Characterization of heterogeneous LSU rRNA profiles in Streptomyces coelicolor under different growth stages and conditions.

The Streptomyces coelicolor genome harbors six copies of divergent large subunit (LSU) rRNA genes that constitute five kinds of LSU rRNA species in a cell. We report here that each heterogeneous LSU rRNA species is differentially expressed during morphological development. However, differential expression of rRNA species was not affected by depletion of a specific nutrient such as carbon, nitrogen, or phosphate from the culture medium. Analysis of the upstream region of the rRNA operons revealed that each operon contains a different composition of conserved rRNA gene promoters, indicating that each operon is independently regulated at the transcriptional level. These findings imply the existence of a regulatory mechanism that controls the independent expression of each LSU rRNA and a possible role of different species of LSU rRNA in posttranscriptional regulation of gene expression during the life cycle of this developmentally complex microorganism.