(-)-Germacrene D receptor neurones in three species of heliothine moths: structure-activity relationships.
Specificity of olfactory receptor neurones plays an important role in food and host preferences of a species, and may have become conserved or changed in the evolution of polyphagy and oligophagy. We have identified a major type of plant odour receptor neurones responding to the sesquiterpene germacrene D in three species of heliothine moths, the polyphagous Heliothis virescens and Helicoverpa armigera and the oligophagous Helicoverpa assulta. The neurones respond with high sensitivity and selectivity to (-)-germacrene D, as demonstrated by screening via gas chromatography with numerous mixtures of plant volatiles. Germacrene D was present in both host and non-host plants, but only in half of the tested species. The specificity of the neurones was similar in the three species, as shown by the "secondary" responses to a few other sesquiterpenes. The effect of (-)-germacrene D was about ten times stronger than that of the (+)-enantiomer, which again was about ten times stronger than that of (-)-alpha-ylangene. Weaker effects were obtained for (+)-beta-ylangene, (+)-alpha-copaene, beta-copaene and two unidentified sesquiterpenes. The structure-activity relationship shows that the important properties of (-)-germacrene D in activating the neurones are the ten-membered ring system and the three double bonds acting as electron-rich centres, in addition to the direction of the isopropyl-group responsible for the different effects of the germacrene D enantiomers.
Stranden
M
M
Neuroscience Unit, Department of Biology, Norwegian University of Science and Technology, 7489 NO-Trondheim, Norway. Marit.Stranden@bio.ntnu.no
Liblikas
I
I
König
W A
WA
Almaas
T J
TJ
Borg-Karlson
A-K
AK
Mustaparta
H
H
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology / Q000379:methods; D005247:Feeding Behavior / Q000187:drug effects* / Q000502:physiology; D005260:Female; D009036:Moths / Q000737:chemistry; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009833:Olfactory Pathways / Q000187:drug effects / Q000502:physiology; D018034:Olfactory Receptor Neurons / Q000378:metabolism*; D010944:Plants / Q000737:chemistry; D012679:Sense Organs / Q000033:anatomy & histology / Q000187:drug effects; D012717:Sesquiterpenes / Q000737:chemistry / Q000494:pharmacology*; D045788:Sesquiterpenes, Germacrane; D013045:Species Specificity; D013237:Stereoisomerism; D013268:Stimulation, Chemical; D013329:Structure-Activity Relationship
D012717:Sesquiterpenes; D045788:Sesquiterpenes, Germacrane; C027259:germacrene D