<scp>PPSR1</scp> Protein Functions as an Important 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 adaptations 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 deficiency adaptations. 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. 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 graft-transmissible, and 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 production in canola under N-, Pi-, or K-deficient conditions, within the controlled environment. These findings provide novel insights into PPSR1-mediated molecular coordination to enhance plant resilience to mineral nutrient deficiency.