scholarly journals Visualization of Drosophila melanogaster chorion genes undergoing amplification.

1988 ◽  
Vol 8 (7) ◽  
pp. 2811-2821 ◽  
Author(s):  
Y N Osheim ◽  
O L Miller ◽  
A L Beyer
Keyword(s):  
Time Frame ◽  
Maximum Activity ◽  
Follicle Cells ◽  
Control Element ◽  
Active Gene ◽  
Chorion Genes ◽  
Temporal Specificity ◽  
Preferential Amplification ◽  
Essential Region ◽  
Large Clusters

We visualized by electron microscopy the preferential amplification of Drosophila chorion genes in late-stage follicle cells. Chromatin spreads revealed large clusters of actively transcribed genes of the appropriate size, spacing, and orientation for chorion genes that were expressed with the correct temporal specificity. Occasionally the active genes were observed within or contiguous with intact replicons and replication forks. In every case, our micrographs are consistent with the hypothesis that the central region of each chorion domain contains a replication origin(s) used during the amplification event. In one case, a small replication bubble was observed precisely at the site of the essential region of the X chromosome amplification control element. The micrographs also suggest that forks at either end of a replicon frequently progress very different distances, presumably due to different times in initiation or different rates of movement. It appears that all chorion genes (even those coding for minor proteins) are transcribed in a "fully on" condition, albeit for varied durations, and that if replication fork passage does inactivate a promoter, it does so very transiently. Furthermore, a DNA segment containing one active gene is likely to have an additional active gene(s). Surprisingly, during the time frame of expected maximum activity, approximately half of the chorion sequences appear transcriptionally inactive.

Visualization of Drosophila melanogaster chorion genes undergoing amplification

1988 ◽  
Vol 8 (7) ◽  
pp. 2811-2821
Author(s):  
Y N Osheim ◽  
O L Miller ◽  
A L Beyer
Keyword(s):  
Time Frame ◽  
Maximum Activity ◽  
Follicle Cells ◽  
Control Element ◽  
Active Gene ◽  
Chorion Genes ◽  
Temporal Specificity ◽  
Preferential Amplification ◽  
Essential Region ◽  
Large Clusters

We visualized by electron microscopy the preferential amplification of Drosophila chorion genes in late-stage follicle cells. Chromatin spreads revealed large clusters of actively transcribed genes of the appropriate size, spacing, and orientation for chorion genes that were expressed with the correct temporal specificity. Occasionally the active genes were observed within or contiguous with intact replicons and replication forks. In every case, our micrographs are consistent with the hypothesis that the central region of each chorion domain contains a replication origin(s) used during the amplification event. In one case, a small replication bubble was observed precisely at the site of the essential region of the X chromosome amplification control element. The micrographs also suggest that forks at either end of a replicon frequently progress very different distances, presumably due to different times in initiation or different rates of movement. It appears that all chorion genes (even those coding for minor proteins) are transcribed in a "fully on" condition, albeit for varied durations, and that if replication fork passage does inactivate a promoter, it does so very transiently. Furthermore, a DNA segment containing one active gene is likely to have an additional active gene(s). Surprisingly, during the time frame of expected maximum activity, approximately half of the chorion sequences appear transcriptionally inactive.

Drosophila chorion gene amplification requires an upstream region regulating s18 transcription

1986 ◽  
Vol 6 (12) ◽  
pp. 4624-4633
Author(s):  
T L Orr-Weaver ◽  
A C Spradling
Keyword(s):  
Gene Expression ◽  
Ovarian Follicle ◽  
Follicle Cells ◽  
Upstream Region ◽  
Transcription Control ◽  
The Third ◽  
Chorion Genes ◽  
Specific Amplification ◽  
Essential Region ◽  
Per Se

A cluster of Drosophila melanogaster chorion genes at locus 66D on the third chromosome amplifies 60-fold in the ovarian follicle cells prior to the onset of gene expression. A 3.8-kilobase (kb) region of the gene cluster can induce tissue-specific amplification in transformants. Previous models postulated that amplification is activated in follicle cells by transcription of one of the two chorion genes (s15 and s18) located within the 3.8-kb essential region. In this study, we showed that neither s15 nor s18 chorion gene transcription was required for amplification. However, a 510-bp region upstream from s18 contained sequences essential for both amplification and s18 transcription. No other region within the 3.8-kb fragment was required for amplification. We propose that upstream transcription control elements rather than transcription per se are involved in controlling amplification during development.

scholarly journals Drosophila chorion gene amplification requires an upstream region regulating s18 transcription.

