The Insect Chemoreceptor Superfamily in Drosophila pseudoobscura: Molecular Evolution of Ecologically-Relevant Genes Over 25 Million Years

The insect chemoreceptor superfamily, consisting of the odorant receptor (Or) and gustatory receptor (Gr) families, exhibits patterns of evolution ranging from highly conserved proteins to lineage-specific gene subfamily expansions when compared across insect suborders and orders. Here their evolution across the timespan of 25 million years is examined which yield orthologous divergences ranging from 5–50%. They also reveal the beginnings of lineage-specific gene subfamilies as multiple duplications of particular gene lineages in either or both Drosophila melanogaster and D. pseudoobscura (Frolova and Astaurov) (Diptera: Drosophilidae). Gene losses and pseudogenes are similarly evident in both lineages, and even in closer comparisons of D. melanogaster with D. yakuba, leaving these species with roughly similar numbers of chemoreceptors despite considerable gene turnover. The large range of divergences and gene duplications provide abundant raw material for studies of structure and function in this novel superfamily, which contains proteins that evolved to bind specific ligands that mediate much of the ecology and mating behavior of insects

A Target Restricted Assembly Method (TRAM) for Phylogenomics

While next generation sequencing technology can produce sequences covering the entire genome, assembly and annotation are still prohibitive steps for many phylogenomics applications. Here we describe a method of Target Restricted Assembly (TRAM) of a single lane of Illumina sequences for genes of relevance to phylogeny reconstruction, i.e. single copy protein-coding genes. This method has the potential to produce a data set of hundreds of genes using only one Illumina lane per taxon

Evolution of the sugar receptors in insects

<p>Abstract</p> <p>Background</p> <p>Perception of sugars is an invaluable ability for insects which often derive quickly accessible energy from these molecules. A distinctive subfamily of eight proteins within the gustatory receptor (Gr) family has been identified as sugar receptors (SRs) in <it>Drosophila melanogaster </it>(Gr5a, Gr61a, and Gr64a-f). We examined the evolution of these SRs within the 12 available Drosophila genome sequences, as well as three mosquito, two moth, and beetle, bee, and wasp genome sequences.</p> <p>Results</p> <p>While most Drosophila species retain all eight genes, we find that the three Drosophila subgenus species have lost Gr64d, while <it>D. grimshawi </it>and the <it>D. pseudoobscura/persimilis </it>sibling species have also lost Gr5a function. The entire Gr64 gene complex was also duplicated in the <it>D. grimshawi </it>lineage, but only one potentially functional copy of each gene has been retained. The numbers of SRs range from two in the hymenopterans <it>Apis mellifera </it>and <it>Nasonia vitripennis </it>to 16 in the beetle <it>Tribolium castaneum</it>. An unusual aspect is the evolution of a novel exon from intronic sequence in an expanded set of four SRs in <it>Bombyx mori </it>(BmGr5-8), which appears to be the first example of such exonization in insects. Twelve intron gains and 63 losses are inferred within the SR family.</p> <p>Conclusion</p> <p>Examination of the SRs in these fly, mosquito, moth, beetle, and hymenopteran genome sequences reveals that they appear to have originated independently from single ancestral genes within the dipteran and coleopteran lineages, and two genes in the lepidopteran and hymenopteran lineages. The origin of the insect SRs will eventually be illuminated by additional basal insect and arthropod genome sequences.</p

The chemoreceptor genes of the waterflea Daphnia pulex: many Grs but no Ors

<p>Abstract</p> <p>Background</p> <p>Chemoreception is vitally important for all animals, yet little is known about the genetics of chemoreception in aquatic organisms. The keystone species <it>Daphnia pulex</it>, a well known crustacean, is the first aquatic invertebrate to have its genome sequenced. This has allowed us the initial investigation of chemoreceptor genes in an aquatic invertebrate, and to begin the study of chemoreceptor evolution across the arthropod phylum.</p> <p>Results</p> <p>We describe 58 Grs (gustatory receptors), belonging to the insect chemoreceptor superfamily, which were identified bioinformatically in the draft genome of the crustacean waterflea <it>Daphnia pulex</it>. No genes encoding proteins similar to the insect odorant receptors (Ors) were identified. These 58 Grs form 3 distinctive subfamilies of 37, 12, and 5 genes, as well as a highly divergent singleton (Gr58). In addition, Grs55–57 share distinctive amino acid motifs and cluster with the sugar receptors of insects, and may illuminate the origin of this distinctive subfamily. ESTs, tiling array, and PCR amplification results support 34 predicted gene models, and preliminary expression data comparing the sexes indicates potential female-biased expression for some genes.</p> <p>Conclusion</p> <p>This repertoire of 58 chemoreceptors presumably mediates the many chemoperception abilities of waterfleas. While it is always possible that the entire Or gene lineage was lost at some point in the history of <it>Daphnia pulex</it>, we think it more likely that the insect Or lineage is indeed a relatively recently expanded gene lineage concomitant with the evolution of terrestriality in the insects or their hexapod ancestors.</p

