Next generation auxins and anti-auxins : principles for binding and design

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We will quantify the initial molecular events in auxin binding and, with the aid of chemometrics, develop principles for the development of next-generation selective auxins, both agonists and antagonists.

Surface plasmon resonance will be used to measure on- and off-rates for TIR1 and AFB5 in the absence of co-receptor to define binding to this pocket alone. Isothermal titration calorimetry will be used to determine thermodynamic parameter differences in deltaH, deltaG and deltaS between TIR1 and AFB5. Values measured will be combined with compound chemometrics.

We believe that the TIR1/AFBs may have auxin-dependent prolyl cis-trans isomerase activity. NMR will be used to clarify degron transitions in solution and bound. Importantly, the structure of full-length Aux/IAA proteins will be determined to report on the endogenous disposition of the degron. We will add co-receptor degron peptides to measure thermodynamics associated with cis-trans isomerisation. Stapled peptides will be used to measure TIR1/AFB5 isomer preferences by SPR.
Having determined detailed information on the two initial steps of co-receptor assembly we will refine our chemometric ligand classifications and combine the information to create a platform for discovery of TIR1/AFB selective compounds. We will screen a knowledge-led selection of the Syngenta compound library to add robustness to existing datasets and test for early compound predictions. Adding fragment bin screening with SPR will add naive information about each distinct binding pocket to create distinct pharmacophoric models based on receptor binding alone. With these anchor-sites defined, selective anti-auxins will be designed elaborated in chemical space outside the TIR1/AFB binding pocket using what is learnt from degron presentation. Anti-auxin synthesis (Prof Hayashi) and evaluation will follow, using both biophysical and in vivo plant assays and novel reporter lines generated to provide target-specific readouts.

Our primary route to exploitation will be in collaboration and under the guidance of Syngenta working with our University technology transfer offices . The PI and Co-I have a long-established relationship with Syngenta Jealott's Hill. Some of the key resources provided in the previous IPA project are still in use under agreement (e.g. recombinant baculovirus lines) and we value this relationship highly. A new Agreement for access and confidentiality, covering IP generated in this project by individual parties and joint discovery, and covering rights for exploitation by all partners will be drawn up if, and as soon as, the project is supported (as noted in the letter of support from Syngenta).
We expect the project to create a novel platform from which new auxinics may be predicted or designed. This platform, based on the many quantitative datasets generated by the PI and Co-I and the chemometric analyses contributed by Ferro (Bonn), will be tested through the synthetic chemistry of Hayashi. These third parties bring much foreground IP to the partnership and this will be recognised. The platform itself may have high exploitation value and we would work closely with our University technology transfer offices to ensure that the partners recognise all subsequent income, but our primary drive will be to make the research work available. It is expected that most parts of the raw research findings, synthetic procedures, understanding of plant processes will be published in refereed journals without undue delay. Syngenta have always supported open access publication of jointly supported research results. The algorithms generated by Ferro may need special consideration, but this will be primarily an agreement between IPTC Bonn and Syngenta, although the PI and Co-I will be involved because the algorithms will be fed by the data from this project.
Beneficiaries include not only Syngenta, but other agrochemical companies as more is learnt and published about the principal target sites for auxinic herbicides. Managing resistance to herbicides is becoming an increasing problem worldwide. Auxinics are amongst the oldest lineages of herbicides and resistance is widespread, but local in nature. Indeed, the next generation of GM herbicide tolerant crops will target auxin (oxyacetic acid) metabolism (Dow AgroSciences) on top of glyphosate resistance (Monsanto), showing that there is confidence that there remain considerable commercial potential in auxinic products. Nevertheless, all stakeholders need to be wise to, and manage these products for the future and greater knowledge of the protein target sites will be invaluable. Further, from our work, novel routes to selective auxinic resistance can be envisaged such that new generations of herbicide tolerant crops may be realised through (natural variation using markers, TILLED breeding selections etc., as well as GM). We will put forward additional project proposals to follow such opportunities.
Given the utility of auxins as agrochemicals (in e.g. fruit farming as well as herbicides), beneficiaries further downline include farmers and growers, and ultimately all those with responsibility towards Food Security. Herbicides are essential for sustaining and growing the productivity of all managed crops (outside the organics sector), The PI and co-I will ensure we take the research and its more general importance out to public and non-specialist audiences in order to contribute to awareness on the issues of herbicides in agriculture and of the importance of blue-skies research for agriculture and food security.
This project will help establish the leadership for this research in the UK, and with the primary route to exploitation benefitting the UK economy through Syngenta and lead partners. Part of our role as leaders will be to ensure that the PDRAs and students who become associated with the work are trained for drug discovery in the agricultural sector.