Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. Extracytoplasmic function (ECF) sigma factors are held in an inactive form by a cognate anti-sigma factor until released. Sigma-E controls a transcriptional response to singlet oxygen, a by-product of photosynthesis; its continuous activity requires constant exposure to singlet oxygen. The regulon has about 180 genes that protect against or repair damage induced by singlet oxygen, including itself and rpoH2, a heat shock-responsive sigma factor. Interacts transiently with the RNA polymerase catalytic core formed by RpoA, RpoB, RpoC and RpoZ (2 alpha, 1 beta, 1 beta' and 1 omega subunit) to form the RNA polymerase holoenzyme that can initiate transcription. Forms a 1:1 complex (via sigma-70 factor domain 4) with anti-sigma factor ChrR; this inhibits the interaction of RpoE with the RNA polymerase catalytic core. Induced under conditions that produce singlet oxygen (shift from anaerobic photosynthetic to aerobic growth in light). Not induced by H(2)O(2), paraquat (stimulates superoxide formation) or diamide (alters the thiol redox state). Autoregulated. Part of the rpoE-chrR operon. The sigma-70 factor domain-2 mediates sequence-specific interaction with the -10 element in promoter DNA, and plays an important role in melting the double-stranded DNA and the formation of the transcription bubble. The sigma-70 factor domain-2 mediates interaction with the RNA polymerase subunits RpoB and RpoC (By similarity). The sigma-70 factor domain-4 contains a helix-turn-helix (H-T-H) motif that mediates interaction with the -35 element in promoter DNA. The domain also mediates interaction with the RNA polymerase subunit RpoA (By similarity). Interactions between Sigma-70 factor domain-4 and anti-sigma factors prevents interaction of sigma factors with the RNA polymerase catalytic core (PubMed:17803943) (Probable). For single rpoE mutant increased sensitivity to singlet oxygen when carotenoid levels are low. For double rpoE-chrR deletion mutant no effect on anaerobic photosynthetic growth. In illuminated aerobically growing cells single and double deletion is bacteriostatic. Belongs to the sigma-70 factor family. ECF subfamily.