Evolution of the Gene Lineage Encoding the Carbon Dioxide Receptor in Insects

A heterodimer of the insect chemoreceptors Gr21a and Gr63a has been shown to be the carbon dioxide receptor in Drosophila melanogaster (Meigen) (Diptera: Drosophilidae). Comparison of the genes encoding these two proteins across the 12 available drosophilid fly genomes allows refined definition of their N-termini. These genes are highly conserved, along with a paralog of Gr21a, in the Anopheles gambiae, Aedes aegypti, and Culex pipiens mosquitoes, as well as in the silk moth Bombyx mori and the red flour beetle Tribolium castaneum. In the latter four species we name these three proteins Gr1, Gr2, and Gr3. Intron evolution within this distinctive three gene lineage is considerable, with at least 13 inferred gains and 39 losses. Surprisingly, this entire ancient gene lineage is absent from all other available more basal insect and related arthropod genomes, specifically the honey bee, parasitoid wasp, human louse, pea aphid, waterflea, and blacklegged tick genomes. At least two of these species can detect carbon dioxide, suggesting that they evolved other means to do so

Calculations of periodicity from H<i>α</i> profiles of Proxima Centauri

We investigate retrieval of the stellar rotation signal for Proxima Centauri. We make use of high-resolution spectra taken with UVES and HARPS of Proxima Centauri over a 13-yr period as well as photometric observations of Proxima Centauri from ASAS and HST. We measure the Hα equivalent width and Hα index, skewness and kurtosis and introduce a method that investigates the symmetry of the line, the peak ratio, which appears to return better results than the other measurements. Our investigations return a most significant period of 82.6 ± 0.1 days, confirming earlier photometric results and ruling out a more recent result of 116.6 days which we conclude to be an alias induced by the specific HARPS observation times. We conclude that whilst spectroscopic Hα measurements can be used for period recovery, in the case of Proxima Centauri the available photometric measurements are more reliable. We make 2D models of Proxima Centauri to generate simulated Hα, finding that reasonable distributions of plage and chromospheric features are able to reproduce the equivalent width variations in observed data and recover the rotation period, including after the addition of simulated noise and flares. However the 2D models used fail to generate the observed variety of line shapes measured by the peak ratio. We conclude that only 3D models which incorporate vertical motions in the chromosphere can achieve this

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

The Application and Performance of Single Nucleotide Polymorphism Markers for Population Genetic Analyses of Lepidoptera

Microsatellite markers are difficult to apply within lepidopteran studies due to the lack of locus-specific PCR amplification and the high proportion of “null” alleles, such that erroneous estimations of population genetic parameters often result. Herein single nucleotide polymorphism (SNP) markers are developed from Ostrinia nubilalis (Lepidoptera: Crambidae) using next generation expressed sequence tag (EST) data. A total of 2742 SNPs were predicted within a reference assembly of 7414 EST contigs, and a subset of 763 were incorporated into 24 multiplex PCR reactions. To validate this pipeline, 5 European and North American sample sites were genotyped at 178 SNP loci, which indicated 84 (47.2%) were in Hardy–Weinberg equilibrium. Locus-by-locus FST, analysis of molecular variance, and STRUCTURE analyses indicate significant genetic differentiation may exist between European and North American O. nubilalis. The observed genetic diversity was significantly lower among European sites, which may result from genetic drift, natural selection, a genetic bottleneck, or ascertainment bias due to North American origin of EST sequence data. SNPs are an abundant source of mutation data for molecular genetic marker development in non-model species, with shared ancestral SNPs showing application within closely related species. These markers offer advantages over microsatellite markers for genetic and genomic analyses of Lepidoptera, but the source of mutation data may affect the estimation of population parameters and likely need to be considered in the interpretation of empirical data

Changes in the Peripheral Chemosensory System Drive Adaptive Shifts in Food Preferences in Insects

A key challenge in understanding the evolution of animal behaviors is to identify cellular and molecular mechanisms that underlie the evolution of adaptive traits and behaviors in polymorphic populations under local selection pressures. Despite recent advances in fish, mice, and insects, there are still only a few compelling examples of major genes and cellular mechanisms associated with complex behavioral changes. Shifts in food or host preferences in insects, accompanied by changes in the peripheral chemosensory system, offer some of the best examples of adaptive behavioral evolution. A remarkable example is the German cockroach, Blattella germanica, a major indoor pest with a highly diverse omnivorous diet. Strong and persistent selection pressure with toxic-baits has induced rapid evolution of behavioral resistance in multiple cockroach populations. While typical cockroaches detect and accept the sugar glucose as a feeding-stimulant, behaviorally resistant cockroaches avoid eating glucose-containing toxic baits by sensing glucose as a deterrent. We review the peripheral gustatory neural mechanisms of glucose-aversion and discuss how the rapid emergence of taste polymorphisms can impede pest control efforts and affect foraging and mate-choice in adapted cockroach populations

8‐Year‐Old Boy with Progressive Headache

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99694/1/bpa12074.pd