Cytogenetics in Brachidontes rodriguezi d'Orb (Bivalvia, Mytilidae)

The chromosomes of Brachidontes rodriguezi were analysed by means of direct Giemsa staining, silver staining, fluorescent in-situ hybridization (FISH) with 18S + 28S rDNA probes, replication banding and chromomycin A3 (CMA) and DAPI fluorescence banding techniques. The diploid chromosome number in this species is 32 and the karyotype is composed of two pairs of metacentric chromosomes, 2 pairs of telo/subtelocentric chromosomes and 12 pairs of subtelocentric chromosomes. 18S + 28S rDNA clusters were located on the short arms of the two pairs of telo/subtelocentric chromosomes. The replication band pattern induced in this species facilitates chromosome pairing and differentiation. The nucleolar organizing regions (NORs) replicate late in the S phase and were associated with bright CMA fluorescence and dull DAPI fluorescence, but not all the four NORs showed bright CMA fluorescence in a given cell; intra- and interindividual variability was found for this character. This revised version was published online in August 2006 with corrections to the Cover Date.     

Karyotype analysis of Helianthus annuus using Giemsa banding and fluorescence in situ hybridization

The karyotype of H. annuus was analysed by computer-aided image processing with respect to the chromosome length, arm ratio, occurrence and chromosomal position of intercalary heterochromatin and the location of 18S/25S and 5S ribosomal RNA genes. The karyotype was subdivided into a group of four acrocentric chromosome pairs, of which two were distinguishable by HKG (HCl, KOH, Giemsa) banding and a group of 13 meta- to submetacentric pairs. The latter could be subdivided into seven pairs with one and six pairs with two HKG bands. Three pairs of submetacentric satellite chromosomes revealed 18S/25S rDNA loci after fluorescence in situ hybridization (FISH) and silver staining . A fourth, smaller and possibly inactive, locus occurred in the terminal position on a metacentric pair. One submetacentric satellite chromosome pair revealed a 5S rRNA gene locus in the pericentromeric position; a second locus marked a submetacentric pair with one HKG band. The C-banding technique marks exclusively centromeric heterochromatin. Measurements of chromosomes in combination with Giemsa banding and FISH enabled the discrimination of most chromosome pairs of the sunflower.This revised version was published online in November 2005 with corrections to the Cover Date.     

An XX/XY Sex Chromosome System in a Fish Species, Hoplias malabaricus, with a Polymorphic NOR-Bearing X Chromosome

Cytogenetic studies were carried out in the fish, Hoplias malabaricus, from the Parque Florestal do Rio Doce (Brazil). This population is characterized by 2n = 42 chromosomes for both males and females and an XX/XY sex chromosome system, confirmed through several banding methods. Females show 24 metacentric, 16 submetacentric and 2 subtelocentric chromosomes. Males show 24 metacentric, 17 submetacentric and 1 subtelocentric chromosomes. While the X chromosome is easily recognized (the only subtelocentric element), the Y chromosome is somewhat difficult to identify but appears to correspond to the smallest submetacentric in the male karyotype. In-situ hybridization with an 18S rDNA probe showed 10 well-labeled chromosomes, including the X chromosome. The 5S rDNA is interstitially located in a single metacentric pair independent of the 18S rDNA sites. The NOR on the X chromosome is always active and occurs adjacent to a heterochromatic distal segment on the long arm. Variations in size of the NORs and/or heterochromatic segment correspond to a polymorphic size condition observed in the X chromosome. The present results confirm the XX/XY sex chromosome system in the population analyzed as well as a new cytotype in the Hoplias malabaricus group.     

