The repair of ultraviolet light-induced DNA damage in plant cells

Abstract

In comparison with other eucaryotic systems, our understanding of the repair of ultraviolet light-induced DNA damage in plants is still rather limited. Morphological features and pigments afford considerable protection and attenuate the dose of ultraviolet light reaching the plant cell DNA. Nevertheless, the available evidence supports the additional existence of enzyme-mediated photoreactivation and excision-repair mechanisms in a variety of systems including pollen, whole seedlings and plants and protoplasts derived from leaves and cultured cells. The properties of these mechanisms appear similar to those of other eucaryotes. The action spectra of photolyases isolated from beans and maize are similar to those of the flavin-containing enzymes from bacteria and yeast. In the absence of visible light, pyrimidine dimers are excised from the DNA of whole plants and isolated protoplasts at rates typical of animal cells i.e. 25–30 000 dimers/cell/h. UV-stimulated repair replication has been demonstrated in non-replicating pollen and leaf protoplasts and also in dividing cultured protoplasts in the presence of a novel replicational inhibitor, compactin. This process appears to be initiated by a high-molecular-weight UV-endonuclease which has been partially purified and which recognises bulky lesions in DNA, including pyrimidine dimers.