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J. Bacteriol., 11 1995, 6401-6410, Vol 177, No. 22
N Kudo, M Kimura, T Beppu and S Horinouchi
A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) is
essentially required for aerial mycelium formation and streptomycin
production in Streptomyces griseus. A DNA fragment which induced aerial
mycelium formation and sporulation in an A-factor-deficient mutant strain,
S. griseus HH1, was cloned from this strain on a high-copy- number plasmid.
Subcloning and nucleotide sequencing revealed that one open reading frame
with 218 amino acids, named AmfC, served as a multicopy suppressor of the
aerial mycelium-defective phenotype of the A-factor-deficient strain. The
amfC gene did not restore A-factor or streptomycin production, indicating
that amfC is involved in aerial mycelium formation independently of
secondary metabolic function. Disruption of the chromosomal amfC gene in
the wild-type S. griseus strain caused a severe reduction in the abundance
of spores but no effect on the shape or size of the spores. The infrequent
sporulation of the amfC disruptant was reversed by introduction of amfC on
a plasmid. The amfC-defective phenotype was also restored by the orf1590
gene but not by the amfR-amfA-amfB gene cluster. Nucleotide sequences
homologous to the amfC gene were distributed in all of 12 Streptomyces
species tested, including Streptomyces coelicolor A3(2). The amfC homolog
of S. coelicolor A3(2) was cloned and its nucleotide sequence was
determined. The AmfC products of S. griseus and S. coelicolor A3(2) showed
a 60% identity in their amino acid sequences. Introduction of the amfC gene
of S. coelicolor A3(2) into strain HH1 induced aerial mycelium formation
and sporulation, which suggests that both play the same functional role in
morphogenesis in the strains.
Copyright © 1995, American Society for Microbiology
Cloning and characterization of a gene involved in aerial mycelium formation in Streptomyces griseus
Department of Biotechnology, University of Tokyo, Japan.
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