Search

Arcady A Putilov,1,* Evgeniy G Verevkin,1,* Dmitrii V Petrovskii,2,* Lyudmila P Zakharenko2,* 1Independent Research Group “biomedical Systems Math-Modeling”, Berlin, 12489, Germany; 2Department of Insect Genetics, Institute of Cytology and Genetics of the Siberian Branch, the Russian Academy of Sciences, Novosibirsk, 630090, Russia*These authors contributed equally to this workCorrespondence: Arcady A Putilov, Independent Research Group “Biomedical Systems Math-Modeling, 11, Nipkowstr, Berlin, 12489, Germany, Tel/Fax +0049-30-53674643, Email arcady.putilov@gmail.comPurpose: Two previously proposed modelling approaches to explain the bimodal pattern of activity and/or sleep in Drosophila melanogaster are based on 1) the concept of morning and evening oscillators underlying the peaks of activity in the morning and evening, respectively, and 2) the concept of two cycles of buildup and decay of sleep pressure, gated only by the circadian oscillator. Previously, we simulated 24-h alertness–sleepiness curves in humans using a model postulating the circadian modulation of the buildup and decay phases of two (wake and sleep) homeostatic processes. Here, we tested whether a similar model could be applied to simulate the bimodal 24-h rhythm of fly locomotor activity and sleep.Methods: To obtain typical curves for the simulations, a sample of 4263 individual 24-h curves of locomotor activity and sleep were subjected to principal component analysis. It yielded three principal components, which explained more than 70% of the individual variations in these curves. We calculated the typical curves using scores on the 1st, 2nd, and 3rd principal components and simulated these curves and the sample-averaged curves.Results: We found that these curves are always characterized by two peaks with varying sizes and timings. They can be fitted by proposing the variation of some of the parameters of the two homeostatic processes reflecting the 24-h rhythmicity of the drive for wake and the 12-h rhythmicity of the drive for sleep.Conclusion: Postulation of two separate circadian oscillators is not necessary to explain the bimodal curves in Drosophila melanogaster.Plain language summary: This study tested whether a model postulating circadian modulation of the buildup and decay phases of two homeostatic processes (wake and sleep) can be applied to simulate the bimodal 24-h rhythm of fruit fly activity and sleep. The simulations suggested that the typical bimodal curves can be simulated by proposing variation of some of the parameters of the two underlying homeostatic processes that represent the 24-h variation in the drive for wakefulness and the 12-h variation in the opposing drive for sleep.Keywords: sleep–wake regulating process, bimodal 24-h rhythm, fruit fly, math-modelling

Lyudmila P Zakharenko,1,2 Dmitrii V Petrovskii,1 Arcady A Putilov3 1Department of Insect Genetics, Institute of Cytology and Genetics of the Siberian Branch, the Russian Academy of Sciences, Novosibirsk, Russia; 2Faculty of Natural Science, Novosibirsk State University, Novosibirsk, Russia; 3Research Group for Biomedical Systems Modeling, Research Institute for Molecular Biology and Biophysics, Novosibirsk, Russia Purpose: Drosophila melanogaster and our own species share (Homo sapiens) the history of relatively rapid out-of-Africa dispersal. In Eurasia, they had faced a novel adaptive problem of adjustment of their circadian rhythmicity and night sleep episode to seasonal variation in day length and air temperature. Both species usually respond to heat and a short duration of night by reduction of the amount of night sleep and prolongation of “siesta”. To further explore similarities between the two species in the ways of adjustment of their sleep–wake behavior to extreme environmental factors, this study examined the possibility to distinguish four extreme chronotypes among fruit flies and the possibility of the differential response of such chronotypes to light and heat stressors. Materials and methods: Circadian rhythms of locomotor activity and sleep–wake pattern were tested in constant darkness, and four strains of fruit flies originating from three wild populations of Africa, Europe, and the USA were selected to represent four distinct chronotypes: “larks” (early morning and evening activity peaks), “owls” (late morning and evening peaks), “swifts” (early morning and late evening peaks), and “woodcocks” (late morning and early evening peaks). The circadian rhythms and sleep efficiency of the selected chronotypes were further tested under such extreme conditions as either long day (LD20:4 at 20°C) or a combination of LD20:4 with hot temperature (29°C). Results: Despite the identity of such experimental conditions for four chronotypes, their circadian rhythms and sleep timing showed significantly distinct patterns of response to exposure to heat and/or long days. All two-way repeated measures analysis of variances yielded a significant interaction between chronotype and time of the day (P

