ZmPHO2 ‐Mediated Phosphorus Homeostasis Modulates PAMP ‐Triggered Immunity and Disease Resistance in Maize

Maize production is influenced by both macronutrient-driven growth and resistance to various abiotic and biotic stresses. While phosphorus (P) is essential for maize growth and productivity, its role in maize immunity remains elusive. Here, we characterized a maize lesion mimic mutant, les33, which exhibits enhanced resistance to southern corn rust (SCR) and Curvularia leaf spot (CLS). Positional cloning indicated that ZmPHO2, encoding an E2 ubiquitin-conjugating enzyme involved in P homeostasis, was the causal gene. In les33, increased P level was accompanied by upregulated defence-related gene expression and elevated accumulation of phenylalanine-derived salicylic acid, lignin, and flavonoids, establishing a genetic link between P status and immune activation. Consistently, exogenous phosphate (Pi) application activates defence-related gene expression and enhances resistance to SCR and CLS in a hydroponics system. In particular, flg22-triggered defence marker gene expression, phosphorylation of mitogen-activated protein kinase (MAPK), and burst of reactive oxygen species (ROS) were enhanced by Pi application, indicating a positive role of P in potentiating PAMP-triggered immunity (PTI). Moreover, field trials showed that application of Pi fertilizer improved SCR resistance in a Pi-dose-dependent manner, further supporting a critical role of P in maize immunity. Taken together, this study provides both genetic and agronomic evidence that P primes defence responses, and highlights optimized Pi fertilization as a practical strategy to coordinate growth and immunity in maize production.