Sing orthologues among large families of paralogues is less severe with the phylogenetically distinct ECF class of sigmas and their antisigma partners, which are more diverse than the class regulated through BldG-like cascades, and usually show high partner specificity (Staron et al., 2009). bldN, a direct target of BldD, encodes one of about 50 S. coelicolor ECF sigma factors (Bibb et al., 2000;