Stuck in one place, plants must endure a host of pests and problems. Too much light, too little light, bacterial invaders, insect infestation--the list seems overwhelming. Yet plants persevere, adapting to changing conditions both in their physiology and their genomes. Now scientists have shown that this ability to increase the frequency of genetic mutation in response to stress is passed through as many as four subsequent generations.

Barbara Hohn of the Friedrich Miescher Institute for Biomedical Research in Basel, Switzerland, and her colleagues subjected several thale cress plants--Arabidopsis thaliana--to harsh levels of ultraviolet light or evidence of bacterial pathogens. The plants survived the ordeal by upping the frequency of homologous recombination (genetic swapping) during cell division as expected. More importantly, the plants passed this elevated mutation rate onto their offspring¿at a rate two to four times higher than in the progeny of unstressed parents--even when these offspring were not challenged with UV or pathogens.

This trait persisted when only one of the parent plants was stressed and regardless of its gender. Yet, the increased frequency does not derive from a random change in the genetic code of the plants, because the entire population of stressed plants responded in similar ways. "The epigenetic change revealed may be inscribed on the entire genome, on a particular locus, or on the transgene of the treated plants," the researchers speculate in the paper presenting the finding, published online yesterday in Nature. "We propose that the environmental influences that lead to increased genomic dynamics even in successive, untreated generations may increase the potential for adaptive evolution."