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Questions and Answers
What is the primary characteristic of Systemic Acquired Resistance (SAR) in plants?
What is the primary characteristic of Systemic Acquired Resistance (SAR) in plants?
What is the name of the proteins encoded by the SAR genes?
What is the name of the proteins encoded by the SAR genes?
Who is credited with the discovery of Systemic Acquired Resistance (SAR) in 1933?
Who is credited with the discovery of Systemic Acquired Resistance (SAR) in 1933?
What is the role of salicylic acid (SA) in Systemic Acquired Resistance (SAR)?
What is the role of salicylic acid (SA) in Systemic Acquired Resistance (SAR)?
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What is the result of applying salicylic acid, aspirin, and benzoic acid to tobacco plants?
What is the result of applying salicylic acid, aspirin, and benzoic acid to tobacco plants?
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Systemic Acquired Resistance (SAR) is a short-lasting resistance state that lasts only for a few hours.
Systemic Acquired Resistance (SAR) is a short-lasting resistance state that lasts only for a few hours.
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SAR is effective against only a narrow spectrum of pathogens, including viruses and bacteria.
SAR is effective against only a narrow spectrum of pathogens, including viruses and bacteria.
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The establishment of SAR does not depend on the type of inducing factor.
The establishment of SAR does not depend on the type of inducing factor.
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The application of salicylic acid, aspirin, and benzoic acid has no effect on plant resistance to pathogens.
The application of salicylic acid, aspirin, and benzoic acid has no effect on plant resistance to pathogens.
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Salicylic acid (SA) is not an endogenous signal molecule required for the induction of SAR.
Salicylic acid (SA) is not an endogenous signal molecule required for the induction of SAR.
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Study Notes
Systemic Acquired Resistance (SAR)
- Plants infected with necrotizing pathogens develop enhanced resistance to subsequent infections by various fungal, bacterial, and viral pathogens, known as Systemic Acquired Resistance (SAR).
- SAR confers broad-spectrum resistance, effective against many but not all pathogens, including Phytophthora parasitica, Cercospora nicotianae, Peronospora tabacina, tobacco mosaic virus, and Pseudomonas syringae pv.tabaci.
Characteristics of SAR
- SAR is characterized by a heightened state of resistance in distal tissues of the plant after pathogen recognition and HR.
- It is a long-lasting heightened resistance state, lasting for a few weeks to sometimes the entire life of the plant.
- SAR is effective against a broad-spectrum of pathogens, including viruses, bacteria, fungi, and oomycetes.
- The time needed for the establishment of SAR depends on both the plant and type of inducing factor.
Historical Perspective
- SAR was first recognized as a significant phenomenon in 1933 by Chester.
- Infection of plants with necrotizing pathogens often results in enhanced resistance to subsequent infections by various fungal, bacterial, and viral pathogens.
- SAR was associated with the coordinated induction of a set of SAR genes encoding proteins known as Pathogenesis-related (PR) proteins.
Signal Molecule and PR Proteins
- Salicylic acid (SA) is the endogenous signal molecule required for the induction of SAR.
- SAR is characterized by the increased expression of a large number of pathogenesis-related genes (PR genes) in both local and systemic tissues.
- SA application on tobacco leaves mimics pathogen-induced expression of PR genes and pathogen resistance in treated tissues.
Key Discoveries
- White (1979) found that the application of aspirin, salicylic acid, and benzoic acid resulted in enhanced resistance to TMV.
- Malamy et al. (1990) showed that the endogenous SA concentration rises in both local and systemic tissues after infection of tobacco with TMV, correlating with PR gene induction.
- Ryals and co-workers (1994) demonstrated that tobacco plants defective in SA accumulation were also defective in their ability to develop SAR and accumulate PR proteins.
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Description
Learn about Systemic Acquired Resistance (SAR), a physiological immunity that provides plants with broad-spectrum resistance against various fungal, bacterial, and viral pathogens. Discover how SAR confers enhanced resistance to subsequent infections.
