CSK, the redox messenger
John F. Allen* and Sujith Puthiyaveetil
School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS U.K.
Why are there genes in chloroplasts and mitochondria? The CoRR hypothesis states that organellar genes and their gene products are Co-located for Redox Regulation. CoRR predicts (i) that an irreducible core of genes must be retained by chloroplasts and mitochondria from their bacterial ancestors, and (ii) that a bacterial redox signalling pathway exerts regulatory control over expression of these genes, using components that have operated continuously throughout the transition from prokaryote to bioenergetic organelle. Chloroplast Sensor Kinase (CSK) is a chloroplast stromal protein that is the product of the nuclear gene At1g67840 of Arabidopsis thaliana. T-DNA insertion lines are impaired in plastoquinone redox control of transcription of chloroplast genes for reaction centre apoproteins of photosystem I and II and do not adjust PS I/PS II stoichiometry. CSK is homologous with bacterial histidine sensor kinases and yet is universal in photosynthetic eukaryotes. We propose that CSK provides the redox regulation that alone justifies the huge cost of maintaining a small quasi-autonomous genetic system in the chloroplast.
Puthiyaveetil S, Kavanagh TA, Cain P, Sullivan JA, Newell CA, Gray JC, Robinson C, van der Giezen M, Rogers MB, Allen JF (2008) The ancestral symbiont sensor kinase CSK links photosynthesis with gene expression in chloroplasts. Proceedings of the National Academy of Sciences of the United States of America 105: 10061-10066. | Supporting information.
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