In this study, we raised the following question: "Does metamorphosis, being a "reboot" of all systems of the organism, erase the changes that occurred at earlier stages of insect development?" To answer this question, we investigated several behavioral, metabolic and neuroendocrine parameters in Drosophila melanogaster imago that had undergone heat stress at the 3rd larval instar (32 °C, 48 h). We discovered that larval stress negatively affected feeding and locomotor behavior, as well as total lipid content in adult flies. At the same time, these flies demonstrated a considerable increase in carbohydrate content and expression level of insulin/insulin-like growth factor signaling (IIS) pathway genes, dfoxo, dilp6 and dInR. The data obtained allow us to conclude that metamorphosis does not erase the effect of stress exposure at early developmental stages and causes dramatic changes in carbohydrate and lipid metabolism as well as locomotor activity of adult insects, which is at least in part due to changes in IIS activity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Drosophila melanogaster provides a powerful platform to study the physiology and genetics of aging, i.e., the mechanisms underpinnings healthy aging, age-associated disorders, and acceleration of the aging process under adverse environmental conditions. Here, we tested the responses of daily rhythms to age-accelerated factors in two wild-type laboratory-adapted strains, Canton-S and Harwich., Methods: On the example of the 24 h patterns of locomotor activity and sleep, we documented the responses of these two strains to such factors as aging, high temperature, carbohydrate diet, and diet with different doses of caffeine-benzoate sodium., Results: The strains demonstrated differential responses to these factors. Moreover, compared to Canton-S, Harwich showed a reduced locomotor activity, larger amount of sleep, faster rate of development, smaller body weight, lower concentrations of main sugars, lower fecundity, and shorter lifespan., Conclusions: It might be recommended to use at least two strains, one with a relatively fast and another with a relatively slow aging process, for the experimental elaboration of relationships between genes, environment, behavior, physiology, and health.

Background: Activity plays a very important role in keeping bodies strong and healthy, slowing senescence, and decreasing morbidity and mortality. Drosophila models of evolution under various selective pressures can be used to examine whether increased activity and decreased sleep duration are associated with the adaptation of this nonhuman species to longer or harder lives., Methods: For several years, descendants of wild flies were reared in a laboratory without and with selection pressure. To maintain the "salt" and "starch" strains, flies from the wild population (called "control") were reared on two adverse food substrates. The "long-lived" strain was maintained through artificial selection for late reproduction. The 24 h patterns of locomotor activity and sleep in flies from the selected and unselected strains (902 flies in total) were studied in constant darkness for at least, 5 days., Results: Compared to the control flies, flies from the selected strains demonstrated enhanced locomotor activity and reduced sleep duration. The most profound increase in locomotor activity was observed in flies from the starch (short-lived) strain. Additionally, the selection changed the 24 h patterns of locomotor activity and sleep. For instance, the morning and evening peaks of locomotor activity were advanced and delayed, respectively, in flies from the long-lived strain., Conclusion: Flies become more active and sleep less in response to various selection pressures. These beneficial changes in trait values might be relevant to trade-offs among fitness-related traits, such as body weight, fecundity, and longevity.

Cases of horizontal transfer of transposable elements (TEs) between species are known for the Drosophilidae family. In the middle of the last century, the case of horizontal transfer of the P-element from the Drosophila willistoni to the D. melanogaster was described. A novel P-element invasion into the D. simulans genome from D. melanogaster occurred approximately 10 years ago. Currently, the P-element has spread across all D. melanogaster population and 30% of D. simulans populations in Europe, Africa and America. In this paper, we investigated the presence of the P-element in D. simulans lines caught in different years in three Asian populations (Tashkent, Nalchik and Sakhalin Island). We also examined the physiological characteristics (cytotype, lifespan, fecundity and locomotor activity) of D. simulans lines with and without the P-element to determine the significance of this new mobile element in the genome. The P-element was found in lines isolated from nature after 2012. The number of P-element copies per genome (two-to-three dozen according to fluorescence in situ hybridization data) was greater than in the American and comparable to the African populations. There were signs of intraspecific hybrid dysgenesis for some pairs of lines. However, in general the presence of the P-element did not adversely affect the physiological characteristics. Either adaptation to the new TE occurs very quickly, or the rate of movement of the P-element is so insignificant that its appearance in the genome remains unnoticed.

