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DNA damage and repair

The plastid DNA of maize seedlings is subjected to increasing damage as the seedlings develop. The DNA damage is due to oxidative environments created by photo-oxidative reactions and photosynthetic / respiratory electron transfer. Some DNA molecules are repaired but DNA with unrepaired damage is apparently degraded to non-functional fragments.

DNA repair proteins are encoded by the cell's nuclear genome and then translocated to plastids where they maintain genome stability/ integrity by repairing the plastid's DNA. For example, in chloroplasts of the moss Physcomitrella patens, a protein employed in DNA mismatch repair (Msh1) interacts with proteins employed in recombinational repair (RecA and RecG) to maintain plastid genome stability.