Reducing polyketide synthase (PKS); part of the Tox1A locus, one of the 2 loci that mediate the biosynthesis of T-toxin, a family of linear polyketides 37 to 45 carbons in length, of which the major component is 41 carbons, and which leads to high virulence to maize (PubMed:8953776, PubMed:20192833). One of the PKSs (PKS1 or PKS2) could synthesize a precursor, used subsequently by the other PKS as starter unit, to add additional carbons (PubMed:16529376). Variability in the length of the final carbon backbone C35-47 could be achieved by varying the number of condensation cycles, or use of different starter or extender units or might be due to decarboxylation of the penultimate product, catalyzed by DEC1 (PubMed:12236595). Additional proteins are required for the biosynthesis of T-toxin, including oxidoreductases RED1, RED2, RED3, LAM1 and OXI1, as well as esterase TOX9 (PubMed:20192833). Mycotoxin biosynthesis. Leads to the loss of T-Toxin production, resulting in low virulence for maize (PubMed:8953776, PubMed:12236595).