Humans and fruit flies demonstrate similarity in sleep-wake behavior, e.g., in the pattern of sleep disturbances caused by an exposure to high temperature. Although research has provided evidence for a clear connection between sleeping problems and infertility in women, very little is known regarding the mechanisms underlying this connection. Studies of dysgenic crosses of fruit flies revealed that an exposure to elevated temperature induces sterility in female intra-specific hybrids exclusively in one of two cross directions (progeny of Canton-S females crossed with Harwich males). Given the complexity and limitations of human studies, this fruit flies' model of temperature-sensitive sterility might be used for testing whether the effects of high temperature on fertility and on 24-h sleep pattern are inter-related. To document this pattern, 315 hybrids were kept for at least five days in constant darkness at 20 °C and 29 °C. No evidence was found for a causal link between sterility and sleep disturbance. However, a diminished thermal responsiveness of sleep was shown by females with temperature-induced sterility, while significant responses to high temperature were still observed in fertile females obtained by crossing in the opposite direction (i.e., Canton-S males with Harwich females) and in fertile males from either cross.

Gonadal atrophy is the most typical and dramatic manifestation of intraspecific hybrid dysgenesis syndrome leading to sterility in Drosophila melanogaster dysgenic progeny. The P-M system of hybrid dysgenesis is primarily associated with germ cell degeneration during the early stages of Drosophila embryonic development at elevated temperatures. In the present study, we have defined the phase of germ cell death as beginning at the end of embryogenesis immediately following gonad formation. However, the temperature-dependent screening of germ cell developmental patterns in the dysgenic background showed that early germ cells are susceptible to the hybrid dysgenesis at any Drosophila life-cycle stage, including in the imago. Electron microscopy of germ cells after dysgenesis induction revealed significant changes in subcellular structure, especially mitochondria, prior to cellular breakdown. The mitochondrial pathology can promote the activation of cell death pathways in dysgenic germ cells, which leads to gonadal atrophy., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Intraspecific hybrid dysgenesis (HD) appears after some strains of D. melanogaster are crossed. The predominant idea is that the movement of transposable P elements causes HD. It is believed that P elements appeared in the D. melanogaster genome in the middle of the last century by horizontal transfer, simultaneously with the appearance of HD determinants. A subsequent simultaneous expansion of HD determinants and P elements occurred. We analyzed the current distribution of HD determinants in natural populations of D. melanogaster and found no evidence of their further spread. However, full-sized P elements were identified in the genomes of all analyzed natural D. melanogaster strains independent of their cytotypes. Thus, the expansion of P elements does not correlate with the expansion of HD determinants. We found that the ovaries of dysgenic females did not contain germ cells despite the equal number of primordial germ cells in early stages in dysgenic and non-dysgenic embryos. We propose that HD does not result from DNA damage caused by P element transposition, but it would be the disruption in the regulation of dysgenic ovarian formation that causes the dysgenic phenotypes.

There is wide-spread interest in understanding the rate of transposable element movement within populations and between species. A recent study using interprecific crosses between D. buzzatii and D. koepferae indicated that transposition rates in hybrids may be quite high. However, we suggest caution should be taken in this interpretation since AFLP methods to detect transposition events may lead to overestimated rate estimates. Comparative analyses of genome instability received by different methods suggest that transposition rates can be higher in intraspecific crosses compared to interspecific crosses.

Data disputing the unique role of transposable elements (TEs) in the induction of intraspecific gonadal dysgenesis (GD) in Drosophila are discussed. Transposable elements (TEs) occupy the fifth part of the genome of Drosophila melanogaster.

This paper studies the metabolism of the juvenile hormone, which affects gonads functioning in Drosophila melanogasterfemales under P-M hybrid dysgenesis. It is shown that dysgenic females grown at 29°C have increased levels of the juvenile hormone (its degradation and stress reactivity are reduced), which apparently is a compensatory response to ovarian hypoplasia.

