A rare leucine codon in adpA is implicated in the morphological defect of bldA mutants of Streptomyces coelicolor

Abstract

SummaryStreptomycetes are mycelial bacteria that produce sporulating aerial hyphae on solid media. Bald ( bld ) mutants fail to form aerial mycelium under at least some conditions. bldA encodes the only tRNA species able to read the leucine codon UUA efficiently, implying the involvement of a TTA-containing gene in initiating aerial growth. One candidate for such a gene was bldH , because the bldH109 mutant of Streptomyces coelicolor resembles bldA mutants in some aspects. In the work reported here, adpA c , an S. coelicolor gene similar to the Streptomyces griseus A factor-regulated adpA g , was found to complement the bldH109 mutant partially at both single and multiple copies. The sequence of adpA c from the bldH109 mutant revealed a frameshift. A constructed in frame deletion of adpA c conferred a bald colony phenotype, and the mutant behaved like bldA mutants and bldH109 in its pattern of extracellular signal exchange. Both adpA c and adpA g contain a TTA codon. A TTA-free version of adpA c was engineered by replacing the TTA leucine codon with a cognate TTG leucine codon. The adpA (TTA AE AE AE AE TTG) gene could partially restore aerial mycelium formation to a bldA mutant when it was followed in cis by the gene ornA , as in the natural chromosomal arrangement. This indicated that the UUA codon in adpA c mRNA is the principal target through which bldA influences morphological differentiation. It also implied that translational arrest at the UUA codon in adpA c mRNA caused a polar effect on the downstream ornA , and that the poor translation of both genes contributes extensively to the deficiency of aerial mycelium formation in bldA mutants. Unlike the situation in S. griseus , adpA c transcription does not depend on the host's g g g gbutyrolactone signalling system, at least in liquid cultures. In addition, sigma factor BldN, which is the homologue of an S. griseus sigma factor AdsA that is absent from adpA g mutants of S. griseus , was present in the constructed adpA c null mutant of S. coelicolor .

The pleitropic regulator AdpAch is required for natamycin biosynthesis and morphological differentiation in Streptomyces chattanoogensis

“…While in S. coelicolor, adpA c transcription does not depend on the butyrolactone system, the DadpA c mutant is conditionally defective in morphological differentiation. In S. coelicolor, AdpA c has also been shown to be essential for actinorhodin production, though not for undecylprodigiosin biosynthesis (Takano et al, 2003). These results suggest that the mechanism of AdpA regulation of morphological differentiation and secondary metabolism varies in a strain-specific manner.…”

“…It was first discovered in Streptomyces griseus and has also been characterized in Streptomyces coelicolor (Takano et al, 2003). In S. griseus, adpA is the sole target of the A-factor receptor (ArpA).…”

Altered desferrioxamine-mediated iron utilization is a common trait of bald mutants of Streptomyces coelicolor

“…From the 145 genes that possess a TTA codon, 33 at least one, adpA (bldH), is required for sporulation on glucose-containing media. 34,35 This suggests that the ability of iron to promote development must act upstream of the adpA regulatory network. The failure of iron to recover actinorhodin production is readily explained by the presence of a TTA codon within the sequence of the pathwayspecific activator actII-ORF4 gene which is required for activation of actinorhodin biosynthesis, as well as in actII-ORF2 for actinorhodin export.…”

Alternative oxygen‐dependent and oxygen‐independent ribonucleotide reductases in Streptomyces: cross‐regulation and physiological role in response to oxygen limitation

“…A search of the S. coelicolor genome using nrdS as the query revealed 10 ORFs sharing 48-34% sequence identity. One, SCO2792, is a close homologue of the Streptomyces griseus AdpA transcriptional regulator (84.4% identity between the gene products) (Ohnishi et al, 1999;Horinouchi, 2002) and has recently been shown to be necessary for normal S. coelicolor aerial mycelium formation: it is the bldH gene (Nguyen et al, 2003;Takano et al, 2003). A second, SCO7512, is a close homologue of the Streptomyces aureofaciens GapR regulator (89% identity between the gene products) (Sprusansky et al, 2001).…”

“…The best characterized of the Streptomyces AraC-like proteins is AdpA, a master regulator of differentiation and in S. griseus of secondary metabolism (Horinouchi, 2002;Chater and Horinouchi, 2003;Takano et al, 2003). Another AraC-like protein, the S. aureofaciens GapR protein, regulates expression of the gap gene encoding glyceraldehyde-3-phosphate dehydrogenase (Sprusansky et al, 2001).…”