Electron microscopy of the formation of the cellular blastoderm in Drosophila melanogaster

ABSTRACTSpiroplasmabacteria are highly motile bacteria with no cell wall and a helical morphology. This clade includes many vertically transmitted insect endosymbionts, includingSpiroplasma poulsonii, a natural endosymbiont ofDrosophila melanogaster.S. poulsoniibacteria are mainly found in the hemolymph of infected female flies and exhibit efficient vertical transmission from mother to offspring. As is the case for many facultative endosymbionts,S. poulsoniican manipulate the reproduction of its host; in particular,S. poulsoniiinduces male killing inDrosophila melanogaster. Here, we analyze the morphology ofS. poulsoniiobtained from the hemolymph of infectedDrosophila. This endosymbiont was not only found as long helical filaments, as previously described, but was also found in a Y-shaped form. The use of electron microscopy, immunogold staining of the FtsZ protein, and antibiotic treatment unambiguously linked the Y shape ofS. poulsoniito cell division. Observation of the Y shape in anotherSpiroplasma,S. citri, and anecdotic observations from the literature suggest that cell division by longitudinal scission might be prevalent in theSpiroplasmaclade. Our study is the first to report the Y-shape mode of cell division in an endosymbiotic bacterium and addsSpiroplasmato the so far limited group of bacteria known to utilize this cell division mode.IMPORTANCEMost bacteria rely on binary fission, which involves elongation of the bacteria and DNA replication, followed by splitting into two parts. Examples of bacteria with a Y-shape longitudinal scission remain scarce. Here, we report thatSpiroplasma poulsonii, an endosymbiotic bacterium living inside the fruit flyDrosophila melanogaster, divide with the longitudinal mode of cell division. Observations of the Y shape in anotherSpiroplasma,S. citri, suggest that this mode of scission might be prevalent in theSpiroplasmaclade.Spiroplasmabacteria are wall-less bacteria with a distinctive helical shape, and these bacteria are always associated with arthropods, notably insects. Our study raises the hypothesis that this mode of cell division by longitudinal scission could be linked to the symbiotic mode of life of these bacteria.

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Atypical centrioles are present in Tribolium sperm

Open Biology ◽

10.1098/rsob.160334 ◽

2017 ◽

Vol 7 (3) ◽

pp. 160334 ◽

Cited By ~ 11

Author(s):

E. L. Fishman ◽

Kyoung Jo ◽

Andrew Ha ◽

Rachel Royfman ◽

Ashtyn Zinn ◽

...

Keyword(s):

Electron Microscopy ◽

Drosophila Melanogaster ◽

Cell Division ◽

Tribolium Castaneum ◽

Normal Cell ◽

Somatic Cells ◽

Red Flour Beetle ◽

Flour Beetle ◽

And Function

Typical centrioles are made of microtubules organized in ninefold symmetry. Most animal somatic cells have two centrioles for normal cell division and function. These centrioles originate from the zygote, but because the oocyte does not provide any centrioles, it is surprising that the zygotes of many animals are thought to inherit only one centriole from the sperm. Recently, in the sperm of Drosophila melanogaster , we discovered a second centriolar structure, the proximal centriole-like structure (PCL), which functions in the zygote. Whether the sperm of other insects has a second centriolar structure is unknown. Here, we characterized spermiogenesis in the red flour beetle, Tribolium castaneum . Electron microscopy suggests that Tribolium has one microtubule-based centriole at the tip of the axoneme and a structure similar to the PCL, which lacks microtubules and lies in a cytoplasmic invagination of the nucleus. Immunostaining against the orthologue of the centriole/PCL protein, Ana1, also recognizes two centrioles near the nucleus during spermiogenesis: one that is microtubule-based at the tip of the axoneme, suggesting it is the centriole; and another that is more proximal and appears during early spermiogenesis, suggesting it is the PCL. Together, these findings suggest that Tribolium sperm has one microtubule-based centriole and one microtubule-lacking centriole.

