Plant systemic defense pathways (SAR/ISR)

Plant systemic defense pathways, primarily Systemic Acquired Resistance (SAR) and Induced Systemic Resistance (ISR), are complex signaling networks that provide long-lasting, broad-spectrum resistance to pathogens throughout the plant [1]. SAR is typically triggered by necrotizing pathogens and is mediated by the signaling molecule salicylic acid (SA), leading to the expression of pathogenesis-related (PR) proteins [2]. ISR is often triggered by beneficial soil-borne microbes and relies on jasmonic acid (JA) and ethylene signaling pathways [1]. These pathways are targeted in agriculture by 'plant activators' or elicitors, such as acibenzolar-S-methyl, which mimic natural signals to prime the plant's immune system without direct antimicrobial activity [3]. While effective for crop protection, activating these pathways can lead to a 'growth-defense trade-off,' where the plant diverts energy from growth and reproduction to defense, potentially reducing crop yield [4].

Other names

Systemic Acquired ResistanceInduced Systemic ResistancePlant ImmunitySystemic Induced ResistancePlant Systemic Acquired Resistance (SAR)Plant Induced Systemic Resistance (ISR)

Activation of systemic resistance via salicylic acid or jasmonic acid/ethylene signaling pathways, inducing pathogenesis-related (PR) gene expression and immune priming [1, 2].