Hydrogen Peroxide Positively Regulates Phosphate Starvation Responses in Rice.

Phosphorus is an essential macronutrient for plant growth and development. Under phosphate (Pi) starvation conditions, plants activate a series of adaptive responses, among which reactive oxygen species (ROS) accumulation in root tissues represents a notable yet poorly characterized phenomenon. This study investigated the regulatory role of hydrogen peroxide (HO) in rice adaptation to Pi deficiency through pharmacological intervention using potassium iodide (KI), a specific HO scavenger. Physiological analysis revealed that root-specific HO depletion via KI treatment significantly impaired both Pi uptake and root growth under Pi-deficient conditions. Transcriptomic profiling demonstrated that HO elimination substantially modulated the expression of 196 Pi starvation-responsive genes, particularly those involved in SPX-mediated phosphate sensing, extracellular acid phosphatases (APase) biosynthesis, high-affinity phosphate transporters, lipid metabolism enzymes, and redox homeostasis maintenance. Subsequent biochemical validation confirmed that both KI and diphenyleneiodonium (DPI) treatments suppressed Pi-starvation-induced APase activity and compromised Pi uptake ability. Notably, comparative analysis with the phr1/2/3 triple mutant revealed a 24% overlap in differentially expressed genes between HO and PHR-deficient plants, with 90% of shared genes exhibiting congruent expression patterns. These findings collectively establish that HO serves as a pivotal signaling mediator in the Pi starvation regulatory network, orchestrating metabolic reprogramming and developmental adaptation to Pi stress in rice.