Canavalia ensiformis lectin induced oxidative stress mediate both toxicity and genotoxicity in Drosophila melanogaster.

Mannose/glucose-binding lectin from Canavalia ensiformis seeds (Concanavalin A - ConA) has several biological applications, such as mitogenic and antitumor activity. However, most of the mechanisms involved in the in vivo toxicity of ConA are not well known. In this study, the Drosophila melanogaster model was used to assess the toxicity and genotoxicity of different concentrations of native ConA (4.4, 17.5 and 70 µg/mL) in inhibited and denatured forms of ConA. The data show that native ConA affected: the survival, in the order of 30.6 %, and the locomotor performance of the flies; reduced cell viability to levels below 50 % (4.4 and 17.5 µg/mL); reduced nitric oxide levels; caused lipid peroxidation and increased protein and non-protein thiol content. In the Comet assay, native ConA (17.5 e 70 µg/mL) caused DNA damage higher than 50 %. In contrast, treatments with inhibited and denatured ConA did not affect oxidative stress markers and did not cause DNA damage. We believe that protein-carbohydrate interactions between ConA and carbohydrates of the plasma membrane are probably the major events involved in these activities, suggesting that native ConA activates mechanisms that induce oxidative stress and consequently DNA damage.

Evolution of DNMT2 in drosophilids: Evidence for positive and purifying selection and insights into new protein (pathways) interactions.

The DNA methyltransferase 2 (DNMT2) protein is the most conserved member of the DNA methyltransferase family. Nevertheless, its substrate specificity is still controversial and elusive. The genomic role and determinants of DNA methylation are poorly understood in invertebrates, and several mechanisms and associations are suggested. In Drosophila, the only known DNMT gene is Dnmt2. Here we present our findings from a wide search for Dnmt2 homologs in 68 species of Drosophilidae. We investigated its molecular evolution, and in our phylogenetic analyses the main clades of Drosophilidae species were recovered. We tested whether the Dnmt2 has evolved neutrally or under positive selection along the subgenera Drosophila and Sophophora and investigated positive selection in relation to several physicochemical properties. Despite of a major selective constraint on Dnmt2, we detected six sites under positive selection. Regarding the DNMT2 protein, 12 sites under positive-destabilizing selection were found, which suggests a selection that favors structural and functional shifts in the protein. The search for new potential protein partners with DNMT2 revealed 15 proteins with high evolutionary rate covariation (ERC), indicating a plurality of DNMT2 functions in different pathways. These events might represent signs of molecular adaptation, with molecular peculiarities arising from the diversity of evolutionary histories experienced by drosophilids.

Evolution of DNMT2 in drosophilids: Evidence for positive and purifying selection and insights into new protein (pathways) interactions

Abstract The DNA methyltransferase 2 (DNMT2) protein is the most conserved member of the DNA methyltransferase family. Nevertheless, its substrate specificity is still controversial and elusive. The genomic role and determinants of DNA methylation are poorly understood in invertebrates, and several mechanisms and associations are suggested. In Drosophila, the only known DNMT gene is Dnmt2. Here we present our findings from a wide search for Dnmt2 homologs in 68 species of Drosophilidae. We investigated its molecular evolution, and in our phylogenetic analyses the main clades of Drosophilidae species were recovered. We tested whether the Dnmt2 has evolved neutrally or under positive selection along the subgenera Drosophila and Sophophora and investigated positive selection in relation to several physicochemical properties. Despite of a major selective constraint on Dnmt2, we detected six sites under positive selection. Regarding the DNMT2 protein, 12 sites under positive-destabilizing selection were found, which suggests a selection that favors structural and functional shifts in the protein. The search for new potential protein partners with DNMT2 revealed 15 proteins with high evolutionary rate covariation (ERC), indicating a plurality of DNMT2 functions in different pathways. These events might represent signs of molecular adaptation, with molecular peculiarities arising from the diversity of evolutionary histories experienced by drosophilids.

High diversity of Drosophilidae (Insecta, Diptera) in the Pampas Biome of South America, with descriptions of new Rhinoleucophenga species.

In the last three decades some faunal surveys of Drosophilidae have been done in several environments in the Neotropical region, especially in Brazil. But approximately 30 to 50% of the drosophilids in Brazil have not yet been described, and the degradation of some biomes causes a profound loss of species diversity, as well as the loss of information about the present structureof their communities. This is the situation with the pampas biome, which covers southernmost Brazil, all of Uruguay, and the central region of eastern Argentina. For the present study, seasonal collections were made in a natural area of pampas within the limits of the municipality of Bossoroca in the state of Rio Grande do Sul, Brazil (28°45'01"S 54°56'55"W), from April 2011 to April 2012. A total of 7,164 drosophilids of 51 species were collected, comprising 36 species belonging to Drosophila Fallén, ten of Rhinoleucophenga Hendel, two of Amiota Loew, two of Zygothrica Wiedemann and one of Zaprionus Coquillett. Some species were recorded for the first time in pampas: Drosophila briegeri Pavan & Breuer, D. fuscolineata Duda, Rhinoleucophenga obesa (Loew), R. punctulata Duda, R. subradiata Duda and Zygothrica orbitalis (Sturtevant). Furthermore, three new species of genus Rhinoleucophenga were described: R. pampeana sp. nov., R. missionera sp. nov. and R. sulina sp. nov. A dichotomous key is given for the Rhinoleucophenga species recorded in pampas. An intensive literature search is reviewed of drosophilid species recorded in pampas of Brazil, Uruguay and Argentina, including taxonomic, genetic, evolutionary, and ecological studies. Despite Brazilian pampas being the richest when compared with Uruguay and Argentina, the three countries presented the same problem: huge areas with a barely surveyed Drosophilidae fauna. The combination of this information and the knowledge of the current state of preservation of pampas stress the necessity and importance of creating new conservation areas to preserve the natural biodiversity of pampas.

Wolbachia pipientis is associated with different mitochondrial haplotypes in natural populations of Drosophila willistoni.

The prevalence of the endosymbiont Wolbachia pipientis and its effects on mitochondrial genetic diversity were analyzed in natural populations of Drosophila willistoni, a neotropical species recently infected. Total infection rate was 55% and no evidence was found that the Wolbachia infection decreased the diversity of mtDNA. Wolbachia was seen to be associated with different mitochondria, suggesting multiple horizontal transmission events and/or transmission paternal leakage of mitochondrial and/or Wolbachia. These hypotheses are evaluated in the context of the present study and other research.

Characterization of mitochondrial control region, two intergenic spacers and tRNAs of Zaprionus indianus (Diptera: Drosophilidae).

The control region in insects is the major noncoding region in animal mitochondrial DNA (mtDNA), and is responsible for a large part of the variation in the DNA sequence and size of the genome of this organelle. In this study, the mtDNA control region, two intergenic spacers and tRNA genes of a Zaprionus indianus strain were cloned, sequenced and compared with other Drosophila species. The overall A+T content in the Z. indianus control region is 94.3%, and a comparison with other Drosophila species demonstrated that the most conserved region appears to be the 420 base pairs nearest to the tRNA(ile), similar to the findings of other authors. We also describe conserved sequence blocks, including a poly-T involved in the replication process of Drosophila mtDNA; a putative secondary structure also involved in the replication process and repeated sequences. tRNA(ile) sequence demonstrated the greatest variability when the tRNA sequences of species were compared.