On the Inside

The Inside Arabidopsis near ChernobylIonizing radiation has dose-dependent effects on plant growth and development, ranging from stimulatory effects at very low doses and increasingly harmful effects for vegetative growth at intermediate levels to pronounced decreases in reproductive fitness and yields at high radiation levels.Previously, most studies concerning the effects of ionizing radiation on plants have examined a single generation of laboratory plants.Studies of the effects of chronic ionizing radiation over the course of multiple generations were rarely undertaken due to difficulties in creating a suitable model environment.Nearly 18 years have passed since the tragic nuclear accident at Chernobyl that resulted in the release of large amounts of radiation into the nearby environment.Interestingly, plants have continued to grow even in the most radioactively contaminated areas near Chernobyl.These plant populations provide a unique opportunity to study how plants adapt to chronic ionizing radiation over many generations.In this issue, report that the progeny of the ''Chernobyl'' Arabidopsis plants are more resistant to high concentrations of chemical mutagens than are wild-type plants.In regard to the possible molecular mechanisms underlying their resistance, the authors report that these plants have a much lower frequency of extrachromosomally regulated homologous recombination, significant differences in the expression of radical scavenging and DNA repair genes upon exposure to mutagens, and a higher level of genomic methylation.These data suggest that adaptation to ionizing radiation is a complex process involving epigenetic regulation of gene expression and genome stabilization.