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Turlings, Ted

Nom
Turlings, Ted
Affiliation principale
Fonction
Professeur ordinaire
Email
ted.turlings@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/330

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  • Publication
    Métadonnées seulement
    A maize (E)-beta-caryophyllene synthase implicated in indirect defense responses against herbivores is not expressed in most American maize varieties
    (2008)
    Kollner, Tobias G
    ;
    Held, Matthias 
    ;
    Lenk, Claudia
    ;
    Hiltpold, Ivan 
    ;
    Turlings, Ted 
    ;
    Gershenzon, Jonathan
    ;
    Degenhardt, Joerg
    The sesquiterpene (E)-beta-caryophyllene is emitted by maize (Zea mays) leaves in response to attack by lepidopteran larvae like Spodoptera littoralis and released from roots after damage by larvae of the coleopteran Diabrotica virgifera virgifera. We identified a maize terpene synthase, Terpene Synthase 23 (TPS23), that produces (E)-beta-caryophyllene from farnesyl diphosphate. The expression of TPS23 is controlled at the transcript level and induced independently by D. v. virgifera damage in roots and S. littoralis damage in leaves. We demonstrate that (E)-beta-caryophyllene can attract natural enemies of both herbivores: entomopathogenic nematodes below ground and parasitic wasps, after an initial learning experience, above ground. The biochemical properties of TPS23 are similar to those of (E)-beta-caryophyllene synthases from dicotyledons but are the result of repeated evolution. The sequence of TPS23 is maintained by positive selection in maize and its closest wild relatives, teosinte (Zea sp) species. The gene encoding TPS23 is active in teosinte species and European maize lines, but decreased transcription in most North American lines resulted in the loss of (E)-beta-caryophyllene production. We argue that the (E)-beta-caryophyllene defense signal was lost during breeding of the North American lines and that its restoration might help to increase the resistance of these lines against agronomically important pests.
  • Publication
    Métadonnées seulement
    Fungal infection reduces herbivore-induced plant volatiles of maize but does not affect naive parasitoids
    (2006)
    Rostas, Michael
    ;
    Ton, Jurriaan
    ;
    Mauch-Mani, Brigitte 
    ;
    Turlings, Ted 
    Plants attacked by insects release volatile compounds that attract the herbivores' natural enemies. This so-called indirect defense is plastic and may be affected by an array of biotic and abiotic factors. We investigated the effect of fungal infection as a biotic stress agent on the emission of herbivore-induced volatiles and the possible consequences for the attraction of two parasitoid species. Maize seedlings that were simultaneously attacked by the fungus Setosphaeria turcica and larvae of Spodoptera littoralis emitted a blend of volatiles that was qualitatively similar to the blend emitted by maize that was damaged by only the herbivore, but there was a clear quantitative difference. When simultaneously challenged by fungus and herbivore, the maize plants emitted in total 47% less of the volatiles. Emissions of green leaf volatiles were unaffected. In a six-arm olfactometer, the parasitoids Cotesia marginiventris and Microplitis rufiventris responded equally well to odors of herbivore-damaged and fungus- and herbivore-damaged maize plants. Healthy and fungus-infected plants were not attractive. An additional experiment showed that the performance of S. littoralis caterpillars was not affected by the presence of the pathogen, nor was there an effect on larvae of M. rufiventris developing inside the caterpillars. Our results confirm previous indications that naive wasps may respond primarily to the green leaf volatiles.
  • Publication
    Métadonnées seulement
    Antennal electrophysiological responses of three parasitic wasps to caterpillar-induced volatiles from maize (Zea mays mays), cotton (Gossypium herbaceum), and cowpea (Vigna unguiculata)
    (2005)
    Gouinguene, Sandrine 
    ;
    Pickett, John A
    ;
    Wadhams, Lester J.
    ;
    Birkett, Michael A
    ;
    Turlings, Ted 
    Many parasitic wasps are attracted to volatiles that are released by plants when attacked by potential hosts. The attractiveness of these semiochernicals from damaged plants has been demonstrated in many tritrophic systems, but the physiological mechanisms underlying the insect responses are poorly understood. We recorded the antennal perception by three parasitoids (Cotesia marginiventris, Microplitis rufiventris, and Campoletis sonorensis) to volatiles emitted by maize, cowpea, and cotton plants after attack by the common caterpillar pest Spodoptera littoralis. Gas chromatography-electroantennography (GC-EAG) recordings showed that wasps responded to many, but not all, of the compounds present at the physiologically relevant levels tested. Interestingly, some minor compounds, still unidentified, elicited strong responses from the wasps. These results indicate that wasps are able to detect many odorant compounds released by the plants. It remains to be determined how this information is processed and leads to the specific behavior of the parasitoids.
