Oviposition Stimulants Research Articles

Gustatory Sensing Mechanism Coding for Multiple Oviposition Stimulants in the Swallowtail Butterfly,Papilio Xuthus

The swallowtail butterfly, Papilio xuthus, selectively uses a limited number of plants in the Rutaceae family. The butterfly detects oviposition stimulants in leaves through foreleg chemosensilla and requires a specific combination of multiple oviposition stimulants to lay eggs on the leaf of its host plants. In this study, we sought to elucidate the mechanism underlying the regulation of oviposition behavior by multiple oviposition stimulants. We classified chemosensilla on the tarsomere of the foreleg into three types (L1, L2, and S) according to their size and response to oviposition stimulants and general tastants. The L1 was more abundant in females than in males and responded preferentially to oviposition stimulants. Both L2 and S were common to both sexes and responded to general tastants. We found that five oviposition stimulants (synephrine, stachydrine, 5-hydroxy-Nω-methyltryptamine, narirutin, and chiro-inositol) elicited spikes from three specific gustatory receptor neurons (GRNs) within L1 sensilla. These three GRNs responded to a mixture of the five stimulants at concentrations equivalent to those found in the whole-leaf extract of citrus, and the mixture induced oviposition at levels comparable to whole-leaf extract. We propose that oviposition is triggered by the firing of three specific GRNs in L1 sensilla that encode the chemical signatures of multiple oviposition stimulants.

Oviposition and flight orientation response of Aedes aegypti to certain aromatic aryl hydrazono esters

Aedes aegypti is a day-biting, highly anthropophilic mosquito and a potential vector of dengue and chikungunya in India. A. aegypti is a container breeder, generally oviposit in the stored and fresh water bodies, and discarded containers near residential areas that provide suitable habitats for oviposition by gravid females. The diurnal activity and endophilic nature of these mosquitoes have increased the frequency of contact with human being. Assured blood meal from human host in an infested area leads to increased disease occurrence. Gravid mosquitoes can potentially be lured to attractant-treated traps and could subsequently be killed with insecticides or growth regulators. In this direction, oviposition by A. aegypti females to aryl hydrazono esters (AHE)-treated bowls at 10 ppm concentration was tested in dual choice experiment, and their orientation response to these ester compounds was studied in Y-tube olfactometer. Among the esters tested, AHE-2, AHE-11 and AHE-12 elicited increased egg deposition with oviposition activity indices (OAI) of +0.39, +0.24 and +0.48, respectively, compared to control; in contrast, AHE-8, AHE-9 and AHE-10 showed negative oviposition response with OAI of -0.46, -0.35 and -0.29, respectively, at 10 mg/L. In the Y-tube olfactometer bioassay, AHE-2 attracted 60 % females compared to control, while to the odour of AHE-11 and AHE-12, about 70 % of the females were trapped in treated chambers. In contrast, only 27-30 % of gravid females entered the chamber releasing AHE-8, AHE-9 and AHE-10 odour plumes, while 70 % entered control chamber, evincing a possible non-preference of treatment odours as well as interference with olfactory receptors. These compounds have the potential for application as oviposition stimulants or deterrents for surveillance and control of mosquito population using ovitraps.

D-Pinitol as a key oviposition stimulant for sulfur butterfly, Colias erate: chemical basis for female acceptance of host- and non-host plants

The sulfur butterfly, Colias erate, utilizes various legumes as host plants. We examined the chemical constituents of its primary host plant, Trifolium repens (white clover), to identify phytochemicals inducing oviposition by C. erate females. Since one of the four aqueous subfractions prepared from a methanolic extract of the plant has previously been shown to be the most responsible for the oviposition-stimulatory activity exerted by the plant, chemical analyses were conducted of the fraction concerned. Activity-directed fractionation of the subfraction by ion-exchange chromatography revealed that the key substance(s) resided in the neutral fraction. Preparative TLC of the neutral fraction and subsequent spectral analyses identified d-(+)-pinitol, glycerin, methyl β-d-glucoside, and myo-inositol as characteristic components together with ubiquitous sugars (e.g., sucrose and glucose). Of these, only pinitol singly evoked significant oviposition responses at concentrations over 0.05%. In dual-choice bioassays, however, females laid significantly more eggs on pinitol solutions admixed with glycerin or methyl β-d-glucoside than on pinitol alone. Two cyanoglucosides, linamarin, and lotaustralin, occurring in the other aqueous subfractions, also synergistically increased the oviposition response in combination with pinitol. The results clearly indicated that pinitol is a crucial oviposition stimulant involved in host recognition, while glycerin, methyl β-d-glucoside, linamarin, and lotaustralin function as synergists. We further examined the oviposition responses of C. erate females to aqueous fractions, along with their chemical compositions, that had been prepared from five other host plants and a non-host plant, Aristolochia debilis (Aristolochiaceae), on which oviposition occasionally took place in an outdoor cage during the experiments. The plant species accepted by ovipositing females were all found to contain pinitol in amounts enough to induce egg laying by the butterfly, thus leading to the conclusion that pinitol serves as the essential mediator in recognizing and accepting potential host plants.

