PLANT PHYSIOLOGY , Vol 111, Issue 1 19-25, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Little or No Repair of Cyclobutyl Pyrimidine Dimers Is Observed in the Organellar Genomes of the Young Arabidopsis Seedling
J. J. Chen, C. Z. Jiang and A. B. Britt
Section of Plant Biology, University of California, Davis, California 95616
A Southern-blot-based, site-specific assay for ultraviolet (UV)-induced
cyclobutyl pyrimidine dimers (CPDs), employing the CPD-specific enzyme T4
endonuclease V, was used to follow the repair of this lesion in particular
DNA sequences in 5- to 6-d-old Arabidopsis thaliana seedlings. CPDs,
measured as enzyme-sensitive sites, in nuclear sequences were removed
rapidly in the light but were repaired slowly, if at all, in the dark. This
result was identical to that obtained in prior analyses of CPDs in total
cellular DNA. Assay of representative chloroplast and mitochondrial
sequences in the same DNA preparations revealed that, in contrast to
nuclear sequences, enzyme-sensitive sites are inefficiently eliminated in
both the presence and absence of visible light. These observations suggest
that Arabidopsis seedlings possess little or no capacity for the repair of
CPDs in the organellar genomes. Given the fact that the UV dose employed
only marginally affected the growth of the seedlings, we suggest that
Arabidopsis seedlings must possess very efficient mechanism(s) for the
tolerance of UV-induced DNA damage.
