Drosophilidae Research Articles

Domesticated retroviral GAG gene in Drosophila: New functions for an old gene

The domestication of foreign genes is a powerful mechanism for new gene formation and genome evolution. It is known that domesticated retroviral gag genes in mammals not only take part in protecting against viral infection but also control cell division, apoptosis, function of the placenta, and other biological processes. In this study, we focused on the domesticated retroviral gag gene homolog (Grp) in the Drosophila melanogaster genome. According to the results of a bioinformatic analysis, the Grp gene product is primarily under purifying selection in Drosophilidae family. The Grp protein has been shown to be transmembrane. The Grp gene is expressed at the adult stage of D. melanogaster in gender-specific and tissue-specific manner. Also the Grp gene expression is increased in response to the gypsy retrovirus. A function of the protein as a component of the endosomic membrane is considered.

ELECTROPHYSIOLOGICAL RESPONSES OF LABELLAR CHEMOSENSILLA OF A WILD TYPE AND A SALT TOLERANT MUTANT (LOT-94) OF DROSOPHILA MELANOGASTER (MEIGEN) (DIPTERA DROSOPHILIDAE)

SUMMARY The labellar chemosensilla of a wild type strain (QA) and a «salt tolerant» mutant (Lot-94) of Drosophila melanogaster (Meigen) (Diptera Drosophilidae) were tested electrophysiologically in order to ascertain whether the altered feeding reflex response of the mutant is related to differences at the chemoreceptor or within the CNS. Four chemosensory units were identified in each chemosensillum of both strains: one unit was most sensitive to NaCl (M1) and a different one to sucrose (M2). The analysis of the spike frequencies of the M1 and M2 units in QA and Lot-94 flies indicates that the altered feeding behaviour observed in the mutant probably depends on variations within the CNS.

Evolution of Three Parent Genes and Their Retrogene Copies inDrosophilaSpecies

Retrogenes form a class of gene duplicate lacking the regulatory sequences found outside of the mRNA-coding regions of the parent gene. It is not clear how a retrogene's lack of parental regulatory sequences affects the evolution of the gene pair. To explore the evolution of parent genes and retrogenes, we investigated three such gene pairs in the family Drosophilidae; in Drosophila melanogaster, these gene pairs are CG8331 and CG4960, CG17734 and CG11825, and Sep2 and Sep5. We investigated the embryonic expression patterns of these gene pairs across multiple Drosophila species. Expression patterns of the parent genes and their single copy orthologs are relatively conserved across species, whether or not a species has a retrogene copy, although there is some variation in CG8331 and CG17734. In contrast, expression patterns of the retrogene orthologs have diversified. We used the genome sequences of 20 Drosophila species to investigate coding sequence evolution. The coding sequences of the three gene pairs appear to be evolving predominantly under negative selection; however, the parent genes and retrogenes show some distinct differences in amino acid sequence. Therefore, in general, retrogene expression patterns and coding sequences are distinct compared to their parents and, in some cases, retrogene expression patterns diversify.

Phylogenetic classification of the Drosophilidae Rondani (Diptera): the role of morphology in the postgenomic era