Classical and molecular cytogenetics of <Emphasis Type="Italic">Khawia sinensis</Emphasis> (Cestoda: Caryophyllidea), invasive parasite of carp, <Emphasis Type="Italic">Cyprinus carpio</Emphasis>

Chromosomes of the invasive tapeworm Khawia sinensis (Caryophyllidea), the specific parasite of common carp, were analyzed by means of conventional Giemsa staining and using fluorescent DAPI and YOYO-1 dyes, silver staining, and fluorescent in situ hybridization (FISH) with 18S rDNA probe. The karyotype is composed of eight pairs of metacentric and telocentric chromosomes (2n = 16, n = 3m + 5t, TCL = 42.54 μm). Constitutive heterochromatin was located at pericentromeric regions of all pairs, except for the largest metacentric pair (no. 1), which possessed no DAPI-positive band. FISH with rDNA probe revealed that both homologues of chromosome pair no. 6 carry a cluster of ribosomal arrays, which were located interstitially close to the centromere. Present results are compared with previous cytogenetic data on Khawia spp., and comments are made on the karyotypes with respect to their phylogenetic links.     

Contrast between extensive variation of 28S rDNA and stability of 5S rDNA and telomeric repeats in the diploid-polyploid Squalius alburnoides complex and in its maternal ancestor Squalius pyrenaicus (Teleostei, Cyprinidae)

The diploid–polyploid Squalius alburnoides complex resulted from interspecific hybridization. The chromosomal mapping of 28S and 5S ribosomal genes and of (TTAGGG)_n telomeric repeats was performed on specimens from the complex and from the sympatric bisexual species S. pyrenaicus (the complex maternal ancestor) as part of an investigation of the evolutionary relationships between genomic constitutions and the consequences of the ongoing polyploidization process in terms of chromosome reshaping. Contrasting results were obtained. While results with 5S rDNA and telomeric probes gave an impression of genomic stability, the variability detected with 28S rDNA probe suggested quite the opposite. The 5S rDNA probe mapped constantly to three chromosomes per haploid genome with apparently conserved locations in morphologically similar chromosomes; conversely, prominent intra- and inter-individual variations of 28S rDNA and of syntenic sites with 5S rDNA were detected with regard to number, size and location. Hypotheses for the causes of such polymorphisms are discussed. The terminal position of most 28S rDNA sites and the absence of detectable interstitial telomeric sequences suggest a mechanism that does not involve major chromosomal rearrangements. These fishes share similar patterns for the studied cytogenetic markers which may be taken as evidence of an apparent stability that may be hiding extensive and subtle genome variations that are possibly related to an ongoing evolutionary process of genome tetraploidization and speciation.     

Physical mapping of rDNA and heterochromatin in chromosomes of 16 Coffea species: A revised view of species differentiation

The chromosome organization among 15 wild diploid Coffea species and cultivated tetraploid C. arabica was determined by fluorochrome banding (CMA, DAPI) and double fluorescence in-situ hybridization (FISH) of 5S and 18S rDNA achieved on the same chromosome plates. Two to five chromosome pairs (plus one putative chromosome B) are marked. Overall, there are two SAT-chromosome pairs for East African species and one for the Malagasy and the West and Central African species. 18S rDNA loci are telomeric and strongly marked the SAT-chromosome pairs. Generally, only one pericentromeric 5S rDNA locus characterized East African species, while an additional minor locus co-localized with the 18S rDNA-SAT locus for the Malagasy species and West and Central African species. A combination of rDNA FISH plus CMA and DAPI banding patterns enables identification of almost all the species, even those for which the genetic or botanical status is still being discussed. C. arabica clearly appears to be an allotetraploid species, including one genome from East Africa and one from West and Central Africa. However, since the minor 5S rDNA-SAT locus present in West/Central African genomes is not detected, two evolutionary hypotheses could be put forward for C. arabica. Considering only the diploid species, global trends are obvious in rDNA signal patterns, genome size variations, and geographic distribution of the species, but there are no clear evolutionary trends. However, complex interactions between these factors and environmental growing conditions exist, which have resulted in loss and gain of rDNA loci and probably also in copy repeat number variations in each rDNA family.     

