scholarly journals Interstitial Telomeric Repeats Are Rare in Turtles

Genes ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 657 ◽  
Author(s):  
Lorenzo Clemente ◽  
Sofia Mazzoleni ◽  
Eleonora Pensabene Bellavia ◽  
Barbora Augstenová ◽  
Markus Auer ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Karyotype Evolution ◽  
Chromosomal Rearrangements ◽  
Telomeric Repeats ◽  
Squamate Reptiles ◽  
Nucleoprotein Complexes ◽  
Interstitial Telomeric Repeats ◽  
Eukaryotic Organisms ◽  
Genomic Regions

Telomeres are nucleoprotein complexes protecting chromosome ends in most eukaryotic organisms. In addition to chromosome ends, telomeric-like motifs can be accumulated in centromeric, pericentromeric and intermediate (i.e., between centromeres and telomeres) positions as so-called interstitial telomeric repeats (ITRs). We mapped the distribution of (TTAGGG)n repeats in the karyotypes of 30 species from nine families of turtles using fluorescence in situ hybridization. All examined species showed the expected terminal topology of telomeric motifs at the edges of chromosomes. We detected ITRs in only five species from three families. Combining our and literature data, we inferred seven independent origins of ITRs among turtles. ITRs occurred in turtles in centromeric positions, often in several chromosomal pairs, in a given species. Their distribution does not correspond directly to interchromosomal rearrangements. Our findings support that centromeres and non-recombining parts of sex chromosomes are very dynamic genomic regions, even in turtles, a group generally thought to be slowly evolving. However, in contrast to squamate reptiles (lizards and snakes), where ITRs were found in more than half of the examined species, and birds, the presence of ITRs is generally rare in turtles, which agrees with the expected low rates of chromosomal rearrangements and rather slow karyotype evolution in this group.

scholarly journals Cytogenetic Analysis Did Not Reveal Differentiated Sex Chromosomes in Ten Species of Boas and Pythons (Reptilia: Serpentes)

Genes ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 934 ◽  
Author(s):  
Augstenová ◽  
Mazzoleni ◽  
Kostmann ◽  
Altmanová ◽  
Frynta ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Sex Chromosomes ◽  
Chromosomal Rearrangements ◽  
Telomeric Repeats ◽  
Molecular Cytogenetic ◽  
Poorly Differentiated ◽  
Python Bivittatus ◽  
Interstitial Telomeric Repeats ◽  
Cytogenetic Methods

Homologous and differentiated ZZ/ZW sex chromosomes (or derived multiple neo-sex chromosomes) were often described in caenophidian snakes, but sex chromosomes were unknown until recently in non-caenophidian snakes. Previous studies revealed that two species of boas (Boa imperator, B. constrictor) and one species of python (Python bivittatus) independently evolved XX/XY sex chromosomes. In addition, heteromorphic ZZ/ZW sex chromosomes were recently revealed in the Madagascar boa (Acrantophis sp. cf. dumerili) and putatively also in the blind snake Myriopholis macrorhyncha. Since the evolution of sex chromosomes in non-caenophidian snakes seems to be more complex than previously thought, we examined ten species of pythons and boas representing the families Boidae, Calabariidae, Candoiidae, Charinidae, Pythonidae, and Sanziniidae by conventional and molecular cytogenetic methods, aiming to reveal their sex chromosomes. Our results show that all examined species do not possess sex-specific differences in their genomes detectable by the applied cytogenetic methods, indicating the presence of poorly differentiated sex chromosomes or even the absence of sex chromosomes. Interestingly, fluorescence in situ hybridization with telomeric repeats revealed extensive distribution of interstitial telomeric repeats in eight species, which are likely a consequence of intra-chromosomal rearrangements.

scholarly journals Insight into the Chromosome Structure of the Cultivated Tetraploid Alfalfa (Medicago sativa subsp. sativa L.) by a Combined Use of GISH and FISH Techniques

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 542
Author(s):  
Egizia Falistocco
Keyword(s):  
In Situ Hybridization ◽  
Medicago Sativa ◽  
Tandem Repeats ◽  
Chromosome Structure ◽  
Substantial Part ◽  
Telomeric Repeats ◽  
Evolutionary Pathway ◽  
Suitable Material ◽  
Interstitial Telomeric Repeats

Cytogenetic research in Medicago sativa subsp. sativa L., the cultivated tetraploid alfalfa (2n = 4x = 32), has lagged behind other crops mostly due to the small size and the uniform morphology of its chromosomes. However, in the last decades, the development of molecular cytogenetic techniques based on in situ hybridization has largely contributed to overcoming these limitations. The purpose of this study was to extend our knowledge about the chromosome structure of alfalfa by using a combination of genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) techniques. The results of self-GISH (sGISH) suggested that a substantial part of the repetitive fraction of the genome of subsp. sativa is constituted by tandem repeats typical of satellite DNA. The coincidence of sGISH and C-banding patterns supported this assumption. The FISH mapping of the Arabidopsis-type TTTAGGG telomeric repeats demonstrated, for the first time, that the alfalfa telomeres consist of this type of sequence and revealed a massive presence of interstitial telomeric repeats (ITRs). In the light of this finding M. sativa appears to be a suitable material for studying the origin and function of such extra telomeric repeats. To further exploit this result, investigation will be extended to the diploid subspp. coerulea and falcata in order to explore possible connections between the distribution of ITRs, the ploidy level, and the evolutionary pathway of the taxa.

scholarly journals Impact of Chromosomal Rearrangements on the Interpretation of Lupin Karyotype Evolution

