Lemna minor plants chronically exposed to ionising radiation:RNA-seq analysis indicates a dose rate dependent shift fromacclimation to survival strategies

Ecotoxicological research provides knowledge on ionising radiation-induced responses in different plantspecies. However, the sparse data currently available are mainly extracted from acute exposure treat-ments. To provide a better understanding of environmental exposure scenarios, the response to stressin plants must be followed in more natural relevant chronic conditions. We previously showed morpho-logical and biochemical responses in Lemna minor plants continuously exposed for 7 days in a dose-ratedependent manner. In this study responses on molecular (gene expression) and physiological (photosyn-thetic) level are evaluated in L. minor plants exposed to ionising radiation. To enable this, we examined thegene expression profiles of irradiated L. minor plants by using an RNA-seq approach. The gene expressiondata reveal indications that L. minor plants exposed at lower dose rates, can tolerate the exposure by trig-gering acclimation responses. In contrast, at the highest dose rate tested, a high number of genes relatedto antioxidative defense systems, DNA repair and cell cycle were differentially expressed suggesting thatonly high dose rates of ionising radiation drive L. minor plants into survival strategies. Notably, the pho-tosynthetic process seems to be unaffected in L. minor plants among the tested dose rates. This study,supported by our earlier work, clearly indicates that plants shift from acclimation responses towardssurvival responses at increasing dose rates of ionising radiation.