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The anatomy of auxin perception: Understanding the formation of the auxin receptor complex

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  • Full or part time
    Dr S Kepinski
  • Application Deadline
    No more applications being accepted
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

The formation of the auxin co-receptor complex is one of the most pivotal protein-ligand interaction events in plant biology. In promoting the association between TIR1/AFB F-box proteins and Aux/IAA co-repressor proteins, auxin regulates almost every aspect of plant development from the earliest events of embryogenesis to the control of architecture of the entire adult plant. The central importance of auxin in plant biology has meant that there has been intense interest in how a single, simple molecule like indole-3-acetic acid (IAA), the principal endogenous auxin, can regulate such a diverse range of growth and developmental processes in plants. For the same reasons, synthetic auxinic molecules that target the auxin co-receptor complex have proved to be very valuable herbicides with low toxicity to non-plant organisms. While these auxinic herbicides are highly effective against broad-leaved dicotyledonous weeds, they are only mildly herbicidal in grasses and other monocotyledonous species. Given that the auxin signalling system is broadley conserved all the way back to early land plants, the ineffectiveness of auxinic herbicides against grass weeds is both an intellectually intriguing and economically important problem in plant biology.

Recent thinking about the TIR1/AFB-auxin-Aux/IAA co-receptor complex has been dominated by a crystal structure of the complex that shows the auxin and Aux/IAA components binding to TIR1 in the same pocket. Within this pocket, auxin acts as a kind of ‘molecular glue’ to stabilise binding of the complex (Tan et al., 2007, Nature 446:640-5). Exciting new data from our lab, obtained using surface plasmon resonance (SPR) and nuclear magnetic resonance (NMR) approaches, has revealed the key events that may determine specificity and selectivity in auxin perception. This project will offer the student the opportunity to define the functional significance of the early events of auxin receptor complex formation and also to test the extent to which they can account for the differences in efficacy of auxinic herbicides among monocot and dicot species. In addressing these questions, the student will learn and use structural and biophysical techniques including protein expression and purification, SPR, isothermal titration calorimetry (ITC), NMR, and cryo-electron microscopy (cryo-EM) as well as molecular genetic approaches that will allow the student to test their findings in vivo.

The project will be co-supervised by Dr Iain Manfield (University of Leeds) and involves close collaboration with the group of Prof. Richard Napier (University of Warwick).

Potential applicants are encouraged to contact Dr Stefan Kepinski ([Email Address Removed]) if they would like to discuss the project.

Funding Notes

Project is eligible for funding under the The Gosden PhD Studentship scheme. Successful candidates will receive a PhD studentship for 4 years, covering fees at UK/EU level and stipend at research council level (£14,777 for 2018-19).

Candidates should have, or be expecting, a 2.1 or above at undergraduate level in a relevant field. If English is not your first language, you will also be required to meet our language entry requirements. The PhD is to start in Oct 2018.

Please apply online here https://www.plants.leeds.ac.uk/studentships/gosden_studentship.php#application_procedure and include project title and supervisor name, and upload a CV and transcripts.


Roychoudhry, S., Kieffer, M., Del Bianco, M., Liao, CY; Weijers, D; Kepinski, S. (2017) The developmental and environmental regulation of gravitropic setpoint angle in Arabidopsis and bean. Scientific Reports 7:42664. doi: 10.1038/srep42664.

Wang, R., Zhang, Y., Kieffer, M., Yu, H., Kepinski, S., and Estelle, M. (2016) HSP90 regulates temperature-dependent seedling growth by
stabilizing the auxin receptor F-box protein TIR1. Nature Communications 7:Article No.10269. doi: 10.1038/ncomms10269.

Boer, D.R., Freire-Rios, A., van den Berg W.A., Saaki, T., Manfield, I.W., Kepinski, S., López-Vidrieo, I., Franco-Zorrilla, J.M., de Vries, S.C., Solano, R., Weijers, D., Coll, M. (2014) Structural basis for DNA binding specificity by the auxin-dependent ARF transcription factors. Cell 156(3):577-89.

Roychoudhry, S., Del Bianco, M., Kieffer, M., Kepinski, S. (2013) Auxin controls gravitropic setpoint angle in higher plant lateral branches. Current Biology 23:1497-504.

Hayashi, K., Neve, J., M., Hirose, M., Kuboki, A., Shimada, Y., Kepinski, S., Nozaki, H. (2012) Rational design of an auxin antagonist of the SCFTIR1 auxin receptor complex. ACS Chemical Biology 7: 590-98

Calderon Villalobos, L-I., Lee, S., Armitage, L., Parry, G., Mao, H., De Oliveira, C., Ivetac, A., Brandt, W., McCammonn, A., Zheng, N., Napier, R., Kepinski, S., Estelle, M. (2012) TIR1/AFBs and Aux/IAAs constitute a combinatorial co-receptor system to perceive auxin with differential sensitivities. Nature Chemical Biology 8: 477–485

Hayashi, K., Tan, X., Zheng, N,. Hatate, T., Kimura,Y., Kepinski, S., Nozaki. H. (2008) Small-molecule agonists and antagonists of F-box protein-substrate interactions in auxin perception and signaling. Proc. Natl. Acad. Sci. U S A 105, 5632-5637

Kepinski, S. .(2007) The anatomy of auxin perception. Bioessays. 29, 953-6

Kepinski, S. & Leyser, O. (2005) The Arabidopsis F-box protein TIR1 is an auxin receptor. Nature 435, 446-451

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