Transcription factors interact with Arabidopsis <scp>UVR8</scp> photoreceptor at distinct sites to <scp>COP1</scp> and <scp>RUP</scp> proteins

Many responses of plants to UV-B radiation are mediated by the UVR8 photoreceptor. UVR8 functions by interacting directly with various proteins. In particular, binding of transcription factors to UVR8 modifies their ability to regulate sets of genes involved in specific responses to UV-B. However, very little information is available on how UVR8 binds to transcription factors, although this is crucial to understand the basis of responses to UV-B. Here, we studied the interaction of UVR8 with four transcription factors: WRKY36, BIM1, BES1 and MYB13, using co-immunoprecipitation assays in Nicotiana. We show that WRKY36 binds to a 9-amino acid region in the UVR8 C-terminus but can also interact with the β-propellor core domain. BIM1 binds to a different region within the C-terminus but there is no evidence of binding to the core domain. The VP motif in the C-terminus required for interaction of COP1 and RUP proteins is not required for binding WRKY36 and BIM1. BES1 and MYB13 do not require interaction with the C-terminus to bind to UVR8. We conclude that transcription factors have different modes of interaction with UVR8 and that those studied here do not interact in the same way as COP1 and RUP proteins. We suggest that the less conserved regions of the C-terminus may facilitate interaction of UVR8 with multiple transcription factors that mediate responses to UV-B in different plant species.