Molecular sequences now overwhelm morphology in phylogenetic inference. Nonetheless, most molecular studies are conducted on a limited number of taxa, as DNA rarely can be analysed from old museum types or fossils. During the last 20 years, more than 150 molecular studies have challenged the current phylogenetic classification of the family Drosophilidae Rondani based on morphological characters. Most studies concerned a single genus, Drosophila Fallén, and included only few representative species from 17 out of the 78 genera of the family. Therefore, these molecular studies were unable to provide an alternative classification scheme. A supermatrix analysis of seven nuclear and one mitochondrial genes (8248 bp) for 33 genera was conducted using outgroups from one calyptrate and four ephydroid families. The Bayesian phylogeny was consistent with previous molecular studies including whole genome sequences and divided the Drosophilidae into four monophyletic clades. Morphological characters, mostly male genitalia, then were compared thoroughly between the four clades and homologous character states were identified. These states were then checked for 70 genera and a revised phylogenetic, family‐group classification for the Drosophilidae is proposed. Two genera –Cladochaeta Coquillett and Diathoneura Duda – of the tribe Cladochaetini Grimaldi are transferred to the family Ephydridae. The Drosophilidae is divided into two subfamilies: Steganinae Hendel (30 genera) and Drosophilinae Rondani (43 genera). A further two genera, Apacrochaeta Duda and Sphyrnoceps de Meijere, are incertae sedis, and Palmophila Grimaldi, is synonymized with Drosophilasyn.n. The Drosophilinae is subdivided into two tribes: the re‐elevated Colocasiomyini Okada (nine genera) and Drosophilini Okada. The paraphyly of the genus Drosophila was not resolved to avoid affecting the binomina of important laboratory model species; however, its subgeneric classification was revised in light of molecular and morphological data. Three subgenera, namely Chusqueophila Brncic, Phloridosa Sturtevant and Psilodorha Okada, were synonymized with the subgenus Drosophila (Drosophila) Fallén syns.n. Among the 45 species groups and 5 species complexes of Drosophila (Drosophila), 22 groups and 1 complex were transferred to the subgenus Drosophila (Siphlodora) Patterson & Mainland and 6 groups, 2 species subgroups and 3 complexes are considered incertae sedis within the genus Drosophila. Different morphological characters provide different signals at different phylogenetic scales: thoracic characters (wing venation and presternal shape) discriminate families; grasping and erection‐related characters discriminate subfamilies to tribes; whereas phallic paraphyses, i.e. auxiliary intromittent organs, discriminate genera and Drosophila subgenera. The study shows the necessity of analysing morphological characters within a molecular phylogenetic framework to translate molecular phylogenies into taxonomically‐comprehensive classifications.

Spermatogenesis of Zaprionus indianus and Zaprionus sepsoides (Diptera, Drosophilidae): Cytochemical, structural and ultrastructural characterization.

Zaprionus indianus is a drosophilid native to the Afrotropical region that has colonized South America and exhibits a wide geographical distribution. In contrast, Z. sepsoides is restricted to certain African regions. The two species differ in the size of their testes, which are larger in Z. indianus than in Z. sepsoides. To better understand the biology and the degree of differentiation of these species, the current study evaluated spermatogenesis in males of different ages by conventional staining techniques and ultrastructural analysis. Spermatogenesis and the ultrastructure of spermatozoa were similar in the two species, and the diploid number was confirmed to be 2n = 12. A greater number of spermatozoa were observed in young Z. indianus (1–3 days old) compared to Z. sepsoides males, which showed a higher frequency of cells at the early stages of spermatogenesis. The head of the sperm was strongly marked by silver staining, lacto-acetic orcein and the Feulgen reaction; the P.A.S. reaction revealed glycogen granules in the testes of both species. Both species presented similar arrangement of microtubules (9+9+2), two mitochondrial derivatives of different size and 64 spermatozoa per bundle. Such similarity within the genus Zaprionus with other species of Drosophila, indicates that these structures are conserved in the family Drosophilidae. The differences observed the number and frequency of sperm cells in the early stages of spermatogenesis, between the young males of Z. indianus and Z. sepsoides, are features that may interfere with reproductive success and be related to the invasive potential of Z. indianus.

First laboratory culture ofPhortica variegata(Diptera, Steganinae), a vector ofThelazia callipaeda

