Pleiotropic morphological and antibiotic deficiencies result from mutations in a gene encoding a tRNA-like product in Streptomyces coelicolor A3(2).

In Streptomyces coelicolor, bldA mutants are defective in antibiotic production and the development of aerial hyphae and spores. Subcloning analysis showed that sequences spanning an NcoI site in cloned bldA+ DNA were needed to allow complementation of a bldA mutant. Nucleotide sequencing revealed a tRNA-like sequence 9 bp downstream from the NcoI site. Five independent bldA mutations all fell in a 16-bp region in the tRNA-like sequence, one of them changing the putative anticodon. In RNA dot-blot analysis, hybridization was detected with a probe specific for the tRNA-like transcript but not with a probe for "anti-tRNA-like" transcripts. The transcripts detected were all in the salt-soluble RNA fraction and accumulated relatively late in growth. It is postulated that bldA specifies a tRNA that would recognize the codon UUA (for leucine). This codon is very rare in Streptomyces genes [which generally contain greater than 70 mole% (G + C)], suggesting a possible role for bldA in translational control of development.