Natural Pheromone Research Articles

Ascaroside activity in Caenorhabditis elegans is highly dependent on chemical structure

The nematode Caenorhabditis elegans secretes ascarosides, structurally diverse derivatives of the 3,6-dideoxysugar ascarylose, and uses them in chemical communication. At high population densities, specific ascarosides, which are together known as the dauer pheromone, trigger entry into the stress-resistant dauer larval stage. In order to study the structure–activity relationships for the ascarosides, we synthesized a panel of ascarosides and tested them for dauer-inducing activity. This panel includes a number of natural ascarosides that were detected in crude pheromone extract, but as yet have no assigned function, as well as many unnatural ascaroside derivatives. Most of these ascarosides, some of which have significant structural similarity to the natural dauer pheromone components, have very little dauer-inducing activity. Our results provide a primer to ascaroside structure–activity relationships and suggest that slight modifications to ascaroside structure dramatically influence binding to the relevant G protein-coupled receptors that control dauer formation.

Detection of ligand–receptor binding using microfluidic frontal affinity chromatography on proteoliposomes derived directly from native cell membranes

A method for characterization of ligand binding to membrane receptors in their native cell membrane is presented. The methodology is based on microfluidic frontal affinity chromatography coupled to mass spectrometry (FAC-MS). Proteoliposomes with receptor of interest are prepared directly from cell membranes and serve as a stationary phase in a microfluidic flow cell for frontal analysis. The G-Protein-Coupled Receptor (GPCR) Ste2 involved in the pheromone-induced yeast mating pathway is used as a model receptor for proof of principle characterization. The ligand affinity of the natural pheromone peptide, the α-factor, is compared to a set of pheromone analogs having different receptor affinities. With short preparation time, preserved lipid composition and the ability to immobilize proteoliposomes from any cell membrane, we propose that our methodology with immobilized proteoliposomes together with microfluidics FAC-MS can be an important improvement for ligand-receptor studies in native membranes.

Sex Pheromones of Three Citrus Leafrollers, Archips atrolucens, Adoxophyes privatana, and Homona sp., Inhabiting the Mekong Delta of Vietnam

Archips atrolucens, Adoxophyes privatana, and Homona sp. are serious defoliators of citrus trees in the Mekong Delta of Vietnam. In order to establish a sustainable pest-management program for the three species, their female-produced sex pheromones were investigated by GC-EAD and GC-MS analyses, and the following multi-component pheromones were identified: (Z)-11-tetradecenyl acetate (Z11-14:OAc), (E)-11-tetradecenyl acetate (E11-14:OAc), and tetradecyl acetate (14:OAc) in a ratio of 64:32:4 for A. atrolucens; Z11-14:OAc and (Z)-9-tetradecenyl acetate (Z9-14:OAc) in a ratio of 92:8 for A. privatana; and Z11-14:OAc and (Z)-9-dodecenyl acetate (Z9-12:OAc) in a ratio of 96:4 for Homona sp. Each lure baited with synthetic components as a mimic of the natural pheromone attracted males of the target species specifically, indicating that each monounsaturated minor component plays a significant role for mating communication and reproductive isolation of the three species inhabiting the same citrus orchards. In an extract of the pheromone glands of A. atrolucens females, the content of 14:OAc was very low, but a synergistic effect was observed clearly when the saturated compound was mixed at the same level as the E11-14:OAc. The synthetic lures will provide useful tools for monitoring flights of adults of the three species.

An approach to sense pheromone concentration by pre‐concentration and gas sensors

AbstractIn this investigation we combined enrichment with different analysis techniques for in situ sensing of the pheromone main component of the European Grapevine Moth (Lobesia botrana). The electroantennographic detection (EAD) offers the lowest in situ detection limit, but has a limited lifetime of only few hours. Based on the enrichment it is possible to pre‐concentrate the natural pheromone level up to a threshold for biomimetic analytic systems. By metal‐oxide semiconductor gas sensors in a ‘selective odorant measurement of a multi‐sensor array’ (SOMMSA) setup it is possible to achieve a system with a suitable lifetime for monitoring applications. Due to the sequential desorption from the enrichment material with increasing temperature steps it is possible to eliminate interfering gas components and therefore increase the selectivity of the complete system and to achieve a tool for monitoring applications, e.g. in a vineyard.

