Spodoptera Littoralis Sex Pheromone Research Articles

Morphological evidence for possible sites of Production of the female sex pheromone of Spodoptera littoralis (Lepidoptera: Noctuidae).

The morphology of the female sex pheromone gland of S. littoralis was studied using scanning electron and light microscopy. This gland is situated ventrally in the intersegmental membrane just in front of the last abdominal segments , the cuticula of the intersegmental membrane between eighth and ninth segments is thickened and slightly raised, bears furrows the rim of which just in front of the ninth is covered with cuticular hairs. The second structure involved in pheromone production is a gland lies in the body cavity situated beneath the eighth and seventh abdominal tergites, as an invagination of the ventral intersegmental membrane between eighth and ninth segments. This gland leads to a duct with an eversible sac. Examination of the tissue with scanning electron microscopy showed the presence of excreted droplets at the tips of cuticular hairs in the glandular area during the period of pheromone production.

Biosynthesis of 10,12-dienoic fatty acids by a bifunctional Δ 11desaturase in Spodoptera littoralis

In the biosynthetic pathway of Spodoptera littoralis sex pheromone, ( E, E)-10,12-tetradecadienoic acid is produced from ( Z)-11-tetradecenoic acid by desaturation and concomitant migration of the precursor double bond. With the aim of identifying the enzyme involved in this biotransformation, yeast Δ elo1/Δ ole mutants, which are both elongase 1 and Δ 9 desaturase-deficient, were transformed with the S. littoralis Δ 11 desaturase gene using a Cu +2 inducible expression vector. The transformants produced a recombinant polyhistidine-tagged Δ 11 desaturase that could be detected by immunoblotting from cell lysates. Lipid analysis revealed that besides producing large quantities of C11-monounsaturated fatty acids, mainly ( Z)-11-hexadecenoic acid, ( E, E)-10,12-tetradecadienoic acid and minor amounts of ( E, Z)-10,12-hexadecadienoic acid were also produced, as well as very low quantities of another tetradecadienoate, which was tentatively identified as the ( E, Z)-10,12-tetradecadienoic isomer. None of these dienes was detected with the Δ 11 desaturase gene of Trichoplusia ni, which does not produce conjugated dienes as pheromone components. We conclude that the Δ 11 desaturase of S. littoralis is a bifunctional enzyme with both Δ 11 and Δ 10,12 desaturation activities. The relationship between the substrate structure and the stereochemical outcome of the reaction is discussed.

Expression and evolution of Δ 9 and Δ 11 desaturase genes in the moth Spodoptera littoralis

Desaturation of fatty acids is a key reaction in the biosynthesis of moth sex pheromones. The main component of Spodoptera littoralis sex pheromone blend is produced by the action of Δ 11 and Δ 9 desaturases. In this article, we report on the cloning of four desaturase-like genes in this species: one from the fat body (Sls-FL1) and three (Sls-FL2, Sls-FL3 and Sls-FL4) from the pheromone gland. By means of a computational/phylogenetic method, as well as functional assays, the desaturase gene products have been characterized. The fat body gene expressed a Δ 9 desaturase that produced ( Z)-9-hexadecenoic and ( Z)-9-octadecenoic acids in a (1:4.5) ratio, whereas the pheromone gland Sls-FL2 expressed a Δ 9 desaturase that produced ( Z)-9-hexadecenoic and ( Z)-9-octadecenoic acids in a (1.5:1) ratio. Although both Δ 9 desaturases produced ( Z)-9-tetradecenoic acid from myristic acid, transformed yeast grown in the presence of a mixture of myristic and ( E)-11-tetradecenoic acids produced ( Z, E)-9,11-tetradecadienoic acid, but not ( Z)-9-tetradecenoic acid. The Sls-FL3 gene expressed a protein that produced a mixture of ( E)-11-tetradecenoic, ( Z)-11-tetradecenoic, ( Z)-11-hexadecenoic and ( Z)-11-octadecenoic acids in a 5:4:60:31 ratio. Despite having all the characteristics of a desaturase gene, no function could be found for Sls-FL4.

