Signal amplification and immune priming: Emerging principles from strigolactone and apoplastic pH signaling

Plant immunity is fundamental for protecting plants from diseases caused by various pathogens. Beyond recognizing pathogens, plants must amplify and spread immune signals to mount effective defenses. However, the integration of innate immunity with core physiological processes to amplify immune signals, strengthen local defense, and prime distal tissues to block disease spread and secondary infection remains largely unknown. This commentary briefly reviews two recent milestone studies in Cell that reveal distinct yet conceptually connected mechanisms of immune signal amplification in plants. Yang et al. demonstrated that strigolactone (SL) signaling amplifies rice antiviral defense by activating the ONAC131-MID1-RDR1/RDR6 module, which increases virus-derived small interfering RNAs (vsiRNAs) and enhances antiviral RNA interference (RNAi). Editing of the SL receptor D14 enables rice to evade viral P3-mediated suppression without compromising yield. Concurrently, Wang et al. discovered that immune-triggered apoplastic alkalinization and phytocytokines establish a self-reinforcing signaling circuit that facilitates communication between locally infected and distally uninfected tissues to prime distal antibacterial immunity. Collectively, these studies indicate that plants utilize SL signaling and apoplastic pH dynamics to facilitate immune amplification and priming in plants, offering new perspectives on growth-immunity coordination and the development of high-yield, disease-resistant crops.