Systemic acquired resistance

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Systemic acquired resistance (SAR) is a plant immune response that provides long-lasting protection against a broad spectrum of pathogens. This defense mechanism is activated in response to a localized infection and subsequently induces resistance throughout the entire plant.

Mechanism

SAR is initiated when a plant recognizes a pathogen attack at a specific site. This recognition triggers a cascade of signaling pathways that lead to the production of salicylic acid (SA), a key signaling molecule in SAR. The accumulation of SA in the infected tissue and its subsequent transport to other parts of the plant activate the expression of pathogenesis-related proteins (PR proteins), which enhance the plant's defensive capabilities.

Signaling Molecules

Several signaling molecules are involved in SAR, including:

• Salicylic acid (SA)
• Jasmonic acid (JA)
• Ethylene

These molecules interact in complex ways to regulate the plant's immune response. SA is particularly important for the activation of SAR, while JA and ethylene are more involved in local defense responses.

Pathogenesis-Related Proteins

PR proteins are a group of proteins that are produced in response to pathogen attack. They play various roles in plant defense, including:

• Chitinases, which degrade fungal cell walls
• Glucanases, which break down glucans in pathogen cell walls
• Thaumatin-like proteins, which have antifungal properties

Role of SAR in Agriculture

SAR is of significant interest in agriculture because it offers a potential method for enhancing crop resistance to diseases. By understanding and manipulating the SAR pathway, scientists aim to develop crops that can better withstand pathogen attacks, reducing the need for chemical pesticides.

Research and Development

Ongoing research is focused on identifying the genes and molecular mechanisms involved in SAR. Advances in genetic engineering and biotechnology hold promise for the development of crops with enhanced SAR capabilities.

See Also

• Plant immune system
• Hypersensitive response
• Induced systemic resistance
• Plant pathology