Identification of novel inhibitors of plant GH3 IAA-amidosynthetases through molecular docking studies

Abstract

Auxins play a critical role in several plant developmental processes and their endogenouslevels are regulated at multiple levels. The enzymes of the GRETCHEN HAGEN 3 (GH3)protein family catalyze the conjugation of amino acids to indoleacetic acid (IAA), themajor endogenous auxin. The GH3 proteins are encoded by multiple redundant genes inplant genomes, making it difficult to perform functional genetic studies to understandtheir role in auxin homeostasis. To address these challenges, we used a chemicalapproach that exploits the reaction mechanism of GH3 proteins to identify small mole-cule inhibitors of their activity from a defined chemical library. The study evaluatedreceptor-ligand complexes based on their binding energy and classified them accordingly.Docking algorithms were used to correct any deviations, resulting in a list of the mostimportant inhibitory compounds for selected GH3 enzymes based on a normalized sumof energy. The study presents atomic details of protein-ligand interactions and quantifiesthe effect of several of the identified small molecule inhibitors on auxin-mediated rootgrowth processes in Arabidopsis thaliana. The direct effect of these compounds onendogenous auxin levels was measured using appropriate auxin sensors and endogenoushormone measurements. Our study has identified novel compounds of the flavonoid bio-synthetic pathway that are effective inhibitors of GH3 enzyme-mediated IAA conjuga-tion. These compounds play a versatile role in hormone-regulated plant developmentand have potential applications in both basic research and agriculture