D. simulans and D. melanogaster present two types of polymorphism in their cuticular hydrocarbon (HC) composition. Especially both sexes of D. simulans, and D. melanogaster males display 7-tricosene (7T) as the major compound type [7T]s and [7T]m, or 7-pentacosene (7P) [7P]s and [7P]m. D. melanogaster females display 7,11-heptacosadiene (7,11HD) as the major compound: [7,11HD]m, or 5,9-heptacosadiene (5,9HD): [5,9HD]m. The [7P]s, [7P]m and [5,9HD]m are mainly present in central Africa. A significant correlation was found between latitude and the proportion of compounds with 23 and 25 carbon atoms, especially 7T and 7P in both sexes of D. melanogaster. [7P]m type of D. melanogaster, characterized with an excess of C25 compounds, presents a higher resistance against desiccation than [7T]m type, where C23 compounds are more abundant. These differences can be correlated with calculated HC fusion temperatures. Moreover, increasing the breeding temperature from 18 to 29 degrees C induces in D. melanogaster males an increase in 25C compounds and a decrease in 23C compounds, but the opposite effect in D. simulans. A mathematical model of biosynthesis, based on kinetics of elongation and decarboxylation enzymes, suggests that a simple variation of the efficiency of an elongation enzyme may account for the differences observed between the [7T]m and [7P]m types of D. melanogaster and [7T]s and [7P]s types D. simulans. Finally on the basis of the geographical distribution of the HC types of both Drosophila species, an evolutionary dispersal pathway is proposed and discussed in relation to the environment and reproductive behavior.

The identification of genes with large effects on sexual isolation and speciation is an important link between classic evolutionary genetics and molecular biology. Few genes that affect sexual isolation and speciation have been identified, perhaps because many traits influencing sexual isolation are complex behaviors. Cuticular hydrocarbons (CHs) of species of the Drosophila melanogaster group play a large role in sexual isolation by functioning as contact pheromones influencing mate recognition. Some of the genes that play key roles in determining species-specific CHs have been identified. We have performed separate quantitative trait locus (QTL) analyses of 7-tricosene (7-T) and 7,11-heptacosadiene (7,11-HD), the two major female CHs differing between D. simulans and D. sechellia. We find that 40% of the phenotypic variance in each CH is associated with two to four chromosomal regions. A region on the right arm of chromosome 3 contains QTL that affect both traits, but other QTL are in distinct chromosomal regions. Epistatic interactions were detected between two pairs of QTL for 7,11-HD such that if either were homozygous for the D. simulans allele, the fly was similar to D. simulans in phenotype, with a low level of 7,11-HD. We discuss the location of these regions with regard to candidate genes for CH production, including those for desaturases.

The piggyBac transposable element was originally isolated from the cabbage looper moth, Trichoplusia ni, in the 1980s. Despite its early discovery and specificity compared to the other Class II elements, the diversity and evolution of this superfamily have been only partially analyzed. Two main types of elements can be distinguished: the piggyBac-like elements (PBLE) with terminal inverted repeats, untranslated region, and an open reading frame encoding a transposase, and the piggyBac-derived sequences (PGBD), containing a sequence derived from a piggyBac transposase, and which correspond to domesticated elements. To define the distribution, their structural diversity and phylogenetic relationships, analyses were conducted using known PBLE and PGBD sequences to scan databases. From this data mining, numerous new sequences were characterized (50 for PBLE and 396 for PGBD). Structural analyses suggest that four groups of PBLE can be defined according to the presence/absence of sub-terminal repeats. The transposase is characterized by highly variable catalytic domain and C-terminal region. There is no relationship between the structural groups and the phylogeny of these PBLE elements. The PGBD are clearly structured into nine main groups. A new group of domesticated elements is suspected in Neopterygii and the remaining eight previously described elements have been investigated in more detail. In all cases, these sequences are no longer transposable elements, the catalytic domain of the ancestral transposase is not always conserved, but they are under strong purifying selection. The phylogeny of both PBLE and PGBD suggests multiple and independent domestication events of PGBD from different PBLE ancestors.

BackgroundAlthough transposons have been identified in almost all organisms, genome-wide information on mariner elements in Aphididae remains unknown. Genomes of Acyrthosiphon pisum, Diuraphis noxia and Myzus persicae belonging to the Macrosiphini tribe, actually available in databases, have been investigated.ResultsA total of 22 lineages were identified. Classification and phylogenetic analysis indicated that they were subdivided into three monophyletic groups, each of them containing at least one putative complete sequence, and several non-autonomous sublineages corresponding to Miniature Inverted-Repeat Transposable Elements (MITE), probably generated by internal deletions. A high proportion of truncated and dead copies was also detected. The three clusters can be defined from their catalytic site: (i) mariner DD34D, including three subgroups of the irritans subfamily (Macrosiphinimar, Batmar-like elements and Dnomar-like elements); (ii) rosa DD41D, found in A. pisum and D. noxia; (iii) a new clade which differs from rosa through long TIRs and thus designated LTIR-like elements. Based on its catalytic domain, this new clade is subdivided into DD40D and DD41D subgroups. Compared to other Tc1/mariner superfamily sequences, rosa DD41D and LTIR DD40-41D seem more related to maT DD37D family.ConclusionOverall, our results reveal three clades belonging to the irritans subfamily, rosa and new LTIR-like elements. Data on structure and specific distribution of these transposable elements in the Macrosiphini tribe contribute to the understanding of their evolutionary history and to that of their hosts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3856-6) contains supplementary material, which is available to authorized users.