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Ultrastructural details as revealed by stereo transmission electron microscopy of high resolution, pre-shadowed surface snd freeze-etch replicas: sample— the drosophila eye

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081589 ◽

1978 ◽

Vol 36 (2) ◽

pp. 144-145

Author(s):

Russell L. Steere

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Drosophila Melanogaster ◽

Flowing Liquid ◽

Specimen Temperature ◽

Transmission Electron ◽

Specimen Tube ◽

Surface Replica ◽

Insect Eye ◽

Solid Copper

Whereas SEM is useful for studying the surface of objects such as an insect eye at relatively low magnifications, TEM of pre-shadowed replicas has advantages for visualization of the ultrastructural details of surfaces, and freeze-fractured, or freeze-etched specimens.For surface replica studies, fruit flies (Drosophila melanogaster) were glued with glycerol onto a solid copper cap which was then placed on the stage of the Denton freezeetch module. Specimens were frozen by flowing liquid nitrogen into the specimen tube. When specimen temperature reached -105°C, the chamber was evacuated and the shroud cooled to -196°C. With a vacuum of 5 x 10-6 mm Hg, the specimen was warmed to -95°C for 3 to 5 minutes to allow sublimation of any ice which might have condensed on its surface. Specimen temperature was then lowered to -150°C and specimen was shadowed with Pt and coated with carbon.

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Fine Structure of Meiotic Prophase Chromosomes in Lilium Longiflorum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060453 ◽

1967 ◽

Vol 25 ◽

pp. 88-89

Author(s):

Peter B. Moens

Keyword(s):

Electron Microscopy ◽

Drosophila Melanogaster ◽

Meiotic Prophase ◽

Lilium Longiflorum ◽

Nurse Cells ◽

Tomato Plants ◽

Regional Conference ◽

Mother Cells ◽

European Regional ◽

Dipteran Species

The presence of the tripartite ribbon within synapsed homologues has been reported for a large number of sexually reproducing organisms (over one hundred species, including fungi, plants, vertebrates and invertebrates). The absence of the ribbon in some species is associated with uncommon synaptic behaviour of meiotic prophase chromosomes (Drosophila melanogaster males, Drosophila melanogaster females homozygous for synapsis suppressing mutant C3G, and achiasmatic Dipteran species, reported by G. F. Meyer, 1964, Third European Regional Conference on Electron Microscopy). The tripartite ribbon, or synaptinemal complex, may therefore be assumed to be related to pairing of homologues at meiosis. The presence of the complexes and multi-complexes in non-meiotic cells such as insect obcyte nurse cells and spermatids suggests a somewhat broader function of the complexes. This is further supported by the occurrence of complexes in non-homologous paired chromosomes in the pollen mother cells of haploid tomato plants.

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Organization of the cytoskeleton during cellularization in Drosophila melanogaster embryos: Confocal laser scanning and electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159850 ◽

1990 ◽

Vol 48 (3) ◽

pp. 462-463

Author(s):

Kazuo Katoh ◽

Harunori Ishikawa

Keyword(s):

Electron Microscopy ◽

Drosophila Melanogaster ◽

Phosphate Buffer ◽

Laser Scanning ◽

Picric Acid ◽

Egg Laying ◽

Laser Scanning Microscopy ◽

Confocal Laser Scanning ◽

Confocal Laser ◽

Thin Sections

The three-dimensional organization of cytoskeletal components in the early Drosophila melanogaster embryos during cellularization was examined by confocal laser scanning microscopy of the whole embryos and thin section electron microscopy.For confocal microscopy, Drosophila embryos at 2-3 hr after egg-laying were dechorionated and fixed with 8% paraformaldehyde-1% picric acid in 0.1M phosphate buffer (pH 7.2). Embryos were first blocked with normal goat serum, incubated with monoclonal antibody raised against Drosophila embryo α-tubulin for 4 hr, and then were incubated with FITC-conjugated anti-mouse IgG for 2 hr. Some embryos were stained with rhodamine-labeled phailoidin for F-actin visualization. After staining, the whole embryos were mounted on slide glass with an appropriate spacer and examined under the confocal microscope (Bio-Rad, Lasersharp MRC-500). For electron microscopy, dechorionated embryos were fixed with 1/2 Karnovsky's fixative followed by OsO4 fixation. To better preserve actin filaments, embryos were fixed with the same 1/2 Karnovsky's fixative containing 10 μM phailoidin and 0.1% saponin in 0.1M phosphate buffer, pH 7.2. Such fixed embryos were dehydrated and then embedded in Epoxy resin. Thin sections were cut and examined under a Hitachi H-800 type electron microscope.

