Electron microscopic studies on the polytene chromosomes of Chironomus thummi salivary glands

Kiknadze, I. I.; Perov, N. A.; Chentsov, Yu. S.

doi:10.1007/bf00288332

Cited by 13 publications

(8 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The average DNA concentration in the bands, 0.17 M nucleotide, was calculated from the known DNA content of C. thummi salivary gland chromosomes (18) and from their dimensions measured before and after squashing. We assumed that the bands, which contain 95% of the total DNA (19,20), occupy 70% of the chromosome volume (21).…”

Section: Antisera Andmentioning

confidence: 99%

Left-handed Z-DNA in bands of acid-fixed polytene chromosomes.

Arndt‐Jovin

Robert‐Nicoud

Zarling

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Antibodies to DNA in the left-handed (Z) conformation bind to acid-fixed polytene chromosomes of both Chironomus thummi and Drosophila melanogaster, as shown by direct and indirect immunofluorescence. Comparison of the phase-contrast, immunofluorescence, and DNA staining patterns shows a predominant localization of the antibody to the regions of high contrast and DNA density, the bands. The immunofluorescence is completely abolished by competition with polynucleotides in the Z conformation but not by those in the B form. DNase but not RNase treatment eliminates the antibody staining. Actinomycin D inhibits binding, whereas mithramycin has no effect. The highly reproducible immunofluorescence patterns obtained with the anti-Z-DNA antibodies demonstrate variations in fluorescence intensity between particular bands, which can be quantitated by laser scanning and photon counting techniques. The telomeric regions and DNA strands associated with end-to-end chromosome linkage and ectopic pairing are exceptionally bright. At saturation, average values of 1 IgG molecule per 3,000 base pairs and 1 per 15,000 base pairs are found in the intensely and weakly staining regions, respectively. An alternative statement is that the left-handed Z-DNA conformation is present at a frequency of 0.02-0.1%. The measured differences reflect variations in the local density of Z-DNA sites and not in the affinity for the specific antibody, which appears to be relatively constant throughout the chromosomes (Kd = 10 nM). These observations taken together with results of biophysical studies on the properties of Z-DNA in solution suggest that regions of DNA in the left-handed conformation could be involved in higher-order structural organization of chromosomes and possibly in modulation of their functional state.Certain polynucleotides with alternating purine-pyrimidine sequences can assume a left-handed helical conformation (Z structure) in crystals (1, 2) and in solution (e.g., refs. 3-5). In the case of poly[d(G-C)], a variety of base modifications, such as methylation (6) and bromination (7,8) and Drosophila melanogaster. Polytene chromosomes are particularly suitable for in situ cytological studies due to their size, the amplification of the DNA sequences, the constancy of their banding pattern, and the structural differences between active and inactive regions.Our results, obtained with fixed polytene chromosome preparations, differ from those of Nordheim et al. (16), who reported that the immunofluorescence is restricted to interband regions. We provide additional information regarding the localization of Z-DNA-rich regions in chromosomes. These data (see also ref. Cytological Preparations. Polytene chromosomes were prepared as squashes from 4th instar larvae of C. thummi thummi and 3rd instar larvae of D. melanogaster by explantation of the salivary glands, fixation for 1 min in freshly prepared solutions of ethanol:acetic acid, 3:1 (vol/vol), and then 5 min in 45% (vol/ vol) acetic acid (or, alternatively, fixation in 45% ac...

show abstract

Section: Antisera Andmentioning

confidence: 99%

Left-handed Z-DNA in bands of acid-fixed polytene chromosomes.

Arndt‐Jovin

Robert‐Nicoud

Zarling

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…(4) Several of the very fine bands in the chromosome map are at the limits of light microscopic resolution and in addition have been identified in all of the previous light microscopic analyses only a few times (Hagele, personal communication). The existence of these bands has been, however, adequately proven through electron microscopic investigations on thin-sectioned chromo- somes (Kiknadze et al, 1976) and on SSP chromosome preparations (Kalisch et al, 1984, and unpublished data).…”

Section: Resultsmentioning

confidence: 99%

Laser scanning microscopy of surface spread polytene chromosomes

Kalisch

Whitmore

Siegel

1985

Journal of Microscopy

View full text Add to dashboard Cite

SUMMARY A new type of a Laser Scan Microscope (Zeiss) was used for the analysis of the band‐interband pattern of polytene chromosomes in Chironomus. In contrast to the previously used techniques of transmission light and electron microscopy, we used differential interference contrast (DIC) in incident light to depict the pattern. Instead of using common squash preparations, we carried out this investigation with surface spread polytene (SSP) chromosome preparations of salivary glands. The combination of techniques used enabled a more detailed light microscopic presentation of polytene structures in individual preparations than conventional techniques used so far for chromosome mapping.

show abstract

“…Therefore, endocycle retains the cyclic expression of several components and regulators of the mitotic cell division machinery. It seems to be of importance that the degree of polytene structure widely varies, and three main types may be distinguished: (1) classic polyteny with characteristical band structure, for example, in the salivary glands of Diptera (Beermann, 1972;Kiknadze et al, 1976;Zhimulev, 1992); (2) the cell with uncomplete expression of polytene features, for example, in the giant trophoblast cells (Zybina, Zybina, 1996, in the suspensor of higher plants (Nagl, 1978(Nagl, , 1981, in trophocytes of insect ovaries (Dej, Spradling, 1999), and in various endocycles of Invertebrata (Nagl, 1978); (3) the cells, in which the polytene features are not revealed, and polyteny may be suggested basing on the multifold DNA replication in the absence of mitosis (Brodsky, Uryvaeva, 1985). At present it is considered that morphological and functional features of the classical polytene chromosomes are accounted for by the following factors.…”

Section: Polytenymentioning

confidence: 99%