Determination of the region of rDNA involved in polytenization in salivary glands of Drosophila hydei

Franz, Gérald; Kunz, Werner; Grimm, Charlotte

doi:10.1007/bf00330892

Cited by 13 publications

(5 citation statements)

References 21 publications

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“…All D. hydei strains used in this study have been used previously for rDNA work and are named for the X and Y chromosomes. Strain bb' (bbl/bbl x bb'/Y) carries a bobbed X chromosome; strain X7 (X7/X7 x X7/Y) is a subline ofthe Dusseldorfwild-type strain; strain X X/Y (XAX/Y x X/Y) females carry a compound X chromosome that has no rDNA (14). Strain wml/Y (wml/Y x X-3/Y) females have a compound X chromosome (wml); males carry a X-autosome 3 translocation that has no rDNA (15).…”

Section: Methodsmentioning

confidence: 99%

Mobile Minos elements from Drosophila hydei encode a two-exon transposase with similarity to the paired DNA-binding domain.

Franz

Loukeris

Dialektaki

et al. 1994

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

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Elements related to the Tcl-like Minos mobile element have been cloned from Drosophila hydei and sequenced. Southern blot and sequence analyses show that (01 the elements are actively transposing in the Drosophila hydei germ line, (it) they are characterized by a striking degree of sequence and size homogeneity, and (ii) like Tcl, they insert at a TA dinucleotide that is probably duplicated during the process. The nucleotide sequences of two elements, Minos-2 and Minos-3, differ at only one position from each other and contain two nonoverlapping open reading frames that are separated by a putative 60-nucleotide intron. The amino-terminal part of the Minos putative transposase shows sequence similarity to the paired DNA-binding domain. Forced transcription of a modified Minos element that was introduced into the Drosophila melanogaster germ line by P element-mediated transformation resulted in the production of accurately spliced polyadenylylated RNA molecules. It is proposed that Minos-2 and/or Minos-3 may encode an active transposase containing an amino-terminal DNA-binding domain that is distantly related to the paired DNA-binding domain.Mobile elements belonging to the Tcl-like family have been identified so far in nematodes, insects, and fish (1-7). They are all characterized by a relatively small length (1.6-1.8 kb), the presence of inverted terminal repeats of various sizes and sequences, and significant sequence similarities in the region between the repeats, which corresponds to the gene encoding transposase.A common characteristic of elements capable of transposing autonomously is the presence of a gene encoding transposase, a protein directly involved in the transposition. With the exception of Tcl, TCb1, and Bari-i, the elements of the family that have been sequenced so far do not encode active transposases, having accumulated nonsense and frameshift mutations in their putative transposase genes. Tcl, a 1611-bp element with 54-bp perfect inverted terminal repeats, contains a gene, TcJA, encoding a transposase that binds specifically at the inverted repeats at the ends of the element and induces transposition of endogenous Tcl elements when overexpressed in Caenorhabditis elegans (8). The Tcl element exhibits a high degree of size and sequence homogeneity, in contrast to other eukaryotic transposons (9-11) that are heterogeneous in size. Another characteristic of Tcl is that it always inserts into a TA sequence, possibly creating a duplication of the dinucleotide in the process (12, 13).Minos has been identified as a dispersed repetitive sequence inserted within the transcribed spacer in one of the repeats of the rDNA locus of Drosophila hydei (6). The element is characterized by 255-bp perfect inverted terminal repeats and the presence of two long nonoverlapping open reading frames (ORFs) on the same strand; the longest of the ORFs (ORF2) shows -=30% sequence identity with TcJA but does not begin with an ATG codon (6). It appears, therefore, that the cloned element represents a defective membe...

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Section: Methodsmentioning

confidence: 99%

Mobile Minos elements from Drosophila hydei encode a two-exon transposase with similarity to the paired DNA-binding domain.

