MarR-type Transcriptional Regulator ChlR Activates Expression of Tetrapyrrole Biosynthesis Genes in Response to Low-oxygen Conditions in Cyanobacteria

The Chlorite Dismutase (HemQ) from Staphylococcus aureus Has a Redox-sensitive Heme and Is Associated with the Small Colony Variant Phenotype

“…Because its cofactors are unstable in air, it is possible that HemN is likewise not stable aerobically in vivo. In a cyanobacterium possessing both hemF and hemN genes, for example, the latter was shown to be preferentially expressed under low O 2 /microaerophilic conditions (72). It is possible that hemQ could encode an O 2 -dependent CPO that is not related to hemF.…”

Transcriptional regulators ChlR and CnfR are essential for diazotrophic growth in nonheterocystous cyanobacteria

“…Three genes, orf332, orf118, and orf136, lie just downstream of modABC in the opposite direction. The amino acid sequence of orf136 shows 55% similarity to that of chlR from the nondiazotrophic cyanobacterium Synechocystis 6803 (28). Seven genes, pflB, pflA, adhE, acs, orf263, orf207, and xfp, most of which encode enzymes for anaerobic metabolism, are found in the leftmost part of the left region.…”

“…chlR encodes a MarR-type transcriptional activator for the low-oxygen induction of a small operon, chlA II -ho2-hemN, in Synechocystis 6803 (28). The ΔchlR mutant of Synechocystis 6803 shows poor growth under microoxic conditions with a very low level of Chl because the chlA II operon is not expressed and Chl biosynthesis is delayed in the steps of oxygen-dependent reactions.…”

“…5). The phenotype of NK11 strongly suggested that orf136 is the L. boryana ortholog of the Synechocystis 6803 chlR gene (28). The diazotrophic growth defect despite of normal nitrogenase activity in NK11 can be explained as follows.…”

Isolation of cyanobacterial mutants exhibiting growth defects under microoxic conditions by transposon tagging mutagenesis of <i>Synechocystis</i> sp. PCC 6803

“…Once cells are exposed to hypoxia, the gene set for low-oxygen-type enzymes is induced to complement the production of Chl a under low-oxygen conditions. ChlR is the transcriptional regulator that activates the transcription of the chlA II operon to enable the production of Chl a, even under low-oxygen conditions (Aoki et al, 2012;Ludwig et al, 2014). This regulation is also critical for nitrogen fixation (Tsujimoto et al, 2014).…”