Manifestation of hybrid dysgenesis in Drosophila melanogaster Harwich line with tetracycline suppressed internal microflora

Aim. To evaluate the dynamics of the manifestation of hybrid dysgenesis in the Harwich line observed under the influence of tetracycline and compare the gathered data with the data for the Oregon-R line. Methods. The line of Drosophila melanogaster Harwich was investigated. This line is considered the standard line of the P cytotype. Removal of Wolbachia from the body was implemented using antibiotic tetracycline. The level of hybrid dysgenesis was studied by the method of extracting gonad flies and assessing their condition. Results. A stable and significant increase in the proportion of dysgenic individuals within the Harwich line was recorded after suppression of the internal microflora - including Wolbachia pipientis – by tetracycline. Conclusions. The suppression of the internal microflora of Drosophila melanogaster by tetracycline significantly affects the level of manifestation of hybrid dysgenesis caused by transpositions of the P-element. The data obtained are similar to the results of a similar study of the level of manifestation of hybrid dys-genesis caused by transpositions of hobo MGE. Keywords: mobile genetic elements, hybrid dysgenesis, P-element, Drosophila melanogaster, Wolbachia pipientis.

Paternally Inherited P-Element Copy Number Affects the Magnitude of Hybrid Dysgenesis in Drosophila simulans and D. melanogaster

Transposable elements (TEs) are repetitive regions of DNA that are able to self-replicate and reinsert themselves throughout host genomes. Since the discovery of TEs, a prevalent question has been whether increasing TE copy number has an effect on the fitness of their hosts. P-elements (PEs) in Drosophila are a well-studied TE that has strong phenotypic effects. When a female without PEs (M) is crossed to a male with them (P), the resulting females are often sterile, a phenomenon called hybrid dysgenesis (HD). Here, we used short- and long-read sequencing to infer the number of PEs in the genomes of dozens of isofemale lines from two Drosophila species and measured whether the magnitude of HD was correlated with the number of PEs in the paternal genome. Consistent with previous reports, we find evidence for a positive correlation between the paternal PE copy number and the magnitude of HD in progeny from ♀M × ♂ P crosses for both species. Other crosses are not affected by the number of PE copies. We also find that the correlation between the strength of HD and PE copy number differs between species, which suggests that there are genetic differences that might make some genomes more resilient to the potentially deleterious effects of TEs. Our results suggest that PE copy number interacts with other factors in the genome and the environment to cause HD and that the importance of these interactions is species specific.

Myc plays an important role in Drosophila P-M hybrid dysgenesis to eliminate germline cells with genetic damage

Genetic damage in the germline induced by P-element mobilization causes a syndrome known as P-M hybrid dysgenesis (HD), which manifests as elevated mutation frequency and loss of germline cells. In this study, we found that Myc plays an important role in eliminating germline cells in the context of HD. P-element mobilization resulted in downregulation of Myc expression in the germline. Myc knockdown caused germline elimination; conversely, Myc overexpression rescued the germline loss caused by P-element mobilization. Moreover, restoration of fertility by Myc resulted in the production of gametes with elevated mutation frequency and reduced ability to undergo development. Our results demonstrate that Myc downregulation mediates elimination of germline cells with accumulated genetic damage, and that failure to remove these cells results in increased production of aberrant gametes. Therefore, we propose that elimination of germline cells mediated by Myc downregulation is a quality control mechanism that maintains the genomic integrity of the germline.

