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Genetics Sep 2022In Drosophila chromosomal rearrangements can be maintained and are associated with karyotypic variability among populations from different geographic localities. The...
In Drosophila chromosomal rearrangements can be maintained and are associated with karyotypic variability among populations from different geographic localities. The abundance of variability in gene arrangements among chromosomal arms is even greater when comparing more distantly related species and the study of these chromosomal changes has provided insights into the evolutionary history of species in the genus. In addition, the sequencing of genomes of several Drosophila species has offered the opportunity to establish the global pattern of genomic evolution, at both genetic and chromosomal level. The combined approaches of comparative analysis of syntenic blocks and direct physical maps on polytene chromosomes have elucidated changes in the orientation of genomic sequences and the difference between heterochromatic and euchromatic regions. Unfortunately, the centromeric heterochromatic regions cannot be studied using the cytological maps of polytene chromosomes because they are underreplicated and therefore reside in the chromocenter. In Drosophila melanogaster, a cytological map of the heterochromatin has been elaborated using mitotic chromosomes from larval neuroblasts. In the current work, we have expanded on that mapping by producing cytological maps of the mitotic heterochromatin in an additional 10 sequenced Drosophila species. These maps highlight 2 apparently different paths, for the evolution of the pericentric heterochromatin between the subgenera Sophophora and Drosophila. One path leads toward a progressive complexity of the pericentric heterochromatin (Sophophora) and the other toward a progressive simplification (Drosophila). These maps are also useful for a better understanding how karyotypes have been altered by chromosome arm reshuffling during evolution.
Topics: Animals; Drosophila; Drosophila Proteins; Drosophila melanogaster; Heterochromatin; Polytene Chromosomes
PubMed: 35946576
DOI: 10.1093/genetics/iyac119 -
Tropical Biomedicine Jun 2022Cytoform C, one of three cytoforms in the Simulium angulistylum Takaoka & Davies complex from a high mountain in northeastern Thailand was morphologically and...
Cytoform C, one of three cytoforms in the Simulium angulistylum Takaoka & Davies complex from a high mountain in northeastern Thailand was morphologically and molecularly investigated. All known life stages (larva, pupa, adult male and female except egg) were morphologically similar to, but distinguishable from S. angulistylum s. str. and S. isanense Takaoka, Srisuka & Saeung in the adults by the relative length of the fore and hind basitarsi and relative length of the tooth to the claw. It is also morphologically distinct from other species of the S. epistum species-group. Here, it is formally described as a new species, S. prayooki. Molecular genetic data based on mitochondrial cytochrome c oxidase subunit I (COI) also supported the morphological similarity between the new species and the two related known species (S. angulistylum s. str. and S. isanense) as phylogenetic analysis retrieved them all from a single clade and with a low level of interspecific genetic divergence (1.74%). This might possibly have resulted from incomplete lineage sorting as they are likely to share a recent common ancestor. Despite limitation of molecular genetic differentiation, the new species was distinctly different from two other cytoforms of S. angulistylum complex based on polytene chromosome banding patterns and ecology of the immature stages. Thus, this study highlights the necessity of using an integrated approach for fully understanding black fly biodiversity.
Topics: Animals; Female; Larva; Male; Phylogeny; Pupa; Simuliidae; Thailand
PubMed: 35838102
DOI: 10.47665/tb.39.2.018 -
Proceedings of the National Academy of... Jun 2022Cryoelectron tomography of the cell nucleus using scanning transmission electron microscopy and deconvolution processing technology has highlighted a large-scale, 100-...
Cryoelectron tomography of the cell nucleus using scanning transmission electron microscopy and deconvolution processing technology has highlighted a large-scale, 100- to 300-nm interphase chromosome structure, which is present throughout the nucleus. This study further documents and analyzes these chromosome structures. The paper is divided into four parts: 1) evidence (preliminary) for a unified interphase chromosome structure; 2) a proposed unified interphase chromosome architecture; 3) organization as chromosome territories (e.g., fitting the 46 human chromosomes into a 10-μm-diameter nucleus); and 4) structure unification into a polytene chromosome architecture and lampbrush chromosomes. Finally, the paper concludes with a living light microscopy cell study showing that the G1 nucleus contains very similar structures throughout. The main finding is that this chromosome structure appears to coil the 11-nm nucleosome fiber into a defined hollow structure, analogous to a Slinky helical spring [https://en.wikipedia.org/wiki/Slinky; motif used in Bowerman , 10, e65587 (2021)]. This Slinky architecture can be used to build chromosome territories, extended to the polytene chromosome structure, as well as to the structure of lampbrush chromosomes.
