Molecular Basis of Alarm Pheromone Detection in Aphids

Abstract

The sesquiterpene (E)-β-farnesene (EBF) is the alarm pheromone for many species of aphids [1]. When released from aphids attacked by parasitoids or predators, it alerts nearby conspecifics to escape by walking away and dropping off the host plant [2, 3]. The reception of alarm pheromone in aphids is accomplished through a highly sensitive chemosensory system. Although olfaction-related gene families including odorant receptors (ORs) and odorant-binding proteins (OBPs) have recently been identified from aphid genomes [4-6], the cellular and molecular mechanisms of EBF reception are still largely unknown. Here we demonstrate that ApisOR5, a member of the large superfamily of odorant receptors, is expressed in large placoid sensillum neurons on the sixth antennal segment and confers response to EBF when co-expressed with Orco, an obligate odorant receptor co-receptor, in parallel heterologous expression systems. In addition, the repellent behavior of Acyrthosiphon pisum to EBF disappears after knocking down ApisOR5 by RNAi as well as two A. pisum odorant-binding proteins known to bind EBF (ApisOBP3 and ApisOBP7). Furthermore, other odorants that can also activate ApisOR5, such as geranyl acetate, significantly repel A. pisum, as does EBF. Taken together, these data allow us to conclude that ApisOR5 is essential to EBF reception in A. pisum. The characterization of the EBF receptor allows high-throughput screening of aphid repellents, providing the necessary information to develop new strategies for aphid control.

Repellence of Myzus persicae (Sulzer): evidence of two modes of action of volatiles from selected living aromatic plants

“…As minor compounds emitted from O. basilicum , α‐terpineol, myrcene, geranyl acetone, and sabinene were demonstrated as repellent at one or more of the concentrations tested. Our results corroborate previous reports on the repellency of these compounds against aphids and other insects …”

Molecular characterization and evolution of a chemosensory receptor gene family in three notorious rice planthoppers, Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus, based on genome and transcriptome analyses

“…In Group 5, which consists mainly of aphid ORs, homologs of two ORs, AgoOR5 and ApOR5 and SfurOR121 and LstrOR15, respectively, were observed. AgoOR5 and ApOR5 have been characterized as receptors of (E)‐β‐farnesene, which is an alarm pheromone found in aphids. ApOR4 tunes to eight common volatiles, salicylaldehyde, 4‐ethylbenzaldehyde, 3‐vinylbenzaldehyde, (1 S )‐(−)‐verbenone, ( S )‐ cis ‐verbenol, (−)‐borneol and (1 R )‐(−)‐myrtenal .…”

Integrative transcriptomic and genomic analysis of odorant binding proteins and chemosensory proteins in aphids

“…The major alarm pheromone component E βf emitted from the cornicles of aphids (Edwards et al ., ) is recognized by large placoid sensillum neurons, which express OR5 on the sixth antennal segment in A. pisum (Zhang et al ., ); OBP3 and OBP7 are both expressed in the large placoid sensilla in M. persicae (Sun et al ., ) and in the type II trichoid sensilla in A. pisum in the antennae (Biasio et al ., ). OBP3 and/or OBP7 proteins in several aphid species ( A. pisum , S. avenae , M. viciae , N. ribisnigri and R. padi ) have high binding affinities with E βf (Qiao et al ., ; Vandermoten et al ., ; Zhong et al ., ; Fan et al ., ), but the cellular location of all M. persicae OBPs in the antennal sensilla and their binding abilities with E βf are still unknown.…”