Gypsy homologous sequences in Drosophila subobscura (gypsyDS)

Catalogue of the Diptera (Insecta) of Morocco- an annotated checklist, with distributions and a bibliography

The faunistic knowledge of the Diptera of Morocco recorded from 1787 to 2021 is summarized and updated in this first catalogue of Moroccan Diptera species. A total of 3057 species, classified into 948 genera and 93 families (21 Nematocera and 72 Brachycera), are listed. Taxa (superfamily, family, genus and species) have been updated according to current interpretations, based on reviews in the literature, the expertise of authors and contributors, and recently conducted fieldwork. Data to compile this catalogue were primarily gathered from the literature. In total, 1225 references were consulted and some information was also obtained from online databases. Each family was reviewed and the checklist updated by the respective taxon expert(s), including the number of species that can be expected for that family in Morocco. For each valid species, synonyms known to have been used for published records from Morocco are listed under the currently accepted name. Where available, distribution within Morocco is also included. One new combination is proposed: Assuaniamelanoleuca (Séguy, 1941), comb. nov. (Chloropidae).

The genetic structure of Balkan populations of Drosophila subobscura

Although Drosophila subobscura has been a model organism for European and American population geneticists, little information is available on the genetic structure of its natural populations. In this paper we report the estimates of some population parameters. We have used data from lethal allelism tests in four Balkan populations (Kamariste, Djerdap and Petnica in Serbia and Zanjic in Montenegro). In all populations, lethal genes were found to have a deleterious effect on heterozygotes. The N(e) values varied greatly from 370 (Petnica) to 19413 (Kamariste), depending on the habitat conditions and some environmental factors. Finally, gene flow between the Balkan populations was detected by the estimates of N(m) (from 4.68 in Petnica to 106.2 in Kamariste) and m (from 0.0041 in Djerdap to 0.0126 in Petnica). These results agree with those obtained in a previous study where the frequencies of allelism between populations were greater than predicted by independently arising lethal genes.

Complex evolution of gypsy in Drosophilid species

In an endeavor to contribute to the comprehension of the evolution of transposable elements (TEs) in the genome of host species, we investigated the phylogenetic relationships of sequences homologous to the retrotransposon gypsy of Drosophila melanogaster in 19 species of Drosophila, in Scaptodrosophila latifasciaeformis, and in Zaprionus indianus. This phylogenetic study was based on approximately 500 base pairs of the env gene. Our analyses showed considerable discrepancy between the phylogeny of gypsy elements and the relationship of their host species, and they allow us to infer a complex evolutionary pattern that could include ancestral polymorphism, vertical transmission, and several cases of horizontal transmission.

Distribution of gypsy sequences in Drosophila species of the obscura subgroup

Eight Drosophila species of the obscura subgroup were screened for sequences homologous to the gypsy retrotransposon of D. melanogaster. Molecular characterization of gypsy sequences was first approached through digesting genomic DNAs from these obscura species with appropriate restriction enzymes and subjecting them to Southern blot analysis. The results of this analysis indicate that gypsy-homologous sequences are well conserved among species of the obscura subgroup. With the exception of D. guanche, all other species bear a 7 kb Xho I fragment that represents the complete element in D. melanogaster. Lower molecular weight fragments that could be deleted elements, are shared by different species. Both types of element probably existed before the divergence of this subgroup. Two different species clusters could be established on the basis of hybridization patterns, one represented by D. subobscura and its relative species D. guanche and D. madeirensis, and the other, in which D. obscura, D. tristis and D. subsilvestris are included.

On the origin of the O5 chromosomal inversion in American populations of Drosophila subobscura

D. subobscura, a typically Palearctic species, has recently colonized the American continent. The population from which the colonization started is still unknown. A complete association between a lethal gene and the O5 chromosomal inversion has been detected in the colonizing populations; this association could be used to ascertain the origin of the colonization. In the present study, three hypotheses on the origin of this association are analyzed and their probabilities are calculated. According to the first hypothesis an O5 chromosome carrying a lethal gene would have been included in the sample from which the colonization started, thus originating the association found in the American populations. The second hypothesis assumes that, at the beginning of the colonization, the association between the O5 inversion and a lethal gene would have been formed from an Ost chromosome carrying a lethal gene, on which a new O5 (or similar) inversion arose. In the last hypothesis, the association between the O5 inversion and the lethal gene would have originated at the beginning of the colonization from a lethal-free O5 chromosome, in which a lethal gene arose due to mutation.

