Increased EAG responses of tortricid moths after prolonged exposure to plant volatiles: evidence for octopamine-mediated sensitization.
As measured by electroantennograms (EAG), both male and female obliquebanded leafrollers, Choristoneura rosaceana (Harris), and redbanded leafrollers, Argyrotaeniavelutinana (Walker), were similarly sensitive to host-related plant volatiles: trans-2-hexenal, benzaldehyde, 1-hexenol, cis-3-hexen-1-ol, geraniol, linalool, (+)-limonene, hexenal and trans-2-hexenol. Females of both species were similarly sensitive to the shared major component of their sex-attractant pheromone ((Z)11-14:Ac). Continuous 60 min pre-exposure of male and female C. rosaceana and A. velutinana to successively higher concentrations of a mixture of the nine plant volatiles in Teflon chambers with continuous air exchange caused a dosage-dependent increase in subsequent responsiveness (sensitization) to green leaf volatiles, as measured by EAGs. In addition, 60 min of pre-exposure of male C. rosaceana to certain individual volatiles ((+)-limonene, geraniol, benzaldehyde) increased EAGs nearly as much as did the mixture of nine volatiles. Pre-exposures to the nine plant-volatile mixture at concentrations achieved by 100 microg and 1 mg loading dosages in 100 microl of mineral oil significantly increased EAG depolarization to pheromone (cross-sensitization) in males but not females of both moth species. Antennae of male C. rosaceana pre-injected with 100 microg of octopamine (OA) without volatile pre-exposure exhibited sensitization nearly identical to that induced by pre-exposing moths to sensitizing concentrations of the plant-volatile mixture. Moreover, injection of the OA antagonist chlorpromazine (CP) blocked sensitization by the plant-volatile pre-exposure. Collectively, these findings suggest that exposures of tortricid moths to certain host-plant related volatiles may modulate subsequent olfactory sensitivity to behaviorally relevant chemical cues and that plant-volatile induced sensitization may be octopamine mediated.
Stelinski
Lukasz L
LL
Department of Entomology, 205 Center for Integrated Plant Systems, Michigan State University, East Lansing, MI 48824, USA. stelinsk@msu.edu
Miller
James R
JR
Ressa
Noah E
NE
Gut
Larry J
LJ
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002746:Chlorpromazine / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D009036:Moths / Q000187:drug effects* / Q000502:physiology*; D009655:Octopamine / Q000494:pharmacology*; D010936:Plant Extracts / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology*; D010944:Plants / Q000737:chemistry*; D012724:Sex Attractants / Q000494:pharmacology; D014835:Volatilization
D000316:Adrenergic alpha-Agonists; D018492:Dopamine Antagonists; D010936:Plant Extracts; D012724:Sex Attractants; D009655:Octopamine; D002746:Chlorpromazine