1986 ◽  
Vol 6 (12) ◽  
pp. 4624-4633 ◽  
Author(s):  
T L Orr-Weaver ◽  
A C Spradling
Keyword(s):  
Gene Expression ◽  
Ovarian Follicle ◽  
Follicle Cells ◽  
Upstream Region ◽  
Transcription Control ◽  
The Third ◽  
Chorion Genes ◽  
Specific Amplification ◽  
Essential Region ◽  
Per Se

A cluster of Drosophila melanogaster chorion genes at locus 66D on the third chromosome amplifies 60-fold in the ovarian follicle cells prior to the onset of gene expression. A 3.8-kilobase (kb) region of the gene cluster can induce tissue-specific amplification in transformants. Previous models postulated that amplification is activated in follicle cells by transcription of one of the two chorion genes (s15 and s18) located within the 3.8-kb essential region. In this study, we showed that neither s15 nor s18 chorion gene transcription was required for amplification. However, a 510-bp region upstream from s18 contained sequences essential for both amplification and s18 transcription. No other region within the 3.8-kb fragment was required for amplification. We propose that upstream transcription control elements rather than transcription per se are involved in controlling amplification during development.

scholarly journals The Drosophila ACE3 chorion element autonomously induces amplification.

1992 ◽  
Vol 12 (5) ◽  
pp. 2444-2453 ◽  
Author(s):  
J L Carminati ◽  
C G Johnston ◽  
T L Orr-Weaver
Keyword(s):  
Dna Replication ◽  
Dna Sequences ◽  
Regulatory Elements ◽  
P Element ◽  
Follicle Cells ◽  
Control Element ◽  
The Third ◽  
Transposon Insertion ◽  
Multiple Copies ◽  
Flanking Sequences

The Drosophila chorion genes amplify in the follicle cells by repeated rounds of reinitiation of DNA replication. ACE3 (amplification control element from the third chromosome) has been identified by a series of deletion experiments as an important control element for amplification of the third-chromosome chorion cluster. Several elements that quantitatively enhance amplification also have been defined. We show that a single 440-bp ACE3 sequence is sufficient to regulate amplification with proper developmental specificity autonomously from other chorion DNA sequences and regulatory elements. Although ACE3 is sufficient for amplification, the levels of amplification are low even when ACE3 is present in multiple copies. When controlled solely by ACE3, amplification initiates either at ACE3 or within closely linked sequences. Amplification of an ACE3 transposon insertion produces a gradient of amplified DNA that extends into flanking sequences approximately the same distance as does the amplification gradient at the endogenous chorion locus. The profile and extent of the amplified gradient imply that the low levels of amplification observed are the result of limited rounds of initiation of DNA replication. Transposon inserts containing multiple copies of ACE3 in a tandem, head-to-tail array are maintained stably in the chromosome. However, mobilization of the P-element transposons containing ACE3 multimers results in deletions within the array at a high frequency.

scholarly journals The Function of the Broad-Complex During Drosophila melanogaster Oogenesis

Genetics ◽  
1999 ◽  
Vol 153 (3) ◽  
pp. 1371-1383
Author(s):  
George Tzolovsky ◽  
Wu-Min Deng ◽  
Thomas Schlitt ◽  
Mary Bownes
Keyword(s):  
Gene Expression ◽  
Dna Replication ◽  
Zinc Finger ◽  
Target Genes ◽  
Ectopic Expression ◽  
Follicle Cells ◽  
Chorion Genes ◽  
Broad Complex ◽  
Late Expression

