Cytogenetic analysis of the paternal sex ratio chromosome of Nasonia vitripennis

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 157-161 ◽  
Author(s):  
Kent M. Reed
Keyword(s):  
Sex Ratio ◽  
Silver Staining ◽  
Organizer Region ◽  
Parasitic Wasp ◽  
Nucleolus Organizer Region ◽  
B Chromosome ◽  
Nucleolus Organizer ◽  
Nasonia Vitripennis ◽  
C Banding ◽  
Paternal Sex Ratio

Paternal sex ratio (PSR) is a B chromosome found in the parasitic wasp Nasonia vitripennis. PSR has a unique etiology in that it destroys the paternal chromosomes of fertilized eggs, resulting in the production of all male families. This study examined structural aspects of PSR including size, C-banding, and silver staining. PSR was found to constitute approximately 5.7% of the genome of carrier males. C-banding confirmed the heterochromatic nature of PSR and the data suggest that PSR remains primarily condensed throughout the cell cycle. Examination of prometaphase spermatocytes revealed a secondary constriction on PSR. The constriction, however, did not stain positive for nucleolus organizer activity. During mitosis, PSR and the pericentromeric regions of the A chromosomes displayed a temporal pattern of silver staining, involving dense precipitation of silver prior to metaphase. This reaction is indicative of a protein complex specific to the heterochromatin of these regions. The implications of these findings to the origin of PSR are discussed.Key words: Nasonia vitripennis, paternal sex ratio, B chromosome, nucleolus organizer region, heterochromatin.

scholarly journals Deletion analysis of the selfish B chromosome, Paternal Sex Ratio (PSR), in the parasitic wasp Nasonia vitripennis.

Genetics ◽  
1993 ◽  
Vol 133 (3) ◽  
pp. 637-648 ◽  
Author(s):  
L W Beukeboom ◽  
J H Werren
Keyword(s):  
Sex Ratio ◽  
Dna Sequences ◽  
Parasitic Wasp ◽  
B Chromosome ◽  
Deletion Analysis ◽  
Functional Domains ◽  
Functional Domain ◽  
Paternal Chromosome ◽  
Nasonia Vitripennis ◽  
Paternal Sex Ratio

Abstract Paternal Sex Ratio (PSR) is a "selfish" B chromosome in the parasitoid wasp Nasonia vitripennis. It is transmitted via sperm, but causes supercondensation and destruction of the paternal chromosomes in early fertilized eggs. Because this wasp has haplodiploid sex determination, the effect of PSR is to convert diploid (female) eggs into haploid (male) eggs that carry PSR. Characterizing its genetic structure is a first step toward understanding mechanisms of PSR action. The chromosome is largely heterochromatic and contains several tandemly repeated DNA sequences that are not present on the autosomes. A deletion analysis of PSR was performed to investigate organization of repeats and location of functional domains causing paternal chromosome destruction. Deletion profiles using probes to PSR-specific repetitive DNA indicate that most repeats are organized in blocks on the chromosome. This study shows that the functional domains of PSR can be deleted, resulting in nonfunctional PSR chromosomes that are transmitted to daughters. A functional domain may be linked with the psr22 repeat, but function may also depend on abundance of PSR-specific repeats on the chromosome. It is hypothesized that the repeats act as a "sink" for a product required for proper paternal chromosome processing. Almost all deletion chromosomes remained either functional of nonfunctional in subsequent generations following their creation. One chromosome was exceptional in that it reverted from nonfunctionality to functionality in one lineage. Transmission rates of nonfunctional deletion chromosomes were high through haploid males, but low through diploid females.

Meiotic behaviour of the holocentric chromosomes of Nezara viridula (Insecta, Heteroptera) analysed by C-banding and silver impregnation

1985 ◽  
Vol 27 (5) ◽  
pp. 491-497 ◽  
Author(s):  
J. P. M. Camacho ◽  
J. Belda ◽  
J. Cabrero
Keyword(s):  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Nucleolus Organizer ◽  
Silver Impregnation ◽  
Nezara Viridula ◽  
Holocentric Chromosomes ◽  
Cytological Analysis ◽  
C Banding ◽  
I Cells ◽  
Do So

