Probable polyketide synthase (By similarity). Produces only acylpyrones; in vitro. 4-coumaroyl-CoA + 2 H(+) + 3 malonyl-CoA = 2',4,4',6'-tetrahydroxychalcone + 3 CO2 + 4 CoA Binds 1 phosphopantetheine covalently. Secondary metabolite biosynthesis; flavonoid biosynthesis. Homodimer. Expressed during development. Expressed maximally in early development before cellular aggregation. Modular protein possessing six classical catalytic domains and a type III polyketide synthase domain. May facilitate covalent transfer of steely N-terminal acyl products directly to the C-terminal type III PKS active sites, which catalyze both iterative polyketide extension and cyclization. In reference to their hybrid nature and to their discovery in D.discoideum, authors term these type I FAS-type III PKS fusion enzymes 'steely'. Encoded by one of the numerous copies of polyketide synthase genes localized in chromosome 1. In the C-terminal section; belongs to the thiolase-like superfamily. Chalcone/stilbene synthases family.