Agonists and Antagonists of Antennal Responses of Gypsy Moth (Lymantria dispar) to the Pheromone (+)-Disparlure and Other Odorants

Abstract

Insects use the sense of smell to guide many behaviors that are important for their survival. The gypsy moth uses a pheromone to bring females and males together over long distances. Male moth antennae are equipped with innervated sensory hairs that selectively respond to pheromone components and other odors. Host plant odors, in particular, are detected by moths and sometimes cause an enhancement of the antennal and behavioral responses of the moths to their pheromone. Inspired by naturally occurring agonists and antagonists of insect pheromone responses, we have screened, by electroantennogram (EAG) recordings, a collection of compound sets and of individual compounds. We have detected interference of some compounds with the EAG responses of male gypsy moth antennae to the pheromone. We describe three activities: (1) short-term inhibition or enhancement of mixed compound + pheromone plumes, (2) long-term inhibition of pure pheromone plumes following a mixed compound + pheromone plume, and (3) inhibition of the recovery phase of mixed compound + pheromone plumes. Long-term inhibition was robust, decayed within 30 s, and correlated with the inhibition of recovery; for both activities clear structure-activity patterns were detected. The commercial repellent N,N-diethyltoluamide (DEET) was included for comparison. The most active and reproducible short-term inhibitor was a mixture of 1-allyl-2,4-dimethoxybenzene and 2-allyl-1,3-dimethoxybenzene. The most active long-term inhibitors were a set of 1-alkoxy-4-propoxybenzenes, DEET, and 1-ethoxy-4-propoxybenzene. DEET was more specific in the olfactory responses it inhibited than 1-ethoxy-4-propoxybenzene, and DEET did not inhibit recovery, whereas 1-ethoxy-4-propoxybenzene did. Target sites for the three activities are discussed.

Can We Disrupt the Sensing of Honey Bees by the Bee Parasite Varroa destructor?

“…This long-term inhibition appeared stronger than the short-term effect for cy { 2,2 } and HCO-2-169, but it was eliminated in a fourth stimulation with bee headspace that was applied after stimulation with air (data not shown). A similar result has been obtained with gypsy moths treated with the sex pheromone, (+)-disparlure, and a blend 3c { 1-5,3 } [19]: the long-term inhibition was reversible, and the response to pure pheromone returned to normal 4–5 puffs after the mixed puff (pheromone + 3c { 1-5,3 }). In the present study, there were different structure-activity relationships for the short-term and long-term effects.…”

“…The effect of the compounds was evaluated relative to the response to the “positive stimulus” before the exposure to the tested compound. According to previous studies [19], [20], two kinds of effect were evaluated: the effect that occurred in the presence of the compound termed “short term effect”, and the effect following the administration of the compound but not in its presence termed “long term effect”. …”

“…Recently, a library of volatile compounds was developed for the disruption of chemical detection by the gypsy moths' antenna [17], [18]. These chemicals apparently interact with the pheromone binding proteins and/or other components of the olfactory system and take an effect only in the presence of a positive chemical stimulus [17], [19], [20]. As the chemical environment of the hive is rich in volatiles, it was interesting to explore the effect of these compounds on host detection and behavior of the Varroa mite.…”

Plant odour stimuli reshape pheromonal representation in neurons of the antennal lobe macroglomerular complex of a male moth

“…Although a few examples of synergistic effects of plant odours added to sex pheromone have been reported (Ochieng et al, 2002;Plettner and Gries, 2010), the most frequently observed effect consisted of a suppression of the pheromonal response when a plant odour is added (Schneider et al, 1964;Den Otter et al, 1978;Kaissling et al, 1989;Pophof and van der Goes van Naters, 2002;Party et al, 2009).…”

Comparing the Expression of Olfaction-Related Genes in Gypsy Moth (Lymantria dispar) Adult Females and Larvae from One Flightless and Two Flight-Capable Populations

“…Thereafter, Plettner and coworkers have made great contributions to our understanding of olfaction in this species, in particular concerning the structure and function of its pheromone binding proteins (Kowcun et al, 2001;Honson et al, 2003;Honson and Plettner, 2006;Plettner and Gries, 2010;Gong and Plettner, 2011;Yu and Plettner, 2013). Recently, the L. dispar olfactory co-receptor (ORCO), a crucial component of olfactory receptor complexes, has been identified (Vosshall and Hansson, 2011;Lin et al, 2015).…”