Larval Feeding Stimulants for a Rutaceae-Feeding Swallowtail Butterfly, Papilio xuthus L. in Citrus unshiu Leaves

Larvae of a swallowtail butterfly, Papilio xuthus L., feed exclusively on plants of the family Rutaceae, including various Citrus crops. Larvae were strongly stimulated to feed on paper strips impregnated with ethanolic extracts of host-plant leaves. Stimulation of feeding on extracts of Citrus unshiu leaves required a mixture of chemicals including sugars (D: -glucose, D: -fructose, and D: -sucrose), a betaine [(-)-stachydrine], a cyclic peptide (citrusin I), a polymethoxyflavone (isosinensetin), and the lipids 1-linolenoylglycerol, 1-linoleoylglycerol, 1-octadecenoylglycerol, 1-stearoylglycerol, and 1,2-dilinolenoyl-3-galactosyl-sn-glycerol. When these compounds were assayed individually, few larvae consumed test strips. However, larvae readily chewed the test strips treated with a mixture of all compounds, indicating that host recognition by P. xuthus larvae is mediated by a specific combination of both primary and secondary substances. Comparison of 11 stimulant components with 10 compounds from C. unshiu leaves previously reported as stimulant components for oviposition by P. xuthus adult females revealed only one compound, stachydrine, as an ingredient in common. While the larval feeding-stimulant mixture is dominated by nutrients and other compounds of general significance for primary metabolism, the component oviposition stimulants are mostly secondary substances, including flavonoid glycosides, protoalkaloids, a cyclitol, and a betaine, that have restricted distributions in plants. Reliance by adult females on unique profiles of secondary compounds presumably reflects the need to locate and recognize specific host-plant species within a diverse flora. Since the initial host choice for the larvae is made typically by the ovipositing female, however, unique secondary compounds may be less important for larval feeding than are compounds useful for indicating food and microhabitat quality once on the host plant.

A gustatory receptor involved in host plant recognition for oviposition of a swallowtail butterfly

Swallowtail butterflies belonging to the family of Papilionidae selectively utilize a limited number of plants from a single or a few families. Female butterflies lay eggs on their host only when they detect specific chemicals through their foreleg chemosensilla while drumming on the leaf surface. Here we show that the butterfly, Papilio xuthus, uses a gustatory receptor specific for synephrine to select its host in oviposition behaviour. We identify a gustatory receptor gene involved in the recognition of an oviposition stimulant, synephrine, from the P. xuthus by a combination of in silico, in vitro and in vivo approaches. The receptor, PxutGr1, responds specifically to synephrine in Sf9 cells. The sensitivity of tarsal taste sensilla to synephrine and the oviposition behaviour in response to synephrine are strongly reduced after injecting double-stranded RNA of PxutGr1 into pupae. These observations indicate that the receptor PxutGr1 represents a key factor in host specialization in P. xuthus.

Host suitability of various stored food products for the cigarette beetle, Lasioderma serricorne (Coleoptera: Anobiidae)

We investigated the attraction to, and ovipositional activity and egg-to-adult survival rate on, 11 stored products of Lasioderma serricorne (F.). These products included polished rice, unpolished rice, wheat flour, corn flour, cocoa powder, roasted coffee beans, green tea leaves, black tea leaves, soybean flour, flue-cured tobacco leaves, and dried small sardines. Tobacco, cocoa, soybean flour, black tea, and wheat flour significantly attracted the beetles. Corn flour, green tea, and coffee tended to attract the beetles. Ovipositional activity of beetle was higher on the food materials than on nonfood materials. The highest ovipositional activity was observed on coffee, followed by cocoa. Ovipositional activity on black tea, unpolished rice, and green tea was also relatively high. Methanol extracts of coffee beans showed oviposition-stimulatory activity. Therefore, the high ovipositional activity observed on coffee beans could be attributed to oviposition stimulants contained in the beans. In the egg-to-adult survival test, all eggs laid on polished rice or tobacco leaves developed successfully into adults, whereas none of the eggs laid on black tea, green tea, or coffee beans developed into adults. These findings suggest that suitability as an attractive target, suitability as an oviposition site, and suitability as larval food are not always compatible.