(6R,10S)-Pallantione: The First Ketone Identified as Sex Pheromone in Stink Bugs

This work describes the structural elucidation of the sex pheromone of the soybean stink bug, Pallantia macunaima. The biological activity of the synthetic pheromone was demonstrated by behavioral and EAD experiments. Furthermore, the absolute configuration of the natural pheromone was determined as (6R,10S)-6,10,13-trimethyltetradecan-2-one. This is the first ketone identified as a male-produced sex pheromone in Pentatomidae, and the trivial name, pallantione, was assigned to this novel pheromone molecule.

(E)-5-Hexadecenyl Acetate: A Novel Moth Sex Pheromone Component From Stathmopoda auriferella

The sex pheromone of Stathmopoda auriferella (Walker), an important pest of kiwifruit in Korea, was studied. Two candidate pheromone components detected in the gland extracts of females were identified as (E)-5-hexadecenyl acetate (E5-16:OAc) and (E)-5-hexadecenol (E5-16:OH) in a ratio of 75:25 by mass spectral analysis of natural pheromone components and dimethyldisulfide adducts, and retention index comparisons with synthetic standards. In the kiwifruit orchards, E5-16:OAc alone was attractive to S. auriferella males and caught significantly more males than live virgin females. However, addition of E5-16:OH strongly inhibited attraction to E5-16:OAc. These results suggest that the major component of the female-produced sex pheromone of S. auriferella is E5-16:OAc. This hexadecenyl acetate is a novel moth sex pheromone component.

Pheromonal bile acid 3-ketopetromyzonol sulfate primes the neuroendocrine system in sea lamprey.

BackgroundVertebrate pheromones are known to prime the endocrine system, especially the hypothalamic-pituitary-gonadal (HPG) axis. However, no known pheromone molecule has been shown to modulate directly the synthesis or release of gonadotropin releasing hormone (GnRH), the main regulator of the HPG axis. We selected sea lamprey (Petromyzon marinus) as a model system to determine whether a single pheromone component alters the output of GnRH.Sea lamprey male sex pheromones contain a main component, 7α, 12α, 24-trihydroxy-5α-cholan-3-one 24-sulfate (3 keto-petromyzonol sulfate or 3kPZS), which has been shown to modulate behaviors of mature females. Through a series of experiments, we tested the hypothesis that 3kPZS modulates both synthesis and release of GnRH, and subsequently, HPG output in immature sea lamprey.ResultsThe results showed that natural male pheromone mixtures induced differential steroid responses but facilitated sexual maturation in both sexes of immature animals (χ2 = 5.042, dF = 1, p < 0.05). Exposure to 3kPZS increased plasma 15α-hydroxyprogesterone (15α-P) concentrations (one-way ANOVA, p < 0.05) and brain gene expressions (genes examined: three lamprey (l) GnRH-I transcripts, lGnRH-III, Jun and Jun N-terminal kinase (JNK); one-way ANOVA, p < 0.05), but did not alter the number of GnRH neurons in the hypothalamus in immature animals. In addition, 3kPZS treatments increased lGnRH peptide concentrations in the forebrain and modulated their levels in plasma. Overall, 3kPZS modulation of HPG axis is more pronounced in immature males than in females.ConclusionsWe conclude that a single male pheromone component primes the HPG axis in immature sea lamprey in a sexually dimorphic manner.