Topics: Cell Nucleus; Chromatin; Chromosomes, Human; Humans; Interphase; Nucleosomes
PubMed: 35749363
DOI: 10.1073/pnas.2119101119 -
Journal of Insect Science (Online) May 2022Drosophila E74 is an early gene located in the polytene chromosome 74EF puff position. E74 controls the production of late genes, indicating that it plays a crucial role...
Drosophila E74 is an early gene located in the polytene chromosome 74EF puff position. E74 controls the production of late genes, indicating that it plays a crucial role in this cascade model. Nilaparvata lugens E74 is closely related to Diaphorina citri, Bemisia tabaci, and Laodelphax striatellus. After downregulating E74, molting, and nymphal mortality were increased, and ovarian development was delayed. Moreover, the expression of Vg was reduced at the transcriptional level, as measured by qRT-PCR, and the content of Vg protein was reduced, as detected by Western blotting. After downregulating E74, the expression of hormone-related genes, including Tai, βFtz-F1, Met, Kr-h1, UspA, UspB, E93, and Br, was changed. The expression of E74 was significantly decreased after downregulating hormone-related genes. When the expression of E74 and βFtz-F1 was downregulated together, nymph mortality and molting mortality were higher than those when E74 or βFtz-F1 was downregulated alone. Thus, E74 probably interacts with βFtz-F1 at the genetic level. In summary, this study showed that E74 plays a crucial role in the development, metamorphosis and reproduction of N. lugens, possibly via the interaction with βFtz-F1 at the genetic level. This study provides a basis for the development of new target-based pesticides and new methods for the effective control of N. lugens.
Topics: Animals; Drosophila; Drosophila Proteins; Hemiptera; Hormones; Metamorphosis, Biological; Nymph
PubMed: 35738261
DOI: 10.1093/jisesa/ieac041 -
Biologia Futura Jun 2022Although benzaldehyde, an aromatic aldehyde, has been declared safe for uses in food, conflicting reports exist regarding its genotoxic and cytotoxic potentials in...
Although benzaldehyde, an aromatic aldehyde, has been declared safe for uses in food, conflicting reports exist regarding its genotoxic and cytotoxic potentials in organisms. Our present study is the first attempt to evaluate the effects of exposure of benzaldehyde on the entire course of development of a eukaryote model organism, Drosophila melanogaster. Total time required for the initial appearance of the third instar larvae, pupae and adults increased dose dependently with the increasing dietary concentration of benzaldehyde. Exposure of flies to each concentration of benzaldehyde caused dose-dependent and significant reductions in the population of pupae and young adults of the fly. Developmental inhibition was associated with dose dependent and significant structural aberrations of larval polytene chromosomes like ectopic pairing, inversion, fusion, etc., and deformities of hemocytes and neuroblasts and death of hemocytes. As much as 34% (SD ± 1.76)-52% (SD ± 1.7) and 18% (SD ± 2.5)-40% (SD ± 3.38) hemocytes and neuroblasts, respectively, underwent nuclear deformations in response to dietary exposures of flies to BA 100-1000 mg/l. Moreover, 16% (SD ± 0.52)-31% (SD ± 1.97) and 19% (SD ± 0.3)-33% (SD ± 1.78) hemocyte mortalities in response to BA 100-1000 mg/l were determined by two cell viability assays. Thus our study revealed that benzaldehyde was genotoxic to Drosophila melanogaster larvae that might be responsible for larval cell death and their subsequent developmental retardation. As this fly possesses substantial genetic homology with human, possibility of developmental inhibition of the later due to exposure of this chemical during pregnancy may not be ruled out.
Topics: Animals; Benzaldehydes; DNA Damage; Drosophila melanogaster; Hemocytes; Larva; Pupa
PubMed: 35690701
DOI: 10.1007/s42977-022-00116-5 -
Insects Apr 2022The represent a diverse group of closely related to Although they have radiated extensively in Australia, they have been the focus of few studies. Here, we...
The represent a diverse group of closely related to Although they have radiated extensively in Australia, they have been the focus of few studies. Here, we characterized the karyotypes of 12 species from several species groups and showed that they have undergone similar types of karyotypic change to those seen in . This includes heterochromatin amplification involved in length changes of the sex and 'dot' chromosomes as well as the autosomes, particularly in the group of species. Numerous weak points along the arms of the polytene chromosomes suggest the presence of internal repetitive sequence DNA, but these regions did not C-band in mitotic chromosomes, and their analysis will depend on DNA sequencing. The nucleolar organizing regions (NORs) are at the same chromosome positions in as in and the various mechanisms responsible for changing arm configurations also appear to be the same. These chromosomal studies provide a complementary resource to other investigations of this group, with several species currently being sequenced.
