The bldD Gene of Streptomyces coelicolor A3(2): a Regulatory Gene Involved in Morphogenesis and Antibiotic Production

Abstract

The bld mutants of Streptomyces coelicolor A3(2) are blocked at the earliest stage of sporulation, the formation of aerial hyphae, and are pleiotropically defective in antibiotic production. Using a phage library of wild-type S. coelicolor DNA, we isolated a recombinant phage which restored both sporulation and antibiotic production to strains carrying the single known bldD mutation. Nucleotide sequence analysis of a 1.3-kb complementing subclone identified an open reading frame, designated bldD, encoding a translation product of 167 amino acid residues. Nucleotide sequence analysis of the bldD-containing fragment amplified from the chromosome of a bldD mutant strain revealed a point mutation changing a tyrosine residue at amino acid position 62 to a cysteine. Although a comparison of the BldD sequence to known proteins in the databases failed to show any strong similarities, analysis of the BldD sequence for secondary structural elements did reveal a putative helix-turn-helix, DNA recognition element near the C terminus of the protein. A comparison of bldD transcript levels in the bldD ؉ and bldD mutant strains using both Northern blot analysis and S1 nuclease protection studies showed vast overexpression of bldD transcripts in the mutant, suggesting that BldD negatively regulates its own synthesis. High-resolution S1 nuclease mapping identified the transcription start point as a G residue 63 nucleotides upstream from the bldD start codon and 7 nucleotides downstream from ؊10 and ؊35 sequences resembling E. coli-like streptomycete promoters.

BldD is a direct regulator of key developmental genes in Streptomyces coelicolor A3(2)

“…BldD was predicted to be a DNA-binding protein (Elliot et al, 1998) and was shown to bind to its own promoter, consistent with the marked upregulation of bldD transcription in a bldD mutant (Elliot and Leskiw, 1999). Here, we identify three additional chromosomal targets for BldD, which show that BldD is a regulator of key genes associated with development.…”

“…with a long, disordered linker region (Elliot et al, 1998), which might allow BldD to bind sequences with a relaxed spacer requirement.…”

“…The bld genes were initially identified by mutations that caused the loss of white fuzzy aerial hyphae, resulting in colonies with a smooth, shiny,`bald' appearance. The bld genes encode a diverse range of products, including a tRNA (bldA; Lawlor et al, 1987), an ATP-binding cassette (ABC) membrane-spanning transporter (bldK; Nodwell et al, 1996), a sigma factor (bldN; Bibb et al 2000) and an unrelated anti-anti-sigma factor (bldG; Bignell et al, 2000), as well as numerous transcription factors [bldB (Pope et al, 1998), bldD (Elliot et al, 1998) and bldM (Molle and Buttner, 2000)]. Interestingly, a number of the bld genes also appear to influence antibiotic production, and mutations in some bld genes have been found to affect the regulation of carbon utilization (Pope et al, 1996), suggesting a global regulatory role for the bld genes in colony development.…”

The evolution of development inStreptomycesanalysed by genome comparisons

“…BldD is a regulatory protein that possesses a putative DNAbinding domain similar to those of Xre-like regulators, but is not otherwise closely similar to any known class of regulators (Elliot et al, 1998). It represses its own expression and that of several other developmental genes including bldN and whiG (Elliot & Leskiw, 1999;Elliot et al, 2001).…”

Community structure and antibiotic production of Streptomyces nodosus bioreactors cultured in liquid environments

“…Secondary metabolism usually occurs when growth ceases or slows, and on solid media this usually correlates with aerial hyphae formation (Liu et al, 1975;Elliot et al, 1998). This transition is conveyed to the community via soluble signalling molecules [quorum sensing (QS) molecules or autoinducers] (Horinouchi and Beppu, 1992;Chater and Horinouchi, 2003;Takano, 2006).…”