Microorganisms from aphid honeydew attract and enhance the efficacy of natural enemies.

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their dispersal in natural environment. Here we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which acts as a kairomone enhancing the efficiency of aphid natural enemies. Our findings represent the first case of a host-associated bacterium driving prey location and ovipositional preference for the natural enemy. We show that this bacterium has a key role in tritrophic interactions because it is the direct source of volatiles used to locate prey. Some specific semiochemicals produced by S. sciuri were also identified as significant attractants and ovipositional stimulants. The use of this host-associated bacterium could certainly provide a novel approach to control aphids in field and greenhouse systems.

Synergistic or Antagonistic Modulation of Oviposition Response of Two Swallowtail Butterflies, Papilio maackii and P. protenor, to Phellodendron amurense by Its Constitutive Prenylated Flavonoid, Phellamurin

Papilio maackii females prefer a rutaceous plant, Phellodendron amurense, for oviposition, whereas another semi-sympatric Rutaceae feeder, Papilio protenor, never exploits this plant as a host in nature. However, the larvae of both species perform well on this plant in the laboratory. Phellamurin, a flavonoid present in the organic fraction from P. amurense inhibits egg laying by P. protenor. We examined whether phellamurin is involved in the differential acceptance of P. amurense by the two butterflies. The ovipositing females of P. maackii readily accepted P. amurense and a methanolic extract of the foliage, while P. protenor rejected them entirely. However, the aqueous fraction derived from the extract elicited significant oviposition responses of similar levels from the two species. Phellamurin did not induce oviposition behavior in P. protenor females. In contrast, P. maackii was stimulated to oviposit by phellamurin at concentrations exceeding 0.2%. The response was dose-dependent and reached ca. 70% at 2% phellamurin, which is approximately equivalent to its natural abundance in young leaves of P. amurense. Since the aqueous fraction was very stimulatory to both species, the combined effect of phellamurin and the aqueous fraction on oviposition was tested. The addition of phellamurin to the aqueous fraction enhanced the ovipositional activity of P. maackii, but dramatically suppressed the oviposition response of P. protenor even at 0.1% concentration. These results, taken together with those obtained from electrophysiological recordings with foretarsal chemosensilla, indicate that phellamurin acts as an oviposition stimulant for P. maackii, and as a potent deterrent for P. protenor. The results suggest that host range expansion or host shifts may be made by ovipositing females that overcome phytochemical barriers.

Oviposition Response of the Moth Lobesia botrana to Sensory Cues from a Host Plant

The grapevine moth Lobesia botrana is a generalist insect herbivore and grapevine is one of its hosts. Previous studies have shown that insects use their olfactory abilities to locate hosts from a distance; whereas contact chemoreception mediates the stimulation of oviposition after landing. Little is known about the role of olfaction and its interactions with contact chemoreception and vision once the insect lands on the plant. Plant volatile compounds can be sensed by host-searching insects located some distance from the plant and insects sense both volatile and nonvolatile cues after landing on a plant. In the present study, we investigated the effects of these volatile and nonvolatile cues on the oviposition behavior of L. botrana. A behavioral bioassay with choice was developed in which insects were offered each sensory cue either alone or in combination with one or 2 other cues. Females were allowed to choose between a device with the stimulus and a blank device. Results were evaluated in terms of 2 parameters: quantity of eggs laid (egg counts) and preference for the stimulus (ODI: oviposition discrimination index). Our results suggest that olfaction significantly affects egg quantity and that there is significant synergism between olfaction and vision, in terms of their combined effect on egg quantity. In terms of preference (ODI), our results did not show a significant preference for any single cue; the highest ODI was measured for the full-cue stimulus (olfaction, vision, and contact). For ODI, a significant interaction was observed between olfaction and vision and a nearly significant interaction was observed between the olfactory and contact cues. The results are discussed in relation to the effects of plant sensory cues on the oviposition behavior of L. botrana.