While silver impregnation reveals the presence of kinetochores in monocentric chromosomes, it does not do so in the holocentric system of Nezara viridula. Here, C-banding and silver impregnation techniques reveal that C-heterochromatin is present in the greater part of the Y chromosome and at the nucleolus organizer region (NOR) of the largest autosome (A 1) and in the extra NOR located in the X chromosome of a single exceptional male. Furthermore, one telomere of each autosome appeared lightly C-banded. The largest, A1, bivalent shows chiasmata almost always located at the chromosome ends. This bivalent may orient axially or equatorially in metaphase I cells depending on whether it carries a single chiasma or two chiasmata, respectively. From our cytological analysis we deduce that centromeric activity is preferentially located at the two telomeric ends and that the presence of chiasmata at an end excludes such activity.Key words: diffuse centromere, C-banding, holocentric, insect chromosomes.

A Rapid Silver Staining and Destaining Technique for the Nucleolus Organizer Region

1995 ◽  
Vol 70 (6) ◽  
pp. 302-303 ◽  
Author(s):  
Pawan K. Dhar ◽  
M. R. Kumar ◽  
Satish Nayak ◽  
T. Ramesh Rao ◽  
Anita Joseph ◽  
...  
Keyword(s):  
Silver Staining ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Nucleolus Organizer

Changes in NOR activity pattern in the presence of supernumerary heterochromatin in the grasshopper Eyprepocnemis plorans

Genome ◽  
1995 ◽  
Vol 38 (1) ◽  
pp. 68-74 ◽  
Author(s):  
M. D. López-León ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Activity Patterns ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Adult Life ◽  
B Chromosome ◽  
Nucleolus Organizer ◽  
Supernumerary Chromosome ◽  
Eyprepocnemis Plorans ◽  
X Chromosomes ◽  
Active Nors

Nucleolus organizer region (NOR) activity was analysed in four types of males of the grasshopper Eyprepocnemis plorans, possessing two kinds of supernumerary heterochromatin: a B chromosome and a supernumerary chromosome segment proximally located on the smallest autosome (S11). In males lacking extra heterochromatin, the four active NORs located on the S9, S10, S11, and X chromosomes showed independent activity patterns, but several kinds of dependence appeared in the presence of supernumerary heterochromatin. Furthermore, temporal changes in NOR activity were observed during the first 2 weeks of adult life in standard males but not in males carrying supernumerary heterochromatin. It is suggested that all these effects are related to the DNA content of both types of extra heterochromatin.Key words: NOR, supernumerary heterochromatin, grasshopper, Eyprepocnemis plorans.

The paternal sex ratio chromosome in the parasitic wasp Trichogramma kaykai condenses the paternal chromosomes into a dense chromatin mass

Genome ◽  
2003 ◽  
Vol 46 (4) ◽  
pp. 580-587 ◽  
Author(s):  
Joke F.A van Vugt ◽  
Merijn Salverda ◽  
J Hans de Jong ◽  
Richard Stouthamer
Keyword(s):  
Sex Ratio ◽  
Parasitic Wasp ◽  
Parasitoid Wasp ◽  
B Chromosome ◽  
The Other ◽  
Paternal Chromosome ◽  
Paternal Genome ◽  
Obvious Similarity ◽  
Dense Chromatin ◽  
Paternal Sex Ratio

A recently discovered B chromosome in the parasitoid wasp Trichogramma kaykai was found to be transmitted through males only. Shortly after fertilization, this chromosome eliminates the paternal chromosome set leaving the maternal chromosomes and itself intact. Consequently, the sex ratio in these wasps is changed in favour of males by modifying fertilized diploid eggs into male haploid offspring. In this study, we show that in fertilized eggs at the first mitosis the paternal sex ratio (PSR) chromosome condenses the paternal chromosomes into a so-called paternal chromatin mass (PCM). During this process, the PSR chromosome is morphologically unaffected and is incorporated into the nucleus containing the maternal chromosomes. In the first five mitotic divisions, 67% of the PCMs are associated with one of the nuclei in the embryo. Furthermore, in embryos with an unassociated PCM, all nuclei are at the same mitotic stage, whereas 68% of the PCM-associated nuclei are at a different mitotic phase than the other nuclei in the embryo. Our observations reveal an obvious similarity of the mode of action of the PSR chromosome in T. kaykai with that of the PSR-induced paternal genome loss in the unrelated wasp Nasonia vitripennis.Key words: paternal sex ratio, PSR, Trichogramma kaykai, B chromosome, paternal chromatin mass, embryogenesis.

