Role of Glucosinolates in Insect-Plant Relationships and Multitrophic Interactions

Department of Ecology, Swedish University of Agricultural Sciences, Uppsala S-750 07, Sweden.
Annual Review of Entomology (Impact Factor: 13.73). 10/2008; 54(1):57-83. DOI: 10.1146/annurev.ento.54.110807.090623
Source: PubMed


Glucosinolates present classical examples of plant compounds affecting insect-plant interactions. They are found mainly in the family Brassicaceae, which includes several important crops. More than 120 different glucosinolates are known. The enzyme myrosinase, which is stored in specialized plant cells, converts glucosinolates to the toxic isothiocyanates. Insect herbivores may reduce the toxicity of glucosinolates and their products by excretion, detoxification, or behavioral adaptations. Glucosinolates also affect higher trophic levels, via reduced host or prey quality or because specialist herbivores may sequester glucosinolates for their own defense. There is substantial quantitative and qualitative variation between plant genotypes, tissues, and ontogenetic stages, which poses specific challenges to insect herbivores. Even though glucosinolates are constitutive defenses, their levels are influenced by abiotic and biotic factors including insect damage. Plant breeders may use knowledge on glucosinolates to increase insect resistance in Brassica crops. State-of-the-art techniques, such as mutant analysis and metabolomics, are necessary to identify the exact role of glucosinolates.

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    • "Some VOCs are instantaneously released in high amounts from damaged plant tissues (Matsui, 2006). Herbivore-induced plant volatiles (HIPVs) play a crucial role in tritrophic interactions by being involved in a mechanism of indirect defense that attracts predators and parasitoids of the herbivores (Dicke, 2009; Hopkins et al., 2009; Llusi a and Pe~ nuelas, 2001; Whitman and Eller, 1990). HIPVs also mediate plant-to-plant communication by inducing defensive responses against herbivores in neighboring undamaged plants or in undamaged tissues of the same plant (Blande et al., 2010; Heil, 2014; Rodriguez-Saona and Frost, 2010; Seco et al., 2011). "
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    ABSTRACT: The main function of floral emissions of volatile organic compounds (VOCs) in entomophilous plants is to attract pollinators. Floral blends, however, can also contain volatile compounds with defensive functions. These defensive volatiles are specifically emitted when plants are attacked by pathogens or herbivores. We characterized the changes in the floral emissions of Diplotaxis erucoides induced by folivory and florivory by Pieris brassicae. Plants were continually subjected to folivory, florivory and folivory + florivory treatments for two days. We measured floral emissions with proton transfer reaction/mass spectroscopy (PTR-MS) at different times during the application of the treatments. The emissions of methanol, ethyl acetate and another compound, likely 3-butenenitrile, increased significantly in response to florivory. Methanol and 3-butenenitrile increased 2.4- and 26-fold, respectively, in response to the florivory treatment. Methanol, 3-butenenitrile and ethyl acetate increased 3-, 100- and 9-fold, respectively, in response to the folivory + florivory treatment. Folivory alone had no detectable effect on floral emissions. All VOC emissions began immediately after attack, with no evidence of delayed induction in any of the treatments. Folivory and florivory had a synergistic effect when applied together, which strengthened the defensive response when the attack was extended to the entire plant.
    Biochemical Systematics and Ecology 12/2015; 63:51-58. DOI:10.1016/j.bse.2015.09.022 · 0.97 Impact Factor
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    • "More than 120 different GSLs have been identified in Brassicaceae, of which approximately 50 % are aliphatic glucosinolates (AGSLs). These are methionine derived GSLs that mainly occur in leaves and flowers (Fahey et al. 2001; Halkier and Gershenzon 2006; Hopkins et al. 2009). Glucosinolate composition and content can vary widely within and between species. "
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    ABSTRACT: Aims: This study explores the biofumigation effects of glucosinolate (GSL) containing Brassica oleracea plant material on beneficial, non-target soil organisms, and aims to relate those effects to differences in GSL profiles. Methods: Leaf material of purple sprouting broccoli ‘Santee’, Savoy cabbage ‘Wintessa’, and the wild B. oleracea accession Winspit was analysed for GSL production and used for biofumigation experiments on the beneficial soil invertebrates, Folsomia candida (springtail) and Eisenia andrei (earthworm) and the soil bacterial community. Results: When mixed into soil, the Winspit plant material exerted the highest toxic effects on beneficial soil invertebrates by reducing survival and reproduction. Total GSL levels varied substantially between genotypes, in particular the aliphatic GSL (AGSL) sinigrin and gluconapin being highly abundant or exclusively present in Winspit. Differences between the genotypes regarding biofumigation effects on the soil microbial community were only observed on a temporal basis with the largest difference in bacterial community structure after 1 week. Conclusions: The high total GSL content in biofumigated soil could explain the toxicity of Winspit for soil invertebrates. These effects are likely to be the results of high AGSL levels in Winspit. The use of wild B. oleracea crops, such as Winspit, for biofumigation practices would need a proper assessment of the overall impact on soil biota before being applied on a wide scale.
    • "Field studies that monitored plant colonization by insects season wide, show that early-season herbivory may enhance the presence of other herbivores, in particular specialists (Van Zandt & Agrawal, 2004; Viswanathan et al., 2005; Poelman et al., 2010). One explanation for this phenomenon may be found in the fact that these specialist herbivores use their food plant-specific secondary chemistry as token stimulus for oviposition (Hopkins et al., 2009). As part of induced resistance to herbivory, often the concentration of these compounds increases and thus these plants become more apparent to specialist herbivores that may impose negative effects on plant fitness (Poelman et al., 2008, 2010). "
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    ABSTRACT: Plant–insect interactions typically take place in complex settings of interactions among multiple trophic levels as well as multiple species in each trophic level. The complex interaction network may strongly impact on extrapolations of resistance traits to have a defensive function. For example, the induced response plants express to their current attacker often enhances resistance to that attacker, but may make a plant more susceptible to attack by another herbivore. Hence, the defensive function or plant fitness benefit of the response to a single attacker may be misinterpreted from pairwise interactions. Moreover, plant physiological responses to a first stress by herbivory may hamper the response to a second stress and lead to conclusions of maladaptation in plant defence responses. In light of the entire community of attackers and beneficial organisms the plant interacts with, the susceptibility to some attackers may be a consequence of adaptations that reduce fitness costs of herbivory when considering the full sweep of species that affect plant fitness. A similar argumentation may apply for indirect resistance in which predators or parasitoids dampen the effect of herbivores on plants. Plant volatiles that attract third trophic level organisms such as parasitoids may at the same time attract enemies of the parasitoids in the fourth trophic level, hyperparasitoids, which again dampen the effect of parasitoids on herbivores. In addition, the effectiveness of predators and parasitoids may be dependent on habitat complexity. Here, I plea for studies on the full plant-associated community to understand the fitness outcome of an (induced) plant trait and hence coin it induced direct or indirect plant defence.
    Entomologia Experimentalis et Applicata 09/2015; 157(1). DOI:10.1111/eea.12334 · 1.62 Impact Factor
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