salicylates and 3-hexen-1-ol

Vegetation emits a class of oxygenated hydrocarbons--the green leaf volatiles (GLVs)--under stress or damage. Under foggy conditions GLVs might be a source of secondary organic aerosol (SOA) via aqueous reactions with hydroxyl radical (OH), singlet oxygen ((1)O2*), and excited triplet states ((3)C*). To examine this, we determined the aqueous kinetics and SOA mass yields for reactions of (3)C* and (1)O2* with five GLVs: methyl jasmonate (MeJa), methyl salicylate (MeSa), cis-3-hexenyl acetate (HxAc), cis-3-hexen-1-ol (HxO), and 2-methyl-3-butene-2-ol (MBO). Second-order rate constants with (3)C* and (1)O2* range from (0.13-22) × 10(8) M(-1) s(-1) and (8.2-60) × 10(5) M(-1) s(-1) at 298 K, respectively. Rate constants with (3)C* are independent of temperature, while values with (1)O2* show significant temperature dependence (Ea = 20-96 kJ mol(-1)). Aqueous SOA mass yields for oxidation by (3)C* are (84 ± 7)%, (80 ± 9)%, and (38 ± 18)%, for MeJa, MeSa, and HxAc, respectively; we did not measure yields for other conditions because of slow kinetics. The aqueous production of SOA from GLVs is dominated by (3)C* and OH reactions, which form low volatility products at a rate that is approximately half that from the parallel gas-phase reactions of GLVs.

Topics: Acetates; Aerosols; Cyclopentanes; Hexanols; Hydroxyl Radical; Kinetics; Oxygen; Oxylipins; Pentanols; Plant Leaves; Salicylates; Singlet Oxygen; Temperature; Volatile Organic Compounds; Volatilization; Water

In the last decade plant-to-plant communication has received an increasing attention, particularly for the role of Volatile Organic Compounds as possible elicitors of plant defense. The role of β-ocimene as an interspecific elicitor of plant defense has been recently assessed in multitrophic systems including different plant species (Solanaceae, Poaceae, legumes) and different pest species including chewer insects and phytophagous mites. Both chewer insects and phytophagous mites are known to elicit specific plant defensive pathways which are different (at least in part) from those elicited by sap feeders. The aim of this research was to fill this gap of knowledge and to assess the role of β-ocimene as an elicitor of plant defense against aphid pests, which are sap feeders. For this purpose we used as transgenic tobacco plant releasing an odour plume enriched in this compound as emitter and a tomato plant as receiver. We selected the aphid Macrosiphum euphorbiae and its natural enemy, the parasitoid Aphidius ervi, as the targets of plant induced defense. Tomato plant defense induced by β-ocimene was assessed by characterizing the aphid performance in terms of fixing behaviour, development and reproduction (direct plant defense) and the parasitoid performance in terms of attraction towards tomato plants (indirect plant defense). The characterization of tomato response to β-ocimene was completed by the identification of Volatile Organic Compounds as released by conditioned tomato plants. Tomato plants that were exposed to the volatiles of transgenic tobacco enriched in β-ocimene resulted in less suitable for the aphids in respect to control ones (direct defense). On tomato plants "elicited" by β-ocimene we recorded: a significant lower number of aphids settled; a significant lower number newborn nymphs; a significant lower weight of aphids feeding. In addition, tomato plants "elicited" by β-ocimene resulted became more attractive towards the parasitoid A. ervi than control ones. These results could be explained at least in part by examining the composition of the Volatile Organic Compounds released by tomato plants "elicited" by β-ocimene. Indeed, we found a significantly higher release of several compounds including methyl salicylate and cis-3-hexen-1-ol. These two compounds have been demonstrated to impair aphid development and reproduction and to be involved in the attraction of the aphid parasitoid A. ervi. By considering the ubiquity of β-ocimene and i

Topics: Acyclic Monoterpenes; Alkenes; Animals; Aphids; Gene Expression; Hexanols; Host-Parasite Interactions; Nicotiana; Plant Immunity; Plants, Genetically Modified; Salicylates; Solanum lycopersicum; Volatile Organic Compounds

Olfaction is crucial for short distance host location and pheromone detection by insects. Complexes of olfactory receptors (ORs) are composed of odor-specific ORs and OR co-receptors (Orco). Orcos are widely co-expressed with odor-specific ORs and are conserved across insect taxa. A number of Orco orthologs have been studied to date, although none has been identified in cereal aphids. In this study, an Orco gene ortholog was cloned from the grain aphid, Sitobion avenae, and named "SaveOrco"; RNA interference (RNAi) reduced the expression of SaveOrco to 34.11% in aphids, resulting in weaker EAG (electroantennogram) responses to plant volatiles (Z-3-hexene-1-ol; methyl salicylate, MeSA) and aphid alarm pheromone (E-β-farnesene, EBF). Aphid wing differentiation induced by EBF was investigated in both RNAi treated and untreated aphids. EBF induced production of winged aphids in both pre-natal and post-natal periods in untreated aphids, but no such induction was observed in the RNAi-treated aphids. We conclude that SaveOrco is crucial for the aphid's response to pheromones and other volatiles, and is involved in wing differentiation triggered by EBF.