Ribosomal DNA locus evolution in Nemesia: transposition rather than structural rearrangement as the key mechanism?

We investigated chromosome evolution in Nemesia using fluorescent in-situ hybridization (FISH) to identify the locations of 5S and 45S (18–26S) ribosomal genes. Although there was conservation between Nemesia species in chromosome number, size and centromere position, there was large variation in both number and position of ribosomal genes in different Nemesia species (21 different arrangements of 45S and 5S rRNA genes were observed in the 29 Nemesia taxa studied). Nemesia species contained between one and three pairs of 5S arrays and between two and four pairs of 45S arrays. These were either sub-terminally or interstitially located and 45S and 5S arrays were often located on the same chromosome pair. Comparison of the positions of rDNA arrays with meiotic chromosome behaviour in interspecific hybrids of Nemesia suggests that some of the changes in the positions of rDNA have not affected the surrounding chromosome regions, indicating that rDNA has changed position by transposition. Chromosome evolution is frequently thought to occur via structural rearrangements such as inversions and translocations. We suggest that, in Nemesia, transposition of rDNA genes may be equally if not more important in chromosome evolution.     

Chromosomal study of a lamprey (<Emphasis Type="Italic">Lampetra zanandreai</Emphasis> Vladykov, 1955) (Petromyzonida: Petromyzontiformes): conventional and FISH analysis

Karyotype and other chromosomal characteristics in the Adriatic brook lamprey Lampetra zanandreai, representative of one of the most ancestral group of vertebrates, were examined using conventional (Ag-staining, C-banding as well as CMA₃ and DAPI fluorescence) and molecular (FISH with 18/28S rDNA and EcoRI satDNA as probes) protocols with metaphase chromosomes derived from whole blood cultures. The chromosome complement had a modal diploid chromosome number of 2n = 164, as in other petromyzontid lamprey species. Ag-staining and CMA₃ fluorescence, as well as FISH with 18/28S rDNA probes, detected nucleolar organizer regions (NORs) close to the centromeres of the biarmed chromosomes of pairs 1 and 2, the largest chromosome pairs of the complement. In addition to NORs, CMA₃ fluorescence revealed positive signals in approximately 40 other chromosomes. DAPI stained mostly centromeric regions of many chromosomes as well as conspicuously massive blocks overlapping NOR sites. C-banding evidenced a large amount of constitutive heterochromatin in somatic chromosomes, with approximately 40 C-positive acrocentric elements completely heterochromatic, corresponding with the 40 CMA₃+ chromosomes and positive heterochromatic blocks in pericentromeric regions of chromosome pairs 1 and 2. Polymerase chain reaction (PCR)-based cloning of satellite DNA with primers derived from Petromyzon marinus centromeric sequences was successful for L. zanandreai genomic DNA. The sequence was AT-rich (59%) and characterized by short consensus motifs similar to other centromeric satellite motifs. FISH using satDNA clones as a probe produced a fluorescent signal on a single pair of small chromosomes. This sequence was PCR-amplified also in L. planeri and P. marinus genomic DNA, and the evolution of this repetitive element in the above species was analysed.     

Analysis of NORs and NOR-associated heterochromatin in the mussel Mytilus galloprovincialis Lmk

The chromosomes of the mussel Mytilus galloprovincialis were analysed by means of chromomycin A3 (CMA), distamycin A/DAPI (DA/DAPI), DAPI/actinomycin D (DAPI/AMD) and chromomycin A3/distamycin A/DAPI(CDD) fluorescence banding techniques, C-banding, silver staining, N-banding and in situ hybridization with 18S+28S rDNA and telomere probes. 18S+28S rDNA clusters were located on the telomeres of two pairs of submeta/subtelocentric chromosomes. The nucleolar organizing regions (NORs) were associated with bright CMA fluorescence, dull DAPI fluorescence and C- and N-positive bands, but not all four NOR-associated heterochromatin bands showed bright CMA fluorescence in a given cell; intra- and interindividual variability was found in this character. Additional non-ribosomal C-bands did not show any differential fluorescent behaviour.This revised version was published online in November 2005 with corrections to the Cover Date.     