Ecotoxicological effects of diuron and chlorotoluron nitrate‐induced photodegradation products: Monospecific and aquatic mesocosm‐integrated studies

The ecotoxicological impact of nitrate-induced photodegradation products of diuron and chlorotoluron was studied through monospecific biotests conducted in conjunction with experiments in outdoor aquatic mesocosms. Organisms representing three trophic levels were used: two heterotrophic microorganisms, the luminescent bacterium Vibrio fischeri and the ciliated protozoa Tetrahymena pyriformis, and one metazoa, the gastropod Lymnaea stagnalis. Among the variety of the phenylurea photoproducts, the N-formylated ones appeared clearly more toxic than the parent compounds towards the microorganisms, whereas the nitroderivatives showed a similar toxicity. Using photodegraded solutions of diuron, toxicity was maintained or even increased during disappearance of the initial herbicide, demonstrating that some of the photoproducts may have an impact additively or in synergy. Enzymatic biomarker assays performed on Lymnaea stagnalis exposed under monospecific conditions showed significant effects, due to the combination of nitrate with the pesticide and its photoproducts. A positive impact on snail fecundity was observed with chlorotoluron both under monospecific laboratory and integrated mesocosm conditions. Oviposition stimulation took place when first- and second-generation photoproducts were predominant.

An introduction device for the aphidophagous hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae)

Augmentative biocontrol constitutes a safe option to reduce pest populations through the enhancement of natural enemies’ activity. In this context, the aphidophagous syrphid Episyrphus baltetaus (De Geer) (Diptera: Syrphidae) is a promising candidate for aphid biological control: larvae of this syrphid attack and consume a wide range of aphid species and are found on many vegetable crops. Because natural populations of beneficial insects are not always sufficient to regulate the pest infestations, this work has focused on the conception of a biological control device containing syrphid eggs which ones can easily be introduced in fields or greenhouses. Using semiochemicals [E-(β)-farnesene, R-(+)-limonene and (Z)-3-hexenol], honeydews and “artificial honeydews” (10% or 30% aqueous solutions of sucrose, fructose and glucose), the syrphid oviposition was artificially induced on an inert surface. Specifically, E-(β)-farnesene and concentrated mono-sugars (30%) were identified as the most efficient ovipositional stimulants. To test and validate the biological control device described above, laboratory and field experiments were performed: a plastic lamella covered with syrphid eggs was suspended on aphid infested plants in order to measure the efficiency of the device. The results obtained were promising since populations of 500 aphids were eliminated in 10 days when 15 syrphid eggs were introduced. The use of such a biological control device could certainly contribute to the biological control to reduce the aphid infestations.

Oviposition activity of Aedes aegypti L. (Diptera: Culicidae) in responseto different organic infusions

The present study investigates new sources of infusion as an oviposition attractant for Aedes aegypti L. Infusions with fetid and non-fetid odors were compared as an oviposition stimulant. Traps baited with infusions of dehydrated cashew leaves (Anacardium occidentale), potato peels (Solanum tuberosum) and graminea (Panicum maximum) were compared as attractants, and the effect of odor (fetid and unfetid) on attractiveness was tested. Oviposition activity changed significantly according to the concentration and type of infusion (F = 4.1279; gl = 2; P = 0.0231). A larger number of eggs were observed in cups containing 50% A. occidentale (non-fetid odor) and 30% P. maximum (fetid odor). When compared in the same cage, comparable oviposition was found between A. occidentale and P. maximum. Moreover, approximately 20% more eggs were recorded in the infusion without odor when compared to the grass infusion and water. These findings suggest A. occidentale as a new stimulant for use in ovitraps for Aedes surveillance and control, with the benefit of having an agreeable odor.

Pre-harvest infestation of beans ( Phaseolus vulgaris L.) by Acanthoscelides obtectus Say (Coleoptera: Bruchidae) in relation to bean pod maturity and pod aperture

Acanthoscelides obtectus is a bruchid beetle that oviposits into ripening bean pods in the field. More precise data are needed for developing management strategies for small-scale farmers in East Africa. In farmers' fields, an infestation rate of 6.9% infested bean seeds was recorded in dry pods, but in wilting yellow pods there was a lower infestation of 2.5%. No wilting green pod had been infested. After releasing 680 bruchids in an open field, the infestation rate in dry pods increased to 39 and 7% in wilting yellow pods, but again no wilting green pod was found to be infested. In no-choice laboratory trials, however, A. obtectus infests wilting pods; and pod aperture did not influence infestation rates. Stimulants for oviposition were evaluated in no-choice trials. Bean pods containing seeds were as attractive as bean seeds alone, and significantly more attractive as empty opened bean pods. Bean pods without seeds were more attractive than the empty control. The natural infestation rate in fields close to homesteads was higher than in fields more than 1 km away from any habitation. Farmers are advised to be aware of the infestation danger in the field, and to consider early harvest if they have infestation-free storage.

