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Published online 19 December 2002 The function of genomes in bioenergetic organelles

Summary: Published online 19 December 2002
The function of genomes in bioenergetic organelles
John F. Allen
Plant Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden
( john.allen@plantbio.lu.se)
Mitochondria and chloroplasts are energy-transducing organelles of the cytoplasm of eukaryotic cells.
They originated as bacterial symbionts whose host cells acquired respiration from the precursor of the
mitochondrion, and oxygenic photosynthesis from the precursor of the chloroplast. The host cells also
acquired genetic information from their symbionts, eventually incorporating much of it into their own
genomes. Genes of the eukaryotic cell nucleus now encode most mitochondrial and chloroplast proteins.
Genes are copied and moved between cellular compartments with relative ease, and there is no obvious
obstacle to successful import of any protein precursor from the cytosol. So why are any genes at all
retained in cytoplasmic organelles? One proposal is that these small but functional genomes provide a
location for genes that is close to, and in the same compartment as, their gene products. This co-location
facilitates rapid and direct regulatory coupling. Redox control of synthesis de novo is put forward as the
common property of those proteins that must be encoded and synthesized within mitochondria and
chloroplasts. This testable hypothesis is termed CORR, for co-location for redox regulation. Principles,
predictions and consequences of CORR are examined in the context of competing hypotheses and cur-
rent evidence.
Keywords: chloroplasts; mitochondria; photosynthesis; respiration; gene expression; redox regulation


Source: Allen, John F. - School of Biological and Chemical Sciences, Queen Mary, University of London


Collections: Renewable Energy; Biology and Medicine