[Extract] The family Drosophilidae includes ~4,500 species in the two subfamilies Drosophilinae and Steganinae that are generally known as fruit flies or pomace flies because of their habit of feeding and growing on fermenting fruit. Within the Drosophilinae, Drosophila species are among the best characterized model organisms in genetic and genomic research. Conversely, knowledge of species ranked within the Steganinae is limited to a few morphological, taxonomic, and systematic investigations of selected members and information of the biology and ecology of most species is scarce. Over the past decade, fruit flies of the genus Phortica have been the subject of intense investigations aimed at identifying the arthropod vector and intermediate host of Thelazia spp. eyeworms (Otranto et al. 2003, 2005, 2006a, 2006b, Dorchies et al. 2007, Roggero et al. 2010). In particular, while Phortica okadai (Maca, 1977), Phortica magna (Okada 1968), and Amiota nagatai Okada, 1971 are vectors of Thelazia spp. in Asian countries (Kamakura et al. 1998), Phortica variegata (Fallen 1823) has been demonstrated, under both experimental (Otranto et al. 2005) and natural conditions (Otranto et al. 2006b), to harbor larvae of Thelazia callipaeda Railliet and Henry 1910 eyeworm nematodes in Europe. Phortica spp. differ remarkably from other fruit flies in that they are known to feed not only on decaying fruit and slime fluxes, but also on lachrymal secretions of animals and humans (Bachli et al. 2004). When feeding on the conjunctiva of vertebrates infested with T. callipaeda, P. variegata ingests the first-stage larvae released by adult female nematodes; within the body cavities of the arthropod vector, these larvae develop to second-stage larvae and, subsequently, to infective third-stage larvae which reach the proboscis of the fly and are invade the conjunctival sac of a new, receptive host (reviewed by Otranto et al. 2003). While both adult female and male P. variegata have been shown to harbour larvae of T. callipaeda under experimental settings (Otranto et al. 2005), only the latter gender has been demonstrated to act as a vector of this parasitic nematode under natural conditions (Otranto et al. 2006b, reviewed by Otranto et al. 2008a). The biological bases of this host-parasite relationship are still unclear.

Pupation Site Selection in Four Drosophilid Species: Aggregation and Contact

This study of pupation site selection was undertaken to assess the frequency and orientation of pupae making physical contact in four sympatric species in the family Drosophilidae: Drosophila melanogaster, D. simulans, D. funebris, and Zaprionus tuberculatus. Pupation behavior was assayed in a vial containing a small food cup. Using nearest-neighbor analysis, we found that pupae were aggregated. Furthermore, the frequency of contact between pupae was far greater than could be explained by chance, in all four species. In the three species of Drosophila, about a third of the contacts were between intimately paired pupae whose long axes were parallel; we call this arrangement synapsis. In Z. tuberculatus, most pupal contacts were unoriented. When D. melanogaster larvae were reared with each of the other species, heterospecific pupal contact, including synapsis, occurred. Our discovery of pupal contact in several drosophilids expands the known repertory of social behavior in this family.

Phylogenetic relationships between Sophophora and Lordiphosa, with proposition of a hypothesis on the vicariant divergences of tropical lineages between the Old and New Worlds in the family Drosophilidae

Despite many studies on the phylogeny of the subgenus Sophophora, its monophyly has not been established, especially in relation to its putative relative, the genus Lordiphosa. We analyzed their phylogenetic relationships using DNA sequence data of two mitochondrial genes ( ND2 and COII) and two nuclear genes ( Adh and 28SrRNA). In constructing phylogenetic trees, we accounted for the problem of among-taxa nucleotide compositional heterogeneity, and took a sequence-partitioning approach to allow multiple substitution models for nucleotide sequences that have evolved under different evolutionary processes, particularly developing a novel, sequence-partitioning procedure for Neighbor Joining (NJ) tree construction. Trees constructed by different methods showed an almost identical and strongly supported topology in which Sophophora was paraphyletic: Lordiphosa was placed as the sister to the Neotropical Sophophora consisting of the saltans and willistoni groups, and Sophophora was divided into the clade of Lordiphosa + Neotropical Sophophora and the clade of the obscura + melanogaster groups. Based on the estimated time, 45.9 Mya, of divergence between the Old World Lordiphosa and the Neotropical Sophophora and evidence from paleontology, paleo-geography and -climatology, we propose a hypothesis that this vicariant divergence should have occurred when the North Atlantic Land Bridge between Europe and North America broke in the middle Eocene Epoch.

