AFSR IS A PLEIOTROPIC BUT CONDITIONALLY REQUIRED REGULATORY GENE FOR ANTIBIOTIC PRODUCTION IN STREPTOMYCES-COELICOLOR A3(2)

The N-terminal region of AfsR, a putative pleiotropic regulatory prote in for antibiotic production in Streptomyces coelicolor A3(2), is homo logous to RedD and ActII-ORF4, pathway-specific regulatory proteins re quired for the production of the antibiotics undecylprodigiosin (Red) and actinorhodin (Act), respectively, The recent identification of afs S, which lies immediately 3' of afsR and which stimulates antibiotic p roduction when cloned at high copy number, questioned whether afsR was a pleiotropic regulatory gene. In this study we demonstrate that mult iple copies of afsR can stimulate both Act and Red production and that , despite its homology, it cannot substitute for the pathway-specific regulatory genes, Moreover, an in-frame deletion that removed most of the afsR coding sequence resulted in loss of Act and Red production, a nd a marked reduction in the synthesis of the calcium-dependent antibi otic (CDA), but only under some (non-permissive) nutritional condition s, Although additional copies of afsR resulted in elevated levels of t he actII-ORF4 and redo transcripts, transcription of the pathway-speci fic regulatory genes under non-permissive conditions was unaffected by deletion of afsR. While afsR may operate independently of the pathway -specific regulatory proteins to influence antibiotic production, the activity of ActII-ORF4 and of Redo under non-permissive conditions cou ld depend on interaction with, or modification by, AfsR.