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SPERMATOCYTE GRANULES IN DROSOPHILA MELANOGASTER

Canadian Journal of Genetics and Cytology ◽

10.1139/g69-020 ◽

1969 ◽

Vol 11 (1) ◽

pp. 153-168 ◽

Cited By ~ 3

Author(s):

John Erickson ◽

A. B. Acton

Keyword(s):

Electron Microscopy ◽

Endoplasmic Reticulum ◽

Drosophila Melanogaster ◽

Host Cell ◽

Acridine Orange ◽

Meiotic Drive ◽

Adult Males ◽

Unit Membrane ◽

The Third ◽

The Individual

Granular inclusions are found in testes from a cn bw stock of Drosophila melanogaster, and maternally derived lines, such as SD. In late larval and early pupal stages, these granules show a polarized distribution within primary spermatocytes corresponding to the polarity basic to the type of meiotic drive where certain homologues reach that pole of the spermatocyte leading to functional sperm. In adult males, the granules are found in intercellular patches in the testes. Electron microscopy shows the spermatocyte granules to be spheroids of about 0.7 μ; dividing, or double forms resulting from division, are about 1.8 μ long. They contain numbers of ribosome-like particles and fine strands presumed to be DNA. The acridine orange test for nucleic acids was positive. Each granule is surrounded by two layers of unit membrane and a third such membrane envelopes the individual or the pair of granules, as the case may be. The third membrane layer (and additional membranes sometimes seen) is thought to be due to entrance of the granules into the host cell through the cisternae of the endoplasmic reticulum. Transmission of the granules is strictly maternal and independent of chromosome constitution. Transmission by contagion was not found. Spermatocyte granules are not requisite to the effectiveness of the SD meiotic drive system, which regularly carries them. A slightly lowered fertility of females carrying the granules was found but no similar effect is produced in males. The evidence suggests that they are parasitic organisms, probably Rickettsiae.

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WHOLE MOUNT ELECTRON MICROSCOPY OF THE NUCLEOLUS IN SALIVARY GLAND CELLS OF DROSOPHILA MELANOGASTER

Canadian Journal of Genetics and Cytology ◽

10.1139/g77-003 ◽

1977 ◽

Vol 19 (1) ◽

pp. 21-29 ◽

Cited By ~ 4

Author(s):

Gary D. Burkholder

Keyword(s):

Electron Microscopy ◽

Drosophila Melanogaster ◽

Salivary Gland ◽

Peripheral Region ◽

Core Region ◽

28S Rrna ◽

The Core ◽

Gland Cells ◽

Salivary Gland Cells ◽

Whole Mount

The nucleolus of Drosophila melanogaster salivary gland cells, examined by whole mount electron microscopy, consists of a fibrillar core region and a peripheral region containing both fibres and granules. These regions appear to correspond to the fibrillar and granular components, respectively, seen in thin sections. Most of the nucleoli were attached to the chromocenter region of the polytene chromosomes, containing the nucleolar organizer. Bundles of relatively straight chromatin fibres, 13 nm in diameter, extended from the chromocenter into the core region of the nucleolus, however it was not possible to trace the path of these chromatin fibres through the nucleolus since they were obscured within the mass of nucleolar fibres. The nucleolar fibres in both the core and peripheral regions were irregular and knobby, with a diameter of about 15 nm. In the core region, the fibres appeared to be of considerable length and were characteristically clustered together to form small interconnected masses. The fibres in the peripheral region were relatively short and some appeared to blend with amorphous, poorly-defined pools of material. Electron dense granules 15-20 nm in diameter were also associated with this amorphous substance. It is hypothesized that the formation and subsequent packaging of the 28s rRNA may be represented by a morphological transition of the peripheral fibres, via an amorphous pool-like intermediate stage, into the nucleolar granules. The results of this study indicate that whole mount electron microscopy may be a useful alternative to thin sectioning in high resolution studies of the nucleolus.

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