Evidence for evolutionary constraints in Drosophila metal biology

Mutations in single Drosophila melanogaster genes can alter total body metal accumulation. We therefore asked whether evolutionary constraints maintain biologically abundant metal ions (iron, copper, manganese and zinc) to similar concentrations in different species of Drosophilidae, or whether metal homeostasis is a highly adaptable trait as shown previously for triglyceride and glycogen storage. To avoid dietary influences, only species able to grow and reproduce on a standard laboratory medium were selected for analysis. Flame atomic absorption spectrometry was used to determine metal content in 5-days-old adult flies. Overall, the data suggest that the metallome of the nine species tested is well conserved. Meaningful average values for the Drosophilidae family are presented. Few statistically significant differences were noted for copper, manganese and zinc between species. In contrast, Drosophila erecta and Drosophila virilis showed a 50% increase above average and a 30% decrease below average in iron concentrations, respectively. The changes in total body iron content correlated with altered iron storage in intestinal ferritin stores of these species. Hence, the variability in iron content could be accounted for by a corresponding adaptation in iron storage regulation. We suggest that the relative expression of the multitude of metalloenzymes and other metal-binding proteins remains overall similar between species and likely determines relative metal abundances in the organism. The availability of a complete and annotated genome sequence of different Drosophila species presents opportunities to study the evolution of metal homeostasis in closely related organisms that have evolved separately for millions or dozens of million years.

Introducing <i>Asobara persimilis</i> for control of <i>Scaptomyza flava</i> in South Island brassica crops

Scaptomyza flava (Diptera Drosophilidae) known as European leaf miner has recently been identified as the pest species causing major damage to seed and other brassica crops grown in the South Island This pest is particularly damaging to hybrid Asian brassica seed crops but is also a major pest of seedlings of radish turnip and broccoli plants A larval/pupal parasitoid Asobara persimilis (Hymenoptera Braconidae) is an effective natural enemy of S flava at Pukekohe at certain times of the year A project funded by MAF Sustainable Farming Fund involves massrearing the parasitoids in Auckland and releasing them in unsprayed brassica crops in Canterbury and North Otago A total of 6550 pupae and 760 emerged adults were released over fortnightly periods at 46 sites from October 2010 to April 2011 The pupae included about 80 parasitised pupae and 20 that were unparasitised as a source of hosts for emerging parasitoids Overwintering surveys and further releases are planned for 2011/12 to try and establish this natural enemy as part of the ongoing development of IPM tools for seed forage and vegetable brassica crops grown in the South Island

Spatio-temporal Distribution of Drosophilids: A Study at Jnanabharathi Campus, Bangalore, Karnataka, India

Though studies associated with the geographic distribution of Drosophilidae in India have taken rapid strides in last few years, only a cursory survey has been undertaken in certain areas, whereas a vast area of the Indian subcontinent still awaits exploration. In view of this, an attempt has been made to record the Drosophilid fauna of Jnanabharathi habitat, which is a completely virgin field, to explore with a view to furnish a spatio-temporal distribution pattern of Drosophilid species. The present study has revealed that species diversity has enriched in undisturbed region where human habitat is poor. On the other hand, the diversity and distribution of the Drosophilids have been affected enormously where human habitat is frequently sensed. In addition to this seasonally related environmental factors have a direct or indirect effect on the population density and distribution pattern of Drosophila in space and time. Key words: Drosophila fauna, biodiversity, distribution pattern, spatial, temperature.

Drosofilídeos e seus himenópteros parasitoides em coffea arabica L

The objective of this study was to evaluate the occurrence of Drosophilidae and their parasitoids in coffee fruits in Cravinhos, SP, Brazil. The fruits were collected directly from the tree, and a portion was exposed under the canopy. Fifty-nine drosophilid pupae were collected in all, of which 31 adults (including two Ganaspis exemplars) emerged. The survival rate of all pupae was 49.2%. Thirty-five drosopholid pupae were obtained from the fruit trees, 24 of which later emerged, three different species: Zaprionus indianus Gupta, Drosophila nebulosa Sturtevant and D. simulans Sturtevant. From the fruits under the canopy of plants were obtained 24 pupae of four different species: Z. indianus, D. cardini Sturtevant, D. immigrans Sturtevant and D. willistoni Sturtevant. The emergence of two Ganaspis sp. (Hymenoptera: Figitidae) examples, with a parasitism rate of 8.3%, was also observed. Half of the drosophilids collected are introduced species and represented 79% of the adults emerged. Associations between Z. indianus, D. cardini, D. immigrans, D. nebulosa, D. simulans and D. willistoni and the coffee crop are reported herein.

