1 / 20

Induced Resistance

Plant Defense — Herbivore Offense. Induced Resistance. Advantage: lower allocation costs and ecological costs when herbivores are absent. Disadvantage: Lag-time between first attack and fully induced resistance. Conceptual model. How to reduce the cost of the lag-time?.

jovan
Télécharger la présentation

Induced Resistance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plant Defense — Herbivore Offense Induced Resistance Advantage: lower allocation costs and ecological costs when herbivores are absent. Disadvantage: Lag-time between first attack and fully induced resistance. Conceptual model How to reduce the cost of the lag-time?

  2. Detection and response of plants to oviposition Bruchus pisorum

  3. assay plants damaged plants control plants "Communication" between plants • Baldwin & Schulz (1983): Populus and Acer trees Glasshouse experiment Results: • phenolics increased in damaged plants • phenolics increased in assay plants !!! "Talking trees"

  4. • Karban et al. (2000) Field experiment: Nicotiana Artemisia Prop. leaves damaged (Nicotiana) PPO activity Artemisia clipped/unclipped • Dolch & Tscharntke (2000) Field experiment: Alnus Alnus leaf damage (%) eggs per leaf distance distance from defoliated tree (m)

  5. What signals are emitted by plants after wounding by herbivores? • Volatile organic compounds (VOCs): terpenes, green leafy volatiles • Methyljasmonate (MeJA) Who can perceive and respond to signals? • Neighboring plants (?) • Parasitoids and predators

  6. Parasitoids & Predators Herbivores ? Plants Tri-trophic interactions

  7. Indirect defense in the field Manduca quinquemaculata on Nicotiana attenuata Survival of Manduca Oviposition by Manduca Oviposition rate % survival Con. MeJA 1 2 4 7 8 Con. MeJA Manduca 4 Volatiles applied to plants Kessler & Baldwin (2001)

  8. Indirect defense — slow growth/high mortality hypothesis Slow growth rate of herbivores may lead to increased parasitism/predation Pieris rapae reared on artificial diet and exposed to Cotesia glomerata parasitoid Fast development (warm temperature) Fast development (casein-rich diet) Slow development (cold temperature) Slow development (casein-deficient) Parasitism rate (%) Parasitism rate (%) Larval age (days) Benrey & Denno (1997)

  9. Herbivore offense How insects adapt to defensive chemicals in plants

  10. • Rapid excretion Experiment: Nicotine dose in artificial diet –> 93% excreted within 2 hours! Experiment: Nicotine injected into hemolymph Manduca sexta

  11. • Enzymatic detoxification Mixed-function oxidases (e.g. cytochrome P450) can metabolise a large array of plant secondary chemicals. Ubiquitous in herbivorous insects, in midgut. Example: Spider mites adapted to bean

  12. Helicoverpa zea (Noctuidae) Recent discovery : Cytochrome P450 induced by jasmonate and salicylate!!! (Li et al. 2002)

  13. Disarming the mustard oil bomb - Plutella xylostella using glucosinolate sulfatase (GSS) Ratzka et al. 2002

  14. Disarming the mustard oil bomb - Pieris rapae using nitrile-specifier protein (NSP) NSP Wittstock et al. 2004

  15. • Target-site insensitivity Na+,K+-ATPase is sensitive to ouabain (a cardiac glycoside). In Monarch butterflies a single-point mutation resulted in insensitive ATPase. Other example: induction of proteases in herbivore gut, which are insensitive of proteinase inhibitors

  16. • Sequestration (use of plant toxins by herbivore for his own defense) Involves complex adaptations: 1) Herbivore must be willing to ingest the hosts secondary chemicals 2) Herbivore must be tolerant of chemicals 3) Herbivore must digest chemical without metabolising it into a non-toxic form. 4) Herbivore must deposit chemicals in particular tissues or store them.

  17. Nuptial gifts in Utetheisa ornaztix (moth)

  18. • Compensatory feeding Pieris rapae Consumption rate (mg dry weight per day) Nitrogen content of plant (% dry weight) Slansky and Feeny 1977

  19. • Behaviour

  20. • Symbionts E.g. Buchnera bacteria in aphids

More Related