The effect of selection for radius vein length on the distribution of hybridization sites of the P and hobo transposons and the mdgl and mdg2 retrotransposons on polytene chromosomes of Drosophila melanogaster salivary glands was studied. The patterns of these transposable elements (TEs) distribution were polymorphic in both the parental strain and selected strains. The similarity in mdg1 and mdg2 patterns between strains selected in one direction was closer than between strains selected in opposite directions, but the selected strains were closer to each other than to the parental strain regardless of selection direction. No mdg2 hybridization sites that would be absent in the control were found in the selected strains. There were more mdg2 and hobo hybridization sites in the strains selected in the (+) direction than in the (-) direction. The mobility of hobo copies in the strains studied correlated with the presence of its full-sized copy in the genome. The polymorphism of all TEs studied except for mdgl was greater for strains selected in the (+) direction that in the (-) direction. These facts suggest that some TEs migrate over the genome independently of selection, and others are markers of evolutionary events rather than their causes.

The distribution patterns pf hobo transposon and Dm412 retrotransposon hybridization sites on the salivary gland polytene chromosomes from the larvae of Drosophila melanogaster isogenic strain 51, used for analyzing the effect of transposable element (TE) transposition on the selection for quantitative traits, were studied, It was demonstrated that at least half Dm412 hybridization sites were retained 15 years after isogenization; the frequency of Dm412 transposition varied from 2.0 x 10(-4) to 8.8 x 10(-5) depending on whether the appearance of the same hybridization sites in some individuals were regarded as independent events or as a manifestation of the sample heterogeneity. The distribution patterns of hobo hybridization sites in two isofemale strains derived from isogenic strain 51 differed more noticeably: the number of hobo sites in one of the derivative strains was threefold smaller than in another and only a fraction of the sites was common. Within each derivative strain, the TE distribution was uniform, suggesting that inbreeding had no effect on the Dm412 activity in this strain. The rates of change in the distribution patterns of various TEs in strain 51 corresponded to their spontaneous transposition rates. As isogenic strain accumulates the polymorphism in TE distribution without selection, the TEs are more likely to be the markers of selection events than their inducers. Thus, when studying the effects of various environmental factors on TE transposition even in isogenic strains, it is necessary to perform rounds of close inbreeding to reduce the potential polymorphism.

The 3D-FISH was employed to investigate the telomere topology in polytene nuclei of salivary glands of Drosophila melanogaster. The majorities of telomeres in polytene nuclei of salivary glands in Drosophila strain y(2-717) are localized in the nuclear central area and have no contacts with nuclear membrane. In females of this strain, ectopic contacts between telomeres occur at 25 % higher frequency than in males. HeT-A DNA in y(2-717alk3-2) strain, which is a derivative of y(2-717) carrying an inversion between 1D and 13C bands, is found in region 13 of X chromosome. The frequency of ectopic contacts of telomeres in y(2-717alk3-2) males is 10 % higher than that in y(2-717) strain. The number of ectopic contacts can be significantly different in independent experiments, possibly indicating the role of random factors in the contact formation.

We studied molecular characteristics of yellow (y; 1-0.0) locus, which determines the body coloration of phenotypically wild-type and mutant alleles isolated from geographically distant populations of Drosophila melanogaster in different years. According to Southern data, restrictions map of yellow locus of all studied strains differ from each other as well as from that of Oregon stock. FISH analysis shows that in the neighborhood of yellow locus in X chromosome neither P nor hobo elements are found in y1-775 stock, while only hobo is found there in y1-859 and y1-866 stocks, only P element in y+sn849 stock, and both elements in y1-719 stock. Thus, all studied mutant variants of yellow are of independent origin. Yellow locus residing at the very end of X chromosome (region 1A5-8 of cytologic map) carries significantly more transposon than retrotransposon-induced mutations, as compared to white locus (regions 3C2). It is possible that transposons are more active than retrotransposons at the chromosomal ends of D. melanogaster.

The genome of Drosophila melanogaster strain y cn bw sp has been sequenced and the transposable elements insertion sites have been determined. We hybridized fluorescence-labeled probes directed to the hobo transposon, Dm412 and mdg1 retrotransposons to polytene chromosomes and compared the observed sites to those published in the annotated genome sequence. We observed an almost twofold increase in the number of hobo hybridization sites (46 found as compared to 24 annotated sites). There was no evidence that the hobo transposition rate is slowing over the 10-year period. The patterns of Dm412 and mdg1 sites have changed less dramatically since the time of genome sequencing. Three novel Dm412 hybridization sites were detected while 4 out of 30 annotated sites were missing. Only one additional mdg1 site was found, while 1 out of 29 annotated sites has been lost.

