Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of orcinol depsidone grayanic acid (GRA), the only major secondary metabolite known in C.grayi (PubMed:21289108). The first step consists in the ring and depside synthesis by PKS16 leading to 4-O-demethylsphaerophorin, involving different orcinol-like rings, one with acetyl CoA and the other with octanoyl CoA as the starter (Probable). Further depsidone formation by the GRA cluster-specific cytochrome P450 leads to 4-O-demethylgrayanic acid (Probable). Finally, the cluster specific O-methyltransferase probably converts the 4-O-demethylgrayanic acid into grayanic acid (Probable). Secondary metabolite biosynthesis. Expression is induced during grayanic acid production conditions. 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.