Franz

Loukeris

Dialektaki

et al. 1994

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

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“…Recent studies have established that, at the level of the total polyploid tissue DNA, the overall contribution of the two NOs to the polyploidization of the rDNA is a function of the pair of NOs examined (6,(8)(9)(10)(11)(12). In some cases, one NO is replicated to the virtual exclusion of the other, whereas for other NO pairs, cistrons from both NOs are equally well represented in the total polyploid tissue DNA.…”

Section: Introductionmentioning

confidence: 99%

“…The mechanisms underlying this independent regulation of rDNA polyploidization are not understood but the studies of Spear and Gall (2, 3) have established that in polytene salivary gland tissue, the rDNA is autonomously replicated to a constant level that is independent of both the amount of rDNA initially present in the diploid genome and the number of nucleolar organizer (NO) regions within the genome in which this rDNA is distributed. It has been suggested that endoreplication of rDNA cistrons from only one NO may in part explain these observations (1, 5-7).Recent studies have established that, at the level of the total polyploid tissue DNA, the overall contribution of the two NOs to the polyploidization of the rDNA is a function of the pair of NOs examined (6,(8)(9)(10)(11)(12). In some cases, one NO is replicated to the virtual exclusion of the other, whereas for other NO pairs, cistrons from both NOs are equally well represented in the total polyploid tissue DNA.…”

mentioning

confidence: 99%

A stochastic mechanism controls the relative replication of equally competent ribosomal RNA gene sets in individual dipteran polyploid nuclei.

Belikoff¹,

Beckingham²

1985

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

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The endoreplication of the two nucleolar organizers (NOs) of the diploid genome has been examined in individual polyploid nuclei of the dipteran Calliphora erythrocephala. Crosses between two strains with diagnostic nontranscribed spacer polymorphisms in their rRNA genes were used to provide progeny with distinguishable NOs, and single nuclei of two highly polyploid cell types-salivary gland and nurse cells--were examined from individual F1 animals.Initially the representation of the two NOs in total polyploid tissue DNA was determined. This revealed that, although the NO regions present in one of the strains (Tom) were very similar in spacer composition, they displayed two types of behavior in the hybrids containing the single NO region typical of the second strain (Karla). In TW phenotype F1 progeny, very little replication of the Tom NO relative to the Karla NO occurred, whereas in TS phenotype progeny replication of the Tom and Karla NOs was approximately equivalent. When individual polyploid nuclei of the TS phenotype animals were examined, however, the relative replication of the Tom and Karla NOs was found not to be a fixed genetic property but to vary dramatically from cell to cell. This was true even for the nurse cell nuclei within a single ovarian follicle, which are the products of only four mitotic divisions of a single germ-line cell. These findings indicate that for NOs of similar replicative competence, a stochastic mechanism governs the relative usage of each NO for endoreplication and that the relative activity of the two NOs is not stably determined through the mitotic divisions preceding polyploidization. Stochastic selection after mitotic DNA replication could be a general phenomenon governing the relative usage (transcription) of different, but equally competent, alleles of any gene in individual cells, if the required factors are in short supply.Within the Diptera, the replication of the rRNA genes (rDNA) during polyploidization has long been known to be independent of the replication of the euchromatic genome (1-4). The mechanisms underlying this independent regulation of rDNA polyploidization are not understood but the studies of Spear and Gall (2, 3) have established that in polytene salivary gland tissue, the rDNA is autonomously replicated to a constant level that is independent of both the amount of rDNA initially present in the diploid genome and the number of nucleolar organizer (NO) regions within the genome in which this rDNA is distributed. It has been suggested that endoreplication of rDNA cistrons from only one NO may in part explain these observations (1, 5-7).Recent studies have established that, at the level of the total polyploid tissue DNA, the overall contribution of the two NOs to the polyploidization of the rDNA is a function of the pair of NOs examined (6,(8)(9)(10)(11)(12). In some cases, one NO is replicated to the virtual exclusion of the other, whereas for other NO pairs, cistrons from both NOs are equally well represented in the total polyploid tissue DNA...