Engineered Quorum Sensing Using Pheromone-Mediated Cell-to-Cell Communication in Saccharomyces cerevisiae

Population-density-dependent control of gene expression, or quorum sensing, is widespread in nature and is used to coordinate complex population-wide phenotypes through space and time. We have engineered quorum sensing in S. cerevisiae by rewiring the native pheromone communication system that is normally used by haploid cells to detect potential mating partners. In our system, populations consisting of only mating type "a" cells produce and respond to extracellular α-type pheromone by arresting growth and expressing GFP in a population-density-dependent manner. Positive feedback quorum sensing dynamics were tuned by varying α-pheromone production levels using different versions of the pheromone-responsive FUS1 promoter as well as different versions of pheromone genes (mfα1 or mfα2). In a second system, pheromone communication was rendered conditional upon the presence of aromatic amino acids in the growth medium by controlling α-pheromone expression with the aromatic amino acid responsive ARO9 promoter. In these circuits, pheromone communication and response could be fine-tuned according to aromatic amino acid type and concentration. The genetic control programs developed here are responsive to dynamic spatiotemporal and chemical cellular environments, resulting in up-regulation of gene expression. These programs could be used to control biochemical pathways for the production of fuels and chemicals that are toxic or place a heavy metabolic burden on cell growth.

Stylopsal: The First Identified Female-produced Sex Pheromone of Strepsiptera

A female-produced sex pheromone of Stylops muelleri was identified as an unusually branched saturated aldehyde (9R)-3,5-syn-3,5,9-trimethyldodecanal. We named it stylopsal. Its structure was established by using mass spectrometry, infrared spectroscopy, and organic synthesis of candidate compounds. The synthetic standard of (9R)-3,5-syn-3,5,9-trimethyldodecanal gave identical chromatographic and mass spectrometric data as the natural pheromone and also was active in electroantennographic and behavioral assays. The female fat body lipids contained the corresponding fatty acid, indicating a possible link between lipid metabolism and the pheromone biosynthesis.

Defensive Compounds and Male-Produced Sex Pheromone of the Stink Bug, Agroecus griseus

Agroecus griseus is a serious corn pest in Brazil. Contents of the dorsal abdominal glands (DAGs) in nymphs, and the metathoracic gland (MTG) in adults of this species were characterized and quantified. Compounds found were similar to those of other Pentatomidae species and included aliphatic hydrocarbons, aldehydes, oxo-alkenals, and esters. However, two compounds were found in the MTG that have not been described previously for this family. Mass spectrometry, infrared spectroscopy, and gas chromatographic analysis using coinjection with authentic standards confirmed the identities of the compounds as enantiopure (S)-2-methylbutyl acetate and 3-methyl-2-butenyl acetate. The five nymphal instars showed significantly different ratios of components, mainly between those of the first and later instars. No significant differences were detected in MTG contents between sexes. Gas chromatography (GC) analysis of aeration extracts of males and females showed the presence of a compound released exclusively by males. Gas chromatography - electroantennographic detection (GC-EAD) assays indicated that the male-specific compound is bioactive in females, suggesting the presence of an attractant pheromone. The mass spectrum and infrared data for this compound matched with methyl 2,6,10-trimethyltridecanoate, a sex pheromone component previously detected in the stink bugs, Euschistus heros and E. obscurus. The synthetic standard coeluted with the natural pheromone on two different GC stationary phases, confirming the proposed structure. Y-tube olfactometer assays showed that the synthetic standard was strongly attractive to females, and GC-EAD tests produced responses with antennae from females similar to those of the natural pheromone.

Enantioselective Synthesis of α‐Alkyl‐β‐ketoesters: Asymmetric Roskamp Reaction Catalyzed by an Oxazaborolidinium Ion

Breaking kamp: A catalytic route toward chiral α-alkyl-β-ketoesters using the title reaction of α-alkyl diazoester with aldehydes has been developed (see scheme). The reaction proceeds with high to excellent enantioselectivities and this methodology was applied to a concise two-step synthesis of the natural pheromone sitophilate.

