Transgeneration memory of stress in plants

Owing to their sessile nature, plants are constantly exposed to a multitude of environmental stresses to which they react with a battery of responses. The result is plant tolerance to conditions such as excessive or inadequate light, water, salt and temperature, and resistance to pathogens. Not only is plant physiology known to change under abiotic or biotic stress, but changes in the genome have also been identified(1-5). However, it was not determined whether plants from successive generations of the original, stressed plants inherited the capacity for genomic change. Here we show that in Arabidopsis thaliana plants treated with short-wavelength radiation (ultraviolet-C) or flagellin ( an elicitor of plant defences(6)), somatic homologous recombination of a transgenic reporter is increased in the treated population and these increased levels of homologous recombination persist in the subsequent, untreated generations. The epigenetic trait of enhanced homologous recombination could be transmitted through both the maternal and the paternal crossing partner, and proved to be dominant. The increase of the hyper-recombination state in generations subsequent to the treated generation was independent of the presence of the transgenic allele ( the recombination substrate under consideration) in the treated plant. We conclude that environmental factors lead to increased genomic flexibility even in successive, untreated generations, and may increase the potential for adaptation.