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E S Belyaeva

Publications and source records attributed to E S Belyaeva.

47 records · Page 3Linked to original sources
PubMed1981

Cytogenetic analysis of the 2B3-4-2B11 region of the X chromosome of Drosophila melanogaster. II. Changes in 20-OH ecdysone puffing caused by genetic defects of puff 2B5.

Larvae homozygous or hemizygous for the l(1)t435 mutation located within the early ecdysteroid puff 2B5, or carrying a deletion of the 2B5 band, die at the end of the third larval instar. In the salivary gland chromosomes of these larvae only intermoult puffs are detected. If these salivary glands are incubated in vitro with 20-OH ecdysone for 6 h the intermoult puff 68 C remains large, some early puffs (74EF and 75B) are induced to 30-40% of their normal size, other early (63F) and all late puffs (62E, 78D, 82F and 63E) are not induced at all. Puff 2B5 reaches its normal size but does not regress after 6 h incubation with 20-OH ecdysone, as it does in normal stocks. The data obtained in this study show the existence of a locus (or loci) in the band (puff) 2B5 which is necessary for the normal response of the salivary gland chromosomes to the hormone 20-OH ecdysone.

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PubMed1980

Cytogenetic analysis of the 2B3-4--2B11 region of the X-chromosome of Drosophila melanogaster. I. Cytology of the region and mutant complementation groups.

There are, at least, 11 distinct single bands and one real doublet in the region 2B1-2--2C1-2 of the X-chromosome of Drosophila melanogaster. This figure coincides with that in Bridges' revised map with most of the "doublet" bands being artifacts. Three puffs appear in the region. The early ecdysone-specific puff 2B5-6, small at PS(puffing stage) 1, increases sharply at PS 2. The late ecdysone-specific puff 2C1-2 appears at PS 4--5. At PS 9--10, when 2B5-6 disappears completely and 2C1-2 decreases, a third puff at 2B11 appears. None of these puffs is active at PS 11. Morphological analysis of puff appearance and autoradiographic study of 3H-uridine incorporation into chromosomes carrying rearrangements within the 2B region suggest that the early ecdysone-specific puff derives from bands 2B5 and may be 2B6, while the neighbouring bands 2B1-4, and 2B7-10 do not show appreciable transcription at the investigated stages. There are 42 mutations affecting viability in the region where the 2B5-6 puff is located. The mutations belong to 6 complementation groups; two of the groups dor and swi, are independent while the rest are overlapped by several lethal mutations (overlapping complex.) Mutants of the different groups have series of similar characteristics: temperature sensitivity, dose sensitivity, larva-pupal lethality and similar morphological abnormalities. It can be assumed that there is a functionally linked cluster of genes within the region 2B. Complementation groups br, rbp, l(1)pp-1, l(1)pp-2 (overlapping complex) have been located by rearrangements in very narrow cytological limit 2B3-4--2B5 that is in the area of developing puff. Two other loci dor and swi are situated some to the right of 2B5.

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PubMed1976

Comparative study of the function of polytene chromosomes in laboratory stocks of Drosophila melanogaster and the l(3)tl mutant (lethal tumorous larvae). II. Changes of banding pattern and transcriptional activity in the salivary chromosome of l(3)tl.

The salivary chromosomes of the l(3)tl mutant of D. melanogaster are considerably thicker and shorter than those of normal larvae. In most nuclei, chromosome shortening is associated with morphological changes of two types. a) The bands lose their distinctive pattern and become loose. The chromosome appears as a granular mass. In extreme cases pompon-like chromosomes arise. Most frequently male X-chromosomes undergo such changes and begin to shorten as early as in the middle of third larval instar. "Pompon" transformation is not associated with a change in the relative intensity of RNA synthesis: the ratio of silver grain number over the male X-chromosome to that over regions 61A-63F is the same in pompon-like l(3)tl chromosomes and in the male and female X-chromosomes of the normal lines. b) Shortened chromosomes occassionally retain distinct band organization and, in these cases, chromosome shortening is observed to be due to the condensation of the chromatin of many puffs and interbands resulting in the fusion of a large number of bands into "new" chromatin blocks. In regions of fused bands, transcriptional activity is decreased as compared with regions where this union does not occur. The chromosomes of l(3)tl larvae lack ecdysone-stimulated puffs and other prominent puffs. In 144-192 hour larvae, puffs can be induced by ecdysone and until 384 hours by temperature shock. The capacity of puff induction decreases with larval age.

