Hormonal Signaling Mechanisms in Plant Defense Systems

Plants deploy a sophisticated network of phytohormones to perceive, prioritise and execute defence programmes against a spectrum of pathogens and herbivores. Central to this network are salicylic acid (SA), jasmonic acid (JA), ethylene (ET) and abscisic acid (ABA), which interact through both synergistic and antagonistic mechanisms to fine-tune immune outputs. SA typically orchestrates resistance against biotrophic pathogens by inducing local and systemic acquired resistance, while JA and ET co-regulate responses to necrotrophs and insect herbivores, driving the production of defensive metabolites, proteinase inhibitors and volatile deterrents. ABA modulates stomatal closure and cell-wall fortification, often acting in concert with JA during herbivore attack. Crosstalk among these pathways is mediated by hormone receptors, transcriptional repressors and activators, and post-translational modifications, ensuring that plants mount context-appropriate defences without incurring prohibitive fitness costs. Understanding these signalling circuits underpins the development of crops with durable resistance and minimal yield penalties.

Research from Nature Portfolio

Recent studies have revealed a non-canonical signalling route through which SA perception directly potentiates JA responses during effector-triggered immunity. Upon biotrophic invasion, SA receptors NPR3 and NPR4 facilitate the targeted degradation of JAZ repressors, permitting rapid JA synthesis and activation of JA-responsive transcriptional programmes. This mechanism resolves the apparent conflict between SA- and JA-mediated defences during programmed cell death, enabling plants to resist biotrophic pathogens without compromising resistance to necrotrophs.

Hormonal Signaling Mechanisms in Plant Defense Systems publication trend

The graph below shows the total number of articles in hormonal signaling mechanisms in plant defense systems across all publications each year (not limited to Nature Index journals).

Technical terms

Antagonism: Mutual suppression between two hormonal pathways, often observed between SA and JA, to allocate resources to the most urgent defence.

Elicitors: Molecules from pathogens or herbivores that activate plant immune signalling cascades.

NPR Proteins: SA receptors (Nonexpressor of pathogenesis-related genes) that regulate gene expression in systemic acquired resistance.

JAZ Repressors: Jasmonate ZIM-domain proteins that inhibit JA-responsive transcription factors until degraded upon JA perception.

Systemic acquired resistance (SAR): A long-lasting, broad-spectrum defensive state activated by local infection, primarily mediated by SA.

References

1. Defense strategies and associated phytohormonal regulation in Brassica plants in response to chewing and sap-sucking insects. Frontiers in Plant Science (2024).
2. Integrative transcriptomics reveals association of abscisic acid and lignin pathways with cassava whitefly resistance. BMC Plant Biology (2023).
3. Salicylic acid receptors activate jasmonic acid signalling through a non-canonical pathway to promote effector-triggered immunity. Nature Communications (2016).