Inhibition of the acyl-CoA desaturases involved in the biosynthesis of Spodoptera littoralis sex pheromone by analogs of 10,11-methylene-10-tetradecenoic acid

The desaturase inhibitory activity of the cyclopropenyl alcohols 9,10-methylene-9-tetradecen-1-ol (9-MTOL), 10,11-methylene-10-tetradecen-1-ol (10-MTOL) and 11,12-methylene-11-tetradecen-1-ol (11-MTOL), which are structural analogs of 10,11-methylene-10-tetradecenoic acid (10-MTA), is reported. At equimolar ratios with respect to the different substrates, the three compounds completely inhibited the three desaturation reactions involved in the biosynthesis of Spodoptera littoralis sex pheromone. The dose-dependence of inhibition was determined for 10-MTA and its alcohol derivative. Both compounds inhibited the transformation of perdeuterated palmitic acid into perdeuterated ( Z)-11-hexadecenoic acid and that of ( E)-11-tridecenoic acid into ( Z, E)-9,11-tridecadienoic acid with similar IC 50 values. The overall results presented in this work support scattered data that neither the free carboxyl groups nor their acyl-CoA esters are a requisite for inhibition of desaturases. Since the synthesis of cyclopropenols is much more convenient than that of cyclopropene fatty acids, this finding is of economical relevance regarding the putative use of cyclopropene derivatives in pest control.

Analytical studies of Spodopteralittoralis sex pheromone components by electroantennography and coupled gas chromatography–electroantennographic detection

In this paper we present analytical studies of the sex pheromone components of the Egyptian armyworm Spodoptera littoralis (Lepidoptera, Noctuidae) by electroantennography (EAG) and coupled gas chromatography-electroantennographic detection (GC-EAD). EAG responses in three different preparations, using an insect's head, an excised antenna and a live insect, have been recorded. EAG depolarizations of live insects were significantly higher than those elicited by the insect's head or the excised antenna. The responses were dose-dependent. Live insects also allowed regular pheromone stimulations for 40 min with only 38% decrease of the EAG initial depolarization. The synthetic pheromone blend elicited the highest EAG activity (2.0±0.3 mV), followed by the major compound ( Z, E)-9,11-tetradecadienyl acetate ( I) (1.54±0.1mV), and the minor components ( Z)-9-tetradecenyl acetate ( II), ( E)-11-tetradecenyl acetate ( III), tetradecyl acetate ( IV) and ( Z)-11-tetradecenyl acetate ( V) (1.21-1.32 mV range). ( Z, E)-9,12-tetradecadienyl acetate ( VI), although not present in the pheromone blend of our strain, also showed an EAG activity (1.32±0.09 mV) similar to that of the monoenic components. GC-EAD responses confirmed the composition of the sex pheromone blend, the major response being elicited by the main component I followed by the other minor compounds II-V. The new dienic compound found in the female pheromone gland, ( E, E)-10,12-tetradecadienyl acetate ( VII), was not electrophysiologically active. Regarding sensitivity, the minimum amount detectable to elicit an antennal response in our GC-EAD system was 15 pg of the major component. In our system, which was built with cheap and easily available materials, no cooling of the effluent at the outlet of the chromatographic column is required.

Direct inhibition of (Z)-9 desaturation of (E)-11-tetradecenoic acid by methylenehexadecenoic acids in the biosynthesis of Spodoptera littoralis sex pheromone.

Analysis by gas chromatography coupled to mass spectrometry demonstrated that 11,12-methylenehexadec-11-enoic acid and 12,13-methylenehexadec-12-enoic acid are beta-oxidized in Spodoptera littoralis sex pheromone gland to 9, 10-methylenetetradec-10-enoic acid and 10,11-methylenetetradec-10-enoic acid, respectively. This result supported our previous hypothesis that inhibition of the (Z)-9 desaturation of (E)-11-tetradecenoic acid by those C-16 fatty acids is actually caused by their corresponding beta-oxidation products. However, although (2,2,3,3-2H4)-11,12-methylenehexadec-11-enoic acid was not chain-shortened to the C-14 derivative, its activity as inhibitor of the (Z)-9 desaturation reaction was similar to that exhibited by 11,12-methylenehexadec-11-enoic acid. Therefore, the C-16 cyclopropene fatty acids may inhibit the (Z)-9 desaturation enzyme by themselves, probably through interaction of the cyclopropene ring with a binding site of the enzyme with the substrate double bond.

