Molecular basis of female-specific odorant responses in Bombyx mori.

Males and females of many moth species exhibit important differences in sexual behaviours. Much research in this field has focused on the male-specific behaviour, electrophysiology and molecular biology of sex pheromone reception. Female-specific behaviours have been less well studied although, like male-specific behaviours, they could provide opportunities for intervention and management of lepidopteran pests. Previously, we identified genes encoding putative odorant receptors (ORs) from the genome of the silkworm, Bombyx mori, some of which have higher levels of steady-state transcript in the antennae of adult females compared with males. We have identified the full-length cDNA sequences of some of these ORs and described a novel OR that is part of a female-biased clade. Using expression in Sf9 cells and a calcium-imaging assay, we tested a range of compounds for their ability to activate the most highly female-biased ORs, BmOR19, BmOR30, BmOR45 and BmOR47. BmOR19 responds to linalool, while BmOR45 and BmOR47 respond to benzoic acid > 2-phenylethanol > benzaldehyde. No activating ligands were found for BmOR30. RNA in situ hybridisation experiments reveal that BmOR19 is expressed in female olfactory sensory neurons that are co-located in the same sensilla as a second ORN expressing BmOR45 and/or BmOR47. Taken together the activity and expression of these receptors is likely explanatory of the observed electrophysiology of long sensilla trichoidea of female B. mori, previously shown to each contain one terpene (BmOR19) and one benzoic acid (BmOR45, BmOR47) sensory neuron. Plant volatiles such as linalool, benzoic acid, 2-phenylethanol and benzaldehyde are oviposition cues for females of some moths. These compounds have also been found in male-produced pheromone blends extracted from the hair pencils of many noctuid species. Hair pencil structures have not previously been reported for B. mori, but we have found hair pencil-like structures in adult male B. mori that are absent in female moths. It is proposed that BmOR19, BmOR45 and BmOR47 account for some of the female-specific odorant responses in B. mori, such as oviposition and/or detection of an as yet unidentified male-produced sex pheromone.

Systematic Synthesis of Multifluorinated alpha,alpha-Difluoro-gamma-lactones through Intramolecular Radical Cyclization.

Carbon radicals from allyl O-(trimethylsilyl)-alpha-bromo-alpha,alpha-difluoroacetal can cyclize onto the olefinic part regiospecifically to give gamma-lactols in good yield. The lactols are then converted to the corresponding alpha,alpha-difluoro-gamma-lactones. Systematic synthesis of multifluorinated-alpha,alpha-difluoro-gamma-lactones has thus been accomplished through intramolecular radical cyclization as a key reaction. Semiempirical MO calculation study suggested a unique nature of alpha,alpha-difluoroacetate in that complete delocalization of the electrons in the SOMO orbital of alpha,alpha-difluoroacetyl radical occurred; this caused unsuccessful cyclization. To apply the present radical reaction, the first synthesis of both enantiomers of difluoroeldanolide, analogues of the sex pheromone of the male African sugarcane borer, has been demonstrated. Electrophysiological tests revealed that the difluorinated analogues were as active as the natural eldanolide on the olfactory receptors.