How does salicylic acid induce systemic resistance

Question

against pathogens?

Answer 1

Salicylic acid, also known as SA, is a naturally occurring plant hormone and a key signaling molecule involved in plant defense against pathogens. It plays a critical role in triggering and regulating the plant's immune response. Salicylic acid induces systemic resistance against pathogens through multiple mechanisms:

1. Activation of defense genes: Salicylic acid acts as a signal that triggers the expression of various defense-related genes. It activates genes involved in the production of antimicrobial compounds, such as phytoalexins and pathogenesis-related (PR) proteins. These compounds help inhibit the growth and spread of pathogens in the plant.

2. Protein phosphorylation: Salicylic acid modulates the phosphorylation of proteins involved in defense signaling pathways. This phosphorylation regulates the activity and function of specific proteins, enhancing the plant's defense responses against pathogens.

3. Systemic acquired resistance (SAR): Salicylic acid is a key regulator of SAR, a long-lasting defense response that provides resistance against a broad range of pathogens. When a plant is infected by a pathogen, salicylic acid is synthesized and transported throughout the plant. It triggers the production of defense-related compounds in uninfected parts, preparing them to mount an effective defense upon subsequent pathogen attack.

4. Priming: Salicylic acid primes the plant's immune system by preparing it to respond more rapidly and efficiently to subsequent pathogen attacks. It improves the readiness of defense-related genes and enhances the production of defense compounds, resulting in a quicker and stronger defense response when the plant encounters pathogens.

5. Systemic signaling: Salicylic acid acts as a mobile signal that can move within the plant and between different plant organs. This allows for the systemic transmission of the defense response, enabling distant tissues to initiate their own defense mechanisms upon receiving the signal.

Overall, salicylic acid induces systemic resistance against pathogens by activating defense genes, modulating protein phosphorylation, triggering SAR, priming the immune system, and facilitating systemic signaling within the plant.