Efficient separation of fatty acyl precursors ofSpodoptera littoralis sex pheromone by reversed-phase high-performance liquid chromatography

Chromatographic conditions are reported for the efficient separation of fatty acyl precursors of Spodoptera littoralis sex pheromone by reversed-phase high-performance liquid chromatography. The procedure was optimized with a mixture of phenacyl derivative standards, using an octadecylsilane column, mixtures of acetonitrile-water, methanol-water, and methanol-isopropanol-water as mobile phases, and temperature control. This optimized method allowed the satisfactory separation of phenacyl esters obtained directly from S. littoralis sex pheromone gland extracts. © 1996 Wiley-Liss, Inc.

Effect of the pheromone biosynthesis activating neuropeptide on sex pheromone biosynthesis in Spodoptera littoralis isolated glands

AbstractThe control of Spodoptera littoralis sex pheromone biosynthesis has been investigated with synthetic pheromone biosynthesis activating neuropeptide (PBAN) and different labeled tracers using an in vitro isolated gland system. Responsiveness of the glands to PBAN stimulation was impaired by careless tissue manipulation. The fact that PBAN is active in the isolated gland system suggests that this might be a target organ for this peptide in S. littoralis. As reported previously with Br‐SOG extracts and intact females, label incorporation into the pheromone increased in glands treated with PBAN from all the precursors tested. However, the formation of labeled intermediates from d5E11–14:Acid also occurred in glands incubated in the absence of the peptide, but the amounts of d5Z9, E11–14:Acid were lower in PBAN treated glands than in controls. These results indicate that PBAN controls pheromone biosynthesis in S. littoralis by regulating the reduction of acyl moieties. © 1994 Wiley‐Liss, Inc.

Inhibition of sex pheromone biosynthesis in Spodoptera littoralis by cyclopropene fatty acids

This study shows that 10,11-methylenehexadec-10-enoic and 11,12-methylenehexadec-11-enoic acids interfere with the production of (Z)-9-tetradecenyl and (Z,E)-9,11-tetradecadienyl acetates, two components of spodoptera littoralis sex pheromone blend. This effect is caused by inhibition of both Δ-11 desaturation of palmitic acid and Δ-9 desaturation of (E)-11-tetradecenoic acid. Inhibition of the Δ-11 desaturase is dose dependent and the dose-response curves follow similar patterns for the two acids. At 10 ng, these two compounds and the previously reported 12,13-methylenehexadec-12-enoic acid are equally strong inhibitors of palmitic acid Δ-11 desaturation.

Synthesis of biosynthetic inhibitors of the sex pheromone of Spodoptera littoralis. Part II: acetylenic and cyclopropane fatty acids

The synthesis of new acetylenic and cyclopropane fatty acids, as potential inhibitors of the β-oxidation step in the proposed biosynthesis of the sex pheromone of the Egyptian armyworm Spodoptera littoralis, is reported. The biological activity of the compounds has been determined by in vitro and in vivo bioassays, and among all the compounds tested, dichlorocyclopropane acid has shown the highest inhibition activity displayed so far.

Synthesis of potential inhibitors of the biosynthesis of the sex pheromone of Spodoptera littoralis. Part I: Monofluorinated fatty acids

Several monofluorinated fatty acids, structurally related to palmitic acid, have been synthesized and fully characterized for the first time and assayed as inhibitors of the β-oxidation step, in the proposed biosynthesis of the sex pheromone of the Egyptian armyworm Spodoptera littoralis. Silver fluoride, diethylaminosulfur trifluoride (DAST) and dichlorofluoromethane were used as fluorination agents in the synthesis of 2-fluoropalmitic acid. 3- and 4-fluoropalmitic acid and ( Z)-5-fluoro-4-hexadecenoic acid, respectively. Stereoselective 1,4-reduction of the conjugated fluorodienic ester with sodium dithionite has been utilized to prepare the required fluorinated intermediate ester for the synthesis of ( Z)-5-fluoro-4-hexadecenoic acid. A preliminary account of the biological activity of the synthetic compounds along with 2-bromopalmitic acid is also reported.

