Phosphate Starvation Primes Plant Immunity through an ABA-OsbZIP12-Phytoalexin Signaling Network

Phosphate (Pi) starvation is a major constraint on crop productivity, yet its impact on disease resistance is poorly understood. Abscisic acid (ABA) is central to abiotic stress responses, but its interplay with nutritional cues and immunity remains elusive. Here, we reveal how Pi starvation enhances rice blast resistance through a complex ABA-mediated signaling network. We found that Pi-starvation rice exhibits elevated ABA, increased accumulation of the phytoalexin sakuranetin (SAK), and enhanced resistance to Magnaporthe oryzae. Strikingly, ABA exerts a biphasic effect on immunity: brief, high-concentration exposure suppresses resistance, while sustained, low-level treatment promotes it by differentially regulating SAK biosynthesis and endogenous ABA homeostasis. We identified the transcription factor OsbZIP12 as the central integrator of these signals. OsbZIP12 directly activates the SAK biosynthesis gene OsNOMT and is itself regulated by distinct inputs from both Pi starvation (ABA-independent) and ABA signaling. Genetic analyses confirmed that OsbZIP12 is essential for this SAK-dependent resistance. Our findings establish a novel Pi-ABA-immunity network orchestrated by OsbZIP12, providing molecular targets for strategies that leverage nutritional stress to enhance crop resilience.