Changes in the intralinear level of hybrid dys-genesis manifestation in Drosophila melanogaster in crosses with individuals with tetracycline suppressed internal microflora

Aim. To assess the frequency of hybrid dysgenesis in the offspring of reciprocal crosses of individuals of the Oregon-R line, with individuals of the same line, from the organism of which Wolbachia pipientis was eliminated. Methods. The line of Drosophila melanogaster Oregon R (Cambridge), in the genome of which there are MGE hobo, was investiga-ted. This line is infected with wolbachia of the wMel strain. Removal of Wolbachia from the body was implemented using antibiotic tetracycline. The study used the fifth of the generations obtained on a normal handling medium after the removal of Wolbachia. The level of hybrid dysgenesis was studied by the method of extracting gonad flies and assessing their condition. Results. In the progeny from experimental crossing of females from which Wolbachia was eli-minated, with males of the control line, the proportion of females with fully reduced gonads is significantly higher than in the offspring of reciprocal crossing. Conclusions. The results obtained may be a sign of the action of the system of specific interactions of Wolbachia pipientis and Drosophila’s MGE. Keywords: mobile genetic elements, hybrid dysgenesis, Drosophila melanogaster, Wolbachia pipientis.

Effect of suppression of internal microflora by tetracycline on the level of manifestation of the hybrid dysgenesis of Drosophila melanogaster

Aim. The main goal of this article was to assess changes in the frequency of the development of hybrid dysgenesis in the Oregon-R line of Drosophila melanogaster, observed under the influence of tetracycline. Methods. The line of Drosophila melanogaster Oregon R (Cambridge), in the genome of which there are full-sized and functionally active copies of the MGE hobo, was investigated. Also, this line is infected with wolbachia of the wMel strain. Removal of Wolbachia from the body was implemented using antibiotic tetracycline. The level of hybrid dysgenesis was studied by the method of extracting gonad flies and assessing their condition. Results. This article presents the results of studying the effect of suppression of the internal microflora of Drosophila melanogaster – in particular, the parasitic bacterium Wolbachia pipientis - on the level of manifestation of hybrid dysgenesis. After exposure to tetracycline, a significant increase in the proportion of dysgenic individuals within the line was observed. Conclusions. The results obtained may be associated with a violation of the system of specific interactions of the host organism and internal microflora. Keywords: mobile genetic elements, hybrid dysgenesis, Drosophila melanogaster, Wolbachia pipientis.

A rapid change in P-element-induced hybrid dysgenesis status in Ukrainian populations of Drosophila melanogaster

The Drosophila melanogaster P-transposable element is an example of mobile DNA transferred horizontally and known to have spread globally over the last 50–60 years. In Drosophila , the P-element causes a syndrome known as ‘P–M hybrid dysgenesis' that obstructs normal ovary development in the female progeny of susceptible populations. Despite extensive research, the stability and global population dynamics of P–M dysgenic phenotypes remain poorly understood. Here, we report a recent and rapid transition in the P–M status of D. melanogaster populations from Ukraine. We demonstrate that these populations are currently dominated by the P′-cytotype characterized by active genomic P-elements and unknown from Ukraine just two decades ago. Our results suggest a recent invasion of the P-element in Ukraine, a pattern that matches recent discoveries from Turkey.

The meiotic recombination landscape ofDrosophila virilisis robust to mitotic damage during hybrid dysgenesis

ABSTRACTGermline DNA damage is a double-edged sword. Programmed double-strand breaks establish the foundation for meiotic recombination and chromosome segregation. However, double-strand breaks also pose a significant challenge for genome stability. Because of this, meiotic double-strand break formation is tightly regulated. However, natural selection can favor selfish behavior in the germline and transposable elements can cause double-strand breaks independent of the carefully regulated meiotic process. To understand how the regulatory mechanisms of meiotic recombination accommodate unregulated transposition, we have characterized the female recombination landscape in a syndrome of hybrid dysgenesis inDrosophila virilis. In this system, a cross between two strains ofD. viriliswith divergent transposable element and piRNA profiles results in germline transposition of diverse transposable elements, reduced fertility, and male recombination. We sought to determine how increased transposition during hybrid dysgenesis might perturb the meiotic recombination landscape. Our results show that the overall frequency and distribution of meiotic recombination is extremely robust to germline transposable element activation. However, we also find that hybrid dysgenesis can result in mitotic recombination within the female germline. Overall, these results show that landscape of meiotic recombination may be insensitive to the DNA damage caused by transposition during early development.