Anti-sigma factor that inhibits the activity of the extracytoplasmic function (ECF) sigma-E factor (RpoE), thereby indirectly regulating the transcription of the cycA and rpoE genes. ECF sigma factors are held in an inactive form by a cognate anti-sigma factor. Binds 2 Zn(2+) ion per subunit. The Zn(2+) bound by the N-terminus is required for anti-sigma function, the function of the Zn(2+) bound by the C-terminus is unknown. Forms a 1:1 complex with cognate ECF RNA polymerase sigma factor RpoE; this inhibits the interaction of RpoE with the RNA polymerase catalytic core. Induced by singlet oxygen. Autoregulated. Part of the rpoE-chrR operon. The N-terminal anti-sigma domain (residues 1-85) is necessary and sufficient to bind sigma-E and inhibit its activity. The C-terminal domain (residues 86-194) is required to respond to singlet oxygen (PubMed:17803943). For single chrR mutant about 12-fold increase in rpoE-regulated genes. For double rpoE-chrR deletion mutant no effect on anaerobic photosynthetic growth. In illuminated aerobically growing cells double deletion is bacteriostatic. Belongs to the zinc-associated anti-sigma factor (ZAS) superfamily.