UVR8 photoreceptor action and regulation

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 on biochemical composition, plant architecture and defence. The effects of UV-B are due to its ability to regulate the expression of numerous plant genes, including those involved in metabolic pathways, UV-protection, morphogenesis and defence against pests and pathogens. It is therefore important to understand how UV-B is perceived by plants and how it initiates responses. A key component involved in these processes is a protein called UVR8, which acts as a photoreceptor to detect UV-B light. UVR8 physically interacts with other proteins, COP1 and a number of transcription factors, to initiate responses to UV-B in plants. Further proteins, termed RUP proteins 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. Hence the aim of this project is to understand how UVR8 interacts with key regulatory proteins. 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-specific 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. However, we have little understanding of the molecular mechanisms that determine how UVR8 interacts differentially with these proteins to control its dimer/monomer status and 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. We will identify specific amino acids involved in these interactions and the mechanisms involved in controlling differential binding. This will involve assays of interaction in vivo using UVR8 mutants. We will examine the effects of altered interaction on UVR8 function in physiological conditions. 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.

Beneficiaries: The beneficiaries and users of the research will include: organisations in the commercial sector interested in novel strategies to improve crop productivity; academic researchers interested in plant biology and photobiology and the regulation of plant processes by UV-B; organisations (e.g. scientific societies and associations, and Glasgow Science Centre) and individuals (including text book authors) involved in science communication to researchers, students, schools and the wider public; school and University students learning about the effects of UV light on organisms; the general public, in so far as they are interested in the effects of UV light on organisms.
Benefits: The impact of the research to the beneficiaries derives both from (i) its potential relevance to crop plant improvement and agricultural practice and (ii) its relevance to understanding the impact of UV-B on organisms and the ways organisms perceive and respond to UV-B light. (i) UV-B impacts on agricultural as well as natural ecosystems and therefore has direct relevance to crop plants. UV-B signalling pathways regulate biosynthetic activities (and hence plant biochemical composition), prime defence responses (e.g. UV-B exposure reduces damage by herbivorous insects in a range of species), regulate aspects of morphogenesis and development of relevance to crops (e.g. leaf expansion, extension growth and branching) and modify responses to a variety of abiotic factors (e.g. drought, temperature and various mineral nutrients). Research to understand UV-B perception, signalling and response therefore has the potential to generate novel strategies to improve crop plants and agronomic practices that could benefit farmers, consumers and the environment. (ii) Plants are vital for food security and are also key components of natural ecosystems. UV-B has broad impacts on plants and on ecosystem function. Research on UVR8 has greatly increased understanding of plant UV-B perception, signalling and response. Academic researchers and students interested in learning about how plants perceive and respond to UV-B light will benefit from the new findings in this project. Organisations and individuals involved in science communication will disseminate information about UVR8 function and the applications of UVR8 research to a broad audience. The general public will benefit in a cultural sense from the increase in knowledge and understanding of the effects of UV-B on plants. The public can relate to effects of UV-B such as sunburn and skin cancer and so the idea that plants manage to avoid damage by UV-B through perceiving and responding to UV-B is accessible. The above impacts of the research will be realised during the project and in the longer term. Staff working on the project will obtain knowledge and expertise that can be applied in related research or more widely in the commercial or public sectors.