HYBRIDIZATION AND DNA-SEQUENCE ANALYSES SUGGEST AN EARLY EVOLUTIONARYDIVERGENCE OF RELATED BIOSYNTHETIC GENE SETS ENCODING POLYKETIDE ANTIBIOTICS AND SPORE PIGMENTS IN STREPTOMYCES SPP

The whiE gene cluster of Streptomyces coelicolor, which is related to gene sets encoding the biosynthesis of polycyclic aromatic polyketide antibiotics, determines a spore pigment. Southern blotting using probe s from three different parts of the whiE cluster revealed related gene sets in about half of a collection of diverse Streptomyces strains. A 5.2-kb segment of one such cluster, sch, previously shown to determin e spore pigmentation in Streptomyces halstedii, was sequenced. Seven o pen reading frames (ORFs), two of them incomplete, were found. Six of the ORFs resemble the known part of the whiE cluster closely. The deri ved gene products include a ketosynthase (= condensing enzyme) pair, a cyl carrier protein and cyclase, as well as two of unidentified functi on. The seventh ORF diverges from the main cluster and encodes a prote in that resembles a dichlorophenol hydroxylase. Comparison with sequen ces of related gene sets for the biosynthesis of antibiotics suggests that gene clusters destined to specify pigment production diverged fro m those destined to specify antibiotics early in the evolution of the Streptomyces genus.