The PHR2-DGP1 Signaling Integrates Carbon and Nitrogen Assimilatory Metabolisms under Phosphorus Deficiency Stress in Rice Plants [ChIP-Seq]
Carbon (C), nitrogen (N) and phosphorus (Pi) are crucial macronutrients for plants. While substantial knowledge exists on C/N balance signaling physiological and molecular perspectives, the core regulatory mechanism governing C/N and Pi balance remains largely unexplored. This study reveals that C/N assimilatory metabolisms matching the Pi-deficiency stress is integrated by a DEEP GREEN PANICLE1 (DGP1)-mediated regulatory network in rice (Oryza sativa). We found that low-Pi stress triggers DGP1 expression in a dose-responsive manner, facilitated by the PHOSPHATE STARVATION RESPONSE REGULATOR (PHR2). Intriguingly, DGP1 interacts with transcription factors (GLK1 and GLK2) and mitochondrial factors (GDCH and QCR9), modulating their roles in photosynthetic gene expression, the glycine cleavage system and the mitochondrial electron transport chain (mETC), respectively. Additionally, DGP1 influences aminoacyl-tRNA synthetases and ribosomal subunits, impacting protein biosynthesis, and intervenes in various metabolic pathways, including glycolysis and the citrate cycle. Phenotypically, we observed that under short-term Pi-deficiency, wild-type plants exhibit compromised photosynthesis, photorespiration and mETC-driven ATP synthesis, whereas dgp1 and phr2 mutants display reduced sensitivity to these conditions. Conversely, DGP1 overexpressors show decreased yield under normal conditions due to altered cell metabolomes and protein biosynthesis inadequacy, despite unaffected 15NO3– uptake and transport. In conclusion, the PHR2-DGP1 module orchestrates a comprehensive signaling network, harmonizing C and N metabolic fluxes under Pi limitation through coordinated interactions among cytoplast, chloroplast and mitochondria. Overall design: ChIP-seq assay of the combined GLK1 and GLK2 binding signals in the leaves of phr2 mutant under normal condition or after Pi-deficiency stress.