Elucidating tissue and sub-cellular specificity of the entire SUMO network reveals how stress responses are fine-tuned in a eukaryote

SUMOylation is essential in plant and animal cells, but it remains unknown how SUMO components act in concert to modify specific targets in response to environmental stresses. In this study we characterise every SUMO component in the Arabidopsis root to create the first complete SUMO Cell Atlas in eukaryotes. This unique resource reveals wide spatial variation, where SUMO proteins and proteases have sub-functionalized in both their expression and subcellular localisation. During stress SUMO conjugation is mainly driven by tissue specific regulation of the SUMO E2 ligase. Stress-specific modulation of the SUMO pathway reveals unique combinations of Proteases being targeted for regulation in distinct root tissues by salt, osmotic and biotic signals. Our SUMO Cell Atlas resources reveal how this PTM influences cellular and tissue scale adaptations during root development and stress responses. We provide the first comprehensive study elucidating how multiple stress inputs can regulate an entire PTM system.