Telomeric and interstitial telomeric sequences in holokinetic chromosomes of Lepidoptera: Telomeric DNA mediates association between postpachytene bivalents in achiasmatic meiosis of females

Telomeres, besides their main role in the protection and maintenance of chromosome ends, have several other vital functions in the cell cycle. We studied their role in the achiasmatic meiosis of female Lepidoptera, insects with holokinetic chromosomes. By fluorescence in-situ hybridization (FISH) with the insect telomeric probe, (TTAGG) _n , we mapped the distribution of telomeric and interstitial telomeric sequences (ITS) in female meiotic chromosomes of two species, Orgyia antiqua with a reduced chromosome number (2n=28) and Ephestia kuehniella mutants, possessing a radiation-induced chromosome fusion in the genome (2n=59). In addition to the strong typical telomeric signals, O. antiqua displayed weaker hybridization signals in interstitial sites of pachytene bivalents. The observed ITS most probably reflect remnants of chromosomal rearrangements and support the hypothesis that the Orgyia karyotype had arisen by multiple fusions of ancestral chromosomes. On the other hand, the absence of ITS in the chromosome fusion of Ephestia indicated the loss of telomeres before the two original chromosomes fused. When the telomeric probe was amplified by enzymatic reaction with tyramid, the number of ITS observed increased in Orgyia, and a few ITS were also observed in several chromosomes of Ephestia but not in the fused chromosome. This suggests that the genomes of both species also contain ITS other than those originating from chromosome fusions. The analysis of female meiotic prophase I revealed non-homologous associations of postpachytene bivalents mediated by telomeric DNA, which were not observed in the pachytene stage. Surprisingly, in early postpachytene nuclei the telomeric associations also involved ITS, whereas later postpachytene nuclei displayed chains of bivalents interconnected only by true telomeres. This finding favours a hypothesis that telomeric associations between bivalents play a role in chromosome segregation in the achiasmatic meiosis of female Lepidoptera. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cytogenetics of the bleak (Alburnus alburnus), with special emphasis on the B chromosomes

Some of the largest B chromosomes so far discovered in vertebrates are present in the cyprinid fish Alburnus alburnus. Previous cytogenetic analyses revealed a diploid chromosome number of 2n = 50. In addition, in some individuals one or two unusually large B chromosomes are present. Two morphologically different types of B chromosomes were observed. The frequency of animals bearing a supernumerary chromosome was found to vary considerably between different populations. A more detailed analysis of the A and B chromosomes of A. alburnus by conventional banding techniques, as well as fluorescence in-situ hybridization (FISH) with the telomeric DNA repeats (GGGTTA)₇/(TAACCC)₇, 18S + 28S rDNA and 5S rDNA were performed in the present study. Furthermore, a B chromosome-specific DNA probe obtained by amplified length polymorphism (AFLP) was hybridized on metaphases of A. alburnus carrying supernumerary B chromosomes. The banding analyses showed that the B chromosomes are completely heterochromatic, consist of GC-rich DNA sequences, replicate their DNA in the very late S-phase of the cell cycle and are composed mainly of a specific retrotransposable DNA element. Finally, blood probes from A. alburnus were collected for DNA-flow cytometric measurements. It could be shown that the huge supernumerary chromosomes represent nearly 10% of the total genome size of A. alburnus.     

