Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of pestheic acid, a diphenyl ether which is a biosynthetic precursor of the unique chloropupukeananes (PubMed:24302702). The biosynthesis initiates from condensation of acetate and malonate units catalyzed by the non-reducing PKS ptaA (PubMed:24302702). As the ptaA protein is TE/CLC domain-deficient, hydrolysis and Claisen cyclization of the polyketide could be catalyzed by ptaB containing a beta-lactamase domain (PubMed:24302702). The ptaB protein might hydrolyze the thioester bond between the ACP of ptaA and the intermediate to release atrochrysone carboxylic acid, which is spontaneously dehydrated to form endocrocin anthrone (PubMed:24302702). Endocrocin anthrone is then converted to endocrocin, catalyzed by the anthrone oxygenase ptaC (PubMed:24302702). Spontaneous decarboxylation of endocrocin occurs to generate emodin (PubMed:24302702). An O-methyltransferase (ptaH or ptaI) could methylate emodin to form physcion (PubMed:24302702). PtaJ could then catalyze the oxidative cleavage of physcion, and rotation of the intermediate could then afford desmethylisosulochrin (PubMed:24302702). PtaF, a putative NADH-dependent oxidoreductase, might also participate in the oxidative cleavage step (PubMed:24302702). Desmethylisosulochrin is then transformed by another O-methyltransferase (ptaH or ptaI) to form isosulochrin (PubMed:24302702). Chlorination of isosulochrin by ptaM in the cyclohexadienone B ring then produces chloroisosulochrin (PubMed:24302702). PtaE is responsible for the oxidative coupling reactions of both benzophenones isosulochrin and chloroisosulochrin to RES-1214-1 and pestheic acid respectively, regardless of chlorination. 8 H(+) + holo-[ACP] + 8 malonyl-CoA = atrochrysone carboxyl-[ACP] + 8 CO2 + 8 CoA + 2 H2O Secondary metabolite biosynthesis. The cluster is expressed in rice fermentation medium (PubMed:25623211). Expression is correlated with the production of pestheic acid (PubMed:24302702). Three regulators are located in the cluster (ptaR1, ptaR2 and ptaR3), suggesting that the production of pestheic acid is controlled by a complex regulatory mechanism (PubMed:24302702). Multidomain protein; including a starter unit:ACP transacylase (SAT) that selects the starter unit; 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 product template (PT) domain that controls the immediate cyclization regioselectivity of the reactive polyketide backbone; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm (By similarity). Totally abolishes the production of pestheic acid but does not affect the production iso-A82775C, another precursor of chloropupukeananes (PubMed:24302702).