UV RESISTANCE LOCUS 8 signalling enhances photosynthetic resilience to herbicide‐induced damage in Arabidopsis thaliana

Perception of low irradiance ultraviolet B (UV-B) light (280-315 nm) by the UV RESISTANCE LOCUS 8 (UVR8) photoreceptor initiates signalling pathways that enhance plant defences to UV-B damage, mitigating the effects of higher photon irradiances. We therefore questioned whether UVR8 signalling could also prime plants against herbicide-induced damage, promoting postspray survival. We assessed the effects of a 2 d, low irradiance UV-B pretreatment on the photosynthetic resilience and survival of Arabidopsis thaliana plants treated with herbicides promoting photosynthetic disruption and oxidative stress. UV-B acclimation increased leaf carotenoid production, antioxidant activity and nonphotochemical quenching (NPQ) and delayed herbicide-induced reductions in electron transport rate (ETR), facilitating postspray regrowth and enhancing plant survival. In the absence of UV-B, this protection declined within 4 d, suggesting that it is unlikely to result from structural modifications. UV-B-mediated enhancement of photosynthetic resilience was abolished in the uvr8-6 mutant and increased in the UV-B hyper-responsive repressor of UV-B photomorphogenesis1/2 (rup1rup2) mutant, highlighting the involvement of UVR8 signalling. UV-B filtering during daylight acclimation also increased herbicide efficacy in Chenopodium, suggesting similar responses in agricultural weeds. UV-B-induced photoprotection enhances the resilience of plant photosystems to herbicide damage, providing a key target for increasing product efficacy and reducing usage.