Streptomycesgenes involved in aerial mycelium formation

Cloning of genes as suppressors of the aerial mycelium-defective phenotype of Streptomyces griseus HH1 resulting from A-factor-deficiency has led to the identification of several genes, including amfR, amfAlamfB, amfC, and orf1590. These genes are involved in aerial mycelium formation independent of secondary metabolic function. Among these, AmfR which belongs to the family of response regulators of two-component regulatory systems and AmfA/AmfB similar to ATP-dependent membrane translocators are analogous to the multicomponent phosphorelay and the Spo0K system, respectively, both of which are required for the initiation of sporulation in Bacillus subtilis. Involvement of a protein serine/threonine kinase in aerial mycelium formation is also suggested, because the Streptomyces coelicolor A3(2) afsK gene encoding a ‘eukaryotic’-type protein kinase reverses the aerial mycelium-defective phenotype of strain HH1, independent of secondary metabolic function.