Modification of the attractiveness of the primary pheromone component of the Egyptian cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), by secondary pheromone components and related chemicals

AbstractKnown components of the female sex pheromone of Spodoptera littoralis (Boisd.), tetradecyl acetate (I), (Z)-9-tetradecenyl acetate (IIA), (Z,E)-9, 11-tetradecadienyl acetate (III) and (Z,E)-9, 12-tetradecadienyl acetate (IV), and related compounds dispensed from polyethylene vials were used to bait water traps and funnel traps in lucerne fields in Crete. In comparison with the catches of males in traps baited with the primary component (III) alone, catches were increased by the addition of 1–100% of I in relation to the amounts of III, decreased by the addition of 5% or more of IIA and decreased by the addition of more than 5% of IV. The diene III was more attractive than any of the other three geometric isomers, although combining the Z,Z isomer (V) or the E,E isomer (VI) with III increased catches while the addition of the E,Z isomer (VII) decreased catches. The alcohols VIII and IX corresponding to the acetates III and IIA were not attractive but caused a marked reduction in trap catch when combined with III. The homologue of III (Z,E)-11-methyl–9, 11-tetradecadienyl acetate (X), was unattractive to males but increased trap catches when combined with III. 9-Tetradecynyl acetate (XI) exhibited neither attractant nor inhibitory activity, and similar results were obtained with ethyl cyclohexane carboxylate (XII) and 2-nonynal dimethyl acetal (XIII), compounds which have similar far-infrared spectra to that of diene III. The distributions of males landing on sticky board traps 70 cm in diameter baited with III or mixtures of III with I, IIA or IV showed that a greater percentage of the moths landed at the periphery of the traps baited with certain combinations of III with I and IV than on traps baited with III alone. Collection and analysis of the volatiles emitted by virgin females of different origins indicated that those from Crete produced I and III only, those from Israel produced I, III and IV, while those from Egypt produced I, III, IV and IIA and/or (E)-11-tetradecenyl acetate (IIB). The results are discussed in relation to previous work on S. littoralis and current theories on insect communication, and also in terms of their relevance to the practical field usage of pheromones in control of this pest.

Field studies of the female sex pheromone of the cotton leafworm Spodoptera littoralis (Boisd.) in Cyprus

AbstractThe four components of the synthesised sex pheromone of Spodoptera littoralis (Boisd.) are tetradecan-1-yl acetate (I); cis-9-tetradecen-1-yl acetate (IIA); trans-11-tetradecen-1-yl acetate (IIB); and cis-9, trans-11-tetradecadien-1-yl acetate (III). Dissolved in hexane they were dispensed in small polythene containers either singly or in combination over water-trough (WT) traps located in the potato-growing region of south-east Cyprus. Only III was necessary to attract male moths. Increased loadings of III resulted in an increased catch during the 20-day test periods; at a loading of 500 μg per dispenser the material was attractive for approximately 20 days, and at 5000 μg for up to 40 days. IIA combined with III in WT traps or with virgin females in the vane traps markedly reduced the catch of male moths. The level of inhibition induced by IIA on the attraction of female moths was related to the loading of this substance in the dispensers. An inhibitory effect on the attraction of female moths in vane traps was also shown for cis-11-tetradecen-1-yl acetate, although this substance was less active compared with IIA at the same loading. No marked attraction or inhibition was shown for I or IIB, neither was any synergistic action demonstrated for these substances when in combination with III. When 200 polythene dispensers each containing 500 μg of III were evenly distributed throughout a potato field of 2000 m2 during the test period of 19 days virtually no males were caught in a trap baited with virgin females located in the centre of the field. Using only 100 point sources of III at twice the loading, only a slight reduction in catch compared with control catches was noted.