Genes ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 259 ◽  
Author(s):  
Karolina Susek ◽  
Wojciech Bielski ◽  
Katarzyna B. Czyż ◽  
Robert Hasterok ◽  
Scott A. Jackson ◽  
...  
Keyword(s):  
Karyotype Evolution ◽  
Chromosomal Rearrangements ◽  
Chromosome Mapping ◽  
Artificial Chromosome ◽  
Basic Chromosome Number ◽  
Plant Genome ◽  
Old World ◽  
Whole Genome Duplications ◽  
Genome Duplications

Plant genome evolution can be very complex and challenging to describe, even within a genus. Mechanisms that underlie genome variation are complex and can include whole-genome duplications, gene duplication and/or loss, and, importantly, multiple chromosomal rearrangements. Lupins (Lupinus) diverged from other legumes approximately 60 mya. In contrast to New World lupins, Old World lupins show high variability not only for chromosome numbers (2n = 32–52), but also for the basic chromosome number (x = 5–9, 13) and genome size. The evolutionary basis that underlies the karyotype evolution in lupins remains unknown, as it has so far been impossible to identify individual chromosomes. To shed light on chromosome changes and evolution, we used comparative chromosome mapping among 11 Old World lupins, with Lupinus angustifolius as the reference species. We applied set of L. angustifolius-derived bacterial artificial chromosome clones for fluorescence in situ hybridization. We demonstrate that chromosome variations in the species analyzed might have arisen from multiple changes in chromosome structure and number. We hypothesize about lupin karyotype evolution through polyploidy and subsequent aneuploidy. Additionally, we have established a cytogenomic map of L. angustifolius along with chromosome markers that can be used for related species to further improve comparative studies of crops and wild lupins.

ISH–facilitated analysis of meiotic bivalent pairing

Genome ◽  
1996 ◽  
Vol 39 (4) ◽  
pp. 784-792 ◽  
Author(s):  
M. Humberto Reyes-Valdés ◽  
Yuanfu Ji ◽  
Charles F. Crane ◽  
M. Nurul Islam-Faridi ◽  
H. James Price ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Key Words ◽  
Mathematical Relationship ◽  
Rflp Map ◽  
Meiotic Configuration ◽  
Eukaryotic Organisms ◽  
Biased Estimates ◽  
Meiosis I ◽  
Proper Orientation

Chiasmata constitute one of the cornerstones of sexual reproduction in most eukaryotes. They mediate the reciprocal genetic exchange between homologues and are essential to the proper orientation of the homologous centromeres in meiosis I. As markers of recombination, they offer a cytological means of mapping. Rather than trying to accurately count individual chiasmata, we have examined properties of the mathematical relationship between frequencies of nonadorned disomic configurations in meiosis (ring, rods, and univalents) and the probabilities at which arms of the respective chromosomes are chiasmate (one or more chiasma per arm). Numerical analyses indicated that conventionally analyzed bivalents with nonidentified arms yield statistically biased estimates of chiasma probabilities under a broad range of circumstances. We subsequently analyzed estimators derived from adorned configurations with ISH-marked arms, which were found to be statistically far superior, and with no assumptions concerning interference across the centromere. We applied this methodology in the study of chromosomes 16 and 23 of cotton (Gossypium hirsutum), and estimated their arm lengths in centimorgans. The results for chromosome 23, the only one of the two chromosomes with a documented RFLP map, were consistent with the literature. Similar molecular-meiotic configuration analyses can be used for a wide variety of eukaryotic organisms and purposes: for example, providing far more powerful meiotic comparisons of genomes of chromosomes, and a rapid means of evaluating effects on recombination. Key words : meiotic configurations, chiasma frequencies, in situ hybridization, cotton.

Karyotype Evolution in Harvestmen of the Suborder Cyphophthalmi (Opiliones)

2016 ◽  
Vol 148 (2-3) ◽  
pp. 227-236 ◽  
Author(s):  
Hana Svojanovská ◽  
Petr Nguyen ◽  
Matyáš Hiřman ◽  
Ivan H. Tuf ◽  
Rodzay Abdul Wahab ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Ribosomal Rna ◽  
Chromosome Pair ◽  
Karyotype Evolution ◽  
Rdna Locus ◽  
Ancestral Karyotype ◽  
Rdna Probe ◽  
Basal Group ◽  
Rna Genes

The morphologically uniform suborder Cyphophthalmi represents a basal group of harvestmen (Opiliones). As such, it plays an important role in the reconstruction of the karyotype evolution within this arachnid order. The cytogenetic analysis of 6 representatives of the suborder Cyphophthalmi, namely Miopsalis sp. (2n = 30; Stylocellidae), Austropurcellia arcticosa (Cantrell, 1980) (2n = 30; Pettalidae), Parapurcellia amatola de Bivort & Giribet, 2010 (2n = 32; Pettalidae), Paramiopsalis aff. ramulosus Juberthie, 1962 (2n = 28; Sironidae), Cyphophthalmus duricorius Joseph, 1868 (2n = 24; Sironidae), and Siro carpaticus Rafalski, 1956 (2n = 52; Sironidae) was performed. Fluorescence in situ hybridization with 18S rDNA probe was used to analyze the distribution of major ribosomal RNA genes in harvestmen. We confront the obtained cytogenetic data with current hypotheses on cyphophthalmid phylogeny to reconstruct their karyotype evolution. We conclude that the ancestral karyotype of harvestmen consisted of 2n = 30 elements with 1 chromosome pair bearing terminal rDNA clusters. The rDNA locus was multiplicated in the evolution of Cyphophthalmi. However, decreases as well as increases in the number of chromosomes have been detected in the karyotype evolution of Cyphophthalmi. Our data thus reveal unexpected diversity in cyphophthalmid karyotypes.

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