A chromosome study and localization of 18S rDNA in Khawia saurogobii (Cestoda: Caryophyllidea)

This paper reports results of the first cytogenetic study carried out on a recently described monozoic tapeworm, Khawia saurogobii Xi et al., 2009, from the Chinese lizard gudgeon (Saurogobio dabryi). The karyotype of this species is composed of eight pairs of metacentric and telocentric chromosomes (2n?=?16; $ n = {\text{3m}} + {\text{5t}} $ ), metacentric chromosomes representing the first, sixth, and eight pairs. All chromosomes except the largest pair displayed 4′,6-diamidino-2-phenylidole (DAPI) positive heterochromatin in centromeric regions. In mitotic preparations stained with Giemsa, one of the homologues of a smaller metacentric chromosome pair (No. 7) showed a distinct secondary constriction, whereas the other did not. Fluorescent in situ hybridization (FISH) with 18S ribosomal DNA (rDNA) probe revealed that the chromosomes No. 7 carry each a cluster of ribosomal genes associated with the centromeric heterochromatin and confirmed that this chromosome pair contains a nucleolar organizer region (NOR). The rDNA-FISH also confirmed heteromorphism in the size of NOR (i.e., secondary constriction) observed after Giemsa staining. The present cytogenetic analysis revealed species-specific characters of K. saurogobii and showed that FISH may represent a new valuable cytogenetic tool suitable for comparative taxonomic or phylogenetic studies within the order Caryophyllidea in the future.     

The 5S rDNA of mussels Mytilus galloprovincialis and M. edulis: sequence variation and chromosomal location

The 5S ribosomal DNA of the mussels Mytilus galloprovincialis and M. edulis was amplified by PCR using contiguous primers. The most general 5S rDNA amplification pattern consisted of several products in both mussels. Two main PCR products of about 250 bp and 760 bp were cloned and sequenced, revealing two classes of 5S rDNA units. These were characterized as containing an identical coding region of 119 bp but with highly divergent spacers. Clones of each unit type exhibited minimal differences except those of the large unit of M. edulis. The sequences analysed of the two mussels possess the same coding region and only six fixed base changes on the spacers. FISH, carried out with specific probes, consistently showed hybridization signals on the largest metacentric pair (two differentiated sites) and with variable frequency on two other metacentric pairs (one site on each pair). Differences in the 5S rDNA distribution between both mussels were not found. In M. edulis, chromosomes carrying 18S-28S rDNA were also identified by FISH. These correspond to two submetacentric-subtelocentric pairs, as was previously reported in M. galloprovincialis, demonstrating that the two rDNA multigene families are located on different chromosome pairs in these mussels.     

The very long telomeres in <Emphasis Type="Italic">Sorex granarius</Emphasis> (Soricidae,Eulipothyphla) contain ribosomal DNA

Two closely related shrew species, Sorex granarius and Sorex araneus, in which Robertsonian rearrangements have played a primary role in karyotype evolution, present very distinct telomere length patterns. S. granarius displays hyperlong telomeres specifically associated with the short arms of acrocentrics, whereas telomere lengths in S. araneus are rather short and homogenous. Using a combined approach of chromosome and fibre FISH, modified Q-FISH, 3D-FISH, Ag-NOR staining and TRF analysis, we carried out a comparative analysis of telomeric repeats and rDNA distribution on chromosome ends of Sorex granarius. Our results show that rDNA sequences forming active nuclear organizing regions are interspersed with the long telomere tracts of all short arms of acrocentrics. These observations suggest that the major rearrangements that gave rise to today’s karyotype in S. granarius were accompanied by a profound reorganization of chromosome ends, which comprised extensive amplification of telomeric and rDNA repeats on the short arms of acrocentrics and finally contributed to the stabilization of telomeres. This is the first time that such telomeric structures have been observed in any mammalian species.     

