How do Phototropin Receptor Kinases Initiate Signalling from the Plasma Membrane?

Improving crop yield has the potential to overcome the challenges facing global agriculture. Strategies to increase plant biomass have centred on enhancing photosynthetic productivity. Phototropin receptor kinases (phots) play an important role in this regard as they function to control a wide range of physiological responses that collectively serve to optimise photosynthetic efficiency. These include chloroplast relocation movements, leaf positioning and expansion, stomatal opening and phototropism, all of which influence a plant's photosynthetic competence by improving the efficiency of light capture, reducing photodamage, and regulating gas exchange between leaves and the atmosphere. Manipulating these processes could offers considerable potential to alter plant growth through changes in photosynthetic performance. Yet, despite two decades of research, our understanding of how these autophosphorylating kinases are activated, how they are regulated and how they initiate signalling from the plasma membrane is far from complete. Obtaining a better grasp of the underlying mechanisms involved will be essential if we are to harness the full potential of altering phot function for agronomic gain. This proposal will capitalise on a substantial body of preliminary work to answer key gaps in our knowledge regarding the molecular basis underlying phot receptor activation and signalling by light. The outcomes of this work will ultimately offer new opportunities to coordinate enhancements in photosynthetic performance with an aim to increase yield and grow crops more efficiently. Knowledge gained from this work will also translate to related kinases with key roles in controlling plant immunity and the hormonal regulation of plant development.

Enhancing photosynthesis represents a major challenge for improving plant productivity. Phototropins (phots) are plasma membrane-associated receptor kinases that are pivotal for plant growth by regulating a range of physiological processes that serve to optimise photosynthetic efficiency. Thus, modulating phot function offers considerable potential to manipulate plant growth through changes in photosynthetic performance. Indeed, genetic manipulation of phot-dependent stomatal opening has already proved successful in increasing yield. Extending this approach to coordinate further stepwise enhancements in photosynthetic efficiency will require a deeper understanding of how these light-activated kinases promote growth by maximising light capture, reducing photodamage, and regulating gas exchange between leaves and the atmosphere. This proposal capitalises on a substantial body of preliminary work to answer key gaps in our knowledge regarding the molecular basis underlying phot receptor function. Specifically, we will determine how lipid binding/modification, dimerization and phosphorylation impacts the plasma membrane localisation dynamics of phots, and those of early signalling components, at spatiotemporal resolution. The contribution of these processes to phot function will provide new mechanistic information on how these kinases are activated, how they are regulated and how they initiate signalling from the plasma membrane. In addition, kinase engineering approaches together with our progress in genetic suppressor screening will be used to identify new phot signalling components. This project is therefore of central importance to understanding how light is integrated to control a variety of responses that collectively promote plant growth and will ultimately provide new strategies to manipulate yield for agronomic gain.

Beneficiaries: Beneficiaries of the research will include academic scientists interested in the plant photobiology, receptor kinase signalling and the hormonal regulation of plant development. Commercial organisations interested in developing new strategies to manipulate plant growth, particularly by altering processes associated with impacting photosynthetic productivity will also benefit in the longer term. Individuals and organisations involved in science communication to schools and to the wider public will also benefit from additional activities building on the background work for this proposal (text books for teaching, development and implementation of school teaching resources).

Benefits: This project falls squarely within the remit of the BBSRC Committees B (Plants, microbes, food and sustainability). The impact of the research is derived from its relevance to understand how light coordinates a variety of processes that serve to optimise photosynthetic efficiency and promote plant growth with potential relevance to crop improvement for agronomic gain. Outcomes of this research has the potential to offer new strategies to manipulate plant biomass through alterations in photosynthetic performance. Knowledge gained from this work will not only provide a better grasp of how phototropin receptor kinases coordinate plant growth, but will translate to related kinases with key roles in controlling plant immunity and the hormonal regulation of plant development. In the longer term, these outcomes will have the potential to create new avenues for crop improvement that could benefit farmers, consumers and the environment and contribute to the economic competitiveness of the UK. The staff assigned to the project will obtain knowledge and expertise that can be applied in related research fields or more widely in the commercial or public sectors. Career progression and training of the PDRA will also benefit directly from the various collaborative aspects of the proposed research.

Activities: The project will be continually managed by the PI to engage potential beneficiaries. The PI will publish the research in high-impact scientific journals, write reviews and book chapters and inform the University Media Relations Office of research highlights. Discussions with relevant commercial organisations will be initiated when appropriate to promote exploitation. The PI and PDRA will communicate the research and utilise summer studentships to develop and implement teaching resources designed to engage school pupils in key concepts of photobiology and plant science. The PI will also initiate discussions with the Glasgow Science Centre to design poster displays to raise public awareness on plant photobiology and its potential applications. In addition, the PI will present lectures at national and international conferences, as well as within Universities throughout the UK. The PI will also update online facilities including webpages and University social media to advertise and communicate research.