Identification of candidate olfactory genes in Leptinotarsa decemlineata by antennal transcriptome analysis

Insect Molecular Biology

Schneider

Schwartz

et al. 2019

168

The insect odorant receptors (ORs) are amongst the largest gene families in insect genomes and the primary means by which insects recognize volatile compounds. The evolution of ORs is thus instrumental in explaining the chemical ecology of insects and as a model of evolutionary biology. However, although ORs have been described from numerous insect species, their analysis within and amongst the insect orders has been hindered by a combination of limited genomic information and a tendency of the OR family toward rapid divergence, gain, and loss. We addressed these issues in the insect order Coleoptera through a targeted genomic annotation effort that included 1181 ORs from one species of the sister order Strepsiptera and 10 species representing the four coleopteran suborders. The numbers of ORs in each species varied from hundreds to fewer than 10, but coleopteran ORs could nevertheless be represented within a scheme of nine monophyletic subfamilies. We observed many radiations and losses of genes amongst OR subfamilies, and the diversity of ORs appeared to parallel the host breadth of the study species. However, some small lineages of ORs persisted amongst many coleopteran families, suggesting receptors of key function that underlie the olfactory ecology of beetles.

Section: Introductionmentioning

confidence: 98%

“…(summarized in Robertson, 2019). Transcriptomes are numerous, but generally do not describe the full suite of receptors owing to low and/or spatiotemporal expression of some OR genes (eg Liu et al, 2015vs. Schoville et al, 2018.…”

Section: Introductionmentioning

confidence: 99%

The diversity and evolution of odorant receptors in beetles (Coleoptera)

Insect Molecular Biology

Schneider

Schwartz

et al. 2019

168

“…Analyses of insect genomes are crucial in addressing this question, because the more common approach of using transcriptomes [47] generally misses a large proportion of the genes present in the genome [c.f. 48,49]. While chemosensory genes from the Diptera, Hymenoptera, and Lepidoptera have been more thoroughly compared in this regard [50][51][52], the largest order of insects, Coleoptera, remains poorly investigated.…”

Section: Introductionmentioning

confidence: 99%

Genomic content of chemosensory genes correlates with host range in wood-boring beetles (Dendroctonus ponderosae, Agrilus planipennis, and Anoplophora glabripennis)

Andersson¹,

Keeling

2019

Preprint

Background Olfaction and gustation underlie behaviors that are crucial for insect fitness, such as host and mate selection. The detection of semiochemicals is mediated via proteins from large and rapidly evolving chemosensory gene families; however, the links between a species’ ecology and the diversification of these genes remain poorly understood. Hence, we annotated the chemosensory genes from genomes of select wood-boring coleopterans, and compared the gene repertoires from stenophagous species with those from polyphagous species. Results We annotated 86 odorant receptors (ORs), 60 gustatory receptors (GRs), 57 ionotropic receptors (IRs), 4 sensory neuron membrane proteins (SNMPs), 36 odorant binding proteins (OBPs), and 11 chemosensory proteins (CSPs) in the mountain pine beetle (Dendroctonus ponderosae), and 47 ORs, 30 GRs, 31 IRs, 4 SNMPs, 12 OBPs, and 14 CSPs in the emerald ash borer (Agrilus planipennis). Four SNMPs and 17 CSPs were annotated in the polyphagous wood-borer Anoplophora glabripennis. The gene repertoires in the stenophagous D. ponderosae and A. planipennis are reduced compared with those in the polyphagous A. glabripennis and T. castaneum, which is largely manifested through small gene lineage expansions and entire lineage losses. Alternative splicing of GRs was limited in D. ponderosae and apparently absent in A. planipennis, which also has lost one carbon dioxide receptor (GR1). A. planipennis has two SNMPs which are related to SNMP3 in T. castaneum. D. ponderosae has two alternatively spliced OBPs, a novel OBP “tetramer”, and as many as eleven IR75 members. Simple orthology was generally rare, but we report one clade of orthologous putative bitter-taste GRs (named the “GR215 clade”), and conservation of IR60a from Drosophila melanogaster also in beetles. Conclusions Our annotation represents significant quantitative and qualitative improvements compared to original datasets derived from transcriptomes of D. ponderosae and A. planipennis. These gene sets facilitate evolutionary analysis of chemosensory genes in the Coleoptera where only a few genomes were annotated previously, and suggests a correlation between chemosensory gene content and host specificity in beetles. Future studies should include additional species to consolidate this correlation, and functionally characterize identified proteins, as an important step towards improved control of these destructive pests.

“…Analyses of insect genomes are crucial in addressing this question, because studies of antennal transcriptomes, which is a more common approach [47], generally miss a large proportion of the genes present in the genome [c.f. 48,49].…”

Section: Introductionmentioning

confidence: 99%

Genomic content of chemosensory genes correlates with host range in wood-boring beetles (Dendroctonus ponderosae, Agrilus planipennis, and Anoplophora glabripennis)

Andersson¹,

Keeling

2019

Preprint

Background Olfaction and gustation underlie behaviors that are crucial for insect fitness, such as host and mate selection. The detection of semiochemicals is mediated via proteins from large and rapidly evolving chemosensory gene families; however, the links between a species’ ecology and the diversification of these genes remain poorly understood. Hence, we annotated the chemosensory genes from genomes of wood-boring coleopterans, and compared the gene repertoires from stenophagous species with those from polyphagous species. Results We annotated 86 odorant receptors (ORs), 60 gustatory receptors (GRs), 57 ionotropic receptors (IRs), 4 sensory neuron membrane proteins (SNMPs), 36 odorant binding proteins (OBPs), and 11 chemosensory proteins (CSPs) in the mountain pine beetle (Dendroctonus ponderosae), and 47 ORs, 30 GRs, 31 IRs, 4 SNMPs, 12 OBPs, and 14 CSPs in the emerald ash borer (Agrilus planipennis). Four SNMPs and 17 CSPs were annotated in the polyphagous wood-borer Anoplophora glabripennis. The gene repertoires in the stenophagous D. ponderosae and A. planipennis are reduced compared with those in the polyphagous A. glabripennis and T. castaneum, which is largely manifested through small gene lineage expansions and entire lineage losses. Alternative splicing of GR genes was limited in D. ponderosae and apparently absent in A. planipennis, which also seems to have lost one carbon dioxide receptor (GR1). A. planipennis has two SNMPs, which are related to SNMP3 in T. castaneum. D. ponderosae has two alternatively spliced OBP genes, a novel OBP “tetramer”, and as many as eleven IR75 members. Simple orthology was generally rare in beetles; however, we found one clade with orthologues of putative bitter-taste GRs (named the "GR215 clade"), and conservation of IR60a from Drosophila melanogaster. Conclusions Our genome annotations represent important quantitative and qualitative improvements of the original datasets derived from transcriptomes of D. ponderosae and A. planipennis, facilitating evolutionary analysis of chemosensory genes in the Coleoptera where only a few genomes were previously annotated. Our analysis suggests a correlation between chemosensory gene content and host specificity in beetles. Future studies should include additional species to consolidate this correlation, and functionally characterize identified proteins as an important step towards improved control of these pests.