PPSR1 protein functions as an important hub regulator to enhance plant growth performance under N, P and K deficient stress conditions
Phosphorus (P) is an essential macronutrient for various biological processes in plant growth. Modern agricultural science has advanced the knowledge of regulatory mechanisms underlying phosphorus starvation responses (PSRs), aiming to develop phosphate-efficient crops with sustainable production under reduced Pi fertilizer application. However, information regarding coordinated shoot and root adaptation in response to combined nutrient stresses is limited. This study investigated the role of Phloem Phosphate Stress Repressed 1 (PPSR1) in modulating PSRs and other nutrient adaptation. The Arabidopsis functional homologue of Cucumis sativus PPSR1 (CsPPSR1), designated AtPPSR1, was identified. AtPPSR1 encodes a glycine-rich domain-containing protein, and its ectopic expression confers enhanced growth performance to plants. Transcriptomic analyses revealed AtPPSR1 as a regulatory mediator of PSRs, photosynthesis and root development. We revealed that AtPPSR1 interacted with PHOSPHATE STARVATION RESPONSE 1 (PHR1) to regulate PHR1-target genes for adaptive root development, in response to Pi-starvation stress. Additionally, AtPPSR1 was discovered as graft-transmissible, and the shoot-borne AtPPSR1 played a role in restoring the root phenotype of the ppsr1 mutant. Physiological analyses revealed that enhanced AtPPSR1 expression enabled resilience to nitrogen (N) and potassium (K)-starvation, as well as to Pi-deficiency. Furthermore, we identified homologues of CsPPSR1 and AtPPSR1 in Brassica napus (canola), which displayed similar expression patterns in response to Pi-starvation stress. Overexpression of PPSR1, identified from Arabidopsis, cucumber and canola, improved growth performance and seed yield in canola under N-, Pi- or K-deficient conditions. These findings provide novel insights into PPSR1-mediated molecular coordination to improve growth performance under mineral nutrient-stresses conditions. Overall design: Transcriptomics analyses on leaves and roots of Col-0 (WT), ppsr1(KO), and a representative AtPPSR1 overexpression line (OE), which were grown hydroponically for four weeks, and given a Pi-sufficient (200 µM Pi, C200) or Pi-deficient (0 µM Pi, C0) treatment for twenty-four hours.