Beyond Arabidopsis: Differential UV-B Response Mediated by UVR8 in Diverse Species

Abstract

Ultraviolet-B radiation (UV-B, 280-315 nm) is an important environmental signal thatregulates growth and development in plants. Two dose-dependent UV-B responsepathways were described in plants: a specific one, mediated by UVR8 (the specificUV-B receptor) and an unspecific one, activated by the oxidative damage produced byradiation. The constitutively expressed receptor appears inactive as a dimer, with thetwo monomers dissociating upon UV-B irradiation. The monomer then interacts withCOP1, an ubiquitin ligase, hindering its ability to poly-ubiquitinate transcriptional factorHY5, thus averting its degradation and activating the photomorphogenic response. HY5induces the synthesis of proteins RUP1 and RUP2, which interact with UVR8, releasingCOP1, and inducing the re-dimerization of UVR8. This mechanism has been thoroughlycharacterized in Arabidopsis, where studies have demonstrated that the UVR8 receptoris key in UV-B response. Although Arabidopsis importance as a model plant manymechanisms described in this specie differ in other plants. In this paper, we reviewthe latest information regarding UV-B response mediated by UVR8 in different species,focusing on the differences reported compared to Arabidopsis. For instance, UVR8 is notonly induced by UV-B but also by other agents that are expressed differentially in diversetissues. Also, in some of the species analyzed, proteins with low homology to RUP1 andRUP2 were detected. We also discuss how UVR8 is involved in other developmental andstress processes unrelated to UV-B. We conclude that the receptor is highly versatile,showing differences among species.