Martine Lettere

Pheromone binding proteins of the moth Mamestra brassicae: Specificity of ligand binding

Several isoforms of pheromone-binding proteins (PBP) and general odorant-binding proteins (GOBP) were previously characterized in the antennae of the cabbage armyworm Mamestra brassicae L. (Lepidoptera: Noctuidae). In further investigations, we used two-dimensional electrophoresis and Western-blotting with antibodies raised against the PBPs of the male: this method revealed more proteins with molecular weight and isoelectric points similar to those of OBPs and confirmed the high level of microdiversity suspected for this family of proteins. The binding of the tritiated major pheromone compound, Z11-16:Ac, with male and female antennal extracts and purified PBPs from male antennae was studied. Only the two isoforms Mbra-1 and Mbra-1′ (N-terminus: SKELI) bound the labelled pheromone, whereas no binding was observed with the Mbra-2 (N-terminus: SQEIM). In female antennal extracts, binding was shown between Z11-16:Ac and the proteins Mbra-1 and GOBP2. These results constitute an unambiguous demonstration of the binding specificity of a PBP to a pheromonal ligand, supporting the hypothesis of active participation of PBPs in odor discrimination, as a filter for odorants, prior to the receptor activation.

Male-produced aggregation pheromone of the american palm weevil,Rhynchophorus palmarum (L.) (Coleoptera, Curculionidae): Collection, identification, electrophysiogical activity, and laboratory bioassay

Male American palm weevils (APWs),Rhynchophorus palmarum (L.) produced two sex-specific compounds, which were disclosed by volatile collections on Supelpak-2 and gas chromatography. One was a minor compound, not always detected. The major male-produced volatile was identified as (2E)-6-methyl-2-hepten-4-ol through coupled gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared spectrometry, proton nuclear magnetic resonance spectrometry, and rational synthesis. We propose the trivial name rhynchophorol for this new molecule, which proved to be the essential component of the APW aggregation pheromone by electroantennography, coupled gas chromatography-electroantennography and behavioral bioassays.

Male aggregation pheromone of date palm fruit stalk borer Oryctes elegans

Laboratory and field investigations were carried out to characterize the chemical communication system of the date palm fruit stalk borer, Oryctes elegans, and to develop pheromone-based trapping in Eastern Iran. Adults of both sexes feeding on date palm pieces attracted conspecifics, whereas date palm alone was minimally attractive. Males were twice as attractive as females. More beetles were captured at the palm crown than at ground level. Odors from adults feeding on sugarcane were sampled and analyzed by gas chromatography and mass spectrometry. Whereas females did not emit sex specific volatiles, males emitted a blend of 4-methyloctanoic acid (1: major component) and ethyl 4−methyloctanoate (2), occasionally mixed with minor components: 4-methyloctanyl acetate (3), methyl 4-methyloctanoate (4), 4-methyloctanol (5), and nonanyl acetate (6). Electroantennography and field trapping experiments demonstrated that compound 1 is an essential component of the male aggregation pheromone of O. elegans. It was barely attractive by itself but synergistic with fresh date palm odor. It attracted many more beetles than any of compounds 2–6. The addition of one or several of compounds 2–6 to 1 did not improve trap captures. During the course of 2 years, we captured 4000 beetles, with a weekly average of 6.3 beetles/trap, and were able to monitor the seasonal flight of O. elegans. Our results provide the basis for developing mass trapping for control of this pest.

(Z)-dodec-3-en-1-ol, a novel termite trail pheromone identified after solid phase microextraction from Macrotermes annandalei.

(Z)-dodec-3-en-1-ol was isolated and identified by GC-MS as the major component of the trail-following pheromone from whole body and sternal gland extracts of workers of the fungus-growing termite, Macrotermes annandalei (Silvestri) (Termitidae, Macrotermitinae). For the first time, this trail pheromone was also identified by using solid phase microextraction from the surface of the secretory sternal gland of workers. Bioassays showed that synthetic dodecenol induced both orientation and recruitment behavioral effects. The activity threshold of (Z)-dodec-3-en-1-ol in eliciting trail-following is similar to that of (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol in the Rhinotermitidae, but amounts of dodecenol secreted are 100 times higher than those of dodecatrienol. There is about 1 ng of (Z)-dodec-3-en-1-ol per worker. Artificial trails made of synthetic dodecenol are able to compete with natural trails in the field. The activity duration of synthetic (Z)-dodec-3-en-1-ol trails is shorter than that of trails made from whole sternal secretion of workers. Observations showed that (Z)-dodec-3-en-1-ol is probably the only major component of the trail-following pheromone of M. annandalei and that it could be associated with other compounds in a pheromonal blend providing specificity and/or stability to trails.

