Deubiquitinating enzymes UBP12 and UBP13 stabilize the brassinosteroid receptor BRI1

Protein ubiquitination is a dynamic and reversible post‐translational modification that controls diverse cellular processes in eukaryotes. Ubiquitin‐dependent internalization, recycling, and degradation are important mechanisms that regulate the activity and the abundance of plasma membrane (PM)‐localized proteins. In plants, although several ubiquitin ligases are implicated in these processes, no deubiquitinating enzymes (DUBs), have been identified that directly remove ubiquitin from membrane proteins and limit their vacuolar degradation. Here, we discover two DUB proteins, UBP12 and UBP13, that directly target the PM‐localized brassinosteroid (BR) receptor BR INSENSITIVE1 (BRI1) in Arabidopsis . BRI1 protein abundance is decreased in the ubp1 2 i / ubp13 double mutant that displayed severe growth defects and reduced sensitivity to BRs. UBP13 directly interacts with and effectively removes K63‐linked polyubiquitin chains from BRI1, thereby negatively modulating its vacuolar targeting and degradation. Our study reveals that UBP12 and UBP13 play crucial roles in governing BRI1 abundance and BR signaling activity to regulate plant growth. Synopsis The deubiquitinating enzymes UBP12 and UBP13 act as negative regulators of brassinosteroid (BR) receptor BRI1 degradation in the vacuole through the deubiquitination of BRI1, thus playing positive roles in BR‐responsive plant growth. Loss of UBP12 and UBP13 ( ubp12i / ubp13) results in severe growth defects, and UBP12 and UBP13 positively regulate BR signaling. UBP12 and UBP13 are essential to maintain BRI1 protein abundance. UBP13 interacts with BRI1 and cleaves K63‐linked polyubiquitin chains from BRI1 to limit its internalization and vacuolar targeting. Graphical Abstract The deubiquitinating enzymes UBP12 and UBP13 act as negative regulators of brassinosteroid (BR) receptor BRI1 degradation in the vacuole through the deubiquitination of BRI1, thus playing positive roles in BR‐responsive plant growth.