Control of light-dependent keto carotenoid biosynthesis in Nostoc 7120 by the transcription factor NtcA

Z Naturforsch C J Biosci. 2016 Sep 1;71(9-10):303-311. doi: 10.1515/znc-2016-0117.


In Nostoc PCC 7120, two different ketolases, CrtW and CrtO are involved in the formation of keto carotenoids from β-carotene. In contrast to other cyanobacteria, CrtW catalyzes the formation of monoketo echinenone whereas CrtO is the only enzyme for the synthesis of diketo canthaxanthin. This is the major photo protective carotenoid in this cyanobacterium. Under high-light conditions, basic canthaxanthin formation was transcriptionally up-regulated. Upon transfer to high light, the transcript levels of all investigated carotenogenic genes including those coding for phytoene synthase, phytoene desaturase and both ketolases were increased. These transcription changes proceeded via binding of the transcription factor NtcA to the promoter regions of the carotenogenic genes. The binding was absolutely dependent on the presence of reductants and oxo-glutarate. Light-stimulated transcript formation was inhibited by DCMU. Therefore, photosynthetic electron transport is proposed as the sensor for high-light and a changing redox state as a signal for NtcA binding.

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Canthaxanthin / biosynthesis
  • Carotenoids / biosynthesis*
  • Diuron / pharmacology
  • Dose-Response Relationship, Radiation
  • Gene Expression Regulation, Bacterial / drug effects
  • Gene Expression Regulation, Bacterial / radiation effects
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Enzymologic / radiation effects
  • Geranylgeranyl-Diphosphate Geranylgeranyltransferase / genetics
  • Geranylgeranyl-Diphosphate Geranylgeranyltransferase / metabolism
  • Herbicides / pharmacology
  • Light*
  • Nostoc / genetics
  • Nostoc / metabolism
  • Nostoc / radiation effects*
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism
  • Oxygenases / genetics
  • Oxygenases / metabolism
  • Promoter Regions, Genetic / genetics
  • Protein Binding
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription Factors / metabolism*
  • beta Carotene / metabolism


  • Bacterial Proteins
  • Herbicides
  • Transcription Factors
  • beta Carotene
  • Carotenoids
  • Canthaxanthin
  • Diuron
  • Oxidoreductases
  • Oxygenases
  • beta-carotene ketolase
  • phytoene dehydrogenase
  • Geranylgeranyl-Diphosphate Geranylgeranyltransferase
  • echinenone