Functional paradigms of PUB-RLK signaling modules in plant growth and biotic stress adaptation

We define three core paradigms for PUB-RLK module function. First, negative feedback loops, where ligand-activated RLKs phosphorylate PUB ligases, which in turn ubiquitinate the activated RLK to attenuate signaling, forming a self-limiting circuit. Second, basal inhibition and release, where PUB ligases constitutively degrade or inactivate RLKs, maintaining signaling quiescence until ligand perception disrupts this inhibition. Third, signal relay mechanism, where activated RLKs phosphorylate PUBs, reprogramming their substrate specificity to target downstream signaling components, thus propagating the response. We conclude by discussing the phylogenetic relationships of these PUBs and their potential as molecular targets for engineering crops with improved stress resilience without compromising growth.