UVR8 photoreceptor action

Ultraviolet-B (UV-B) radiation is a minor but very energetic component of sunlight. Exposure to UV-B wavelengths (280-315 nm) has numerous effects on plants, including changes in metabolism and development that impact biochemical composition, plant architecture and defence against pests and pathogens. The effects of UV-B radiation are due to its ability to regulate the expression of numerous plant genes, including those involved in metabolic pathways, UV-protection, morphogenesis and defence. It is therefore important to understand how UV-B radiation is perceived by plants and how it initiates responses. A pivotal component involved in these processes is a protein called UVR8, which acts as a photoreceptor to detect UV-B radiation. UVR8 physically interacts with several other proteins, including a number of proteins that regulate gene expression, to initiate responses to UV-B in plants, but also with proteins that repress UVR8 activity. However, we have little understanding of the molecular mechanisms that determine how UVR8 interacts differentially with these proteins to control its activity, although we know that it involves a particular region of the UVR8 protein. The basis of this project is that we have recently identified a mechanism that is important in regulating which proteins interact with UVR8 to modulate responses. Hence the aim of this project is to gain a more complete understanding of this mechanism and how it affects UVR8 action. In addition to establishing the molecular basis of UVR8 action, the information gained opens up the possibility of identifying variants of UVR8 and its interacting proteins that would allow manipulation of UVR8 activity in crop plants to enhance aspects of quality and productivity.

UV-B wavelengths induce a range of physiological responses in plants, but the mechanisms by which these responses are initiated are not fully understood. Our research has shown that the Arabidopsis protein UV RESISTANCE LOCUS8 (UVR8) is a UV-B photoreceptor that regulates the expression of a set of genes involved in metabolism, aspects of morphogenesis and physiological responses. UV-B absorption converts the UVR8 protein from a dimer to a monomer and induces its direct interaction with the protein COP1 and with several transcription factor proteins to initiate transcriptional responses. Conversely, interaction with RUP proteins represses UVR8 activity by impairing the interaction with COP1 and promoting dimerisation and also by targeting proteins for proteolysis. However, we have little understanding of the molecular mechanisms that determine how UVR8 interacts differentially with these proteins to control its activity, although we know that the interactions involve a particular region of the UVR8 protein. Hence the aim of this project is to understand the molecular mechanisms through which UVR8 interacts with key regulatory proteins to initiate responses, building on recent new insights into these mechanisms. In addition to establishing the molecular basis of UVR8 action, the information gained opens up the possibility of identifying variants of UVR8 and its interacting proteins that would allow manipulation of UVR8 activity in crop plants to enhance aspects of quality and productivity.