title: Antennal transcriptome analysis of the chemosensory gene families in the tree killing bark beetles, Ips typographus and Dendroctonus ponderosae (Coleoptera: Curculionidae: Scolytinae).
abstract: BACKGROUND
  The European spruce bark beetle, Ips typographus, and the North American mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae: Scolytinae), are severe pests of coniferous forests. Both bark beetle species utilize aggregation pheromones to coordinate mass-attacks on host trees, while odorants from host and non-host trees modulate the pheromone response. Thus, the bark beetle olfactory sense is of utmost importance for fitness. However, information on the genes underlying olfactory detection has been lacking in bark beetles and is limited in Coleoptera. We assembled antennal transcriptomes from next-generation sequencing of I. typographus and D. ponderosae to identify members of the major chemosensory multi-gene families.
  
  
  RESULTS
  Gene ontology (GO) annotation indicated that the relative abundance of transcripts associated with specific GO terms was highly similar in the two species. Transcripts with terms related to olfactory function were found in both species. Focusing on the chemosensory gene families, we identified 15 putative odorant binding proteins (OBP), 6 chemosensory proteins (CSP), 3 sensory neuron membrane proteins (SNMP), 43 odorant receptors (OR), 6 gustatory receptors (GR), and 7 ionotropic receptors (IR) in I. typographus; and 31 putative OBPs, 11 CSPs, 3 SNMPs, 49 ORs, 2 GRs, and 15 IRs in D. ponderosae. Predicted protein sequences were compared with counterparts in the flour beetle, Tribolium castaneum, the cerambycid beetle, Megacyllene caryae, and the fruit fly, Drosophila melanogaster. The most notable result was found among the ORs, for which large bark beetle-specific expansions were found. However, some clades contained receptors from all four beetle species, indicating a degree of conservation among some coleopteran OR lineages. Putative GRs for carbon dioxide and orthologues for the conserved antennal IRs were included in the identified receptor sets.
  
  
  CONCLUSIONS
  The protein families important for chemoreception have now been identified in three coleopteran species (four species for the ORs). Thus, this study allows for improved evolutionary analyses of coleopteran olfaction. Identification of these proteins in two of the most destructive forest pests, sharing many semiochemicals, is especially important as they might represent novel targets for population control.
authors.affiliation: Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, SE-230 53, Alnarp, Sweden. martin_n.andersson@biol.lu.se
authors.forename: Martin N
authors.initials: MN
authors.lastname: Andersson
authors.forename: Ewald
authors.initials: E
authors.lastname: Grosse-Wilde
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Keeling
authors.forename: Jonas M
authors.initials: JM
authors.lastname: Bengtsson
authors.forename: Macaire M S
authors.initials: MM
authors.lastname: Yuen
authors.forename: Maria
authors.initials: M
authors.lastname: Li
authors.forename: Ylva
authors.initials: Y
authors.lastname: Hillbur
authors.forename: Jörg
authors.initials: J
authors.lastname: Bohlmann
authors.forename: Bill S
authors.initials: BS
authors.lastname: Hansson
authors.forename: Fredrik
authors.initials: F
authors.lastname: Schlyter
mesh_terms: D000818:Animals; D057506:Arthropod Antennae / Q000378:metabolism*; D001517:Coleoptera; D015870:Gene Expression; D020869:Gene Expression Profiling; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family
chemical_list: D019476:Insect Proteins