Salicylic Acid Mechanisms in Plant Defense
Summary
Salicylic acid (SA) is a small phenolic phytohormone that underpins local and systemic defence responses in virtually all higher plants. Synthesised via two principal routes—chloroplastic isochorismate and cytosolic phenylalanine ammonia-lyase pathways—SA accumulates rapidly at sites of pathogen challenge. Once formed, free SA can be modified by glycosylation, methylation or hydroxylation, allowing storage, controlled release and fine-tuning of defence signals. SA orchestrates a complex network of transcriptional reprogramming through key regulators such as NPR1, which, upon SA perception and redox-driven conformational change, activates pathogenesis-related genes. The hormone also primes systemic tissues for enhanced responsiveness, a phenomenon known as systemic acquired resistance (SAR). Crosstalk with other hormones, notably jasmonic acid and ethylene, confers specificity to biotic and abiotic stress responses. While elevated SA levels boost resistance to biotrophic pathogens, they often impose a growth penalty, highlighting the need to balance defence and development in agricultural contexts. Advances in understanding SA transporters and its molecular targets are paving the way for more sustainable crop protection strategies.
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Salicylic Acid Mechanisms in Plant Defense publication trend
The graph below shows the total number of articles in salicylic acid mechanisms in plant defense across all publications each year (not limited to Nature Index journals).
Technical terms
Salicylic acid (SA): A phenolic plant hormone central to defence against pathogens.
Isochorismate synthase (ICS): Enzyme that converts chorismate to isochorismate in chloroplasts for SA synthesis.
Phenylalanine ammonia-lyase (PAL): Enzyme in the phenylpropanoid pathway initiating cytosolic SA precursor formation.
Systemic acquired resistance (SAR): A defence state conferring long-lasting, whole-plant immunity following local infection.
NPR1: A master co-activator that perceives SA signals and remodels defence gene expression.
References
- 2,4‐Dihydroxybenzoic Acid, a Novel SA Derivative, Controls Plant Immunity via UGT95B17‐Mediated Glucosylation: A Case Study in Camellia Sinensis. Advanced Science (2023).
- Altering cold-regulated gene expression decouples the salicylic acid–growth trade-off in Arabidopsis. The Plant Cell (2024).
- Salicylic Acid Biosynthesis in Plants. Frontiers in Plant Science (2020).
- Salicylic acid signal transduction: the initiation of biosynthesis, perception and transcriptional reprogramming. Frontiers in Plant Science (2014).
- Intra and Extracellular Journey of the Phytohormone Salicylic Acid. Frontiers in Plant Science (2019).
- Export of Salicylic Acid from the Chloroplast Requires the Multidrug and Toxin Extrusion-Like Transporter EDS5. Plant Physiology (2013).
- Multiple Targets of Salicylic Acid and Its Derivatives in Plants and Animals. Frontiers in Immunology (2016).
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