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PRN Biologie

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CH
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Academic Institute
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  • Publication
    Métadonnées seulement
  • Publication
    Métadonnées seulement
    Manipulation of chemically mediated interactions in agricultural soils to enhance the control of crop pests and to improve crop yield
    (2012)
    Hiltpold, Ivan 
    ;
    Turlings, Ted 
    In most agro-ecosystems the organisms that feed on plant roots have an important impact on crop yield and can impose tremendous costs to farmers. Similar to aboveground pests, they rely on a broad range of chemical cues to locate their host plant. In their turn, plants have co-evolved a large arsenal of direct and indirect defense to face these attacks. For instance, insect herbivory induces the synthesis and release of specific volatile compounds in plants. These volatiles have been shown to be highly attractive to natural enemies of the herbivores, such as parasitoids, predators, or entomopathogenic nematodes. So far few of the key compounds mediating these so-called tritrophic interactions have been identified and only few genes and biochemical pathways responsible for the production of the emitted volatiles have been elucidated and described. Roots also exude chemicals that directly impact belowground herbivores by altering their behavior or development. Many of these compounds remain unknown, but the identification of, for instance, a key compound that triggers nematode egg hatching to some plant parasitic nematodes has great potential for application in crop protection. These advances in understanding the chemical emissions and their role in ecological signaling open novel ways to manipulate plant exudates in order to enhance their natural defense properties. The potential of this approach is discussed, and we identify several gaps in our knowledge and steps that need to be taken to arrive at ecologically sound strategies for belowground pest management.
  • Publication
    Accès libre
    Belowground and aboveground herbivory differentially affect the transcriptome in roots and shoots of maize
    (2022-7-22)
    Ye, Wenfeng
    ;
    Degen, Thomas 
    ;
    Erb, Matthias 
    ;
    Turlings, Ted 
    Plants recognize and respond to feeding by herbivorous insects by upregulating their local and systemic defenses. While defense induction by aboveground herbivores has been well studied, far less is known about local and systemic defense responses against attacks by belowground herbivores. Here, we investigated and compared the responses of the maize transcriptome to belowground and aboveground mechanical damage and infestation by two well-adapted herbivores: the soil-dwelling western corn rootworm Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) and the leaf- chewing fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae). In responses to both herbivores, maize plants were found to alter local transcription of genes involved in phytohormone signaling, primary and secondary metabolism. Induction by real herbivore damage was considerably stronger and modified the expression of more genes than mechanical damage. Feeding by the corn rootworm had a strong impact on the shoot transcriptome, including the activation of genes involved in defense and development. By contrast, feeding by the fall armyworm induced only few transcriptional changes in the roots. In conclusion, feeding by a leaf chewer and a root feeder differentially affects the local and systemic defense of maize plants. Besides revealing clear differences in how maize plants respond to feeding by these specialized herbivores, this study reveals several novel genes that may play key roles in plant–insect interactions and thus sets the stage for in depth research into the mechanism that can be exploited for improved crop protection.
  • Publication
    Accès libre
    Climate Change in the Underworld: Impacts for Soil-Dwelling Invertebrates
    (New York: Wiley Online library, 2016)
    Hiltpold, Ivan 
    ;
    Johnson, Scott N.
    ;
    Le Bayon, Renée-Claire 
    ;
    Nielsen, Uffe N.
    This chapter reviews and discusses the impact of elevated atmospheric CO2 and climatic changes on three of the functionally most important invertebrate taxa in soil ecosystems: nematodes, insects, and earthworms. The effects of climate and atmospheric CO2 change on soil abiotic conditions vary and numerous biotic feedbacks occur. Many soil‐dwelling insects are herbivores and devastate crops, which impact human societies through yield decreases; therefore an understanding of how climate change will affect their pest status is essential. The chapter discusses potential broader impacts of soil nematode community responses to climate change on ecosystems. Soil‐dwelling insects that feed on roots are usually the juvenile stages of insects that live aboveground as adults. These soil invertebrates can reach astonishing densities, with root‐feeding cicadas of deciduous forests of North America having the largest collective biomass per unit area of any terrestrial animal.
  • Publication
    Métadonnées seulement
    A tritrophic signal that attracts parasitoids to host-damaged plants withstands disruption by non-host herbivores
    (2010)
    Erb, Matthias 
    ;
    Foresti, N.
