Salicylate-mediated interactions between pathogens and herbivores
Jennifer S Thaler1, Anurag A Agrawal, Rayko Halitschke
1Department of Entomology, 4138 Comstock Hall, Cornell University, Ithaca, New York 14853, USA. thaler@cornell.edu
Ecology
|May 14, 2010
Summary
Plant defense pathways, jasmonate and salicylate, mediate interactions between pathogens and herbivores. Jasmonate confers resistance independently, while salicylate can increase susceptibility to some pests.
Area of Science:
- Plant Biology
- Chemical Ecology
- Plant Pathology
Background:
- Plants utilize hormone-mediated signaling pathways, primarily jasmonate and salicylate, for defense against biotic stresses.
- The interplay between these pathways and their differential effects on herbivore and pathogen interactions are not fully understood.
Purpose of the Study:
- To investigate the relative contributions of jasmonate and salicylate pathways in mediating plant defense against specific pathogens and subsequent herbivore attack.
- To determine how pathogen infection influences these defense pathways and their consequences for plant resistance.
Main Methods:
- Field experiments were conducted using tomato plants (wild-type and salicylate-deficient transgenic) challenged with two distinct pathogens: Pseudomonas syringae (Pst) and tobacco mosaic virus (TMV).
- Jasmonic acid levels, proteinase inhibitor activity, and herbivore performance (Spodoptera exigua caterpillars and aphids) were quantified.
- Salicylic acid induction was monitored in response to pathogen infection.
Main Results:
- Pst infection induced jasmonic acid and reduced caterpillar growth, independent of salicylate levels.
- TMV infection induced salicylic acid in wild-type plants, leading to reduced aphid growth but increased caterpillar growth.
- Salicylate-deficient plants showed altered responses to both pathogens and associated herbivores.
Conclusions:
- Jasmonate-mediated defense can be activated independently of salicylate by certain pathogens.
- Salicylate-mediated responses can confer resistance to aphids but induce susceptibility to chewing herbivores.
- A predictive model for plant defense pathway expression and its consequences is proposed based on these findings.
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