Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released (PubMed:18208527). This sigma factor is responsible for the expression of sporulation specific genes in the forespore (PubMed:18208527). Activity repressed by anti-sigma-G factor Gin (csfB) and Lon protease during the early stages of forespore development (PubMed:17921305). When both Gin and sigma-G are expressed in E.coli Gin inhibits sigma-G activity, strongly suggesting Gin inhibits by direct physical interaction (PubMed:19497328). Interacts with anti-sigma-G factor Gin (csfB) (PubMed:18208527, PubMed:19497328). Active only in the forespore (PubMed:18208527). Expressed and active 2 hours after sporulation starts (at protein level); stimulates its own transcription (PubMed:18208527). Recognition of anti-sigma-G factor Gin (csfB) occurs via the first 71 residues (PubMed:18208527). Belongs to the sigma-70 factor family.