The effects of genotype of the laboratory strains, C(1)DX, ywf/Y, 23.5 MRF/CyL4, and C(1)DX,yf; pi2, on locus-specific instability in the yellow gene of the strains y(2-717, y(2-715), and y(2-700 ) from Uman' population of Drosophila melanogaster was studied. Crosses of the males from Uman'-derived lines with the C(1)DX, ywf/Y females yielded a cascade of derivatives, mostly consisting of y+ and y2 alleles, while their crosses with the 23.5 MRF/CyL4 and C(1)DX,yf; pi2 females mostly resulted in the appearance of y+ and y(1) derivatives. The genomes of laboratory strains used in the study contained the full-sized hobo elements, which could differ from one another relative to the structure of variable region and affinity to different DNA sequences.

According to FISH data the presence of multiple hobo element copies in the unstable yellow and Notch loci in y(2-717) and Uc-1 Drosophila melanogaster stocks, respectively, was found. Locus-specific instability in these strains is caused by hobo multiplication in the respective loci and its subsequent recombination with neighboring hobo copies rather than its insertion-excision.

Using fluorescent in situ hybridization technique (FISH), the frequency of hobo and P mobile elements transpositions on X chromosomes from the y2-717, isolated from the Uman' population of Drosophila melanogaster, as well as from its phenotypically normal and mutant derivatives, obtained as a result of crosses the males examined with the C(I)DX, ywf/Y females, was evaluated. It was demonstrated that the maximum frequency of hobo transpositions on X chromosomes of the males from derivative strains, subjected to repeated hobo-dysgenic crosses reached a value of 1.2 x 10(-2) per site per X chromosome per generation. The number of hobo copies in male X chromosomes from derivative strains was 3 times higher than in the original initial strain. Furthermore, the "old" hobo sites remained unchanged. In derivative strains, the frequency of hobo insertions was higher than that of excisions. One of the derivative strains, y1t-717alk3-2, was characterized by high intra-strain instability of hobo element localization. In the y2-717a1k3 and y1t-717alk3-2 strains a large inversion, In(1)1B; 13CD, was described. At the absence of the full-sized P element in the strains involved in crosses, maximum frequency of P element transpositions in the derivative strains reached a value of 1.2 x 10(-2) per site per X chromosome per generation.

The transposition frequency of the hobo mobile element in four successive generations of Drosophila melanogaster strain y2-717 after an acute gamma-irradiation with a dose of 30 Gr amounted to 7.5 x 10(-4) per site per genome per generation. Under the same conditions, PCR analysis of the genomic DNA of y2-717 flies detected new variants of defective hobo sequence. No changes in the hobo localization and PCR products compared with the control were detected in the case of single irradiation with doses of 3 and 30 Gr. The localizations of hobo element on polytene chromosomes of y2-717 strain did not change during 11 generations after five exposures of flies to 30 Gr. Irradiation of a highly unstable D. melanogaster strain y+743 did not increase the number of families with mutant progeny, yet increased the total number of mutant descendants almost twofold, from 5 to 9%.

Somatic mutation and recombination test on wing cells of Drosophila melanogaster showed that the recombination frequency in the somatic tissues of strains studied correlated with the presence of a full-length copy of the hobo transposable element in the genome. Transposition of hobo in somatic tissue cells at a frequency 3.5 x 10-2 per site per X chromosome was shown by fluorescence in situ hybridization with salivary gland polytene chromosomes of larvae of one of the D. melanogaster strains having a full-length hobo copy.

Babesia infection was studied in 21 blood samples of dogs with symptoms of babesiosis and among 72 Dermacentor reticulatus and 70 Ixodes persulcatus ticks from southwestern Siberia, Russia. Babesia DNA was detected by hemi-nested PCR based on the 18S rRNA gene with subsequent direct sequencing. All of the analyzed canine blood samples and three D. reticulatus, but none from I. persulcatus ticks studied were shown to contain Babesia DNA. Nucleotide sequences of the Babesia 18S rRNA gene fragment of 354 bp long for all 24 positive samples appeared to belong to the subspecies Babesia canis canis and differed only at three positions. The Babesia nucleotide sequences from 17 canine blood samples and from one D. reticulatus tick were identical to each other and to previously known B. canis canis from canine blood in Slovenia. Four canine blood samples and the second tick sample contained a mixture of two nucleotide sequences previously found in canine blood. B. canis canis nucleotide sequence from the third tick differed in the unique nucleotide transition and could correspond to a new genetic variant. Thus, the main etiological agent of canine babesiosis in Novosibirsk region is B. canis canis, and D. reticulatus, but not I. persulcatus, ticks could serve as a vector of this infectious agent. To our knowledge, this is the first report of the B. canis canis nucleotide sequences from ticks.