Chemical identification, electrophysiological and behavioral activities of the pheromone of Metamasius hemipterus (Coleoptera: Curculionidae).

Five hydroxylated aliphatic molecules were identified as the pheromone produced by male West Indian Sugarcane Borer (WISB): 4-methyl-5-nonanol (1), 2-methyl-4-heptanol (2), 2-methyl-4-octanol (3), 5-nonanol (4) and 3-hydroxy-4-methyl-5-nonanone (5). Electroantennographic recordings revealed antennal responses to compounds 1, 2, 3 and 4. Significant EAGs were also recorded in response to pheromone compounds of weevils belonging to the same subfamily and structurally related to the WISB pheromone. The natural pheromone elicited aggregation behavior on WISB adults in laboratory bioassays.

FIELD RESPONSE OF MARITIME PINE SCALE, MATSUCOCCUS FEYTAUDI DUC. (HOMOPTERA:MARGARODIDAE), TO SYNTHETIC SEX PHEROMONE STEREOISOMERS

The absolute configuration of the primary component of the maritime pine scale (Matsucoccus feytaudi) pheromone (i.e., (8E, 10E)-3,7,9-trimethyl-8,10-dodecadien-6-one) was determined as 3S,7R by field-trapping experiments using synthetic stereoisomers and according to previous NMR considerations. The 3R,7R isomer showed similar activity to 3S,7R, whereasM. feytaudi males responded very weakly to the two other candidates (3R,7S and 3S,7S). Further studies were conducted to optimize scale trapping for monitoring scale populations. Results of these studies showed that the trapping efficiency was related to pheromone dose, trap area, and wind speed but not to trap height.

Biodegradation of 2-Ethylhexyl Nitrate by Mycobacterium austroafricanum IFP 2173

ABSTRACT 2-Ethyhexyl nitrate (2-EHN) is a major additive of fuel that is used to increase the cetane number of diesel. Because of its wide use and possible accidental release, 2-EHN is a potential pollutant of the environment. In this study, Mycobacterium austroafricanum IFP 2173 was selected from among several strains as the best 2-EHN degrader. The 2-EHN biodegradation rate was increased in biphasic cultures where the hydrocarbon was dissolved in an inert non-aqueous-phase liquid, suggesting that the transfer of the hydrophobic substrate to the cells was a growth-limiting factor. Carbon balance calculation, as well as organic-carbon measurement, indicated a release of metabolites in the culture medium. Further analysis by gas chromatography revealed that a single metabolite accumulated during growth. This metabolite had a molecular mass of 114 Da as determined by gas chromatography/mass spectrometry and was provisionally identified as 4-ethyldihydrofuran-2(3H)-one by liquid chromatography-tandem mass spectrometry analysis. Identification was confirmed by analysis of the chemically synthesized lactone. Based on these results, a plausible catabolic pathway is proposed whereby 2-EHN is converted to 4-ethyldihydrofuran-2(3H)-one, which cannot be metabolized further by strain IFP 2173. This putative pathway provides an explanation for the low energetic efficiency of 2-EHN degradation and its poor biodegradability.

Sex pheromone of the European sunflower moth, Homoeosoma nebulellum (DEN. & SCHIFF.) (Lepidoptera : pyralidae)

Four components, (Z)-9-tetradecenal (8.6%), (Z,E)-9,12-tetradecadienal (4.8%), (Z)-11-hexadecenal (49.5%), and (Z)-13-octadecenal (37.1%), were identified in extracts of female pheromone glands of the European sunflower moth,Homoeosoma nebulellum (Lepidoptera: Pyralidae) using GC and GC-MS analyses. EAG and single-cell recordings of male antennal receptors gave strong evidence for (Z,E)-9,12-tetradecadienal as the antennal key compound of sex pheromone detection in this species. This result was confirmed by field trapping; removal of (Z,E)-9,12-tetradecadienal from quaternary blends completely suppressed the male catches. The synthetic blends with this compound as a major component caught five times less males than the blends reproducing the ratio found in the female extracts [5% of (Z,E)-9,12-tetradecadienal only]. The occurrence of a minor component perceived as the most biologically relevant compound is discussed.