Somatic recombination is a mechanism by which plants can acquire the genetic variability that enables them to respond to environmental stress conditions. In an Advanced Online Publication in Nature Genetics, Lucht et al. report the effect of biotic stress on somatic recombination and plant genome stability (February 11, DOI:10.1038/ng846). They used transgenic Arabidopsis thaliana lines that carry a disrupted β-glucoronidase (GUS) reporter gene that becomes activated by a homologous recombination event. They sprayed transgenic Arabidopsis seedlings with a suspension of the plant pathogen Peronospora parasitica and scored for GUS activation. Infected plants had almost twice as many recombination sectors. Lucht et al. also demonstrated a similar effect when they used chemical stimuli, or genetic mutations, which mimic biotic stress by activating the plant pathogen-defense mechanism. These results suggest that the induction of somatic recombination may be a general response to stress and may influence the plant's ability to adapt to environmental conditions.