Interplay between salicylic acid and plant nutrient homeostasis

Global agricultural intensification fosters crop yields by increasing mineral nutrient inputs; the resulting widespread nutrient imbalances can compromise plant immune responses. Salicylic acid (SA) serves as a regulator of plant defense responses against biotrophic pathogens and environmental stresses. This review summarizes current knowledge on SA biosynthetic pathways in plants, providing a detailed analysis of the distribution, function, and evolutionary history of the isochorismate synthase (ICS) and phenylalanine ammonia-lyase (PAL) pathways. This review examines the interconnections between SA and the homeostasis of phosphorus, nitrogen, and sulfur. We explore how phosphate starvation responses antagonize SA immunity and how nitrogen forms alongside sulfur metabolites to fine-tune SA-mediated resistance. Additionally, we discuss the role of SA in shaping the rhizosphere microbiome. Understanding the interplay between SA, nutrient signaling, and the microbiota is pivotal for developing sustainable agricultural strategies that simultaneously optimize crop yield, disease resistance, and nutrient use efficiency.