Topics: Animals; Aphids; Arthropod Antennae; Electrophysiological Phenomena; Hexanols; Pheromones; Receptors, Odorant; RNA Interference; Salicylates; Sesquiterpenes; Wings, Animal

Traps suitable for catching female Agriotes click beetles may provide better reconnaissance than pheromone-baited traps which catch only males, thereby contributing to more efficient crop protection. The basis for this study came from (i) observations of female Agriotes brevis (Candeze) aggregating beneath foliage of Medicago sativa (L.) and Lolium italicum (A. Br.) placed on plastic sheets on bare soil, and (ii) field tests demonstrating attraction of females to traps baited with foliage from these plants. The aim was to identify and field test volatile compounds from M. sativa and L. italicum leaves.. A number of electrophysiologically active chemicals were identified from headspace extracts of M. sativa and L. italicum. Three different synthetic blends of the identified compounds, comprising four, seven and nine components, were field tested. The four- and nine-component blends caught more female A. brevis than unbaited traps, with the proportion of females not differing between blends.. The plant-derived blends were shown to catch female A. brevis under field conditions when applied in traps. Of these, the four-component blend, given its relatively simple composition [(Z)-3-hexenyl acetate:methyl benzoate:(Z)-3-hexen-1-ol:methyl salicylate 300:5:30:30 mg bait(-1)], may be a suitable 'standard' blend for bait optimisation.

Topics: Acetates; Animals; Arthropod Antennae; Behavior, Animal; Coleoptera; Female; Hexanols; Italy; Lolium; Medicago sativa; Pheromones; Plant Leaves; Salicylates; Volatile Organic Compounds

Green leaf volatiles (GLV), which are rapidly emitted by plants in response to insect herbivore damage, are now established as volatile defense signals. Receiving plants utilize these molecules to prime their defenses and respond faster and stronger when actually attacked. To further characterize the biological activity of these compounds we performed a microarray analysis of global gene expression. The focus of this project was to identify early transcriptional events elicited by Z-3-hexenol (Z-3-HOL) as our model GLV in maize (Zea mays) seedlings. The microarray results confirmed previous studies on Z-3-HOL -induced gene expression but also provided novel information about the complexity of Z-3-HOL -induced transcriptional networks. Besides identifying a distinct set of genes involved in direct and indirect defenses we also found significant expression of genes involved in transcriptional regulation, Ca(2+)-and lipid-related signaling, and cell wall reinforcement. By comparing these results with those obtained by treatment of maize seedlings with insect elicitors we found a high degree of correlation between the two expression profiles at this early time point, in particular for those genes related to defense. We further analyzed defense gene expression induced by other volatile defense signals and found Z-3-HOL to be significantly more active than methyl jasmonate, methyl salicylate, and ethylene. The data presented herein provides important information on early genetic networks that are activated by Z-3-HOL and demonstrates the effectiveness of this compound in the regulation of typical plant defenses against insect herbivores in maize.

Topics: Acetates; Animals; Cyclopentanes; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Regulatory Networks; Genes, Plant; Herbivory; Hexanols; Oligonucleotide Array Sequence Analysis; Oxylipins; Plant Leaves; Reproducibility of Results; RNA, Messenger; Salicylates; Time Factors; Volatile Organic Compounds; Zea mays

Using herbivore-induced plant volatiles (HIPVs) to attract specific natural enemies in the field has proven challenging, partly because of a poor understanding of: (i) which compound(s) to manipulate to attract specific taxa, and (ii) the ecological conditions over which HIPVs are effective. To address these issues, we quantified the response of a complex arthropod community to three common HIPVs (methyl salicylate, cis-3-hexen-1-ol, and phenylethyl alcohol) as individual compounds and equal part blends in corn and soybean fields. Of 119 arthropod taxa surveyed, we found significant responses by four species in corn fields (2 parasitoids, 1 herbivore, and 1 detritivore) and 16 in soybean fields (8 parasitoids, 3 predators, 4 herbivores, and 1 detritivore), with both attractive and repellent effects of the HIPVs observed. For example, tachinid flies were highly attracted to cis-3-hexen-1-ol (ca. 3-fold increase), but repelled by methyl salicylate (ca. 60 % decrease). Surprisingly, we found very few cases in which HIPVs acted synergistically; only two arthropod groups (ichneumonid wasps and phorid flies) were more attracted by a blend of the HIPVs than by the individual compounds composing the blend. Crop type, however, had a strong impact on the strength of arthropod responses to HIPVs. A few arthropod species were broadly affected across both crops (i.e., the herbivore Halticus bractatus was repelled by most of our treatments, regardless of crop background), but overall more arthropod groups responded to HIPVs released in soybean fields compared with corn. This was true despite the fact that taxa responding to HIPVs were present and abundant in both systems, suggesting that crop-based outcomes were likely driven by the plant matrix rather than mere differences in taxonomic composition of the arthropod community in corn vs. soybean fields. As a whole, these results suggest that: (i) repellent effects of HIPVs on natural enemies of herbivorous insects can be observed as frequently as attractive effects; (ii) odor blends may be no more effective than single-compound lures for some taxa; and (iii) crop background alters the magnitude of attraction to HIPVs, depending on the species being targeted.

