The developmental fate of S. coelicolor hyphae depends upon a gene product homologous with the motility σ factor of B. subtilis

In the mycelial prokaryote S. coelicolor, whiG is a gene dispensable for growth but needed for the earliest stages of spore formation in aerial hyphae. Nucleotide sequencing indicates that whiG encodes an RNA polymerase σ factor highly similar to the motility σ factor ( σ 28) of B. subtilis. High copy number of an intact whiG gene caused sporulation in vegetative hyphae that are usually fated to lyse without sporulating. However, the introduction of many copies of a σ 28-dependent promoter from B. subtilis into S. coelicolor reduced sporulation, suggesting partial sequestration of the whiG gene product by the foreign promoter sequences. We propose that the level of whiG σ factor is crucial in determining the developmental fate of hyphae.