In plants, receptor-ligand interactions govern and monitor a large number of physiological processes, including growth, plant development, immunity, and interactions with the environment among other biological responses. By sensing and binding to ligands, receptors activate or inhibit biochemical signaling pathways to regulate cellular processes (Lumba et al., 2010; Couto and Zipfel, 2016; Hohmann et al., 2017, 2018a; Moussu and Santiago, 2019).
Identification of key players and characterization of their biochemical interactions are fundamental for understanding the molecular mechanisms that regulate these processes. A crucial aspect of unraveling the biochemical mechanisms behind cell communication is quantification of the different parameters that drive the formation of signaling complexes (Du et al., 2016). Nowadays, there are different techniques available to quantify biomolecular interactions that provide binding affinity (how strong the interaction is between two molecules), kinetics (how fast the interaction happens), and ligand specificity (how specific the interaction is between two molecules).
This review aims to provide an overview of state-of-the-art in vitro ligand-binding assays to investigate receptor-ligand interactions. An extensive review on methods for the analysis of protein-protein interactions in vivo was recently published by Xing et al. (2016). In addition to introducing method principles and new developments, we highlight the advantages and limitations and provide recommendations with the aim that readers may use this information as a reference when choosing the most suitable protein/receptor-ligand interaction technique(s) to study their system. For reference, we have also included a number of examples of plant ligand-receptor interactions characterized with different methodologies.