Drosophila germline invasion by the endogenous retrovirus gypsy: involvement of the viral env gene

The endogenous retrovirus gypsy is expressed at high levels in mutant flamenco female flies. Gypsy viral particles extracted from such flies can infect naive flamenco individuals raised in the presence of these extracts mixed into their food. This results in the integration of new proviruses into the germline genome. These proviruses can then increase their copy number by (1) expression in the flamenco female somatic cells, (2) transfer into the oocyte and (3) integration into the genome of the progeny. Surprisingly, unlike the infection observed in the feeding experiments, this strategy of endogenous proviral multiplication does not seem to involve the expression of the viral env gene.

Evolution of gypsy endogenous retrovirus in the Drosophila obscura species group

The Ty3/gypsy family of retroelements is closely related to retroviruses, and some of their members have an open reading frame resembling the retroviral gene env. Sequences homologous to the gypsy element from Drosophila melanogaster are widely distributed among Drosophila species. In this work, we report a phylogenetic study based mainly on the analysis of the 5' region of the env gene from several species of the obscura group, and also from sequences already reported of D. melanogaster, Drosophila virilis, and Drosophila hydei. Our results indicate that the gypsy elements from species of the obscura group constitute a monophyletic group which has strongly diverged from the prototypic D. melanogaster gypsy element. Phylogenetic relationships between gypsy sequences from the obscura group are consistent with those of their hosts, indicating vertical transmission. However, D. hydei and D. virilis gypsy sequences are closely related to those of the affinis subgroup, which could be indicative of horizontal transmission.

Evidence for the recent horizontal transfer of long terminal repeat retrotransposon

The evolutionary dynamics existing between transposable elements (TEs) and their host genomes have been likened to an "arms race." The selfish drive of TEs to replicate, in turn, elicits the evolution of host-mediated regulatory mechanisms aimed at repressing transpositional activity. It has been postulated that horizontal (cross-species) transfer may be one effective strategy by which TEs and other selfish genes can escape host-mediated silencing mechanisms over evolutionary time; however, to date, the most definitive evidence that TEs horizontally transfer between species has been limited to class II or DNA-type elements. Evidence that the more numerous and widely distributed retroelements may also be horizontally transferred between species has been more ambiguous. In this paper, we report definitive evidence for a recent horizontal transfer of the copia long terminal repeat retrotransposon between Drosophila melanogaster and Drosophila willistoni.

Molecular structure of a gypsy element of Drosophila subobscura (gypsyDs) constituting a degenerate form of insect retroviruses

We have determined the nucleotide sequence of a 7.5 kb full-size gypsy element from Drosophila subobscura strain H-271. Comparative analyses were carried out on the sequence and molecular structure of gypsy elements of D.subobscura (gypsyDs), D.melanogaster (gypsyDm) and D.virilis (gypsyDv). The three elements show a structure that maintains a common mechanism of expression. ORF1 and ORF2 show typical motifs of gag and pol genes respectively in the three gypsy elements and could encode functional proteins necessary for intracellular expansion. In the three ORF1 proteins an arginine-rich region was found which could constitute a RNA binding motif. The main differences among the gypsy elements are found in ORF3 (env-like gene); gypsyDm encodes functional env proteins, whereas gypsyDs and gypsyDv ORF3s lack some motifs essential for functionality of this protein. On the basis of these results, while gypsyDm is the first insect retrovirus described, gypsyDs and gypsyDv could constitute degenerate forms of these retroviruses. In this context, we have found some evidence that gypsyDm could have recently infected some D.subobscura strains. Comparative analyses of divergence and phylogenetic relationships of gypsy elements indicate that the gypsy elements belonging to species of different subgenera (gypsyDs and gypsyDv) are closer than gypsy elements of species belonging to the same subgenus (gypsyDs and gypsyDm). These data are congruent with horizontal transfer of gypsy elements among different Drosophila spp.

Degenerating gypsy retrotransposons in a male fertility gene on the Y chromosome of Drosophila hydei

During the evolution of the Y chromosome of Drosophila hydei, retrotransposons became incorporated into the lampbrush loop pairs formed by several of the male fertility genes on this chromosome. Although insertions of retrotransposons are involved in many spontaneous mutations, they do not affect the functions of these genes. We have sequenced gypsy elements that are expressed as constituents of male fertility gene Q in the lampbrush loop pair Nooses. We find that these gypsy elements are all truncated and specifically lost those sequences that may interfere with the continuity of lampbrush loop transcription. Only defective coding regions are found within the loop. Gypsy is not transcribed in loops of many other Drosophila species harboring the family. These results suggest that any contribution of gypsy to the function of male fertility gene Q does not depend on a conserved DNA sequence.