Protein Language: Post-Translational Modifications Talking to Each Other

Post-translational modifications (PTMs) are at the heart of many cellular signaling events. Apart from a single regulatory PTM, there are also PTMs that function in orchestrated manners. Such PTM crosstalk usually serves as a fine-tuning mechanism to adjust cellular responses to the slightest changes in the environment. While PTM crosstalk has been studied in depth in various species; in plants, this field is just emerging. In this review, we discuss recent studies on crosstalk between three of the most common protein PTMs in plant cells, being phosphorylation, ubiquitination, and sumoylation, and we highlight the diverse underlying mechanisms as well as signaling outputs of such crosstalk. Recent studies highlight the importance of crosstalk between different PTMs in several plant signaling pathways. Combinatory PTM codes are the result of distinct molecular mechanisms, leading to different outcomes, although mainly to ensure a tight regulation in response to environmental changes. By its abundance, protein phosphorylation has a central role in protein crosstalk, but emerging studies on ubiquitination and sumoylation also highlight roles for these modifications in plant protein crosstalk. Advances in mass spectrometry allow the identification of PTM crosstalk, enabling a more precise understanding of plant signaling processes.