How does salicylic acid induce systemic resistance
against pathogens?
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.
Salicylic acid (SA) is a natural plant hormone that plays a crucial role in inducing systemic resistance against pathogens. Here are the step-by-step processes by which salicylic acid induces systemic resistance:
1. Perception and activation: When a plant is attacked by a pathogen, it recognizes the presence of the pathogen through pattern recognition receptors (PRRs) on the cell surface. This recognition triggers a series of signaling events inside the plant cells.
2. SA biosynthesis: Upon pathogen recognition, the plant cells start producing salicylic acid through a series of biochemical reactions. SA can also be synthesized under non-infectious conditions as a response to various stresses.
3. Signal amplification and transportation: Salicylic acid induces a signaling cascade that amplifies the initial defense response. It activates mitogen-activated protein kinase (MAPK) cascades in the cells, leading to the production of defense-related proteins and other signaling molecules.
4. Systemic acquired resistance (SAR): Salicylic acid acts as a mobile signal, enabling the transfer of resistance from the infected site to non-infected parts of the plant. It is transported through the xylem and phloem tissues, allowing it to reach distant parts of the plant, including leaves, stems, and roots.
5. Induction of defense genes: Salicylic acid activates a variety of defense-related genes in the plant. These genes encode proteins involved in the synthesis of antimicrobial compounds, such as phytoalexins and pathogenesis-related (PR) proteins.
6. Reinforcement of physical barriers: Salicylic acid also enhances the plant's physical barriers, such as the cell wall and cuticle, making it more difficult for pathogens to penetrate and infect plant tissues.
7. Priming of defense responses: Salicylic acid primes the plant's defense responses, making it more responsive and able to mount a faster and stronger defense against subsequent pathogen attacks. This priming increases the efficiency of defense mechanisms, allowing the plant to quickly activate defense responses when needed.
Overall, salicylic acid acts as a key signaling molecule in the plant immune system, regulating the defense responses and triggering systemic acquired resistance against pathogens.