The Plant Sesquiterpene Germacrene D Specifically Activates a Major Type of Antennal Receptor Neuron of the Tobacco Budworm Moth Heliothis virescens

Abstract

Plants release hundreds of volatiles that are important in interactions with insects or other organisms. However, knowledge is scarce as to which of the compounds are detected by the organism's olfactory receptor neurons. In the present study, single receptor neurons on the antennae of the tobacco budworm moth, Heliothis virescens, were screened for their sensitivities to naturally produced plant volatiles by the use of gas chromatography linked to electrophysiological recordings from single cells (GC-SCR). Plant volatiles, collected by aeration of host and non-host plants, were tested on each receptor neuron via parallel GC-columns. Thus, simultaneous recordings of the gas chromatogram and the neuron responses to each component were obtained. One type of receptor neuron, appearing in 80% of all experiments, responded with high sensitivity and selectivity to one particular component, present in host as well as non-host mixtures. The component, identified as a sesquiterpene hydrocarbon by linked gas chromatography-mass spectrometry, was isolated from a sesquiterpene fraction of cubebe oil and identified by NMR as germacrene D. The purified compound was then re-tested via gas chromatography on the same receptor neuron type, verifying the identification. A weaker response to another sesquiterpene hydrocarbon was also recorded.

Chemosensory Selectivity of Output Neurons Innervating an Identified, Sexually Isomorphic Olfactory Glomerulus

“…6,8 E). Other authors found high specificity in pheromone-processing AL neurons Hartlieb et al, 1997;de Bruyne et al, 2001) or ORCs responsive to plant volatiles (Hansson et al, 1999;Røstelien et al, 2000;Angioy et al, 2003) only at low, natural stimulus intensities. These findings, together with ours, illustrate the importance of testing odor stimuli over a range of concentrations to characterize the MRRs of olfactory neurons.…”

Essential oil composition of sweet basil cultivars as affected by nitrogen and potassium fertilization

“…Eugenol, as one of the phenolic compounds characteristic of basil volatile oil, shows antioxidant (Juliani and Simon 2002) and antimicrobial activity (Ali et al 2005). Germacrene C and D, components from the group of sesquiterpene hydrocarbons, exhibit antimicrobial and insecticidal activity (Røstelien et al 2000;Stranden et al 2002).…”

Molecular cloning and expression analysis of a putative sesquiterpene synthase gene from tea plant (Camellia sinensis)

“…This compound was one of the plant second metabolisms known as an essential oil, which was also a volatile with ecological function involved in the interaction among plant insect enemy (Røstelien et al 2000). Germacrene D synthase belonged to the terpene synthase family, and several germacrene D synthase genes had been identified from plants such as Vitis vinifera, Actinidia deliciosa and Zingiber officinale (Lücker et al 2004;Picaud et al 2006).…”