Elucidating molecular level details of the plant Borate transporter structure and function

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Boron (B) is an essential plant nutrient with a key role in the generation of ester cross-linked rhamnogalacturonan II through the formation of apisoyl dimers, essential for structure and function of the extracellular matrix. B deficiency and toxicity are major barriers to efficient crop growth in many parts of the world. B uptake, efflux and distribution are mediated by a complex system of integral membrane channels and transporters, one of which, BOR1, is a membrane transporter with important roles in the active transport of B for xylem loading. Despite the importance of this protein in the effective delivery of B to developing and growing plant tissues, remarkably little is known about its mechanism of action. The precise chemical nature of the substrate and molecular basis of BOR1 energisation are key unknowns. In order to investigate these and other key questions we will employ a combination of high-resolution X-ray crystallographic and plant functional studies. The research leading to this proposal has made significant progress towards the objectives through growth of well diffracting crystals of BOR1 from both the model plant Arabidopsis thaliana, and rice, Oryza sativa. In addition, we have a complete native diffraction dataset for the Oryza sativa BOR1. We aim to optimize the current crystals and solve the high resolution structure of at least one plant BOR1. The structural studies will be complemented with plant cell and whole plant studies aiming to identify and characterize key functional regions of the protein. Taken together with the structure, the plant based functional analysis will provide an opportunity to build a uniquely detailed picture of how BOR1 works. This should form the basis of future studies attempting to generate plants with improved tolerance to suboptimal soil B concentrations.

The main objective of the proposal is to gain highly detailed insight into the mechanism of action of a plant transporter protein through a combination of high resolution structural studies and plant functional analysis. Given that this is very much a basic science project the immediate impact of the results will be in scientific advancement in the areas of membrane transporter biology, structural biology and plant mineral nutrition. However in the longer term the research findings should be of major interest for plant breeders and plant producers having implications for crop productivity. The research undertaken will also have significant impact through the strengthening of collaborative links between the applicants based at Imperial and Warwick. The results of our research will be disseminated to the wider scientific community through the publication of manuscripts in high impact journals and presentations at national and international meetings. Key findings will also be promoted through press releases to the media and through the Imperial College and University of Warwick websites. Where there is scope for further exploitation of the research findings, we will take advantage of the resources at both Imperial and Warwick to protect arising IP. We will additionally use the research findings to establish further collaborations with Industry. We will also undertake public engagement activities in a variety of formats and at both institutions with the aim of making our research findings available and accessible to the general public as well as inspiring the new generation of scientists. The PDRAs funded by the proposal will benefit by developing high quality research skills in world-class research environments as well as having the opportunity to build networks with complementary researchers. It is anticipated that they will also gain significant experience of presenting data at conferences and writing manuscripts. As a member of the Imperial College Post-doc Centre or the Warwick Learning and Development Centre they will also gain training in more generic professional development skills including CV preparation and interview training to facilitate their next step in academia, industry or other relevant careers.