Population genomic analysis of base composition evolution in Drosophila melanogaster.

The relative importance of mutation, selection, and biased gene conversion to patterns of base composition variation in Drosophila melanogaster, and to a lesser extent, D. simulans, has been investigated for many years. However, genomic data from sufficiently large samples to thoroughly characterize patterns of base composition polymorphism within species have been lacking. Here, we report a genome-wide analysis of coding and noncoding polymorphism in a large sample of inbred D. melanogaster strains from Raleigh, North Carolina. Consistent with previous results, we observed that AT mutations fix more frequently than GC mutations in D. melanogaster. Contrary to predictions of previous models of codon usage in D. melanogaster, we found that synonymous sites segregating for derived AT polymorphisms were less skewed toward low frequencies compared with sites segregating a derived GC polymorphism. However, no such pattern was observed for comparable base composition polymorphisms in noncoding DNA. These results suggest that AT-ending codons could currently be favored by natural selection in the D. melanogaster lineage

Free-flight responses of Drosophila melanogaster to attractive odors

Many motile organisms localize the source of attractive odorants by following plumes upwind. In the case of D. melanogaster, little is known of how individuals alter their flight trajectories after encountering and losing a plume of an attractive odorant. We have characterized the three-dimensional flight behavior of D. melanogaster in a wind tunnel under a variety of odor conditions. In the absence of olfactory cues, hungry flies initiate flight and display anemotactic orientation. Following contact with a narrow ribbon plume of an attractive odor, flies reduce their crosswind velocity while flying faster upwind, resulting in a surge directed toward the odor source. Following loss of odor contact due to plume truncation, flies frequently initiate a stereotyped crosswind casting response, a behavior rarely observed in a continuous odor plume. Similarly, within a homogeneous odor cloud, flies move fast while maintaining an upwind heading. These results indicate both similarities and differences between the behavior of D. melanogaster and the responses of male moths to pheromone plumes, suggesting possible differences in underlying neural mechanisms

PERBEDAAN STRAIN DAN UMUR BETINA TERHADAP JUMLAH KETURUNAN LALAT BUAH (Drosophila melanogaster Meigen)

A study was conducted on the differences in strain and female age on the number of descendants of fruit flies (Drospohila melanogaster Meigen) to determine the effect of strain and female age on the number of D. melanogaster offspring in normal, taxi and sepia strains. Five D. melanogaster ? normal crossed with 5 D. D. melanogaster ? normal, 5 D. melanogaster ? taxi crossed with 5 D. D. melanogaster ? taxi, 5 D. D. melanogaster ? sepia crossed with 5 D. D. melanogaster ? sepia. Age of the crossed female is 8-10 hours, 12-14 hours, 16-18 hours, 20-22 hours, and 24-26 hours after hatching from the pupa. Each group of crosses was repeated five times. D. melanogaster crossing was carried out at 25oC. Data were analyzed with factorial anava and then tested further with LSD (Least Significant Difference) of 5% significance level. Based on the results of the study note that there is an influence of strain and female age on the number of offspring. It is also known that normal strains produce the highest number of offspring, whereas taxi strains produce the fewest offspring. Age of females 20-22 hours produces the most number of offspring and is not significantly different from females 24-26 hours, while ages 8-10 hours produce the fewest number of offspring and are not significantly different from ages 12-14 hours.Telah dilakukan penelitian Perbedaan Strain dan Umur Betina Terhadap Jumlah Keturunan Lalat Buah (Drospohila melanogaster Meigen) untuk mengetahui pengaruh strain dan umur betina terhadap jumlah keturunan D. melanogaster pada strain normal, taxi, dan sepia. Sebanyak 5 ekor D. melanogaster ? normal disilangkan dengan 5 ekor D. melanogaster  ? normal, 5 ekor D. melanogaster ? taxi disilangkan dengan 5 ekor D. melanogaster ? taxi, 5 ekor D. melanogaster ? sepia disilangkan dengan 5 ekor D. melanogaster  ? sepia. Umur betina yang disilangkan adalah 8-10 jam, 12-14 jam, 16-18 jam, 20-22 jam, dan 24-26 jam sejak menetas dari pupa. Setiap kelompok persilangan diulang lima kali. Persilangan D. melanogaster dilakukan pada suhu 25oC. Data dianalisis dengan anava faktorial kemudian diuji lanjut dengan BNT (Beda Nyata Terkecil) taraf signifikansi 5%. Berdasarkan hasil penelitian diketahui bahwa ada pengaruh strain dan umur betina terhadap jumlah keturunan. Diketahui pula bahwa strain normal menghasilkan jumlah keturunan terbanyak, sedangkan strain taxi menghasilkan jumlah keturunan paling sedikit. Umur betina 20-22 jam menghasilkan jumlah keturunan yang paling banyak dan tidak berbeda nyata dengan umur betina 24-26 jam, sedangkan umur 8-10 jam menghasilkan jumlah keturunan paling sedikit dan tidak berbeda nyata dengan umur 12-14 jam