Mobile genetic elements are responsible for most spontaneous mutations in Drosophila melenogaster. The discovered in the 1980s phenomenon of frequent change of the wild-type yellow phenotype for a mutant one, and vice-versa, in strains of Drosophila melanogaster isolated from the Uman' natural population can be, according to our data, explained by repeated inversions and reinversions of the gene regulatory region located between the two copies of the hobo transport. However, most molecular genetic events accompanying the process can occur without the phenotype change. After several generations, the strains, remaining phenotypically unchanged, can possess different molecular genetic properties with respect to yellow. Using genetically homogenous or isogenic strains for the genetic analysis or for production of the new plant cultivars or animal breeds, geneticists and breeders often face the problem of stability of the strains. In the present study, the mechanism underlying the generation of instability at the yellow locus of D. melanogaster determined by the hobo-induced genome instability is described.

Using light microscopy, we have shown that chlamydia and/or chlamydia-like microorganisms are registered in 20-25% of the healthy part of human population, whereas in patients of the same age with gynecological problems these were found in 40-50%. Commonly, the infection was slightly manifested (less than 5% of cells are infected). These results were confirmed in four months but only in heavily infected patients. The light microscope data are confirmed by observations with electron microscopy, and by FISH hybridization of the total chlamydial DNA on cytological preparations with chlamydial inclusions. In some cases, microcolonies revealed by FISH hybridization occupied the majority of the cytoplasm volume. Occasionally, the DNA material was found on the nuclear surface. It seems likely that in heavily infected cells chlamydia are able to penetrate into the perinucular space.

The nucleolar and extranucleolar RNA synthesis was studied in the mink blastocysts at different stages of embryonic diapause and during the periimplantation period using cytoradioautography. The data obtained suggest a differential and stage specific activity of the embryonic mRNA and rRNA synthesis during the period of delayed implantation.

In case of a correct sampling, the diagnostic value of optic and electron microscopy for detecting Chlamydia infection is not inferior to that of direct microimmunofluorescence (DMIF) and higher than that of enzyme immunoassay (EIA). Optic microscopy showed that basal vaginal epithelium and buccal mucosa can be infected with Chlamydia. Provazek bodies were detected in the buccal mucosa of the overwhelming majority of patients with genital chlamydiasis. These results were confirmed by DMIF and EIA. Since none of the diagnostic methods is 100% reliable, we recommend using two methods: inexpensive optic microscopy and polymerase chain reaction or DMIF.

A mutation outburst of the yellow gene occurred in a Drosophila melanogaster population from the town of Uman' from 1982 to 1991 and was associated with the instability of several alleles. Molecular genetic analysis revealed a deletion variant of the hobo transposable element in the same site of the regulatory region of yellow in the mutant alleles and their derivatives. The outburst of the yellow-2 mutations was attributed to the spreading of the X chromosome, which contained an inversion of the yellow regulatory region, through the population. Reinversion resulted in the wild-type phenotype. Crossing lines carrying the inversion with laboratory line C(1)DX, ywf induced instability of the yellow alleles, which was associated with duplication or multiplication of a fragment of the yellow gene. Most derivative lines eventually became stable. The loss of instability was not associated with phenotypic changes; molecular genetic changes included a loss of the duplicated sequences or a deletion of the inverted regulatory region of the yellow gene.