Moth Sex Pheromone Receptors and Deceitful Parapheromones

The insect's olfactory system is so selective that male moths, for example, can discriminate female-produced sex pheromones from compounds with minimal structural modifications. Yet, there is an exception for this “lock-and-key” tight selectivity. Formate analogs can be used as replacement for less chemically stable, long-chain aldehyde pheromones, because male moths respond physiologically and behaviorally to these parapheromones. However, it remained hitherto unknown how formate analogs interact with aldehyde-sensitive odorant receptors (ORs). Neuronal responses to semiochemicals were investigated with single sensillum recordings. Odorant receptors (ORs) were cloned using degenerate primers, and tested with the Xenopus oocyte expression system. Quality, relative quantity, and purity of samples were evaluated by gas chromatography and gas chromatography-mass spectrometry. We identified olfactory receptor neurons (ORNs) housed in trichoid sensilla on the antennae of male navel orangeworm that responded equally to the main constituent of the sex pheromone, (11Z,13Z)-hexadecadienal (Z11Z13-16Ald), and its formate analog, (9Z,11Z)-tetradecen-1-yl formate (Z9Z11-14OFor). We cloned an odorant receptor co-receptor (Orco) and aldehyde-sensitive ORs from the navel orangeworm, one of which (AtraOR1) was expressed specifically in male antennae. AtraOR1•AtraOrco-expressing oocytes responded mainly to Z11Z13-16Ald, with moderate sensitivity to another component of the sex pheromone, (11Z,13Z)-hexadecadien-1-ol. Surprisingly, this receptor was more sensitive to the related formate than to the natural sex pheromone. A pheromone receptor from Heliothis virescens, HR13 ( = HvirOR13) showed a similar profile, with stronger responses elicited by a formate analog than to the natural sex pheromone, (11Z)-hexadecenal thus suggesting this might be a common feature of moth pheromone receptors.

Male-Produced Sex Pheromone of the Stink Bug Edessa meditabunda

Edessa meditabunda is a secondary pest within the piercing-sucking stink bug complex that attacks soybean crops in Brazil. The behavioral responses of males and females to aeration extracts from conspecifics suggested the presence of a male-produced sex pheromone. Gas chromatographic (GC) analysis of male and female aeration extracts revealed the presence of two male-specific compounds in a ratio of 92:8. Gas chromatographic -electroantennographic detection (GC-EAD) assays indicated that the major component is bioactive for females, supporting the behavioral data. Analysis of the mass and infrared spectra of the male-specific compounds suggested that they were both methyl-branched long-chain methyl esters. On the basis of the mass spectra of the respective hydrocarbons obtained by micro derivatizations, the structures of these methyl esters were proposed to be methyl 4,8,12-trimethylpentadecanoate (major) and methyl 4,8,12-trimethyltetradecanoate (minor). An 11 step synthetic route that was based on a sequence of Grignard reactions, starting from cyclopropyl methyl ketone, was developed to obtain synthetic standards with a 7.9 % overall yield for the major compound and a 9.9 % yield for the minor. The synthetic standards co-eluted with the natural pheromones on three different GC stationary phases. Y-tube olfactometer assays showed that the synthetic standards, including the major compound alone and a mixture of the major and minor compounds in the proportion found in natural extracts, were strongly attractive to females.

Extracellular Identification of a Processed Type II ComR/ComS Pheromone of Streptococcus mutans

