Diverse mobilome of Dichotomius (Luederwaldtinia) schiffleri (Coleoptera: Scarabaeidae) reveals long-range horizontal transfer events of DNA transposons.

Transposable elements (TEs) are mobile DNA sequences that are able to move from one genomic location to another. These selfish elements are known as genomic parasites, since they hijack the host molecular machinery to generate new copies of themselves. The mobilization of TEs can be seen as a natural mutagen because new TE copies can insert into different loci and impact host genomic structure through different mechanisms. Although our knowledge about TEs is improving with new genomes available, there is still very limited data about the mobilome of species from the Coleoptera order, the most diverse order of insects, including species from the Scarabaeidae family. Therefore, the main goal of this study was to characterize the mobilome of D. (Luederwaldtinia) schiffleri, based on low-coverage genome sequencing, and reconstruct their evolutionary history. We used a combination of four different approaches for TE characterization and maximum likelihood phylogenetic analysis to study their evolution. We found a large and diverse mobilome composed of 38 TE superfamilies, 20 DNA transposon and 18 retrotransposons, accounting for 21% of the genome. Moreover, we found a number of incongruences between the TE and host phylogenetic trees in three DNA transposon TE superfamilies, which represents five TE families, suggesting possible horizontal transfer events between highly divergent taxa. In summary, we found an abundant and diverse mobilome and a number of horizontal transfer events that have shaped the evolutionary history of this species.

Wolbachia from Drosophila incompta: just a hitchhiker shared by Drosophila in the New and Old World?

Wolbachia are intracellular endosymbionts that infect arthropods and filarial nematodes, occasionally causing a wide variety of modifications in host biology, such as male-killing and cytoplasmic incompatibility (CI), amongst others. This study assembled draft genomes for Wolbachia infecting Drosophila incompta, a species that uses flowers as exclusive breeding and feeding sites, in two distinct Brazilian populations. The absence of four genes involved in CI from this genome, together with literature reports of low frequencies of infected flies in wild populations that contain high mitogenome polymorphism, suggests that this bacterium does not induce CI in D. incompta. Phylogenomic analysis placed Wolbachia infecting D. incompta as closely related to the wMel strain which received such name since it was originally detected in Drosophila melanogaster. In addition, phylogenetic analysis using the Wolbachia surface protein gene and five genes used for multilocus sequence typing of Wolbachia found infecting Drosophila and other arthropod species of Old and New World displayed a complex evolutionary scenario involving recent horizontal transfer bursts in all major clades of Wolbachia pipens belonging to the supergroup A in both geographical regions.

Oxidative stress markers in fish (Astyanax sp. and Danio rerio) exposed to urban and agricultural effluents in the Brazilian Pampa biome.

Aquatic ecosystems are under constant risk due to industrial, agricultural, and urban activities, compromising water quality and preservation of aquatic biota. The assessment of toxicological impacts caused by pollutants to aquatic environment using biomarker measurements in fish can provide reliable data to estimate sublethal effects posed by chemicals in contaminated areas. In this study, fish (Astyanax sp. and Danio rerio) exposed to agricultural and urban effluents at the Vacacaí River, Brazil, were tested for potential signs of aquatic contamination. This river comprehends one of the main watercourses of the Brazilian Pampa, a biome with a large biodiversity that has been neglected in terms of environmental and social-economic development. Sites S1 and S2 were chosen by their proximity to crops and wastewater discharge points, while reference site was located upstream of S1 and S2, in an apparently non-degraded area. Fish muscle and brain tissues were processed for determination of acetylcholinesterase as well as oxidative stress-related biomarkers. The results showed signs of environmental contamination, hallmarked by significant changes in cholinesterase activity, expression of metallothionein, antioxidant enzymes, glutathione levels, and activation of antioxidant/cell stress response signaling pathways in fish exposed to contaminated sites when compared to reference. Based on these results, it is evidenced that urban and agricultural activities are posing risk to the environmental quality of water resources at the studied area. It is also demonstrated that cell stress biomarkers may serve as important tools for biomonitoring and development of risk assessment protocols in the Pampa biome.

Characterization of the complete mitochondrial genome of flower-breeding Drosophila incompta (Diptera, Drosophilidae).

Drosophila incompta belongs to the flavopilosa group of Drosophila, and has a restricted ecology, being adapted to flowers of Cestrum as feeding and oviposition sites. We sequenced, assembled, and characterized the complete mitochondrial genome (mtDNA) of D. incompta. In addition, we performed phylogenomic and polymorphism analyses to assess evolutionary diversification of this species. Our results suggest that this genome is syntenic with the other published mtDNA of Drosophila. This molecule contains 15,641 bp and encompasses two rRNA, 22 tRNA and 13 protein-coding genes. Regarding nucleotide composition, we found a high A-T bias (76.6 %). The recovered phylogenies indicate D. incompta in the virilis-repleta radiation, as sister to the virilis or repleta groups. The most interesting result is the high degree of polymorphism found throughout the D. incompta mitogenome, revealing pronounced intrapopulational variation. Furthermore, intraspecific nucleotide diversity levels varied between different regions of the genome, thus allowing the use of different mitochondrial molecular markers for analysis of population structure of this species.

The mariner transposable element in natural populations of Drosophila simulans.

In cosmopolitan species, geographical variations in copy number and/or level of transposition activity have been observed for several transposable elements (TEs). Environment, history and population structure can contribute to such variation in ways that are difficult to tease apart. For the mariner element, previous studies of the geographic variation of its somatic activity in natural populations of Drosophila simulans have shown contradictory results (latitudinal clines of divergent orientations or no apparent structure). To try and resolve these inconsistencies, we gathered all available data on the mariner somatic activity of worldwide natural populations. This includes previously published results by different groups and also new data. The correlations between the level of activity and several geoclimatic factors were tested. Although no general effect of temperature was found, a relationship with the invasion history was detected. It was also shown that recent invasive populations have a higher level of activity than the putative ancestral ones. Our results strongly suggest that variability of the mariner somatic activity among natural populations of D. simulans is mainly due to populational and historical factors probably related to the recent world colonization of this species. Indeed, this activity is correlated to the main route out of Africa (the Nile route) and the recent colonization of continents such as Australia and South America.