An analysis of a Drosophilidae community in Central Chile during a three years period

Monthly collections of Drosophilidae during a three years period, at a small area near Santiago, Chile, were analized by quantitative methods. The diversity analysis, the index of evenness and cluster analysis of the samples and species in time, shows that the community structure changes drastically through the year and, that each species has a clear seasonal pattern. Analyses of the niche breadths for each of the species indicate that the most common species (these are 8 out of the 17 species collected) are all most clear generalists, whereas the remaining 9 species appear rather narrow with regard to seasonality. The analyses of niche overlap revealed that there is a strong tendency for association between certain species. The recently introduced palearctic species D. subobscura tends to be more closely associated to the native species such as D. pavani and the scaptomizids, than to the cosmopolitan species, such as D. simulans and D. melanogaster. Zusammenfassung Analyse einer Drosophila-Gemeinschaft an einem Standort in Zentral-Chile uber einen Zeitraum von drei Jahren Monatliche Drosophila-Fange uber einen Zeitraum von drei Jahren an einem Standort bei Santiago in Chile wurden mit quantitativen Methoden analysiert. Die Diversitatsanalyse, der Index fur Gleich-formigkeit (eveness) und die Clusteranalyse der Stichproben bzw. der Artenzusammensetzung in der Zeit zeigen, das sich die Struktur des Artenspektrums uber das Jahr hinweg drastisch veradert und das jede Art ein deutliches Jahreszeiten-Muster hat. Die Analysen uber die Nischenbreiten fur jede der Arten weisen darauf hin, das die haufigsten Arten (das sind 8 der 17 gefangenen Arten) in allen Fallen allgemeine Generalisten sind, wahrend die verbleibenden 9 Arten durch ein ziemlich kurzes jahreszeitliches Auftreten gekennzeichnet sind. Die Analysen der Nischenuberlappungen ergeben, das es eine strenge Tendenz fur eine Assoziation zwischen bestimmten Arten gibt. Die est vor kurzem eingeschleppte palaarktische Art D. subobscura tendiert mehr dam, gemeinsam mit den endemischen Arten, wie D. pavani und den Scaptomyciden, hufzutreten als mit den kosmopoliten Arten, wie D. simulans und D. melanogaster.

Variation at the α-Gpdh locus of drosophilids

Variability at the α-Gpdh locus of drosophilids was studied by screening the enzymes (α-Gpdh-1) coded by it in 65 species with a variety of techniques. Only four out of these 65 species can be considered to be polymorphic with regard to the α-Gpdh-1 enzyme. Other species are monomorphic and in many cases even for the same morph. The total number of prevalent enzyme morphs in the species studied was observed to be 24, which indicates an unexpectedly low polymorphism at the α-Gpdh locus in the family Drosophilidae. It is supposed that selection operates effectively at the locus. The polymorphism in the four species may be both of the transient and balancing type.

Molecular evolution of mobile elements of the gypsy group: A homolog of the gag gene in Drosophila

Retrotransposons of the gypsy group of Drosophila melanogaster that are structurally similar to retroviruses of vertebrates occupy an important place among retroelements of eukaryotes. The infectious abilities of some retrotransposons of this group (gypsy, ZAM, and Idefix) have been demonstrated experimentally, and therefore they are true retroviruses. It is supposed that retrotransposons can evolve acquiring new components, the sources of which remain to be elucidated. In this work, the CG4680 gene (Gag related protein, Grp) homologous to gag of retrotransposons of the gypsy group has been identified in the genome of D. melanogaster and characterized. The Grp gene product has a highly conserved structure in different species of the Drosophilidae family and is under of stabilizing selection, which suggests its important genomic function in Drosophila. In view of the earlier data, it can be concluded that homologous genes of all components of gypsy retrotransposons are present in the Drosophila genome. These genes can be both precursors and products of domestication of retrovirus genes.

Measuring and comparing evolvability and constraint in multivariate characters

The Lande equation forms the basis for our understanding of the short-term evolution of quantitative traits in a multivariate context. It predicts the response to selection as the product of an additive genetic variance matrix and a selection gradient. The selection gradient approximates the force and direction of selection, and the genetic variance matrix quantifies the role of the genetic system in evolution. Attempts to understand the evolutionary significance of the genetic variance matrix are hampered by the fact that the majority of the methods used to characterize and compare variance matrices have not been derived in an explicit theoretical context. We use the Lande equation to derive new measures of the ability of a variance matrix to allow or constrain evolution in any direction in phenotype space. Evolvability captures the ability of a population to evolve in the direction of selection when stabilizing selection is absent. Conditional evolvability captures the ability of a population to respond to directional selection in the presence of stabilizing selection on other trait combinations. We then derive measures of character autonomy and integration from these evolvabilities. We study the properties of these measures and show how they can be used to interpret and compare variance matrices. As an illustration, we show that divergence of wing shape in the dipteran family Drosophilidae has proceeded in directions that have relatively high evolvabilities.

