Light microscope autoradiography of ribosomal DNA amplification in Xenopus laevis

Chromosoma ◽  
1974 ◽  
Vol 46 (4) ◽  
pp. 421-433 ◽  
Author(s):  
Adrian P. Bird
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Dna ◽  
Light Microscope ◽  
Dna Amplification ◽  
Microscope Autoradiography

scholarly journals OBSERVATIONS ON EARLY GERM CELL DEVELOPMENT AND PREMEIOTIC RIBOSOMAL DNA AMPLIFICATION IN XENOPUS LAEVIS

1974 ◽  
Vol 62 (2) ◽  
pp. 460-472 ◽  
Author(s):  
Marvin R. Kalt ◽  
Joseph G. Gall
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Ribosomal Dna ◽  
Germ Cells ◽  
Dna Hybridization ◽  
Meiotic Prophase ◽  
Germ Line ◽  
Tritiated Thymidine ◽  
Gradient Centrifugation ◽  
Dna Amplification

The origin of premeiotic ribosomal DNA (rDNA) amplification in germ-line cells of Xenopus laevis has been examined using in situ RNA-DNA hybridization on cytological preparations, tritiated thymidine autoradiography, and isopycnic density gradient centrifugation. Primordial germ cells (PGC), from the time they first become localized in the genital ridge at day no. 4 of development, until approximately day no. 22, remain in an extended interphase condition. During this time PGC do not incorporate tritiated thymidine, have near diploid levels of rDNA as demonstrated by cytological RNA-DNA hybridization, and possess only one or two nucleoli. Starting on day no. 22–24, mitosis, sexual differentiation, and rDNA gene amplification all begin in the germ cells. Multiple nucleoli also make their appearance at this stage. Ribosomal DNA amplification continues in gonial cells as long as they remain mitotically active. Amplified copies of rDNA are lost from germ cells at the onset of meiotic prophase. This loss is probably permanent in the male germ line, but variable and temporary in the female germ line. Early gonial cells in the ovary have been deduced to have an average cycle time for each mitotic division of between 3.8 and 4.3 days at a temperature of 21°C. Some oogonia appear to divide only four times before entering meiotic prophase, while the average during the initial wave of germ cell division is nine. Finally, a satellite DNA has been isolated from adult testes which has a density in neutral cesium chloride corresponding to the density of amplified oocyte rDNA. This satellite is not present in DNA isolated from somatic tissues of Xenopus.

The Xenopus laevis ribosomal gene terminator contains sequences that both enhance and repress ribosomal transcription

1989 ◽  
Vol 9 (9) ◽  
pp. 3777-3784
Author(s):  
S Firek ◽  
C Read ◽  
D R Smith ◽  
T Moss
Keyword(s):  
Xenopus Laevis ◽  
Point Mutation ◽  
Ribosomal Dna ◽  
Ribosomal Gene ◽  
Promoter Element ◽  
Base Pairs ◽  
Transcription Terminator ◽  
Upstream Promoter

A DNA segment approximately 200 base pairs upstream of the Xenopus laevis ribosomal promoter acts both as an upstream promoter element that augments transcription and as a transcription terminator. It is, however, unclear to what extent these two activities are related. A segment of the X. laevis ribosomal DNA, containing the terminator and the upstream promoter element, was subjected to point mutation, and the effects of the resulting mutations were investigated by oocyte microinjection. Analysis of 26 point mutants revealed not only sequences that augment 40S transcription but also those that repress it. The sequences that augmented transcription lay within the T3 homology box and also near the site of 3'-end formation. These sequences also played a role in termination. The sequences that repressed transcription lay within the G+C-rich DNA flanking the T3 box. It can be concluded that termination is probably essential but may not be sufficient for the activity of the upstream promoter element.