An oviposition stimulant binding protein in a butterfly

Oviposition is evoked by plant compounds, which are recognized by chemoreceptive organs of insects. The swallowtail butterfly, Atrophaneura alcinous, oviposits its eggs on the host plant, Aristolochia debilis, in the presence of only two stimulating compounds: an alkaloid, aristolochic acid, and a monosaccharide, sequoyitol. In our previous study, a unique protein of 23 kDa [Oviposition stimulant(s) binding protein (OSBP)] was found in the forelegs of female, but not male, A. alcinous. The electrophysiological response of A. alcinous to an extract of A. debilis was depressed by the presence of OSBP antiserum, suggesting that OSBP presumably binds to oviposition stimulant(s). We show here, using a highly sensitive fluorescence micro-binding assay that native OSBP binds to a main oviposition stimulant, aristolochic acid, from its host plant, A. debilis. Three-dimensional molecular modeling studies also gave a reasonable structure for the OSBP / aristolochic acid complex. This is the first report of a native chemoreceptive protein binding to an oviposition stimulant ligand in insects.

Characterization of chemoreceptive protein binding to an oviposition stimulant using a fluorescent micro-binding assay in a butterfly

A native female-specific chemoreceptive protein of a swallowtail butterfly [oviposition stimulant binding protein (OSBP)] was shown to specifically bind to aristolochic acid, a main stimulant for oviposition from its host plant. Oviposition stimulants are recognized by chemoreceptive organs of insects. OSBP isolated previously from the chemoreceptive organs was assumed to bind to an oviposition stimulant. Using a highly sensitive fluorescent micro-binding assay, we clarified OSBP bound to aristolochic acid. Three-dimensional molecular modeling revealed the structure of the OSBP-aristolochic acid complex. This is the first report of a native chemoreceptive protein binding to an oviposition stimulant as a ligand in insects.

Isolation of Three Diterpenoid Acids from Sunflowers, as Oviposition Stimulants for the Banded Sunflower Moth, Cochylis hospes

The banded sunflower moth (BSFM), Cochylis hospes Walshingham (Lepidoptera: Cochylidae) is a specialist insect, the larvae of which feed on sunflowers, Helianthus spp., and a few other species of Compositae. It is one of the most important pests of sunflower in the USA. Previous work on H. annuus, the cultivated sunflower, revealed two diterpenoids that function as oviposition stimulants for female BSFM, and that other, more polar compounds also stimulated oviposition. Using a bioassay-guided approach, we isolated three additional diterpenoids, grandifloric acid (1), 15beta-hydroxy-ent-trachyloban-19-oic acid (2), and 17-hydroxy-16alpha-ent-kauran-19-oic acid (3), from polar fractions of pre-bloom sunflower head extracts. In laboratory bioassays, purified natural samples of each of these compounds stimulated oviposition by female BSFM. Structure-activity relationships of the five diterpenoids known to stimulate oviposition by female BSFM are discussed.

Glucosinolates on the leaf surface perceived by insect herbivores: review of ambiguous results and new investigations

Herbivorous insects identify their host plants either by structural features, chemical cues, or a combination. Some insects probe the host leaf prior feeding or oviposition, other species use olfactorial cues or compounds somewhere on the surface. Insects attacking Brassicaceae are no exception, some are attracted and stimulated by volatile isothiocyanates (ITC), many others depend fully on the non-volatile glucosinolates (GS) for host-plant recognition and acceptance. Since most insects have no access to the leaf interior investigators concluded that GS must be present on the leaf surface and ITC in the headspace. However, peelings of mechanically removed surface waxes were devoid of measurable amounts of GS, whereas solvent surface extractions revealed a correlation between stomatal conditions and GS concentrations. Both observations lead to the conclusion that the presence of GS on the top leaf surface is rather unlikely. In the experimental part we show that a chloroform/methanol/water (2:1:1 vol/vol/vol) solvent leaf extract contains GS and, in addition, thia-triaza-fluorenes (TTF), other oviposition stimulants of the cabbage root fly, Delia radicum. Electrophysiological investigations showed that both, GS and TTF stimulated specific receptor neurones of the fly. We suggest that these compounds probably originated from deeper leaf layers and that herbivorous insects may penetrate the wax layer and perceive the stimulating compounds in deeper layers or through the stomata.

