Expression of the chaplin and rodlin hydrophobic sheath proteins in Streptomyces venezuelae is controlled by σ BldN and a cognate anti‐sigma factor, RsbN

Summary The chaplin and rodlin proteins together constitute the major components of the hydrophobic sheath that coats the aerial hyphae and spores in Streptomyces , and mutants lacking the chaplins are unable to erect aerial hyphae and differentiate on minimal media. We have gained insight into the developmental regulation of the chaplin ( chp ) and rodlin ( rdl ) genes by exploiting a new model species, Streptomyces venezuelae , which sporulates in liquid culture. Using microarrays, the chaplin and rodlin genes were found to be highly induced during submerged sporulation in a bldN ‐dependent manner. Using σ BldN ChIP‐chip, we show that this dependence arises because the chaplin and rodlin genes are direct biochemical targets of σ BldN . sven3186 (here named rsbN for r egulator of s igma B ld N ), the gene lying immediately downstream of bldN , was also identified as a target of σ BldN . Disruption of rsbN causes precocious sporulation and biochemical experiments demonstrate that RsbN functions as a σ BldN ‐specific anti‐sigma factor.