Detection of a global aquatic invasive amphibian, Xenopus laevis, using environmental DNA

2016 ◽  
Vol 37 (1) ◽  
pp. 131-136 ◽  
Author(s):  
Jean Secondi ◽  
Tony Dejean ◽  
Alice Valentini ◽  
Benjamin Audebaud ◽  
Claude Miaud
Keyword(s):  
Invasive Species ◽  
Xenopus Laevis ◽  
Dna Amplification ◽  
Control Program ◽  
Environmental Dna ◽  
Climatic Conditions ◽  
Low Density ◽  
African Species ◽  
A Site ◽  
And Control

Detection is crucial in the study and control of invasive species but it may be limited by methodological issues. In amphibians, classical survey techniques exhibit variable detection probability depending on species and are often constrained by climatic conditions often requiring several site visits. Furthermore, detection may be reduced at low density because probability capture (passive traps), or activity (acoustic surveys) drop. Such limits may impair the study of invasive species because low density is typical of the onset of colonisation on a site. In the last few years, environmental DNA (eDNA) methods have proved their ability to detect the presence of aquatic species. We developed here an eDNA method to detectXenopus laevisin ponds. This austral African species is now present worldwide because of its use in biology and as a pet. Populations have settled and expanded on several continents so that it is now considered as one of the major invasive amphibians in the World. We detected the presence ofX. laevisat density as low as 1 ind/100 m2and found a positive relationship between density in ponds and rate of DNA amplification. Results show that eDNA can be successfully applied to survey invasive populations ofX. laeviseven at low density in order to confirm suspected cases of introduction, delimit the expansion of a colonized range, or monitor the efficiency of a control program.

Properties and Composition of the Isolated Ribosomal DNA Satellite of Xenopus laevis

Nature ◽  
1968 ◽  
Vol 219 (5153) ◽  
pp. 454-463 ◽  
Author(s):  
M. BIRNSTIEL ◽  
J. SPEIRS ◽  
I. PURDOM ◽  
K. JONES ◽  
U. E. LOENING
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Dna

Photosynthetic Bradyrhizobia from Aeschynomene spp. Are Specific to Stem-Nodulated Species and Form a Separate 16S Ribosomal DNA Restriction Fragment Length Polymorphism Group

1999 ◽  
Vol 65 (7) ◽  
pp. 3084-3094 ◽  
Author(s):  
Flore Molouba ◽  
Jean Lorquin ◽  
Anne Willems ◽  
Bart Hoste ◽  
Eric Giraud ◽  
...  
Keyword(s):  
Ribosomal Dna ◽  
Rhodobacter Capsulatus ◽  
Restriction Analysis ◽  
Dna Amplification ◽  
Rrna Gene ◽  
Gene Probe ◽  
16S Ribosomal Dna ◽  
Photosynthetic Genes ◽  
Dna Restriction ◽  
Layer Chromatography

ABSTRACT We obtained nine bacterial isolates from root or collar nodules of the non-stem-nodulated Aeschynomene species A. elaphroxylon, A. uniflora, or A. schimperi and 69 root or stem nodule isolates from the stem-nodulated Aeschynomene species A. afraspera, A. ciliata, A. indica,A. nilotica, A. sensitiva, and A. tambacoundensis from various places in Senegal. These isolates, together with 45 previous isolates from variousAeschynomene species, were studied for host-specific nodulation within the genus Aeschynomene, also revisiting cross-inoculation groups described previously by D. Alazard (Appl. Environ. Microbiol. 50:732–734, 1985). The whole collection ofAeschynomene nodule isolates was screened for synthesis of photosynthetic pigments by spectrometry, high-pressure liquid chromatography, and thin-layer chromatography analyses. The presence ofpuf genes in photosyntheticAeschynomene isolates was evidenced both by Southern hybridization with a Rhodobacter capsulatus photosynthetic gene probe and by DNA amplification with primers defined from photosynthetic genes. In addition, amplified 16S ribosomal DNA restriction analysis was performed on 45 Aeschynomeneisolates, including strain BTAi1, and 19 reference strains fromBradyrhizobium japonicum, Bradyrhizobium elkanii, and other Bradyrhizobium sp. strains of uncertain taxonomic positions. The 16S rRNA gene sequence of the photosynthetic strain ORS278 (LMG 12187) was determined and compared to sequences from databases. Our main conclusion is that photosynthetic Aeschynomene nodule isolates share the ability to nodulate particular stem-nodulated species and form a separate subbranch on the Bradyrhizobium rRNA lineage, distinct from B. japonicum and B. elkanii.

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