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

ABSTRACT

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.