Abstract The Broad-Complex (BR-C) is an early ecdysone response gene that functions during metamorphosis and encodes a family of zinc-finger transcription factors. It is expressed in a dynamic pattern during oogenesis. Its late expression in the lateral-dorsal-anterior follicle cells is related to the morphogenesis of the chorionic appendages. All four zinc-finger isoforms are expressed in oogenesis, which is consistent with the abnormal appendage phenotypes resulting from their ectopic expression. We investigated the mechanism by which the BR-C affects chorion deposition by using BrdU to follow the effects of BR-C misexpression on DNA replication and in situ hybridization to ovarian mRNA to evaluate chorion gene expression. Ectopic BR-C expression leads to prolonged endoreplication and to additional amplification of genes, besides the chorion genes, at other sites in the genome. The pattern of chorion gene expression is not affected along the anterior-posterior axis, but the follicle cells at the anterior of the oocyte fail to migrate correctly in an anterior direction when BR-C is misexpressed. We conclude that the target genes of the BR-C in oogenesis include a protein essential for endoreplication and chorion gene amplification. This may provide a link between steroid hormones and the control of DNA replication during oogenesis.

Organization of regionally expressed silkmoth chorion genes

1986 ◽  
Vol 6 (9) ◽  
pp. 3215-3220
Author(s):  
A K Hatzopoulos ◽  
J C Regier
Keyword(s):  
Gene Expression ◽  
Follicle Cells ◽  
Gene Copy ◽  
Late Period ◽  
Chorion Genes ◽  
Copy Numbers ◽  
Total Dna ◽  
Dna Strand ◽  
Gene Copy Numbers ◽  
Silkmoth Chorion

We described the organization of two silkmoth chorion genes, called E1 and E2, whose expression is largely restricted in time to the very late period of choriogenesis and in space to one of two major subpopulations of follicle cells. Using E1 and E2 clone cDNAs as probes, we showed that gene copy numbers per haploid genome remain constant throughout silkmoth development despite major changes in total DNA content per nucleus. Furthermore, gene copy numbers are the same in both cellular regions of the choriogenic follicle despite differences in nuclear size and levels of E gene expression. Southern analysis indicated between two and four copies each for E1 and E2 genes. Analysis of chromosomal clones showed that single copies of E1 and E2 are separated by about 7.5 kilobases and are transcribed from the same DNA strand. Two distinct pairs of cloned E1 and E2 genes were characterized. No other chorion genes were in their immediate vicinity.

scholarly journals Multiple replication origins are used during Drosophila chorion gene amplification.

1990 ◽  
Vol 110 (4) ◽  
pp. 903-914 ◽  
Author(s):  
M M Heck ◽  
A C Spradling
Keyword(s):  
Gene Amplification ◽  
Regulatory Elements ◽  
Follicle Cells ◽  
The Third ◽  
Multiple Origins ◽  
Chorion Genes ◽  
D Region ◽  
Egg Chambers ◽  
Replication Intermediates ◽  
Multiple Replication

DNA from Drosophila egg chambers undergoing chorion gene amplification was analyzed using the two-dimensional gel technique of Brewer and Fangman. At stage 10, 34% of DNA molecules from the maximally amplified region of the third chromosome chorion gene cluster contained replication forks or bubbles. These nonlinear forms were intermediates in the process of amplification; they were confined to follicle cells, and were found only within the replicating region during the time of amplification. Multiple origins gave rise to these intermediates, since three separate regions of the third chromosome chorion locus contained replication bubbles. However, initiation was nonrandom; the majority of initiations appeared to occur near the Bgl II site located between the s18 and s15 chorion genes. The P[S6.9] chorion transposon also contained abundant replication intermediates in follicle cells from a transformed line. Initiation within P[S6.9] occurred near two previously defined cis-regulatory elements, one near the same Bgl II site (in the AER-d region) and one near the ACE3 element.

scholarly journals Plasma bubble zonal velocity variations with solar activity in the Brazilian region

