elongate the polyketide backbone; a malonyl-CoA:ACP transacylase (MAT) that selects and transfers the extender unit malonyl-CoA; a dehydratase (DH) domain that reduces hydroxyl groups to enoyl groups; a methyltransferase (MET) domain that transfers methyl groups to the growing polyketide; a ketoreductase (KR) domain that catalyzes beta-ketoreduction steps; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm (Probable). Lacks an active enoyl reductase (ER) domain that reduces enoyl groups to alkyl groups, and biosynthesis of fusarielins relies on the trans-acting enoyl reductase FSL5 (Probable). Leads to significant increase in growth (PubMed:16278459). Abolishes the production of fusarielins F, G and H (PubMed:22252016, PubMed:27983606).