Download L16: Plant Defense

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Plant Defense
• Can mycorrhizal connections transport
more than just nutrients & water?
Plant Defense
Lecture 16
Spring 2014
– Role in plant defense?
• Plant defense
– Herbivores
– Pathogens
• Responses
– Constitutive defenses
– Induced defenses
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Constituitive
Constitutive
• Trichome production
• Toxic compounds
• (can be constituitive
or induced)
– often stored in vacuole
– e.g., canavavine
(amino acid) – takes
place of arginine
Fig. 35.9
Oplopanax horridus
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Induced
• Release of signals to attract predatory insects
– Volatile Organic Compounds (VOCs)
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Pathogen Induced
Two responses
• Hypersensitive Response
– rapid and localized
• Systemic Acquired Resistance
Fig. 39.28
– slower and widespread in plant
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Induced
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Hypersensitive Response (HR)
Fig. 39.29
• Virulent vs. avirulent
• Hypersensitive
Response
• Gene-for-gene
recognition
1. Isolate
2. Attack
3. Send alarm
4. Cell death
– Effectors & Avr
genes (pathogen)
– R genes (plant)
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Hypersensitive Response (HR)
Isolate
• Cell wall strengthening
Attack pathogen
• Pathogenesis-related (PR) proteins
• Pytoalexins
• ROI’s (hydrogen peroxide, superoxide,
hydroxyl radical)
– Lignin production
• Reactive Oxygen Intermediates (ROI)
– strengthens
cross-linkages
– enzyme inactivation,
nucleic acid
degradation
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Hypersensitive Response (HR)
Send alarm
• Synthesis and release of a signaling
molecule
Cell death
• ROI’s & Nitric
Oxide
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Hypersensitive Response (HR)
Systemic Acquired Resistance (SAR)
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• Plant-wide expression of defense genes
– Combination
causes cell
death
Fig. 39.29
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Systemic Acquired Resistance (SAR)
Methylsalicylic
acid
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Plant-plant communication
• VOCs
• Importance of
blends
1. Methylsalicylic acid
released by
damaged cell
2. Travels in apoplast
& phloem
3. Salicylic acid or
jasmonic acid
produced
4. Synthesis of
phytoalexins &
other secondary
metabolites
Plant-plant communication
• Herbivore induced plant volatiles (HIPV)
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Plant-plant communication
• Common
mycorrhizael
networks and
transport of plant
defense signals?
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