Dynamics of Wolbachia pipientis gene expression across the Drosophila melanogaster life cycle

Symbiotic interactions between microbes and their multicellular hosts have manifold impacts on molecular, cellular and organismal biology. To identify candidate bacterial genes involved in maintaining endosymbiotic associations with insect hosts, we analyzed genome-wide patterns of gene expression in the alpha-proteobacteria Wolbachia pipientis across the life cycle of Drosophila melanogaster using public data from the modENCODE project that was generated in a Wolbachia-infected version of the ISO1 reference strain. We find that the majority of Wolbachia genes are expressed at detectable levels in D. melanogaster across the entire life cycle, but that only 7.8% of 1195 Wolbachia genes exhibit robust stage- or sex-specific expression differences when studied in the "holo-organism" context. Wolbachia genes that are differentially expressed during development are typically up-regulated after D. melanogaster embryogenesis, and include many bacterial membrane, secretion system and ankyrin-repeat containing proteins. Sex-biased genes are often organised as small operons of uncharacterised genes and are mainly up-regulated in adult males D. melanogaster in an age-dependent manner suggesting a potential role in cytoplasmic incompatibility. Our results indicate that large changes in Wolbachia gene expression across the Drosophila life-cycle are relatively rare when assayed across all host tissues, but that candidate genes to understand host-microbe interaction in facultative endosymbionts can be successfully identified using holo-organism expression profiling. Our work also shows that mining public gene expression data in D. melanogaster provides a rich set of resources to probe the functional basis of the Wolbachia-Drosophila symbiosis and annotate the transcriptional outputs of the Wolbachia genome.Comment: 58 pages, 6 figures, 6 supplemental figures, 4 supplemental files (available at https://github.com/bergmanlab/wolbachia/tree/master/gutzwiller_et_al/arxiv

Fine Mapping of Dominant <i>X</i>-Linked Incompatibility Alleles in <i>Drosophila</i> Hybrids

Sex chromosomes have a large effect on reproductive isolation and play an important role in hybrid inviability. In Drosophila hybrids, X-linked genes have pronounced deleterious effects on fitness in male hybrids, which have only one X chromosome. Several studies have succeeded at locating and identifying recessive X-linked alleles involved in hybrid inviability. Nonetheless, the density of dominant X-linked alleles involved in interspecific hybrid viability remains largely unknown. In this report, we study the effects of a panel of small fragments of the D. melanogaster X-chromosome carried on the D. melanogaster Y-chromosome in three kinds of hybrid males: D. melanogaster/D. santomea, D. melanogaster/D. simulans and D. melanogaster/D. mauritiana. D. santomea and D. melanogaster diverged over 10 million years ago, while D. simulans (and D. mauritiana) diverged from D. melanogaster over 3 million years ago. We find that the X-chromosome from D. melanogaster carries dominant alleles that are lethal in mel/san, mel/sim, and mel/mau hybrids, and more of these alleles are revealed in the most divergent cross. We then compare these effects on hybrid viability with two D. melanogaster intraspecific crosses. Unlike the interspecific crosses, we found no X-linked alleles that cause lethality in intraspecific crosses. Our results reveal the existence of dominant alleles on the X-chromosome of D. melanogaster which cause lethality in three different interspecific hybrids. These alleles only cause inviability in hybrid males, yet have little effect in hybrid females. This suggests that X-linked elements that cause hybrid inviability in males might not do so in hybrid females due to differing sex chromosome interactions.</p

