Odorant and gustatory receptors in the tsetse fly Glossina morsitans morsitans

Tsetse flies use olfactory and gustatory responses, through odorant and gustatory receptors (ORs and GRs), to interact with their environment. Glossina morsitans morsitans genome ORs and GRs were annotated using homologs of these genes in Drosophila melanogaster and an ab initio approach based on OR and GR specific motifs in G. m. morsitans gene models coupled to gene ontology (GO). Phylogenetic relationships among the ORs or GRs and the homologs were determined using Maximum Likelihood estimates. Relative expression levels among the G. m. morsitans ORs or GRs were established using RNA-seq data derived from adult female fly. Overall, 46 and 14 putative G. m. morsitans ORs and GRs respectively were recovered. These were reduced by 12 and 59 ORs and GRs respectively compared to D. melanogaster. Six of the ORs were homologous to a single D. melanogaster OR (DmOr67d) associated with mating deterrence in females. Sweet taste GRs, present in all the other Diptera, were not recovered in G. m. morsitans. The GRs associated with detection of CO2 were conserved in G. m. morsitans relative to D. melanogaster. RNA-sequence data analysis revealed expression of GmmOR15 locus represented over 90% of expression profiles for the ORs. The G. m. morsitans ORs or GRs were phylogenetically closer to those in D. melanogaster than to other insects assessed. We found the chemoreceptor repertoire in G. m. morsitans smaller than other Diptera, and we postulate that this may be related to the restricted diet of blood-meal for both sexes of tsetse flies. However, the clade of some specific receptors has been expanded, indicative of their potential importance in chemoreception in the tsetse.German Academic Exchange Service (DAAD) South African Research Chair Initiative Department of Science and Technology National Research Foundation of South AfricaWeb of Scienc

Chemoreceptor diversity in apoid wasps and its reduction during the evolution of the pollen-collecting lifestyle of bees (Hymenoptera: Apoidea)

Chemoreceptors help insects to interact with their environment, to detect and assess food sources and oviposition sites, and to aid in intra- and interspecific communication. In Hymenoptera, species of eusocial lineages possess large chemoreceptor gene repertoires compared with solitary species, possibly because of their additional need to recognize nest-mates and caste. However, a critical piece of information missing so far has been the size of chemoreceptor gene repertoires of solitary apoid wasps. Apoid wasps are a paraphyletic group of almost exclusively solitary Hymenoptera phylogenetically positioned between ant and bee, both of which include eusocial species. We report the chemosensory-related gene repertoire sizes of three apoid wasps: Ampulex compressa, Cerceris arenaria, and Psenulus fuscipennis. We annotated genes encoding odorant (ORs), gustatory, and ionotropic receptors and chemosensory soluble proteins and odorant-binding proteins in transcriptomes of chemosensory tissues of the above three species and in early draft genomes of two species, A. compressa and C. arenaria. Our analyses revealed that apoid wasps possess larger OR repertoires than any bee lineage, that the last common ancestor of Apoidea possessed a considerably larger OR repertoire (∼160) than previously estimated (73), and that the expansion of OR genes in eusocial bees was less extensive than previously assumed. Intriguingly, the evolution of pollen-collecting behavior in the stem lineage of bees was associated with a notable loss of OR gene diversity. Thus, our results support the view that herbivorous Hymenoptera tend to possess smaller OR repertoires than carnivorous, parasitoid, or kleptoparasitic species

Glossina chemoreceptor expression abundances by RNA-seq data in RPKM.

<p>(<b>A</b>) Expression abundances of <i>GmmORs</i>. There was no sufficient data to support profiles for GmmOR8, 11, 25, 31, and 39. GmmOR15 had abundant transcriptome data of 90.746% relative to sequence reads that mapped onto <i>GmmORs</i>. (<b>B</b>) Expression abundances of <i>GmmGRs</i>. Expression profiles for GmmGR6, GmmGR11 and GmmGR13 were not detected; GmmGR2 and GmmGR3 accounted for 40% and 36% respectively of the total transcripts considered for <i>GRs</i>.</p

Annotations of odorant and gustatory receptor genes in <i>G m. morsitans</i> and their homologs in <i>D. melanogaster</i>.

<p>GmmOR – <i>Glossina morsitans morsitans</i> ordorant receptor; GmmGR- <i>G. m. morsitans</i> gustatory receptor; TMM- Trans-membrane helices; GMOY – <i>Glossina morsitans</i> Yale strain; TMP_Or – Provisional odorant receptor ID; TMP_Gr – Provisional gustatory receptor ID; DmOr- <i>Drosophila melanogaster</i> odorant receptor; DmGR- <i>D. melanogaster</i> gustatory receptor;</p><p>*- longest alternative splice variant in locus OR5;</p>#<p>- pseudogene.</p

Annotated ORs and GRs in <i>G. m. morsitans</i> and other selected insect species.

<p>Figures in parentheses are numbers incomplete genes and or pseudogenes of the receptors.</p><p>*- in parentheses are alternatively spliced forms.</p

Phylogenetic analyses of ORs or GRs in <i>G. m. morsitans</i> and selected Diptera.

<p>(<b>A</b>) Maximum likelihood (ML) tree for GmmORs and DmelOrs; branches annotated blue is an expanded clade orthologous to DmelOr67d; purple branches is the clade orthologous to DmelOr45a; and green branches indicate the orco cluster. (<b>B</b>) Maximum likelihood tree for GmmGRs and DmelGRs. In both trees, blue labels are <i>D. melanogaster</i> receptors and red labels <i>G. m. morsitans</i> receptors (green labels are <i>An. gambiae</i> CO2 receptors). Phylogenetic cluster inferences were deduced using Maximum Likelihood approach with best fitting Wheelan And Goldman+Freq (WAG+F) model <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002663#pntd.0002663-Waterhouse1" target="_blank">[59]</a>. Evolutionary analyses were conducted using MEGA5 suite <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002663#pntd.0002663-Cole1" target="_blank">[60]</a>.</p

Inverse resource allocation between vision and olfaction across the genus Drosophila

Neural architecture may be shaped by selection, but is likely also constrained by development. Here, Keesey and colleagues find an inverse relationship between allocation towards visual and olfactory sensory systems across the genus Drosophila, which may reflect a developmental trade-off