2004 ◽  
Vol 22 (9) ◽  
pp. 3123-3128 ◽  
Author(s):  
P. M. Terra ◽  
J. H. A. Sobral ◽  
M. A. Abdu ◽  
J. R. Souza ◽  
H. Takahashi
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Time Frame ◽  
Maximum Activity ◽  
Bubble Velocity ◽  
Activity Period ◽  
Plasma Bubble ◽  
Plasma Bubbles ◽  
Velocity Magnitude ◽  
Zonal Velocity

Abstract. A statistical study of the zonal drift velocities of the ionospheric plasma bubbles using experimental airglow data acquired at the low-latitude station Cachoeira Paulista (Geogr. 22.5° S, 45° W, dip angle 28° S) during the period of October to March, between 1980 and 1994, is presented here. This study is based on 109 nights of zonal plasma bubble velocity estimations as determined from bubbles signatures on the OI 630nm scanning photometer airglow data. The zonal velocity magnitudes of the plasma bubbles are investigated with respect to solar activity and local time. It is verified that these velocities tend to increase with the solar EUV flux, using the solar 10.7-cm radio flux as a proxy (F10.7). These velocities are seen to be larger during the solar maximum activity period than in the solar minimum period. As to the local time variation, they are seen to peak before midnight, in the 20:30-22:30 LT time frame, depending on the season. The all-data plot based on the 109 nights of airglow experiments shows that the plasma bubble mean zonal drift velocities tend to decrease with local time, but they peak at 22:25 LT, where the velocity magnitude reaches 127.4ms-1. The zonal drift variations with local time and solar flux are shown in Figs. 1 and 2, respectively.

Drosophila chorion gene amplification: a model system for the study of chromosome replication

1984 ◽  
Vol 307 (1132) ◽  
pp. 239-245
Keyword(s):  
Dna Replication ◽  
Dna Sequences ◽  
Ovarian Follicle ◽  
Model System ◽  
P Element ◽  
Follicle Cells ◽  
Tissue Specific ◽  
Chorion Genes ◽  
Specific Amplification

Two chromosomal domains of 80-100 kilobases containing Drosophila chorion genes undergo tissue-specific amplification in ovarian follicle cells during oogenesis. We have investigated the ability of small segments of DNA from within these regions to induce amplification after insertion into new chromosomal sites by P element-mediated transformation. Certain transduced chorion DNA sequences initiated a pattern of tissue-specific differential replication that was identical to norm al chorion amplification. Both the transformed chorion DNA as well as flanking rosy DNA sequences underw ent amplification. O ur results suggest that differential chorion DNA replication is mediated by specific origin-containing sequences located near the centre of the amplified domains. The possible role of such sequences in normal programmes of replication is discussed.

scholarly journals Organization of regionally expressed silkmoth chorion genes.

1986 ◽  
Vol 6 (9) ◽  
pp. 3215-3220 ◽  
Author(s):  
A K Hatzopoulos ◽  
J C Regier
Keyword(s):  
Gene Expression ◽  
Follicle Cells ◽  
Gene Copy ◽  
Late Period ◽  
Chorion Genes ◽  
Copy Numbers ◽  
Total Dna ◽  
Dna Strand ◽  
Gene Copy Numbers ◽  
Silkmoth Chorion

We described the organization of two silkmoth chorion genes, called E1 and E2, whose expression is largely restricted in time to the very late period of choriogenesis and in space to one of two major subpopulations of follicle cells. Using E1 and E2 clone cDNAs as probes, we showed that gene copy numbers per haploid genome remain constant throughout silkmoth development despite major changes in total DNA content per nucleus. Furthermore, gene copy numbers are the same in both cellular regions of the choriogenic follicle despite differences in nuclear size and levels of E gene expression. Southern analysis indicated between two and four copies each for E1 and E2 genes. Analysis of chromosomal clones showed that single copies of E1 and E2 are separated by about 7.5 kilobases and are transcribed from the same DNA strand. Two distinct pairs of cloned E1 and E2 genes were characterized. No other chorion genes were in their immediate vicinity.

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