External control of the Drosophila melanogaster egg to imago development period by specific combinations of 3D low-frequency electric and magnetic fields

We report that the duration of the egg-to-imago development period of the Drosophila melanogaster, and the imago longevity, are both controllable by combinations of external 3-dimensional (3D) low-frequency electric and magnetic fields (LFEMFs). Both these periods may be reduced or increased by applying an appropriate configuration of external 3D LFEMFs. We report that the longevity of D. melanogaster imagoes correlates with the duration of the egg-to-imago development period of the respective eggs. We infer that metabolic processes in both eggs and imago are either accelerated (resulting in reduced time periods) or slowed down (resulting in increased time periods). We propose that external 3D LFEMFs induce electric currents in live systems as well as mechanical vibrations on sub-cell, whole-cell and cell-group levels. These external fields induce media polarization due to ionic motion and orientation of electric dipoles that could moderate the observed effects. We found that the longevity of D. melanogaster imagoes is affected by action of 3D LFEMFs on the respective eggs in the embryonic development period (EDP). We interpret this effect as resulting from changes in the regulation mechanism of metabolic processes in D. melanogaster eggs, inherited by the resulting imagoes. We also tested separate effects of either 3D electric or 3D magnetic fields, which were significantly weaker

Investigation of Neurotransmitter’s Knockdown Effect on Drosophila Melanogaster Female Aggression

Drosophila melanogaster (D. melanogaster) is a popular model organism in neurobiology. While aggression has been studied heavily in male drosophila, there\u27s minimal research on aggression in female drosophila. Neurotransmitters influencing aggressive behaviour in female D. melanogaster are poorly understood. Various neurotransmitters such as dopamine, octopamine, and serotonin influence aggression in D. melanogaster Further investigation of the role of neurotransmitters on aggression is thus important. The purpose of our experiment is to observe the effect of the knockdown of dopamine, octopamine and glutamate on aggression in female D. melanogaster

Mitochondrial-nuclear epistasis affects fitness within species but does not contribute to fixed incompatibilities between species of \u3ci\u3eDrosophila\u3c/i\u3e

Efficient mitochondrial function requires physical interactions between the proteins encoded by the mitochondrial and nuclear genomes. Co-evolution between these genomes may result in the accumulation of incompatibilities between divergent lineages. We test whether mitochondrialnuclear incompatibilities have accumulated within the Drosophila melanogaster species subgroup by combining divergent mitochondrial and nuclear lineages and quantifying the effects on relative fitness. Precise placement of nine mtDNAs from D. melanogaster, D. simulans and D. mauritiana into two D. melanogaster nuclear genetic backgrounds reveals significant mitochondrial-nuclear epistasis affecting fitness in females. Combining the mitochondrial genomes with three different D. melanogaster X chromosomes reveals significant epistasis for male fitness between X-linked and mitochondrial variation. However, we find no evidence that the more than 500 fixed differences between the mitochondrial genomes of D. melanogaster and the D. simulans species complex are incompatible with the D. melanogaster nuclear genome. Rather, the interactions of largest effect occur between mitochondrial and nuclear polymorphisms that segregate within species of the D. melanogaster species subgroup. We propose that a low mitochondrial substitution rate, resulting from a low mutation rate and/or efficient purifying selection, precludes the accumulation of mitochondrial-nuclear incompatibilities among these Drosophila species

