A novel UV-B priming system reveals an UVR8-depedent memory, which provides resistance against UV-B stress in Arabidopsis leaves.

Single treatment of plants with pathogens like can trigger systemic acquired resistance (SAR) that lasts several days to several weeks in . Similar primed resistances were described for abiotic stresses like drought and heat stress. Most studies about plant resistance to ultraviolet (UV)-radiation used low UV-B radiations over a long period. These experimental designs make it difficult to distinguish acclimation effects from real cellular memory which facilitate transcriptional and other responses to a second UV-radiation after a latent phase. Here we present a novel UV-B priming system. We demonstrate that a single UV-B treatment, which causes neither visible damage nor accumulation of pigments, can stimulate resistance against UV-B stress. After a second damaging UV-B treatment, UV-primed plants showed significantly reduced damage in comparison to non-primed plants. Furthermore, the acquirement of the induced UV-B resistance was impaired in mutants suggesting that the UV-B receptor is essential for UV-B stress memory in . We discuss advantages and limits of our UV-B priming system which will be a powerful tool to investigate UV-B memory in future studies.