Plant Innate Immune System Flashcards
What are the stages of induced plant defence?
- Pre-invasive penetration defence: stomatal closure
- Post-invasive early defence: ROS
- Post-invasive late defence: Hormone induced defences
What is salicylic acid (SA) efficient against?
Efficient against biotrophic pathogens
What is jasmonic acid efficient agaisnt?
Efiicient agains necrotrophic pathogens and insects.
What is ethylene efficient against?
Works with JA for necrtotrophic pathogens and with SA for biotrophic pathogens.
When is ABA activated?
Activated when herbivory causes water loss (drought). Also aids JA.
Outline what happens in the jasmonic acid dependent immune system.
Against necrotrophic pathogens
0-10 mins:
- PRR binds to DAMPs
- Transcription factors activated, synthesis of JA.
10 mins - 3 hrs:
- JA and isoleucine complex acts as a label for degradation of JAZ.
- Activates MYC2 which activates defence genes
What is a PRR?
Pattern recognition receptor
What are DAMPs?
Damage associated molecular patterns.
What are PAMPs?
Pathogen associated molecular patterns.
What are MAMPs?
Microbe associated molecular patterns.
Outline the Salicylic acid dependent immune system.
Against necrotrophic pathogens, slower to be undetected.
0-2 hrs:
- PRR binds to PAMPs
- Activates transcription factors, SA is synthesised.
2 -48 hrs:
- Reaches critical threshold and throws off redox state.
- NPR1 is reduced and enters the nucleus, switching on defence genes.
What is NPR1?
Transcription factor that activates defence genes.
What does the spatiotemporal model consist of?
- Non host resistance
- Basal resistance
- Race specific resistance (gene for gene resistance)
What is non-host resistance?
Passive: host is not suitable environment for pathogen
Active: host activates defence response.
e.g. powdery mildew on Arabidopsis, screen for pen mutants
What did screening for pen mutants show in powdery mildew infected Arabidopsis?
Pen = penetration
Pen1: syntaxin- localised to membrane and vesicles
Pen2: glycoside hydrolase- localised to peroxisomes and vesicles
Pen3: abc transporter- localised to membrane at infected sites.
What is basal resistance?
Similar to host resistance but weaker.
e.g. Pseudomonas syringae on Arabidopsis: colonized the plant and it was visibly diseased.
What is gene for gene resistance?
Specific R gene in plant is combined with corresponding Avr gene in pathogen
What happens if Avr genes do not bind to the specific R protein?
Avr gene is actually a virulence gene unless it is recognised by the specific R protein.
Outline the evolutionary model of the plant immune system.
MAMPs (low defence)
Evolution of PRRs -> non-host resistance (increase defence)
Evolution of Avr proteins (decreases defence -> basal resistance)
Evolution of R proteins -> race specific resistance (increases defence)
Evolution of 2nd gen effector protein (reduces defence -> basal resistance)
Evolution of 2nd gen R proteins (increases defence -> race specific resistance)