SUPPRESSION OF DROSOPHILA ANANASSAE FLIES OWING TO INTERSPECIFIC COMPETITION WITH D. MELANOGASTER UNDER ARTIFICIAL CONDITIONS

Interspecific competition between two species of Drosophila: D. ananassae and D. melanogaster was studied at the larval and adult stages. It was found that when D. ananassae and D. melanogaster adult flies were co-cultured, very few D. ananassae offspring could be recovered in the first generation. To investigate the reasons of D. ananassae apparent inhibition, mating behavior of D. ananassae in the presence of D. melanogaster was observed and it was found that the number of matings deviated significantly from those recorded when it was kept alone. To determine larval development of D. ananassae after being initially exposed to D. melanogaster, the females of the two species were separated in different food bottles after 3 days of being kept together. Good D. ananassae cultures could be recovered indicating that initial exposure of D. ananassae to D. melanogaster did not hamper its egg laying capacity or eclosion. However, if they remained together, no D. ananassae could be recovered from larval diet, suggesting that either D. melanogaster adults interfered with fertilization or egg-laying, or their larvae eliminated competitors. To see whether there is larval competition, polytene chromosomes of 54 third instar larvae were analyzed out of which only 5.56 percent were found to be D. ananassae. Thus, if a few eggs are laid by D. ananassae and they develop, all the while facing competition from D. melanogaster and till the third instar larval stage is reached, there is almost complete elimination of D. ananassae. Thus, interspecific competition exists at all stages of life cycle and few if any D. ananassae flies emerge.Se estudió la competencia interespecífica entre dos especies de Drosophila: D. ananassae y D. melanogaster en estado larvario y adulto. Se encontró que al criar simultáneamente adultos de D. ananassae y D. melanogaster, muy poca progenie de primera generación de D. ananassae podia recuperarse. Para investigar las causas de la aparente inhibición de D. ananassae, se observó el comportamiento de apareamiento de D. ananassae en presencia de D. melanogaster y se observó que el número de apareamientos se desvió significatívamente de aquel registrado cuando esta especie se mantuvo sola. Para observar el desarrollo larvario de D. ananassae después de la exposición a D. melanogaster, hembras de ambas especies fueron separadas en botes de alimento después de tres días de confinamiento conjunto. Se obtuvieron buenas crías de D. ananassae, indicando que la exposición de D. ananassae a D. melanogaster no afectó su capacidad de oviposición ni su fertilidad. Sin embargo, cuando ambas especies permanecieron juntas, no se recuperó D. ananassae de la dieta larvaria lo que sugiere que los adultos de D.melanogaster interfirieron con la fertilización u oviposición, o bien sus larvas eliminaron la competencia. Para establecer la existencia de competencia larvaria se examinaron los cromosomas polténicos de 54 larvas de tercer estadio entre las cuáles solo el 5.56 por ciento resultaron ser de D. ananassae. Por lo tanto, si algunos huevos son depositados por D. ananassae y se desarrollan, éstos enfrentan la competencia de D. melanogaster durante todo el desarrollo y hasta el tercer estadio, llegando a la casi total eliminación de D. ananassae. Existe competencia interespecifica en todas las etapas del ciclo de vida resultando en una casi nula emergencia de D. ananassae

An Analysis of Gene-Enzyme Variability in Natural Populations of Drosophila melanogaster and D. simulans

Nine populations of D. melanogaster and two populations of D. simulans were analyzed for polymorphism in 10 gene-enzyme systems by the technique of gel electrophoresis. In the eight natural populations of D. melanogaster, an average of 54% of the enzymes were polymorphic, and the average heterozygosity was 22.7%. An experimental population of D. melanogaster, which has been maintained in a laboratory cage for 20 years, showed levels of polymorphism equivalent to those of natural populations. The D. simulans populations had much less variability. The possible factors involved in maintaining these polymorphisms are discussed