How plants cope with the damaging effects of UV radiation

Because of their dependence on sunlight for photosynthesis, plants are also exposed to the DNA-damaging effects of ultraviolet (UV) radiation. In the 15 March Genes and Development, Roman Ulm of the Friedrich Miescher Institute in Basel and co-workers report on how plants cope with genotoxic stresses, such as UV radiation (Genes Dev 2001, 15:699-709).

Ulm et al. identified a mutation in Arabidopsis thaliana, mkp1, that results in hypersensitivity to the DNA-damaging agent MMS (methyl methanesulphonate) and to UV-C radiation. MMS at 120 parts per million was lethal to Arabidopsis mutants, whereas wild-type plants could tolerate higher concentrations of the drug; UV-C radiation (55 J/m2) arrested the growth of mutant roots but had no effect on wild-type roots. In the absence of genotoxic stresses, the mutants were indistinguishable from their wild-type counterparts, suggesting that the MKP1gene has a specific role in the stress response.

The gene that is disrupted in the mkp1 mutant is normally transcribed into a 3 kb mRNA that encodes a MAP (mitogen-activated protein) kinase phosphatase. These enzymes have been linked to stress responses in mammalian cells.