The competence-stimulating peptide (CSP) and the sigX-inducing peptide (XIP) are known to induce Streptococcus mutans competence for genetic transformation. For both pheromones, direct identification of the native peptides has not been accomplished. The fact that extracellular XIP activity was recently observed in a chemically defined medium devoid of peptides, as mentioned in an accompanying paper (K. Desai, L. Mashburn-Warren, M. J. Federle, and D. A. Morrison, J. Bacteriol. 194:3774-3780, 2012), provided ideal conditions for native XIP identification. To search for the XIP identity, culture supernatants were filtered to select for peptides of less than 3 kDa, followed by C(18) extraction. One peptide, not detected in the supernatant of a comS deletion mutant, was identified by tandem mass spectrometry (MS/MS) fragmentation as identical to the ComS C-terminal sequence GLDWWSL. ComS processing did not require Eep, a peptidase involved in processing or import of bacterial small hydrophobic peptides, since eep deletion had no inhibitory effect on XIP production or on synthetic XIP response. We investigated whether extracellular CSP was also produced. A reporter assay for CSP activity detection, as well as MS analysis of supernatants, revealed that CSP was not present at detectable levels. In addition, a mutant with deletion of the CSP-encoding gene comC produced endogenous XIP levels similar to those of a nondeletion mutant. The results indicate that XIP pheromone production is a natural phenomenon that may occur in the absence of natural CSP pheromone activity and that the heptapeptide GLDWWSL is an extracellular processed form of ComS, possibly the active XIP pheromone. This is the first report of direct identification of a ComR/ComS pheromone.

Effects of Volatile Emissions of Picea abies Fresh Debris on Ips duplicatus Response to Characteristic Synthetic Pheromone

Ips duplicatus is an important pest of Norway spruce (Picea abies) planted outside of its natural range. This species uses olfactory signals to identify the spruce trees favourable for colonisation. The knowledge of the beetles’ response to these stimuli is important for managing this pest. Therefore, the response of Ips duplicatus to a specific synthetic pheromone was investigated under some natural sources of volatile emissions characteristic of Norway spruce. The pheromone traps were installed in two types of forests: one with fresh and large Norway spruce stumps and piles of branches, releasing large amounts of host volatile substances (terpenes and alcohols) and one without such fresh material. The experiment was repeated in three pairs of sites located in plantations out of the natural range of Norway spruce. Finally it was found that Ips duplicatus beetles, regardless of sex, have been concentrated in areas where large amounts of fresh material were available, confirming that Ips duplicatus beetles are using both natural pheromones and specific host volatiles as olfactory stimuli in searching for breeding material.

Male-Produced Pheromone of Spathius agrili, A Parasitoid Introduced For The Biological Control Of The Invasive Emerald Ash Borer, Agrilus planipennis

The braconid wasp, Spathius agrili, has been released in the U.S. as a biocontrol agent for the invasive emerald ash borer (Coleoptera: Buprestidae: Agrilus planipennis), a destructive pest of ash trees (Fraxinus spp.). We identified and synthesized seven male-specific volatile compounds. Three of these, dodecanal, (4R,11E)-tetradecen-4-olide, and (Z)-10-heptadecen-2-one, were the key behaviorally active components in flight tunnel bioassays. Male specificity was demonstrated by gas chromatographic comparison of male and female volatile emissions and whole body extracts. Identifications were aided by coupled gas chromatographic-mass spectrometric (GC-MS) analysis, microchemical reactions, NMR, chiral GC analysis, and GC and MS comparison with authentic standards. Both the racemic and chiral forms of the γ-lactone, as well as both E- and Z-isomers were synthesized. Flight tunnel behavioral tests showed positive male and female S. agrili responses to both natural pheromone and synthetic blends, with upwind flight and landing on the source. Large field-cage tests, using yellow sticky traps baited with pheromone, captured approximately 50% of the released male and female wasps in 24-h periods. The use of pheromone-baited traps in the field could simplify the current detection method for determining parasitoid establishment (i.e., laboriously felling and peeling ash trees for recovery of S. agrili from infested EAB larvae).

