Molecular Interactions between the Specialist HerbivoreManduca sexta (Lepidoptera, Sphingidae) and Its Natural Host Nicotiana attenuata. III. Fatty Acid-Amino Acid Conjugates in Herbivore Oral Secretions Are Necessary and Sufficient for Herbivore-Specific Plant Responses

Abstract

Feeding by the tobacco specialist Manduca sexta (Lepidoptera, Sphingidae) and application of larval oral secretions and regurgitant (R) to mechanical wounds are known to elicit: (a) a systemic release of mono-and sesquiterpenes, (b) a jasmonate burst, and (c) R-specific changes in transcript accumulation of putatively growth-and defense-related mRNAs in Nicotiana attenuata Torr. ex Wats. We identified several fatty acid-amino acid conjugates (FACs) in the R of M. sexta and the closely related species Manduca quinquemaculata which, when synthesized and applied to mechanical wounds at concentrations comparable with those found in R, elicited all three R-specific responses. Ion-exchange treatment of R, which removed all detectable FACs and free fatty acids (FAs), also removed all detectable activity. The biological activity of ion-exchanged R could be completely restored by the addition of synthetic FACs at R-equivalent concentrations, whereas the addition of FAs did not restore the biological activity of R. We conclude that the biological activity of R is not related to the supply of FAs to the octadecanoid cascade for endogenous jasmonate biosynthesis, but that FACs elicit the herbivore-specific responses by another mechanism and that the insect-produced modification of plant-derived FAs is necessary for the plant's recognition of this specialized herbivore.

Exogenous Application of Jasmonic Acid Induces Volatile Emissions in Rice and Enhances Parasitism of Nilaparvata lugens Eggs by theParasitoid Anagrus nilaparvatae

“…Indirect plant defenses have been intensively studied since the late 1980s, and to date, this phenomenon has been reported in more than 23 plant species (see reviews in Vet and Dicke, 1992;Sabelis et al, 1999;Turlings and Wäckers, 2004). Studies on the mechanisms leading to the production of herbivore-induced plant volatiles have revealed the role of herbivore-specific elicitors (Mattiacci et al, 1995;Alborn et al, 1997;Halitschke et al, 2001). These elicitors can activate various signaling pathways in the plant, causing an up-regulation of a large array of defense-related genes through cross-talk and resulting in accumulation or release of defense chemicals (Kessler and Baldwin, 2002).…”

Absolute Configuration of Volicitin from the Regurgitant of Lepidopteran Caterpillars and Biological Activity of Volicitin-Related Compounds

“…Fatty acid-amino acid conjugates and related compounds 2,3) are also present in the oral secretions of other lepidopteran larvae. [4][5][6][7] Interestingly, recent studies have revealed that volicitin activated genes for the synthesis of terpenoids 8) and the nitrogen-containing metabolite indole in corn seedlings. 9) Fatty acid-amino acid conjugates in the oral secretions of two Manduca species elicited bursts in the production of jasmonic acid 5) and ethylene.…”

“…9) Fatty acid-amino acid conjugates in the oral secretions of two Manduca species elicited bursts in the production of jasmonic acid 5) and ethylene. 5,10) These results clearly show that volicitin-related compounds evoked some plant defense responses.…”

“…[4][5][6][7] Interestingly, recent studies have revealed that volicitin activated genes for the synthesis of terpenoids 8) and the nitrogen-containing metabolite indole in corn seedlings. 9) Fatty acid-amino acid conjugates in the oral secretions of two Manduca species elicited bursts in the production of jasmonic acid 5) and ethylene. 5,10) These results clearly show that volicitin-related compounds evoked some plant defense responses.…”

Exploiting scents of distress: the prospect of manipulating herbivore-induced plant odours to enhance the control of agricultural pests

“…Soon afterwards, it was reported that caterpillar-damaged plants release considerable amounts of volatiles that are highly attractive to parasitic wasps [2]. Follow-up work has revealed a remarkable sophistication to the interactions, which were found to involve elicitors in the oral secretions of the herbivores [15][16][17][18] that trigger the systemic emission [19] of variable blends of de novo synthesized [20] volatiles. The induction of volatile emissions occurs not only in response to herbivore feeding on leaves but can also result from the deposition of insect eggs on plant parts [21] and from feeding by insect larvae on roots [22,23 ], again resulting in the attraction of the respective enemies that use the eggs or root feeders as food.…”