Indole-3-acetic acid (auxin) is considered one of the cardinal hormones in plant growth and development. It regulates a wide range of processes throughout the plant. Synthetic auxins exploit the auxin-signaling pathway and are valuable as herbicidal agrochemicals. Currently, despite a diversity of chemical scaffolds all synthetic auxins have a carboxylic acid as the active core group. By applying bio-isosteric replacement we discovered that indole-3-tetrazole was active by surface plasmon resonance spectrometry, showing that the tetrazole could initiate assembly of the Transport Inhibitor Resistant 1 (TIR1) auxin coreceptor complex. We then tested the tetrazole’s efficacy in a range of whole plant physiological assays and in protoplast reporter assays, which all confirmed auxin activity, albeit rather weak. We then tested indole-3-tetrazole against the AFB5 homologue of TIR1, finding that binding was selective against TIR1, absent with AFB5. The kinetics of binding to TIR1 are contrasted to those for the herbicide picloram, which shows the opposite receptor preference, as it binds to AFB5 with far greater affinity than to TIR1. The basis of the preference of indole-3-tetrazole for TIR1 was revealed to be a single residue substitution using molecular docking, and assays using tir1 and afb5 mutant lines confirmed selectivity in vivo. Given the potential that a TIR1-selective auxin might have for unmasking receptor-specific actions, we followed a rational design, lead optimization campaign, and a set of chlorinated indole-3-tetrazoles was synthesized. Improved affinity for TIR1 and the preference for binding to TIR1 was maintained for 4- and 6-chloroindole-3-tetrazoles, coupled with improved efficacy in vivo. This work expands the range of auxin chemistry for the design of receptor-selective synthetic auxins.
The Tetrazole Analogue of the Auxin Indole-3-acetic Acid Binds Preferentially to TIR1 and Not AFB5
Posted by
Mussa Quareshy
on 12 09 2019
Related content
03 10 2022
< 1 minute
Calculate on the cloud
In order to increase the flexibility, access and integrability, Calculators and Predictors have...
12 05 2022
< 1 minute
Coupling stabilizers open KV1-type potassium channels
ABSTRACT: The opening and closing of voltage-gated ion channels are regulated by voltage sensors...
13 11 2021
< 1 minute
Cheminfo Stories 2021 Virtual UGM | Boost analytical experiments with phys-chem properties
TRY CHEMICALIZE Log in for videos & slides
13 11 2021
< 1 minute
Cheminfo Stories 2021 Virtual UGM | Enhancing Sibylla’s innovative drug discovery platform with ChemAxon
Sibylla's innovative pharmacological platform is aimed at discovering new drugs for untreatable...