Identification of bacteria and bacteria-associated chemical cues that mediate oviposition site preferences byAedes aegypti

The yellow fever mosquito, Aedes aegypti, the global vector of dengue and yellow fever, is inexorably linked to water-filled human-made containers for egg laying and production of progeny. Oviposition is stimulated by cues from water containers, but the nature and origin of these cues have not been elucidated. We showed that mosquito females directed most of their eggs to bamboo and white-oak leaf infusions, and only a small fraction of the eggs were laid in plain water containers. In binary choice assays, we demonstrated that microorganisms in leaf infusions produced oviposition-stimulating kairomones, and using a combination of bacterial culturing approaches, bioassay-guided fractionation of bacterial extracts, and chemical analyses, we now demonstrate that specific bacteria-associated carboxylic acids and methyl esters serve as potent oviposition stimulants for gravid Ae. aegypti. Elucidation of these compounds will improve understanding of the chemical basis of egg laying behavior of Ae. aegypti, and the kairomones will likely enhance the efficacy of surveillance and control programs for this disease vector of substantial global public health importance.

Evaluation of sticky ovitraps for the surveillance ofAedes(Stegomyia)albopictus(Skuse) and the screening of oviposition attractants from organic infusions

The performance of sticky ovitraps for investigation of a container-breeding mosquito, Aedes albopictus, has been assessed for the first time, in the field, in Wuhan, China. Almost all (90.0%) of the mosquitoes collected in the ovitraps were Ae. albopictus and, in 2006, the seasonal abundance of this species as measured using the sticky ovitraps was significantly correlated with that measured using standard red ovitraps. The baiting with a Bermuda-grass (Cynodon dactylon) infusion of oviposition cups in the laboratory or standard red ovitraps in the field increased the numbers of Ae. albopictus eggs collected (compared with the numbers seen with a tap-water control). In an adult-counting assay, however, the use of such an infusion significantly increased the numbers of female Ae. albopictus coming to sticky oviposition cups only in the laboratory, not in the field. Under field conditions, when the sticky ovitraps were used, female Ae. albopictus showed no oviposition 'preference' for infusions made from the leaves of the camphorwood tree, box, green bristle grass, Bermuda grass, lotus magnolia or bamboo. In terms of the attractancy of the sticky ovitraps to female Ae. albopictus in the field, the red colour of the ovitraps appeared to contribute more than a Bermuda-grass infusion. It appears that sticky ovitraps could be used to monitor Ae. albopictus in the field effectively. Since mosquitoes that are attracted to organic infusions but lay no eggs cannot be detected using a standard ovitrap but can be collected and counted in sticky ovitraps, the latter may be a better choice when screening for mosquito attractants (rather than oviposition stimulants) in such infusions.

Indole glucosinolate breakdown and its biological effects

Most species in the Brassicaceae produce one or more indole glucosinolates. In addition to the parent indol-3-ylmethylglucosinolate (IMG), other commonly encountered indole glucosinolates are 1-methoxyIMG, 4-hydroxyIMG, and 4-methoxyIMG. Upon tissue disruption, enzymatic hydrolysis of IMG produces an unstable aglucone, which reacts rapidly to form indole-3-acetonitrile and indol-3-ylmethyl isothiocyanate. The isothiocyanate, in turn, can react with water, ascorbate, glutathione, amino acids, and other plant metabolites to produce a variety of physiologically active indole compounds. Myrosinase-initiated breakdown of the substituted indole glucosinolates proceeds in a similar manner to that of IMG. Induction of indole glucosinolate production in response to biotic stress, experiments with mutant plants, and artificial diet assays suggest a significant role for indole glucosinolates in plant defense. However, some crucifer-feeding specialist herbivores recognize indole glucosinolates and their breakdown products as oviposition and/or feeding stimulants. In mammalian diets, IMG can have both beneficial and deleterious effects. Most IMG breakdown products induce the synthesis of phase 1 detoxifying enzymes, which may in some cases prevent carcinogenesis, but in other cases promote carcinogenesis. Recent advances in indole glucosinolate research have been fueled by their occurrence in the well-studied model plant Arabidopsis thaliana. Knowledge gained from genetic and biochemical experiments with A. thaliana can be applied to gain new insight into the ecological and nutritional properties of indole glucosinolates in other plant species.