Genome size diversity in the family Drosophilidae

Flies in the genus Drosophila have been the dominant model organisms in genetics for over a century and, with a dozen complete sequences now available, continue as such in modern comparative genomics. Surprisingly, estimates of genome size for this genus have been relatively sparse, covering less than 2% of species. Here, best practice flow cytometric genome size estimates are reported for both male and female flies from 67 species from six genera in the family Drosophilidae, including 55 species from the genus Drosophila. Direct and phylogenetically corrected correlation analyses indicate that genome size is positively correlated with temperature-controlled duration of development in Drosophila, and there is indication that genome size may be positively related to body size and sperm length in this genus. These findings may provide some explanation for the streamlined genomes found in these insects, and complement recent work demonstrating possible selective constraints on further deletion of noncoding DNA.

Expression study of an α- l-fucosidase gene in the Drosophilidae family

The plasma membrane of Drosophila ( Sophophora) melanogaster spermatozoa contains an α- l-fucosidase that might be involved in fertilization by interacting with α- l-fucose residues on the micropyle of the eggshell. D. ( S.) melanogaster has a single gene called CG6128 or Fuca encoding for a putative α- l-fucosidase. Two transcripts have been annotated, RA of 3514 bp, and RB of 1673 bp. While both transcripts encode an α- l-fucosidase, RA contains an upstream open reading frame, translated into a polypeptide containing a predicted BTB/POZ domain. We demonstrate that Fuca is expressed in male and female germ lines. RT-PCR analysis indicated a broader tissue expression. Homologous genes are expressed in the same tissues in several drosophilid flies belonging to the genera Drosophila and Scaptodrosophila. However, the long transcript is restricted to species belonging to the subgenus Sophophora. The presence of two transcripts in species of the subgenus Sophophora and only one in species belonging to the subgenus Drosophila might be related to the phylogenetic relationships of these subgenera. Immunofluorescence demonstrated that the gene product, localized to the sperm plasma membrane, is absent from Scaptodrosophila lebanonensis spermatozoa. These findings support the hypothesis that the enzyme is involved in the molecular events of primary gamete interactions that are conserved among drosophilids belonging to Drosophila genus.

Evolution of testicular architecture in the Drosophilidae: A role for sperm length

BackgroundEvolutionary biologists have so far largely treated the testis as a black box with a certain size, a matching resource demand and a resulting sperm output. A better understanding of the way that the testis responds to selection may come from recent developments in theoretical biology aimed at understanding the factors that influence the evolution of tissue architecture (i.e. the logical organisation of a tissue). Here we perform a comparative analysis of aspects of testicular architecture of the fruit fly family Drosophilidae. Specifically, we collect published information on the number of first (or primary) spermatocytes in spermatogenesis, which allows to infer an important aspect of testicular architecture.ResultsWe show that testicular architecture is much more variable (both within and between species) than is generally appreciated. Moreover, the number of first spermatocytes is strongly correlated to the sperm length, which is inversely related to the sperm production, and thus the workload of the testis.ConclusionOur study clearly documents that tissue architecture can evolve, and that in the Drosophilidae it may do so in response to sexual selection. We conclude that the testis of the Drosophilidae is a promising model organ to test recent models of tissue architecture.

Drosophila Biology in the Genomic Age

Over the course of the past century, flies in the family Drosophilidae have been important models for understanding genetic, developmental, cellular, ecological, and evolutionary processes. Full genome sequences from a total of 12 species promise to extend this work by facilitating comparative studies of gene expression, of molecules such as proteins, of developmental mechanisms, and of ecological adaptation. Here we review basic biological and ecological information of the species whose genomes have recently been completely sequenced in the context of current research.