Flavin-dependent halogenase; part of the gene cluster that mediates the biosynthesis of DIF-1 (Differentiation Inducing Factor-1), a signal molecule involved in the differentiation of pstO (prestalk-O) cells (PubMed:20231486). The three-step process begins with the formation of (2,4,6-trihydroxyphenyl)-1-hexan-1-one (THPH) by the polyketide synthase StlB (PubMed:16906151). THPH is then dichlorinated by the flavin-dependent halogenase ChlA (PubMed:20231486). The last step of DIF-1 biosynthesis is the O-methylation of dichloro-THPH (or des-methyl-DIF-1) by the methyltransferase DmtA to yield DIF-1 (PubMed:9446571). 2,4,6-trihydroxyphenylhexan-1-one + chloride + FADH2 + O2 = (3-chloro-2,4,6-trihydroxyphenyl)hexan-1-one + FAD + H(+) + 2 H2O (3-chloro-2,4,6-trihydroxyphenyl)hexan-1-one + chloride + FADH2 + O2 = (3,5-dichloro-2,4,6-trihydroxyphenyl)hexan-1-one + FAD + 2 H2O Impairs the production of DIF-1 and leads to deficiencies in slug structure and fruiting body formation. Belongs to the flavin-dependent halogenase family.