  • Publication
    Métadonnées seulement
    In situ modification of herbivore-induced plant odors: A novel approach to study the attractiveness of volatile organic compounds to parasitic wasps
    (2005)
    D'Alessandro, Marco
    ;
    Turlings, Ted 
    Many parasitic wasps (parasitoids) exploit volatile organic compounds (VOCs) emitted by herbivore-infested plants in order to locate their hosts, but it remains largely unknown which specific compounds within the volatile blends elicit the attractiveness to parasitoids. One way of studying the importance of specific VOCs is to test the attractiveness of odor blends from which certain compounds have been emitted. We used this approach by testing the attraction of naive and experienced females of the two parasitoids Cotesia marginiventris and Microplitis rufiventris to partially altered volatile blends of maize seedlings (Zea mays var. Delprim) infested with Spodoptera littoralis larvae. Adsorbing filter tubes containing carbotrap-C or silica were installed in a four-arm olfactometer between the odor source vessels and the arms of the olfactometer. The blends breaking through were tested for chemical composition and attractiveness to the wasps. Carbotrap-C adsorbed most of the sesquiterpenes, but the breakthrough blend remained attractive to naive C. marginiventris females. Silica adsorbed only some of the more polar VOCs, but this essentially eliminated all attractiveness to naive C. marginiventris, implying that among the adsorbed compounds there are some that play key roles in the attraction. Unlike C. marginiventris, M. rufiventris was still attracted to the latter blend, showing that parasitoids with a comparable biology may employ different strategies in their use of plant-provided cues to locate hosts. Results from similar experiments with modified odor blends of caterpillar-infested cowpea (Vigna unguiculata) indicate that key VOCs in different plant species vary greatly in quality and/or quantity. Finally, experienced wasps were more strongly attracted to a specific blend after they perceived the blend while ovipositing in a host. Considering the high number of distinct adsorbing materials available today, this in situ modification of complex volatile blends provides a new and promising approach pinpointing on key attractants within these blends. Advantages and disadvantages compared to other approaches are discussed.
  • Publication
    Métadonnées seulement
    The role of fresh versus old leaf damage in the attraction of parasitic wasps to herbivore-induced maize volatiles
    (2005)
    Hoballah, Maria Elena
    ;
    Turlings, Ted 
    The odor produced by a plant under herbivore attack is often used by parasitic wasps to locate hosts. Any type of surface damage commonly causes plant leaves to release so-called green leaf volatiles, whereas blends of inducible compounds are more specific for herbivore attack and can vary considerably among plant genotypes. We compared the responses of naive and experienced parasitoids of the species Cotesia marginiventris and Microplitis rufiventris to volatiles from maize leaves with fresh damage (mainly green leaf volatiles) vs. old damage (mainly terpenoids) in a six-arm olfactometer. These braconid wasps are both solitary endoparasitoids of lepidopteran larvae, but differ in geographical origin and host range. In choice experiments with odor blends from maize plants with fresh damage vs. blends from plants with old damage, inexperienced C. marginiventris showed a preference for the volatiles from freshly damaged leaves. No such preference was observed for inexperienced M. rufiventris. After an oviposition experience in hosts feeding on maize plants, C. marginiventris females were more attracted by a mixture of volatiles from fresh and old damage. Apparently, C. marginiventris has an innate preference for the odor of freshly damaged leaves, and this preference shifts in favor of a blend containing a mixture of green leaf volatiles plus terpenoids, after experiencing the latter blend in association with hosts. M. rufiventris responded poorly after experience and preferred fresh damage odors. Possibly, after associative learning, this species uses cues that are more directly related with the host presence, such as volatiles from host feces, which were not present in the odor sources offered in the olfactometer. The results demonstrate the complexity of the use of plant volatiles by parasitoids and show that different parasitoid species have evolved different strategies to exploit these signals.