Transcription of mouse rDNA and associated formation of the nucleolus organizer region after gene transfer and amplification in Chinese hamster cells

1985 ◽  
Vol 5 (11) ◽  
pp. 2943-2950
Author(s):  
V N Dhar ◽  
D A Miller ◽  
O J Miller
Keyword(s):  
Silver Staining ◽  
Transcription Initiation ◽  
Large Fraction ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Chinese Hamster ◽  
Initiation Site ◽  
Chinese Hamster Cell ◽  
Nucleolus Organizer ◽  
Chinese Hamster Cells

Mouse rDNA can initiate transcription by using only Chinese hamster cell components, and this is associated with nucleolus organizer activity. To demonstrate this, we transferred a 3.2-kilobase segment of mouse rDNA containing the promoter, the transcription initiation site, and part of the external transcribed spacer to dihydrofolate reductase-deficient Chinese hamster cells by cotransformation with an abbreviated mouse dhfr gene. Stepwise selection for methotrexate resistance produced sublines in which the mouse rDNA was usually coamplified with the donor dhfr DNA and occupied the same site or sites in the hamster genome, as shown by in situ hybridization. Transcription from mouse rDNA was demonstrated in two such lines, and S1 protection mapping indicated faithful initiation of the transcript. In some cells from both lines, the chromosome segments containing amplified mouse rDNA showed multiple silver-staining regions (i.e., active nucleolus organizers). Although the transferred mouse rDNA was able to use the rDNA transcriptional machinery of the Chinese hamster, the level of transcription was much lower than expected from the rDNA copy number, and a large fraction of each amplified region showed no silver staining. Since the absence of silver staining is generally correlated with the absence of transcription, many copies of the amplified mouse rDNA may have been in a chromatin conformation in which they could not be transcribed. This was not associated with the extensive methylation seen in other amplified, inactive rDNA sequences.

A nucleolus organizer region in a B chromosome inactivated by DNA methylation

Chromosoma ◽  
1991 ◽  
Vol 100 (2) ◽  
pp. 134-138 ◽  
Author(s):  
M. D. L�pez-Le�n ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Dna Methylation ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
B Chromosome ◽  
Nucleolus Organizer

scholarly journals Transcription of mouse rDNA and associated formation of the nucleolus organizer region after gene transfer and amplification in Chinese hamster cells.

1985 ◽  
Vol 5 (11) ◽  
pp. 2943-2950 ◽  
Author(s):  
V N Dhar ◽  
D A Miller ◽  
O J Miller
Keyword(s):  
Silver Staining ◽  
Transcription Initiation ◽  
Large Fraction ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Chinese Hamster ◽  
Initiation Site ◽  
Chinese Hamster Cell ◽  
Nucleolus Organizer ◽  
Chinese Hamster Cells

Mouse rDNA can initiate transcription by using only Chinese hamster cell components, and this is associated with nucleolus organizer activity. To demonstrate this, we transferred a 3.2-kilobase segment of mouse rDNA containing the promoter, the transcription initiation site, and part of the external transcribed spacer to dihydrofolate reductase-deficient Chinese hamster cells by cotransformation with an abbreviated mouse dhfr gene. Stepwise selection for methotrexate resistance produced sublines in which the mouse rDNA was usually coamplified with the donor dhfr DNA and occupied the same site or sites in the hamster genome, as shown by in situ hybridization. Transcription from mouse rDNA was demonstrated in two such lines, and S1 protection mapping indicated faithful initiation of the transcript. In some cells from both lines, the chromosome segments containing amplified mouse rDNA showed multiple silver-staining regions (i.e., active nucleolus organizers). Although the transferred mouse rDNA was able to use the rDNA transcriptional machinery of the Chinese hamster, the level of transcription was much lower than expected from the rDNA copy number, and a large fraction of each amplified region showed no silver staining. Since the absence of silver staining is generally correlated with the absence of transcription, many copies of the amplified mouse rDNA may have been in a chromatin conformation in which they could not be transcribed. This was not associated with the extensive methylation seen in other amplified, inactive rDNA sequences.

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