Functional and evolutionary implications of a survey of various actinomycetes for homologues of two Streptomyces coelicolor sporulation genes.

In Streptomyces coelicolor A3(2) the whiB and whiG genes are essential for sporulation, their deduced products being a possible transcriptional activator and an RNA polymerase sigma factor, respectively. In a survey of DNA from diverse actinomycetes by Southern blotting, all samples tested hybridized with whiB, but only those representing genera capable of producing sporulating aerial mycelium hybridized with whiG. It is postulated that whiB may play a more intimate role in hyphal fragmentation processes (including sporulation) than whiG. The whiB and whiG homologues (whiB-Stv and whiG-Stv) of Streptoverticillium griseocarneum were cloned and sequenced, and subjected to functional tests in S. coelicolor whiB and whiG mutants. The genes were closely similar, but not identical, to their S. coelicolor counterparts at the DNA and deduced protein levels, and both Stv. griseocarnum gene products could function well in S. coelicolor. However, studies with hybrid transcription units suggested that the promoter region of whiB-Stv is somewhat inefficient in S. coelicolor.