Unlike the majority of actinomycete secondary metabolic pathways, the biosynthesis of peptidoglycan glycosyltransferase inhibitor moenomycin in
Streptomyces ghanaensis
does not involve any cluster-situated regulators (CSRs). This raises questions about the regulatory signals that initiate and sustain moenomycin production. We now show that three pleiotropic regulatory genes for
Streptomyces
morphogenesis and antibiotic production—
bldA
,
adpA
and
absB
—exert multi-layered control over moenomycin biosynthesis in native and heterologous producers. The
bldA
gene for tRNA
Leu
UAA
is required for the translation of rare UUA codons within two key moenomycin biosynthetic genes (
moe
),
moeO5
and
moeE5
. It also indirectly influences moenomycin production by controlling the translation of the UUA-containing
adpA
and, probably, other as-yet-unknown repressor gene(s). AdpA binds key
moe
promoters and activates them. Furthermore, AdpA interacts with the
bldA
promoter, thus impacting translation of
bldA
-dependent mRNAs—that of
adpA
and several
moe
genes. Both
adpA
expression and moenomycin production are increased in an
absB-
deficient background, most probably because AbsB normally limits
adpA
mRNA abundance through ribonucleolytic cleavage. Our work highlights an underappreciated strategy for secondary metabolism regulation, in which the interaction between structural genes and pleiotropic regulators is
not
mediated by CSRs. This strategy might be relevant for a growing number of CSR-free gene clusters unearthed during actinomycete genome mining.
Genome Engineering Approaches to Improve Nosokomycin A Production by Streptomyces ghanaensis B38.3
