Xu P et al. (2012), Moth sex pheromone receptors and deceitful para...

XB-ART-45912

PLoS One 2012 Jan 01;77:e41653. doi: 10.1371/journal.pone.0041653.

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Moth sex pheromone receptors and deceitful parapheromones.

Xu P , Garczynski SF , Atungulu E , Syed Z , Choo YM , Vidal DM , Zitelli CH , Leal WS .

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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.

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Species referenced: Xenopus
Genes referenced: gnas

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References [+] :

Forstner, A receptor and binding protein interplay in the detection of a distinct pheromone component in the silkmoth Antheraea polyphemus. 2009, Pubmed

	Figure 1. Responses of the peripheral olfactory system of the navel orangeworm to the major constituent of the sex pheromone and its formate analog.(A) Extracellularly recorded single unit responses from ORNs housed in a trichoid sensillum on the antennae, and (B) dose-dependent relationships (n = 5; error bar in all figures represent SEM).
	Figure 2. Screening of AtraOR1.Xenopus oocytes expressing AtraOR1 and AtraOrco were challenged with three aldehydes released by the female pheromone gland, a related alcohol (Z11Z13-16OH) and a behavioral antagonist (Z11Z13-16OAc). (A) Trace obtained with all compounds at 100 µM. (B) Quantification of current responses (n = 5).
	Figure 3. Responses elicited by constituents of the pheromone gland on AtraOR3•AtraOrco-expressing oocytes.(A) Trace generated at 100 µM highlighting a specific response to Z11-16Ald, a gland constituent of unknown function. (B) Quantification of current responses, n = 4.
	Figure 4. Expression profiles of navel orangeworm odorant receptors.The odorant receptor co-receptor, AtraOrco, was expressed equally in male and female antennae. AtraOR1 was highly expressed in male antennae, whereas AtraOR3 was enriched in female antennae.
	Figure 5. Dose-dependent current responses obtained with AtraOR1•AtraOrco-expressing oocytes.Note the curve generated by challenging the oocytes with the formate analog is shifted at least one order of magnitude.
	Figure 6. Total ion-chromatograms.Representative traces obtained with the main constituent of the sex pheromone (blue trace) and its related formate (red). Small peaks eluting just prior to the main peaks are stereoisomers of sex pheromone and parapheromone.
	Figure 7. Gas chromatographic traces obtained with extracts of the odorants used to stimulate receptor-expressing oocytes.The peaks of the formate analog and the related aldehyde pheromone are of nearly the same intensity thus confirming that oocytes are stimulated with nearly the same concentrations of the two compounds.
	Figure 8. Current responses elicited from AtraOR1•AtraOrco-expressing oocytes by challenging the same oocytes with the aldehyde pheromone and its parapheromone.To avoid electrophysiological adaptation, dose-dependence relationships were obtained with a narrow range of concentration, n = 4.
	Figure 9. Current responses obtained from HvirOR13•HvirOrco-expressing oocytes challenged with the cognate aldehyde ligand and a related formate analog.(A) Trace generated with increasing doses of the two ligands, and (B) dose-dependent relationships, n = 5.