Phase separation to visualize protein-protein interactions and kinase activities in planta

Protein complex formation and dynamic post-translational modifications are notoriously difficult to monitor at cellular resolution. Here, we developed a versatile modular toolbox of fluorescently labelled, artificial homo-oligomerizing peptide-tags (HOTag) that install interaction-dependent liquid-liquid phase-separation upon interaction between two proteins of interest. We deployed our novel toolbox for the in planta visualization of inducible, binary and ternary protein-protein interactions (PPIs), as well as specific phosphorylation, showing its great potential to become a robust standard technique to study PPIs and phosphorylation in plants.