PubMed: 35447805
DOI: 10.3390/insects13040364 -
Comparative Cytogenetics 2022
Karyotype characteristics and gene COI sequences of Shilova et Dzhvarsheishvili, 1974 (Diptera, Chironomidae) from the South Caucasus (Republic of Georgia, Paravani river).
PubMed: 35437458
DOI: 10.3897/CompCytogen.v16.i1.79182 -
Genetics and Molecular Biology 2022Transposable elements are abundant and dynamic part of the genome, influencing organisms in different ways through their presence or mobilization, or by acting directly...
Transposable elements are abundant and dynamic part of the genome, influencing organisms in different ways through their presence or mobilization, or by acting directly on pre- and post-transcriptional regulatory regions. We compared and evaluated the presence, structure, and copy number of three hAT superfamily transposons (hobo, BuT2, and mar) in five strains of Drosophila willistoni species. These D. willistoni strains are of different geographical origins, sampled across the north-south occurrence of this species. We used sequenced clones of the hAT elements in fluorescence in-situ hybridizations in the polytene chromosomes of three strains of D. willistoni. We also analyzed the structural characteristics and number of copies of these hAT elements in the 10 currently available sequenced genomes of the willistoni group. We found that hobo, BuT2, and mar were widely distributed in D. willistoni polytene chromosomes and sequenced genomes of the willistoni group, except for mar, which is restricted to the subgroup willistoni. Furthermore, the elements hobo, BuT2, and mar have different evolutionary histories. The transposon differences among D. willistoni strains, such as variation in the number, structure, and chromosomal distribution of hAT transposons, could reflect the genomic and chromosomal plasticity of D. willistoni species in adapting to highly variable environments.
PubMed: 35297941
DOI: 10.1590/1678-4685-GMB-2021-0287 -
Chromosome Research : An International... Dec 2022Studying the probability distribution of replication initiation along a chromosome is a huge challenge. Drosophila polytene chromosomes in combination with...
Studying the probability distribution of replication initiation along a chromosome is a huge challenge. Drosophila polytene chromosomes in combination with super-resolution microscopy provide a unique opportunity for analyzing the probabilistic nature of replication initiation at the ultrastructural level. Here, we developed a method for synchronizing S-phase induction among salivary gland cells. An analysis of the replication label distribution in the first minutes of S phase and in the following hours after the induction revealed the dynamics of replication initiation. Spatial super-resolution structured illumination microscopy allowed identifying multiple discrete replication signals and to investigate the behavior of replication signals in the first minutes of the S phase at the ultrastructural level. We identified replication initiation zones where initiation occurs stochastically. These zones differ significantly in the probability of replication initiation per time unit. There are zones in which initiation occurs on most strands of the polytene chromosome in a few minutes. In other zones, the initiation on all strands takes several hours. Compact bands are free of replication initiation events, and the replication runs from outer edges to the middle, where band shapes may alter.
Topics: Animals; Drosophila; Polytene Chromosomes; Microscopy; DNA Replication; Chromosomes; Drosophila melanogaster
PubMed: 35226231
DOI: 10.1007/s10577-021-09679-w -
Nature Cell Biology Mar 2022Despite the well-established role of nuclear organization in the regulation of gene expression, little is known about the reverse: how transcription shapes the spatial...
Despite the well-established role of nuclear organization in the regulation of gene expression, little is known about the reverse: how transcription shapes the spatial organization of the genome. Owing to the small sizes of most previously studied genes and the limited resolution of microscopy, the structure and spatial arrangement of a single transcribed gene are still poorly understood. Here we study several long highly expressed genes and demonstrate that they form open-ended transcription loops with polymerases moving along the loops and carrying nascent RNAs. Transcription loops can span across micrometres, resembling lampbrush loops and polytene puffs. The extension and shape of transcription loops suggest their intrinsic stiffness, which we attribute to decoration with multiple voluminous nascent ribonucleoproteins. Our data contradict the model of transcription factories and suggest that although microscopically resolvable transcription loops are specific for long highly expressed genes, the mechanisms underlying their formation could represent a general aspect of eukaryotic transcription.
Topics: Chromosomes; Eukaryota; RNA; Ribonucleoproteins; Transcription, Genetic
PubMed: 35177821
DOI: 10.1038/s41556-022-00847-6