    ;
    Turlings, Ted 
    Background: Volatiles emitted by herbivore-infested plants are highly attractive to parasitoids and therefore have been proposed to be part of an indirect plant defense strategy. However, this proposed function of the plant-provided signals remains controversial, and it is unclear how specific and reliable the signals are under natural conditions with simultaneous feeding by multiple herbivores. Phloem feeders in particular are assumed to interfere with plant defense responses. Therefore, we investigated how attack by the piercing-sucking cicadellid Euscelidius variegatus influences signaling by maize plants in response to the chewing herbivore Spodoptera littoralis. Results: The parasitoid Cotesia marginiventris strongly preferred volatiles of plants infested with its host S. littoralis. Overall, the volatile emissions induced by S. littoralis and E. variegatus were similar, but higher levels of certain wound-released compounds may have allowed the wasps to specifically recognize plants infested by hosts. Expression levels of defense marker genes and further behavioral bioassays with the parasitoid showed that neither the physiological defense responses nor the attractiveness of S. littoralis infested plants were altered by simultaneous E. variegatus attack. Conclusions: Our findings imply that plant defense responses to herbivory can be more robust than generally assumed and that ensuing volatiles convey specific information about the type of herbivore that is attacking a plant, even in complex situations with multiple herbivores. Hence, the results of this study support the notion that herbivore-induced plant volatiles may be part of a plant's indirect defense stratagem.
  • Publication
    Métadonnées seulement
    Plant strengtheners enhance parasitoid attraction to herbivore-damaged cotton via qualitative and quantitative changes in induced volatiles
    (2014)
    Sobhy, Islam S.
    ;
    Erb, Matthias 
    ;
    Turlings, Ted 
    Background Herbivore-damaged plants release a blend of volatile organic compounds (VOCs) that differs from undamaged plants. These induced changes are known to attract the natural enemies of the herbivores and therefore are expected to be important determinants of the effectiveness of biological control in agriculture. One way of boosting this phenomenon is the application of plant strengtheners, which has been shown to enhance parasitoid attraction in maize. It is unclear if this is also the case for other important crops. Results We applied the plant strengtheners BTH (benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester) or laminarin to cotton plants and studied the effects on volatile releases and the attraction of three hymenopteran parasitoids, Cotesia marginiventris, Campoletis sonorensis and Microplitis rufiventris. After treated and untreated plants were induced by real or simulated caterpillar feeding, we found that BTH treatment increased the attraction of the parasitoids, whereas laminarin had no significant effect. BTH treatment selectively increased the release of two homoterpenes and reduced the emission of indole, the latter of which has been shown to interfere with parasitoid attraction in earlier studies. Canonical variate analyses of the data show that the parasitoid responses were dependent on the quality rather than the quantity of volatile emission in this tritrophic interaction. Conclusion Overall, these results strengthen the emerging paradigm that induction of plant defences with chemical elicitors such as BTH could provide a sustainable and environment-friendly strategy for biological control of pests by enhancing the attractiveness of cultivated plants to natural enemies of insect herbivores.
  • Publication
    Métadonnées seulement
    Restoring a maize root signal that attracts insect-killing nematodes to control a major pest
    (2009)
    Degenhardt, Jörg
    ;
    Hiltpold, Ivan 
    ;
    Köllner, Tobias G.
    ;
    Frey, M.
    ;
    Gierl, A.
    ;
    Gershenzon, Jonathan
    ;
    Hibbard, Bruce Elliott
    ;
    Ellersieck, M. R.
    ;
    Turlings, Ted 
    When attacked by herbivorous insects, plants emit volatile compounds that attract natural enemies of the insects. It has been proposed that these volatile signals can be manipulated to improve crop protection. Here, we demonstrate the full potential of this strategy by restoring the emission of a specific below ground signal emitted by insect-damaged maize roots. The western corn root-worm induces the roots of many maize varieties to emit (E)-beta-caryophyllene, which attracts entomopathogenic nematodes that infect and kill the voracious root pest. However, most North American maize varieties have lost the ability to emit (E)-beta-caryophyllene and may therefore receive little protection from the nematodes. To restore the signal, a nonemitting maize line was transformed with a (E)-beta-caryophyllene synthase gene from oregano, resulting in constitutive emissions of this sesquiterpene. In root-worm-infested field plots in which nematodes were released, the (E)-beta-caryophyllene-emitting plants suffered significantly less root damage and had 60% fewer adult beetles emerge than untransformed, nonemitting lines. This demonstration that plant volatile emissions can be manipulated to enhance the effectiveness of biological control agents opens the way for novel and ecologically sound strategies to fight a variety of insect pests.