  • Publication
    Métadonnées seulement
    Volicitin, an elicitor of maize volatiles in oral secretion of Spodoptera exigua: Isolation and bioactivity
    (2000)
    Turlings, Ted 
    ;
    Alborn, Hans
    ;
    Loughrin, John H
    ;
    Tumlinson, James H
    Plants respond to insect-inflicted injury by systemically releasing relatively large amounts of several volatile compounds, mostly terpenoids and indole. As a result, the plants become highly attractive to natural enemies of the herbivorous insects. In maize, this systemic response can be induced by the uptake via the stem of an elicitor present in the oral secretions of caterpillars. Such an elicitor was isolated from the regurgitant of Spodoptera exigua larvae, identified as N-(17-hydroxylinolenoyl)-L-glutamine, and named volicitin. Here we present details on the procedure that was used to isolate volicitin and the biosasays that demonstrate its potency as an elicitor of maize volatiles that attract parasitoids. With a series of liquid chromatography purification steps, volicitin was separated from all other inactive substances in the regurgitant of larvae of the noctuid moth S. exigua. Maize seedlings that were incubated in very low concentrations of pure natural volicitin released relatively large amounts of terpenoids and became highly attractive to the parasitoid Microplitis croceipes. The identification of this and other insect-derived elicitors should allow us to determine their precise source and function, and better understand the evolutionary history of the phenomenon of herbivore-induced volatile emissions in plants.
  • Publication
    Métadonnées seulement
    Herbivore-induced volatile emissions from cotton (Gossypium-hirsutum L) seedlings
    (1994)
    McCall, Philip J
    ;
    Turlings, Ted 
    ;
    Loughrin, John H
    ;
    Proveaux, Adron T
    ;
    Tumlinson, James H
    The effect of herbivory on the composition of the volatile blends released by cotton seedlings was investigated by collecting volatiles from undamaged, freshly damaged (0-2 hr after initiation of feeding), and old damaged (16-19 hr after initiation of feeding) plants on which com earworm caterpillars (Helicoverpa zea Boddie) were actively feeding. A blend of 22 compounds was consistently observed to be emitted by the old damaged plants with nine occurring either only in, or in significantly greater amounts in old damaged, as compared with freshly damaged plants. These were (Z)-3-hexenyl acetate, hexyl acetate, (E)-beta-ocimene, (3E)-4,8-dimethyl-1,3,7-nonatriene, (Z)-3-hexenyl butyrate, (E)-2-hexenyl butyrate, (Z)-3-hexenyl 2-methylbutyrate, (E)-2-hexenyl 2-methylbutyrate, and indole, The nature of this response is compared with other studies where herbivore-induced volatile responses are also known. The presence of large amounts of terpenes and aldehydes seen at the onset of feeding and the appearance of other compounds hours later suggest that cotton defense mechanisms may consist of a constitutive repertoire that is augmented by an induced mechanism mobilized in response to attack. A number of the induced compounds are common to many plants where, in addition to an immediate defensive function, they are known to be involved in the attraction of natural enemies.
  • Publication
    Métadonnées seulement
    Systemic release of chemical signals by herbivore-injured corn
    (1992)
    Turlings, Ted 
    ;
    Tumlinson, James H
    Corn seedlings respond to insect herbivore-inflicted injury by releasing relatively large amounts of several characteristic terpenoids and, as a result, become highly attractive to parasitic wasps that attack the herbivores. Chemical evidence showed that the induced emission of volatiles is not limited to the sites of damage but occurs throughout the plant. This evidence was obtained by comparing the release of volatiles from leaves of unharmed (control) seedlings with the release of volatiles from undamaged leaves of seedlings with two injured leaves treated with caterpillar regurgitant. Immediately after injury no differences were measured in the released volatiles, but several hours later the undamaged leaves of injured plants released the terpenoids linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene in significantly larger amounts than leaves of unharmed plants. Other volatiles that are released by herbivore-injured leaves were detected occasionally only in trace amounts from the undamaged leaves of a damaged seedling. The systemic release of volatiles by injured corn coincided with attractiveness to the parasitoid Cotesia margin-iventris; undamaged leaves of injured plants became significantly more attractive than leaves from control seedlings. These findings show conclusively that when a plant is injured by an insect herbivore the whole plant emits chemical signals.
  • Publication
    Métadonnées seulement
    Larval-damaged plants - source of volatile synomones that guide the parasitoid cotesia-marginiventris to the microhabitat of its hosts
    (1991)
    Turlings, Ted 
    ;
    Tumlinson, James H
    ;
    Eller, Fred J
    ;
    Lewis, W Joe
    Single and dual choice tests in a flight tunnel revealed that plants damaged by host larvae are the main source of the volatiles that attract females of the parasitoid Cotesia marginiventris (Cresson) to the microhabitat of its hosts. Frass and host larvae, the other two major components of a complete plant-host complex, were significantly less attractive than the damaged seedlings; frass alone was more attractive than larvae alone. However, a recombination of larvae with the damaged seedlings was significantly more attractive than the damaged leaves alone, or damaged leaves with frass. This was due to the additional feeding damage done by the larvae. The role of plants in the host-finding behaviour of parasitoids is discussed.