A synchronized, large‐scale field experiment using Arabidopsis thaliana reveals the significance of the UV‐B photoreceptor UVR8 under natural conditions

This study determines the functional role of the plant ultraviolet‐B radiation (UV‐B) photoreceptor, UV RESISTANCE LOCUS 8 (UVR8) under natural conditions using a large‐scale ‘synchronized‐genetic‐perturbation‐field‐experiment’. Laboratory experiments have demonstrated a role for UVR8 in UV‐B responses but do not reflect the complexity of outdoor conditions where ‘genotype × environment’ interactions can mask laboratory‐observed responses. Arabidopsis thaliana knockout mutant, uvr8‐7, and the corresponding Wassilewskija wild type, were sown outdoors on the same date at 21 locations across Europe, ranging from 39°N to 67°N latitude. Growth and climatic data were monitored until bolting. At the onset of bolting, rosette size, dry weight, and phenolics and glucosinolates were quantified. The uvr8‐7 mutant developed a larger rosette and contained less kaempferol glycosides, quercetin glycosides and hydroxycinnamic acid derivatives than the wild type across all locations, demonstrating a role for UVR8 under field conditions. UV effects on rosette size and kaempferol glycoside content were UVR8 dependent, but independent of latitude. In contrast, differences between wild type and uvr8‐7 in total quercetin glycosides, and the quercetin‐to‐kaempferol ratio decreased with increasing latitude, that is, a more variable UV response. Thus, the large‐scale synchronized approach applied demonstrates a location‐dependent functional role of UVR8 under natural conditions.