Identification of Odor-Processing Genes in the Emerald Ash Borer, Agrilus planipennis

Praveen Mamidala,Asela J Wijeratne,Michel Cusson,Saranga Wijeratne,Catherine Beliveau,Daniel Doucet,Sohail S Qazi,Therese Poland,Omprakash Mittapalli,Frederic Marion-Poll

doi:10.1371/journal.pone.0056555

Abstract

BackgroundInsects rely on olfaction to locate food, mates, and suitable oviposition sites for successful completion of their life cycle. Agrilus planipennis Fairmaire (emerald ash borer) is a serious invasive insect pest that has killed tens of millions of North American ash (Fraxinus spp) trees and threatens the very existence of the genus Fraxinus. Adult A. planipennis are attracted to host volatiles and conspecifics; however, to date no molecular knowledge exists on olfaction in A. planipennis. Hence, we undertook an antennae-specific transcriptomic study to identify the repertoire of odor processing genes involved in A. planipennis olfaction.Methodology and Principal FindingsWe acquired 139,085 Roche/454 GS FLX transcriptomic reads that were assembled into 30,615 high quality expressed sequence tags (ESTs), including 3,249 isotigs and 27,366 non-isotigs (contigs and singletons). Intriguingly, the majority of the A. planipennis antennal transcripts (59.72%) did not show similarity with sequences deposited in the non-redundant database of GenBank, potentially representing novel genes. Functional annotation and KEGG analysis revealed pathways associated with signaling and detoxification. Several odor processing genes (9 odorant binding proteins, 2 odorant receptors, 1 sensory neuron membrane protein and 134 odorant/xenobiotic degradation enzymes, including cytochrome P450s, glutathione-S-transferases; esterases, etc.) putatively involved in olfaction processes were identified. Quantitative PCR of candidate genes in male and female A. planipennis in different developmental stages revealed developmental- and sex-biased expression patterns.Conclusions and SignificanceThe antennal ESTs derived from A. planipennis constitute a rich molecular resource for the identification of genes potentially involved in the olfaction process of A. planipennis. These findings should help in understanding the processing of antennally-active compounds (e.g. 7-epi-sesquithujene) previously identified in this serious invasive pest.

Highlights

IntroductionOlfaction is the primary sensory perception modality in insects, guiding them to locate food (host cues), conspecifics (mating), suitable oviposition sites (access to nutritious and digestible food for off-spring), and to detect predators and toxic compounds [1,2]
Olfaction is the primary sensory perception modality in insects, guiding them to locate food, conspecifics, suitable oviposition sites, and to detect predators and toxic compounds [1,2]
The antennal expressed sequence tags (ESTs) derived from A. planipennis constitute a rich molecular resource for the identification of genes potentially involved in the olfaction process of A. planipennis

Summary

Introduction

Olfaction is the primary sensory perception modality in insects, guiding them to locate food (host cues), conspecifics (mating), suitable oviposition sites (access to nutritious and digestible food for off-spring), and to detect predators and toxic compounds [1,2]. A number of perireceptor proteins and surface receptors have been identified as having roles in olfaction, depending on the odor context and ORNs involved. These include the odorant binding proteins (OBPs), odorant receptors (ORs), the sensory neuron membrane protein 1 (Snmp1), chemosensory proteins (CSPs), gustatory receptors (GRs) and ionotropic receptors (IRs). We undertook an antennae-specific transcriptomic study to identify the repertoire of odor processing genes involved in A. planipennis olfaction

Methods

Results

Conclusion