Hydroxylation of HPPD facilitates its PUB11-mediated ubiquitination and degradation in response to oxidative stress in Arabidopsis

This is the authors' abstract. We don't add key points for this paper.

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is critical for plant photosynthesis and essential for enhancing tolerance to oxidative stress. However, the precise mechanisms by which plants regulate HPPD in response to oxidative stress remain largely unknown. Here, we show that Arabidopsis thaliana HPPD (AtHPPD) undergoes a previously uncharacterized post-translational modification-phenylalanine hydroxylation-in response to excessive hydroxyl radicals (·OH), thereby mediating oxidative stress tolerance. Biochemical analyses revealed that this hydroxylation impairs the normal function of AtHPPD, accelerating its degradation. We further identified PUB11 as a key interactor of AtHPPD. Both in vitro and in vivo assays demonstrated that this interaction is enhanced under oxidative stress, promoting ubiquitination and facilitating rapid AtHPPD degradation via the 26S proteasome to maintain reactive oxygen species homeostasis. Overall, this work uncovers a novel mechanism by which plants balance photosynthetic efficiency with the repair of oxidative damage, identifies key processes in oxidative stress regulation, and provides a foundation for breeding crops with improved resilience to abiotic stress.