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PubMed1976

Comparison of in vivo and in vitro RNA synthesis on polytene chromosomes of Drosophila.

A comparative radioautographic study of the RNA precursors incorporation on polytene chromosomes of Drosophila in vivo in the cells of salivary glands, and in vitro during incubation of E.coli RNA polymerase on slides with fixed chromosomes was performed.--The pattern of in vivo 3H-uridine incorporation on different sections of the chromosomes drastically differed from the in vitro 3H-UTP incorporation which seems to be much more related to DNA content of the individual small sections. In both cases puffing of the loci resulted in the increase of RNA synthesis but in vitro only 2-3 fold and in vivo much more. Hence, RNA synthesis in vitro was unspecific and did not reflect the in vivo RNA synthesis.--On the other hand, E.coli RNA polymerase completely mimics in vitro the dosage compensation phenomenon making twice as much RNA on one X-chromosome of males (1X2A) as on each of X-chromosomes of diploid (2X2A) and triploid (3X3A) females and super-females (3X2A), and the intermediate amount of RNA on each of X-chromosomes of intersexes (2X3A). It is suggested that the differences in the in vitro template activity of X-chromosomes of cells with different X:A ratio are due to different extent of condensation of their deoxyribonucleoprotein (DNP). Yet, both male and each of female X-chromosomes bind the same amount of thymus histone FI labelled with fluorochrome which indicates that they contain the same amount of "open" regions with exposed chromosomal DNA accessible to external proteins.--On the basis of these observations a hypothesis is put forward which suggests that RNA transcription in animal chromosomes is regulated at two levels by different mechanisms; the first one controls the extent of condensation of DNP of genetic loci and determines their competence to the second mechanism which involves the action of gene-specific activator proteins. According to this hypothesis the phenomenon of dosage compensation of sex-linked genes is due to decondensation of DNP of male X-chromosome which renders its loci twice as responsive to activators as compared to the same loci in females.

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PubMed1976

Genetics of esterases in Drosophila. IV. Slow-migrating S-esterase in Drosophila of the virilis group.

A slow-migrating beta-esterase (S-esterase) is described which has been detected in Drosophila montana, Drosophila imeretensis, and some stocks of Drosophila virilis when mixtures of alpha- and beta-naphthyl acetate are used as substrates in histochemical reactions after electrophoresis. Sexual dimorphism for S-esterase has been demonstrated. This esterase is contained in male genitalia only, predominantly in the ejaculatory bulb (waxy plug). It appears 3-4 days after emergence of flies. In hybrids between S+ and So species, the activity of the slow esterase is either decreased or inhibited. An autonomous synthesis of the S- esterase in the ejaculatory bulb was established by transplantation of imaginal genital discs into larvae of different Drosophila stocks. Based on analysis of physiochemical and immunochemical properties, S-esterase is suggested to be an independent fraction of esterase, possibly dimeric, which does not cross-react with beta-esterase antiserum.

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PubMed1976

RNA synthesis in the Drosophila melanogaster puffs.

Autoradiographical analysis of [3H]-uridine incorporation into three large puffs of Drosophila melanogaster has revealed that after 1 min pulse with isotope the label is observed above the whole puff area. When puffs were induced by high temperature, RNA synthesis was sharply increased (or started) in many sites of the developing puff. No significant delay in the transport of newly-synthesized RNA in large puffs, in comparison with small ones, has been found. In regions without temperature-induced puffs RNA synthesis and its transport are apparently delayed under influence of heat shock.

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