Due to their sessile lifestyle, plants must adapt to the biotic and abiotic factors surrounding them. Plants have evolved a set of mechanisms that allow them to perceive and respond to their environment. Sunlight radiation influences plants during all their life cycle. Plants possess a set of photoreceptors to detect and respond to a range of different wavelengths of sunlight radiation. However, besides its role for growth and development, sunlight can induce harmful damages to plants. Indeed, ultraviolet B radiation can be a source of stress for plant cells. Thanks to its UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8), plants can perceive UV-B photons. This perception regulates plant growth and development (photomorphogenesis), as well as several responses that will allow photoprotection and acclimation to UV-B. UVR8 is a b-propeller protein that converts from an inactive homo-dimeric state to a monomeric state upon UV-B perception. The UVR8 monomer is able to interact with the CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) ubiquitin ligase. COP1, together with the accessory SUPRESSOR OF PHYA-105 1 to 4 (SPA1-4) proteins, targets a set of proteins for ubiquitination and subsequent proteasomal degradation. The UV-B-induced interaction of UVR8 and COP1 stabilizes those targets, including the transcription factor ELONGATED HYPOCOTYL 5 (HY5). HY5 induces a transcriptional reprogramming that activates different plant responses to UV-B. Two of the early genes induced by HY5 stabilization are REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 and 2 (RUP1 and RUP2). These latter are responsible for the reversion of UVR8 monomer to homodimer, thus constituting a negative feedback regulation of UVR8 signaling. Besides interaction with COP1, it was recently shown that UVR8 monomers are able to bind specific transcription factors in order to inhibit their desoxyribonucleic acid (DNA) binding activities. This work attempted to identify genes that are involved in UV-B responses of Arabidopsis thaliana. With a reverse genetic approach, three candidate genes were selected to be further analyzed in more depth for their possible implication in different UV-B responses like inhibition of hypocotyl length, phenylpropanoid derivatives accumulation and photoprotection. UV-B-LIGHT INSENSITIVE 3 (ULI3), EARLY FLOWERING 4 (ELF4) and MYB ONCONGENE DOMAIN CONTAINING PROTEIN 73 (MYB73) encoding the transcription factor MYB73, the three candidates genes of this work, were selected because previous studies showed a potential role in plant UV- B responses or in the UVR8 signaling pathway. In this work, ELF4 and MYB73 showed a potential implication in UV-B-mediated biosynthesis of phenylpropanoid derivatives and photoprotection. The assays performed in this work seem to indicate that MYB73 could be a potential negative regulator of UV-B responses.