In 1981 recurrent local bursts of mutability of the yellow gene were observed in a natural population of Drosophila melanogaster from Uman' (Ukraine). A series of y2-like mutations in the yellow gene were recovered during the period 1982 to 1991. Most of the mutants display the y2-phenotype, i.e. mutant yellow color of wings and body cuticle. Ninety-nine y2 mutants were shown to be generated by an inversion that occurred between two hobo elements, one located 129 bp from the start site of yellow transcription, and the other in the distal telomere region. The y2 phenotype was caused by the separation of the body and wing enhancers from the transcription unit. Many of the y2-like alleles were highly unstable and reverted to y+, which again, gave rise to y2-like mutants. We found that the y2-->y+-->y2 transitions were generated by repeated inversions between the two hobo elements mentioned. The y2 and y+ alleles lost their instability after deletion of the hobo element present at the tip of the X chromosome.

In an isogenic line of Drosophila melanogaster carrying the Mendelian mutation radius incompletus, selection for the total length of two segments of the disrupted longitudinal wing vein was conducted. After gamma-irradiation at a dose of 13 Gy, positive and negative truncation selection became highly effective and was completed in 50 generations. The pattern of mobile genetic element Dm412 was almost completely fixed in the course of selection. In the positive direction of selection, fixations of mobile genetic element (MGE) sites exceeded losses; in the negative direction, this relationship was reversed. The number of MGE sites in the pattern increased from 23 to 33 and to 26 in the positive and negative directions, respectively. The mean heterozygosity of MGE sites decreased respectively ten and six times. The dynamics of some sites (6F, 43B, 66A, 69E, and others) corresponded to that expected with an adaptive response to selection. Two out of these sites (43B and 66A) were previously assigned to hot sites of Dm412 transposition induced by heat shock. Fixation and loss of sites continued on average for tens of generations. Four hypotheses describe the relationship between patterns of polygenes and MGE in the context of explanation of the above facts: (1) genetic drift; (2) the linkage of MGE and polygenes without modification of the latter (hitchhiking); (3) the linkage and modifying effect of MGE on polygenes linked with them; (4) the selection of the "champion" pattern of polygenes and a random or adaptive MGE pattern linked with it. Hypotheses 1 and 2 are unlikely, hypothesis 3 is possible in the case of other selection modes, whereas hypothesis 4 seems to be most plausible.

Raising of gamma-irradiated larvae of Drosophila melanogaster on an ethanol-containing medium resulted in decreased mutation frequency in the wing somatic mutation and recombination test. This decrease in mutagenicity was mainly caused by the reduced recombination frequency. In lines with high activity of cytochrome P450, ethanol did not exhibit the radioprotective effect. Frequency of spontaneous mutations was significantly different in reciprocal crosses, whereas frequency of induced somatic mutations did not depend on the cross direction. Addition of 10% ethanol to the medium did not affect spontaneous mutation frequency.

Genotoxicity of fullerene C60 was been determined in a prokaryotic in vitro test and in an eukaryotic in vivo system. The SOS chromotest of fullerene C60 in the Escherichia coli strain PQ37 revealed no genotoxicity either with or without activation of the rat liver homogenate. To perform the somatic mutation and recombination genotoxicity test (SMART) on somatic wing cells, Drosophila melanogaster larvae were grown on a standard medium with or without fullerene dope. No statistically significant differences were observed at the same fullerene concentrations in the SOS chromotest (0.45 micrograms/ml). Only at the highest possible fullerene concentration of 2.24 micrograms per 1 ml medium, a slight genotoxic effect was observed in wing cells. Fullerol demonstrates no mutagenic effect at a concentration of 2.46 mg/ml.

The problem of identification of true and false mutations of the mwh type was studied by means of gamma-irradiation in a test of somatic mosaics of wing cells of D. melanogaster. It was shown that the level of induction of mwh-like structures consisting of two trichomes and of true mwh mutations is the same if the former are located on the wing surface. Apparently, mwh-like structures located on veins should be assigned to morphoses. The necessity of taking into account two-trichome structures in this test is substantiated.

The content and intensity of incorporation of 3H-uridine in RNA of chromosomes, nucleoli and cytoplasm isolated by microsurgery from the salivary glands of larvae and prepupae of Chironomus thummi were studied following the incubation of salivary glands in the Cannon's medium with 3H-uridine. It was shown that during metamorphosis the content of RNA and intensity of 3H-uridine incorporation decrease in the nucleolus and cytoplasm in a prepupa, as compared with a larva, and suffer no changes in chromosomes in spite of much larger size of many puffs in a prepupa. The patterns of RNA synthesis in the salivary glands of larvae during metamorphosis are discussed.