Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of elsinochromes, pigments consisting of at least four interconvertible tautomers (A, B, C and D) that have a core phenolic quinone to which various side chains are attached and which play an important role in fungal pathogenesis (PubMed:18957608, PubMed:18321192). The non-reducing polyketide synthase PKS1 was proposed to iteratively catalyze decarboxylation between acetyl-CoA and malonyl-CoA subunits for polyketide chain elongation. The released polyketide undergoes cyclization to form an aromatic ring, and proceeds via serial modification steps to produce the heptaketide back- bone of elsinochrome. As elsinochrome has a symmetrical structure, two identical heptaketides are fused to form a core 1,2-dihydrobenzo-perylene ring structure, which can then be successively modified to produce the various derivatives of elsinochrome. Some of these reactions may be cooperatively carried out, at least in part, by the products of RDT1, OXR1 and PKS1. PRF1, embedded within the elsinochrome cluster possibly functions to stabilize some of the biosynthetic enzymes required for elsinochrome production. As prefoldin is a hexamer containing 2 a and 4 b subunits, additional prefoldin subunits, whose coding genes may not immediately link to the elsinochrome biosynthetic gene cluster, are required to fulfill the chaperone function. In addition, no methyltransferase-coding gene exists within the biosynthetic gene cluster, even though elsinochrome has four methyl groups at positions C3, C7, C8 and C12. Apparently, the identified gene cluster does not contain the entire entourage of genes responsible for elsinochrome biosynthesis. Once elsinochrome is synthesized, it must be exported outside the fungal cells, which is probably accomplished by the ECT1 transporter, to avoid toxicity (PubMed:21199563). The promoter contains 4 ambient pH-regulated pacC-binding consensus motifs (GCCARG) and multiple cAMP-inducible C/EBP-binding motifs (CCAAT or CAAT). In addition, the promoter contains 3 MRAGGGR and 2 CATTCY consensus motifs that have been shown to serve as binding sites for the conidial formation-related brlA and abaA transcriptional activators (PubMed:18321192). Expression is up-regulated on exposure to light, in the presence of large amounts of glucose, during nitrogen starvation or at alkaline pH, all conditions highly conducive to elsinochrome accumulation (PubMed:18957608, PubMed:18321192, PubMed:20965063). Expression is positively regulated by the cluster-specific transcription factor TSF1 (PubMed:18957608). Expression is also positively regulated by the STE12 transcription factor in a TSF1-independent manner (PubMed:20965063). 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. The release of the polyketide chain from the non-reducing polyketide synthase is mediated by the thioesterase (TE) domain localized at the C-ter of the protein. Blocks the expression of the elsinochrome cluster genes RDT1, TSF1, PRF1 and ECT1 (PubMed:18957608). Abrogates elsinochrome production, drastically reduces conidiation, and significantly decreases lesion formation on rough lemon leaves (PubMed:18321192).