Identification and Synthesis of a Male-Produced Pheromone for the Neotropical Root Weevil Diaprepes abbreviatus

An unsaturated hydroxy-ester pheromone was isolated from the headspace and feces of male Diaprepes abbreviatus, identified, and synthesized. The pheromone, methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate, was discovered by gas chromatography-coupled electroantennogram detection (GC-EAD), and identified by gas chromatography–mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The synthesis yielded an 86:14 mixture of methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate (active) and methyl (Z)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate (inactive), along with a lactone breakdown product. The activity of the synthetic E-isomer was confirmed by GC-EAD, GC-MS, NMR, and bioassays. No antennal response was observed to the Z-isomer or the lactone. In a two-choice olfactometer bioassay, female D. abbreviatus moved upwind towards the synthetic pheromone or natural pheromone more often compared with clean air. Males showed no clear preference for the synthetic pheromone. This pheromone, alone or in combination with plant volatiles, may play a role in the location of males by female D. abbreviatus.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-012-0096-8) contains supplementary material, which is available to authorized users.

A Flux Capacitor for Moth Pheromones

In this issue of Chemical Senses, Baker et al. propose a provocative and intriguing explanation for a commonly observed phenomenon in moth chemocommunication. Sex pheromones in moths typically consist of mixtures of long-chain unsaturated compounds in specific ratios. These ratios are correspondingly detected by male moths using separate olfactory sensory neurons for each pheromone component housed singly or multiply in long trichoid sensilla on the antennal surface. These neurons are often present in different proportions, typically with the neuron responding to the highest ratio component present in greatest abundance or with the largest dendritic diameter. In their article, Baker et al. postulate that these physical differences in neuron magnitudes arise to compensate for the higher molecular flux present with the most abundant pheromone components. Such a suggestion raises several questions concerning the physiological and behavioral nature of pheromone communication. Specifically, is the flux in a natural pheromone plume high enough to warrant increased flux detection for the most abundant components? Second, how can changes in neuronal number or size lead to increased flux detection? And finally, how would this increased flux detection be accomplished at molecular, cellular, and ultimately network scales? We address each of these questions and propose future experiments that could offer insight into the stimulating proposition raised by Baker et al.

Parallel Ant Colony Optimization Algorithm Based on Multiplicate Pheromon Declining

To overcome the defect of the classical ant colony algorithm’s slow convergence speed, and its vulnerability to local optimization, the authors propose Parallel Ant Colony Optimization Algorithm Based on Multiplicate Pheromon Declining to solve Traveling Salesman Problem according to the characteristics of natural ant colony multi-group and pheromone updating features of ant colony algorithm, combined with OpenMP parallel programming idea. The new algorithm combines three different pheromone updating methods to make a new declining pheromone updating method. It effectively reduces the impact of pheromone on the non-optimal path in the ants parade loop to subsequent ants and improves the parade quality of subsequent ants. It makes full use of multi-core CPU's computing power and improves the efficiency significantly. The new algorithm is compared with ACO through experiments. The results show that the new algorithm has faster convergence rate and better ability of global optimization than ACO.

Chemoenzymatic Synthesis of Stegobinone and Stegobiol, Components of the Natural Sex Pheromone of the Drugstore Beetle (Stegobium paniceum L.) (Eur. J. Org. Chem. 1/2012)

AbstractThe cover picture shows drugstore beetles (Stegobium paniceum) abandoning their wooden tunnel nests to urgently follow the female‐produced sex pheromone. The chemoenzymatic stereoselective synthesis of the two components of the natural sex pheromone of the drugstore beetle was achieved by using ketoreductases in the key steps. Crystalline stegobinone was obtained free of its 1′‐epimer, which is strongly repellent to Stegobium paniceum. The authors thank the young architect George Orfanopoulos for the graphical design. The photographs of the drugstore beetle were taken from http://en.wikipedia.org/wiki/File:Drugstore_beetle_03.jpg under permission of http://creativecommons.org/licenses/by‐sa/3.0/deed.en. Details of the chemoenzymatic synthesis of the sex pheromone are discussed in the Short Communication by D. Kalaitzakis and I. Smonou on p. 43 ff. magnified image