H₂O₂-mediated oxidation of PHOSPHATE STARVATION RESPONSE2 promotes adaptation to low phosphate in rice

Phosphorus (P) is an essential macro-nutrient for plant growth and development. It is preferentially taken as inorganic phosphate (Pi). Plants have evolved elaborate mechanisms to adapt to low Pi (LP) stress through activating Pi-starvation responses. H₂O₂ is an important signal molecule involved in plant adaptation to diverse environmental stresses. However, whether H₂O₂ plays a role in Pi-starvation responses remains unknown. Here, we reveal that H₂O₂ produced by the respiratory burst oxidase homologs OsRBOH-D/H facilitates phosphate uptake and utilization under LP conditions in rice. Mechanistically LP-induced H₂O₂ promotes the oxidization of the key phosphate signaling transcription factor PHOSPHATE STARVATION RESPONSE2 (OsPHR2) at its Cys377 residue to trigger its oligomerization, sequence-specific DNA binding ability, and nuclear translocation, thereby activating Pi-starvation responses to adapt to LP conditions. Additionally, our molecular and biochemical data revealed that OsRBOH-D is a direct target gene of OsPHR2. Thus, OsPHR2 and OsRBOH-D form a positive feedback regulatory loop in which H₂O₂ acts as a second messenger to amplify the Pi-starvation response.