No abstract

Hawaiian Drosophila offer an excellent model for adaptive evolution. More than 500 species are reported in Hawaiian islands, and there is considerable diversity in behavior and morphology. Such diversity is mainly driven by sexual selection. In this study qualitative and quantitative chemical compositions of cuticular hydrocarbons (CHCs) in 138 flies belonging to 27 Hawaiian Drosophila species, picture-winged and non picture-winged, were analyzed regarding sexual dimorphism, differences in saturation, branching position, and lengths of CHCs. We found significant variation in the CHC patterns. In several subgroups, new species show decreases in unsaturated hydrocarbons, and gradual increases in branched compounds, monomethylalkanes and dimethylalkanes, not commonly found in Drosophila. Moreover, branching positions gradually shifted towards internal carbons, and chain lengths increased in the new species. The long-term evolution of CHCs in the light of the recent evolutionary migration and adaptation history of Hawaiian Drosophila species along the developing archipelago was discussed.

BackgroundThe Triatomine bug Rhodnius prolixus is a vector of Trypanosoma cruzi, which causes the Chagas disease in Latin America. R. prolixus can also transfer transposable elements horizontally across a wide range of species. We have taken advantage of the availability of the 700 Mbp complete genome sequence of R. prolixus to study the dynamics of invasion and persistence of transposable elements in this species.ResultsUsing both library-based and de novo methods of transposon detection, we found less than 6 % of transposable elements in the R. prolixus genome, a relatively low percentage compared to other insect genomes with a similar genome size. DNA transposons are surprisingly abundant and elements belonging to the mariner family are by far the most preponderant components of the mobile part of this genome with 11,015 mariner transposons that could be clustered in 89 groups (75 % of the mobilome). Our analysis allowed the detection of a new mariner clade in the R. prolixus genome, that we called nosferatis. We demonstrated that a large diversity of mariner elements invaded the genome and expanded successfully over time via three main processes. (i) several families experienced recent and massive expansion, for example an explosive burst of a single mariner family led to the generation of more than 8000 copies. These recent expansion events explain the unusual prevalence of mariner transposons in the R. prolixus genome. Other families expanded via older bursts of transposition demonstrating the long lasting permissibility of mariner transposons in the R. prolixus genome. (ii) Many non-autonomous families generated by internal deletions were also identified. Interestingly, two non autonomous families were generated by atypical recombinations (5' part replacement with 3' part). (iii) at least 10 cases of horizontal transfers were found, supporting the idea that host/vector relationships played a pivotal role in the transmission and subsequent persistence of transposable elements in this genome.ConclusionThese data provide a new insight into the evolution of transposons in the genomes of hematophagous insects and bring additional evidences that lateral exchanges of mobile genetics elements occur frequently in the R. prolixus genome.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2060-9) contains supplementary material, which is available to authorized users.

Background Mariner elements represent the most successful family of autonomous DNA transposons, being present in various plant and animal genomes, including humans. The introduction and co-evolution of mariners within host genomes imply a strict regulation of the transposon activity. Biochemical data accumulated during the past decade have led to a convergent picture of the transposition cycle of mariner elements, suggesting that mariner transposition does not rely on host-specific factors. This model does not account for differences of transposition efficiency in human cells between mariners. We thus wondered whether apparent similarities in transposition cycle could hide differences in the intrinsic parameters that control mariner transposition.Principal FindingsWe find that Mos1 transposase concentrations in excess to the Mos1 ends prevent the paired-end complex assembly. However, we observe that Mos1 transposition is not impaired by transposase high concentration, dismissing the idea that transposase over production plays an obligatory role in the down-regulation of mariner transposition. Our main finding is that the paired-end complex is formed in a cooperative way, regardless of the transposase concentration. We also show that an element framed by two identical ITRs (Inverted Terminal Repeats) is more efficient in driving transposition than an element framed by two different ITRs (i.e. the natural Mos1 copy), the latter being more sensitive to transposase concentration variations. Finally, we show that the current Mos1 ITRs correspond to the ancestral ones.ConclusionsWe provide new insights on intrinsic properties supporting the self-regulation of the Mos1 element. These properties (transposase specific activity, aggregation, ITR sequences, transposase concentration/transposon copy number ratio…) could have played a role in the dynamics of host-genomes invasion by Mos1, accounting (at least in part) for the current low copy number of Mos1 within host genomes.