LiP-MS reveals a feedback loop of tomato UDP-glucosyltransferases managing bioactive jasmonate homeostasis

Jasmonic acid (JA) is the precursor of the bioactive molecule jasmonoyl-isoleucine (JA-Ile), a plant hormone that regulates fitness and development. Although JA biosynthesis, signaling, and responses have been intensively studied, the catabolism of JA remains incompletely understood. Here, we use the recently developed technique of limited proteolysis-coupled mass spectrometry (LiP-MS) to investigate metabolite-protein interactions in plants, aiming to discover enzymes involved in JA metabolism. We identify several previously reported JA-binding proteins, thus validating the robustness of the method, along with recognized enzymes of the JA pathway and a series of other potential JA-binding proteins. Functional characterization of a set of identified JA-interacting uridine diphosphate (UDP)-glycosyltransferase (UGT) enzymes through omics, biochemical, enzymatic, and structural analyses reveals that two tomato UGTs glucosylate JA into JA-glucosyl esters, potentially playing a role in the regulation of bioactive JA homeostasis. With this, our findings uncover a missing step in the JA metabolic pathway.