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“…AU D. hydei strains used in this study have been used previously for rDNA work and are named for the X and Y chromosomes. Strain bb' (bb'/bb' x bb'/Y) carries a bobbed X chromosome; strain X 7 (X 7 /X 7 x X 7 /Y) is a subline of the Düsseldorf wild-type strain; strain X"X/Y (X'X/Y x X/Y) females carry a compound X chromosome that has no rDNA (14). Strain wml/Y (wml/Y x X-3/Y) females have a compound X chromosome iyvml); males carry a X-autosome 3 translocation that has no rDNA (15).…”

Section: Methodsmentioning

confidence: 99%

“…The transposon Minos was discovered in the rDNA of Drosophila hydei (14) It is ^ 1.8 kbp with long (254 bp) inverted terminal repeats. The Minos element contains two nonoverlapping open reading frames separated by a putative intron and coding for a conceptual polypeptide that shows >40% sequence identity with the Tel transposase of the nematode Caenorhabditis elegans (15).…”

Section: Noti Noti Ecorimentioning

confidence: 99%

Το Μεταθετο Στοιχειο Minos Της D.HYDEI. Χρηση Του Ως Φορεα Μετασχηματισμου Διπτερων

Λουκερησ¹

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bp ITRΕικόνα 3: Διαγραμματική απεικόνηση των περιοχών πρόσδεσης της τρανσποζάσης Ρ και της πρωτεΐνης IRBP στο 5' και 3' άκρο του στοιχείου Ρ.Τα στελέχη Ρ, που απομονώνονται απο φυσικούς πληθυσμούς D. melanogaster, περιέχουν πολλαπλές ενθέσεις στο γονιδίωμα τους. Περίπου το ένα τρίτο των ενθέσεων αυτών είναι πλήρη αυτόνομα στοιχεία, και τα υπόλοιπα είναι, λόγω εσωτερικών ελλείψεων, μικρότερα σε μέγεθος, ατελή και μη αυτόνομα, δηλαδή μη λειτουργικά, στοιχεία. Ολα τα στοιχεία Ρ, αυτόνομα ή μη, περιβάλλονται από τα κατοπτρικώς αντεστραμμένα άκρα, καθώς και απο ένα διπλασιασμό 8 bp της θέσης στόχου που δημιουργείται κατά την ένθεση του στοιχείου. Αλληλουχίες του μεταθετού στοιχείου Ρ απουσιάζουν τελείως απο το γονιδίωμα εργαστηριακών στελεχών Μ. Το φαινόμενο της δυσγενεσίας υβριδίου παρατηρείται όταν αρσενικά άτομα Ρ στελέχους διασταυρώνονται με θηλυκά άτομα Μ στελέχους (POxMQ). Δεν παρατηρείται στις διασταυρώσεις ΜΟχΡΟ, ή MdxMÇ, ή POxPÇ.Μια ενδιάμεση κατηγορία, μεταξύ στελεχών Ρ και Μ, αποτελούν στελέχη τα οποία, αν και έχουν στο γονιδίωμα τους στοιχεία Ρ, συνήθως συμπεριφέρονται σαν στελέχη Μ στις δυσγενικές διασταυρώσεις. Τα στελέχη αυτά ονομάζονται •ψευδό-Μ ή Μ'. Μερικά στελέχη Μ' μπορούν να επάγουν μέρος αλλά όχι το όλον των δυσγενικών φαινοτύπων (Rubin et al. 1982a, Simmons et al. 1985, Engels 1989).

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Determination of the region of rDNA involved in polytenization in salivary glands of Drosophila hydei

Cited by 13 publications

References 21 publications

Mobile Minos elements from Drosophila hydei encode a two-exon transposase with similarity to the paired DNA-binding domain.

Mobile Minos elements from Drosophila hydei encode a two-exon transposase with similarity to the paired DNA-binding domain.

A stochastic mechanism controls the relative replication of equally competent ribosomal RNA gene sets in individual dipteran polyploid nuclei.

Το Μεταθετο Στοιχειο Minos Της D.HYDEI. Χρηση Του Ως Φορεα Μετασχηματισμου Διπτερων

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