How does the plant UV-B photoreceptor UVR8 initiate signalling?

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. Importantly, UV-B stimulates responses in plants that protect them against the potentially damaging consequences of UV-B exposure. The effects of UV-B are due to its ability to regulate the expression of numerous plant genes, including those involved in UV-protection, biosynthesis and chloroplast function. 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 has been identified, a protein called UVR8. UVR8 acts as a photoreceptor to detect UV-B light. UVR8 physically interacts with another protein, COP1, to initiate responses to UV-B in plants. The aim of this project is to enhance understanding of how UVR8 interacts with COP1 to initiate plant responses to UV-B. Establishing the molecular mechanism of this interaction will help us to understand how UV-B regulates aspects of plant growth and development and how plants survive in sunlight.

UV-B wavelengths (280-315 nm) induce a range of physiological responses in plants, but the mechanisms by which these responses are initiated are poorly 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 processes that protect the plant against damage by UV-B, including secondary metabolism, anti-oxidant defence and DNA repair. UVR8 associates with chromatin to regulate the expression of target genes. UV-B absorption converts the UVR8 protein from a dimer to a monomer and induces its direct interaction with the plant protein COP1. Recently we reported the crystal structure of UVR8 and showed how it acts to absorb UV-B and how photoreception causes monomer formation. However, we do not know how photoreception enables UVR8 to interact with COP1. The aim of this project is to gain a molecular understanding of how UV-B absorption changes UVR8 so that it is able to interact physically with COP1 to initiate signal transduction.

Beneficiaries The beneficiaries and users of the research will include: organisations in the commercial sector interested in novel strategies to improve crop productivity; agencies and policy makers interested in the effects of UV-B on organisms and ecosystems in relation to depletion of the ozone layer and effects of increasing UV-B radiation (including the relevant United Nations Environmental Programme - UNEP - panel); individuals (including text book authors) and organisations (e.g. Glasgow Science Centre) involved in science communication to schools and the wider public. The general public, in so far as they are interested in the effects of UV-B on organisms and ecosystems.
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) the relevance to understanding the impact of UV-B on the biosphere. (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) and regulate aspects of morphogenesis and development of relevance to crops (e.g. leaf expansion, extension growth and branching). Furthermore there is evidence that UV-B interacts with a number of signalling pathways to modify responses to a variety of abiotic factors (e.g. drought, low temperature and various mineral nutrients). Research to understand UV-B perception, signalling and response therefore has the potential to generate novel strategies for crop plant improvement that could benefit farmers, consumers and the environment and contribute to the economic competitiveness of the UK. In addition, there are examples where manipulation of the UV-B environment is being used in agriculture to help control pests. Thus it is important to understand how altering the UV-B environment may affect plant processes and investigation of the mechanisms of UV-B perception and signalling is key to this. (ii) Plants are key components of natural ecosystems and UV-B has broad impacts on ecosystem function. Concern over depletion of the stratospheric ozone layer by human activities has promoted an interest in understanding how plants perceive UV-B. This information is being used to inform policy makers who are concerned with maintaining human health and the quality of life. 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 over the short to medium 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.