THE PLANT CELL, Vol 6, Issue 9 1311-1317, Copyright © 1994 by American Society of Plant Biologists
A Light-Dependent Pathway for the Elimination of UV-Induced Pyrimidine (6-4) Pyrimidinone Photoproducts in Arabidopsis
J. J. Chen, D. L. Mitchell and A. B. Britt
Division of Biological Sciences, Section of Plant Biology, University of California, Davis, California 95616
Light-dependent repair of UV-induced cyclobutane pyrimidine dimers (CPDs)
and pyrimidine (6-4) pyrimidinone dimers (6-4 products) was investigated in
an excision repair-deficient Arabidopsis mutant. As previously described,
exposure to broad-spectrum lighting was found to greatly enhance the rate
of repair of CPDs. We demonstrate that 6-4 products are also efficiently
eliminated in a light-dependent manner and that this photoreactivation of
6-4 products occurs independently of the previously described 6-4 product
dark repair pathway. The light-dependent repair of both 6-4 products and
CPDs occurs in the presence of blue light (435 nm) but not upon exposure to
light of longer wavelengths. We also found that high-level expression of
the CPD-specific photoreactivating activity in the Arabidopsis seedling
requires induction by exposure to light prior to as well as during the
period of repair while the 6-4 photoreactivating activity is constitutively
expressed. This differential regulation of the photoreactivating activities
suggests that the Arabidopsis seedling produces at least two distinct
photolyases: one specific for CPDs and the other specific for 6-4 products.