Topics: Animals; Arthropods; Glycine max; Hexanols; Indiana; Phenylethyl Alcohol; Salicylates; Volatile Organic Compounds; Zea mays

The European grape berry moth is an important pest in vineyards. Males respond to the female-produced sex pheromone released from a piezo nebulizer in a dose-dependent manner in a wind tunnel: <50% arrive at the source at 5-50 pg/min (underdosed), 80% arrive at 100 pg/min to 10 ng/min (optimal) and <20% arrive at 100 ng/min (overdosed). Males responding to overdosed pheromone show in flight arrestment at 80 cm from the source. Host plant chemostimuli for Eupoecilia ambiguella increase the responses of males to underdosed and overdosed pheromone. (Z)-3-hexen-1-ol, (+)-terpinen-4-ol, (E)-beta-caryophyllene and methyl salicylate released with the underdosed pheromone cause a significant increase in male E. ambiguella flying to the source. Time-event analysis indicates a positive correlation between faster activation and probability of source contact by the responding males. The four host plant compounds added to the overdosed pheromone permitted males to take off faster and with a higher probability of flying to the source. This suggests that perception of host plant products with the sex pheromone facilitates male E. ambiguella to locate females on host plants, lending credence to the hypothesis that plant products can signal rendezvous sites suitable for mating.

Topics: Animals; Female; Flight, Animal; Hexanols; Host-Parasite Interactions; Male; Moths; Odorants; Organic Chemicals; Polycyclic Sesquiterpenes; Salicylates; Sesquiterpenes; Sex Attractants; Sexual Behavior, Animal; Smell; Terpenes; Time Factors; Vitis; Volatilization

The cabbage moth, Mamestra brassicae L. (Lepidoptera, Noctuidae), is a polyphagous species that is often choosing plants of Brassica as hosts for oviposition. In the search for biologically relevant odorants used by these moths, gas chromatography linked to electrophysiological recordings from single receptor neurons (RNs) has been employed, resulting in classification of distinct types of neurons. This study presents specific olfactory RNs responding to methyl salicylate (MeS) as primary odorant and showing a weak response to methyl benzoate, the 2 aromatic compounds occurring together in several plant species. In 2 cases, the neuron was colocated with another RN type responding to 6 green leaf volatiles: 1-hexanol, (3Z)-hexen-1-ol, (2E)-hexen-1-ol, (3Z)-hexenyl acetate, (2Z)-hexen-1-ol, and an unidentified compound. Whereas the specific RNs detected the minor amounts of MeS in some plants, the compound was not found by gas chromatography linked to mass spectrometry in intact plants, but it was found after herbivore attack. The behavioral effect of MeS was studied in outdoor test arenas with Brassica napus and artificial plants. These experiments indicated that mated M. brassicae females avoid plants with dispensers emitting MeS. As it is induced by caterpillar feeding, this compound may mediate a message to mated M. brassicae females that the plant is already occupied.

Topics: Acetates; Action Potentials; Animals; Arabidopsis; Benzoates; Brassica; Brassica napus; Chromatography, Gas; Electrophysiology; Female; Hexanols; Male; Moths; Odorants; Olfactory Receptor Neurons; Oviposition; Salicylates; Sexual Behavior, Animal

We investigated volatile infochemicals possibly involved in location of the generalist predatory mite Neoseiulus californicus to plants infested with spider mites in a Y-tube olfactometer. The predators significantly preferred volatiles from lima bean leaves infested with Tetranychus urticae to uninfested lima bean leaves. Likewise, they were attracted to volatiles from artificially damaged lima bean leaves and those from T. urticae plus their visible products. Significantly more predators chose infested lima bean leaves from which T. urticae plus their visible products had been removed than artificially damaged leaves, T. urticae, and their visible products. These results suggest that N. californicus is capable of exploiting a variety of volatile infochemicals originating from their prey, from the prey-foodplants themselves, and from the complex of the prey and the host plants (e.g., herbivore-induced volatiles). We also investigated predator response to some of the synthetic samples identified as volatile components emitted from T. urticae-infested lima bean leaves and/or artificially damaged lima bean leaves. The predators were attracted to each of the five synthetic volatile components: linalool, methyl salicylate, (Z)-3-hexen-1-ol, (E)-2-hexenal, and (Z)-3-hexenyl acetate. The role of each volatile compound in prey-searching behavior is discussed.

Topics: Acetates; Acyclic Monoterpenes; Aldehydes; Animals; Chemotactic Factors; Female; Hexanols; Mites; Monoterpenes; Odorants; Phaseolus; Plant Leaves; Predatory Behavior; Salicylates; Smell; Tetranychidae; Volatilization