Molecular structures of centromeric heterochromatin and karyotypic evolution in the Siamese crocodile (Crocodylus siamensis) (Crocodylidae, Crocodylia)

Crocodilians have several unique karyotypic features, such as small diploid chromosome numbers (30–42) and the absence of dot-shaped microchromosomes. Of the extant crocodilian species, the Siamese crocodile (Crocodylus siamensis) has no more than 2n = 30, comprising mostly bi-armed chromosomes with large centromeric heterochromatin blocks. To investigate the molecular structures of C-heterochromatin and genomic compartmentalization in the karyotype, characterized by the disappearance of tiny microchromosomes and reduced chromosome number, we performed molecular cloning of centromeric repetitive sequences and chromosome mapping of the 18S-28S rDNA and telomeric (TTAGGG) _n sequences. The centromeric heterochromatin was composed mainly of two repetitive sequence families whose characteristics were quite different. Two types of GC-rich CSI-HindIII family sequences, the 305 bp CSI-HindIII-S (G+C content, 61.3%) and 424 bp CSI-HindIII-M (63.1%), were localized to the intensely PI-stained centric regions of all chromosomes, except for chromosome 2 with PI-negative heterochromatin. The 94 bp CSI-DraI (G+C content, 48.9%) was tandem-arrayed satellite DNA and localized to chromosome 2 and four pairs of small-sized chromosomes. The chromosomal size-dependent genomic compartmentalization that is supposedly unique to the Archosauromorpha was probably lost in the crocodilian lineage with the disappearance of microchromosomes followed by the homogenization of centromeric repetitive sequences between chromosomes, except for chromosome 2.     

Complex rearrangements are involved in <Emphasis Type="Italic">Cephalanthera</Emphasis> (Orchidaceae) chromosome evolution

The genus Cephalanthera is an excellent plant group for karyotype evolution studies because it exhibits a dysploid series and bimodal karyotypes. With the aim of understanding their chromosomal and phylogenetic relationships, rRNA genes and the Arabidopsis-type telomeric sequence were mapped by fluorescence in-situ hybridization (FISH), and the rDNA intergenic spacer (ITS) was sequenced for the first time in three European species: C. longifolia (2n = 4x = 32), C. damasonium (2n = 4x = 36) and C. rubra (2n = 4x = 44). One 45S and three 5S rDNA sites are observed in C. longifolia, one 45S and two 5S sites in C. damasonium, and two 45S and one 5S site in C. rubra. Telomeric signals were observed at every chromosome end in all three species and C. damasonium also displays interstitial signals on three chromosome pairs. In agreement with chromosome data, molecular analyses support C. longifolia and C. damasonium as closely related taxa, while C. rubra stands apart. Possible pathways of karyotype evolution are discussed in reference to a previous hypothesis. The results indicate that complex chromosomal rearrangements, possibly involving Robertsonian fusions and fissions, loss of telomeric repeats, gain or loss of rDNA sites and other heterochromatic sequences and inversions, may have contributed to generating the present-day karyotypes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Chiasma formation in Arabidopsis thaliana accession Wassileskija and in two meiotic mutants

Meiotic chiasmata were analysed in metaphase I pollen mother cells (PMCs) of wild-type Arabidopsis thaliana and in two meiotic mutants. Fluorescence in situ hybridisation (FISH) with 45S rDNA and 5S rDNA as probes was used to identify the five chromosome pairs. A wild-type chiasma frequency of 9.24 per cell was found, consistent with estimated genetic recombination values. Individual bivalent chiasma frequencies varied according to chromosome size; chromosome 1 had the highest mean chiasma frequency (2.14) while the short acrocentric chromosomes had the lowest frequencies (1.54 and 1.56). FISH analysis was extended to two meiotic mutants (asy1 and dsy1) having low residual bivalent and chiasma frequencies. Mutant dsy1 gave no indication of chromosome preference for residual bivalent formation; instead it showed a general reduction in bivalent and chiasma frequencies. In asy1, the longest chromosome (1) had the lowest bivalent frequency and chiasma frequency while the short acrocentric chromosome 2 had the highest frequencies. This chromosome pair may be preferentially involved in synapsis and chiasma formation because of their association with the nucleolus. However, other factors may be operating since the other acrocentric chromosome (4), with similar size and structure to chromosome 2, did not share these chiasma properties.     

Chromosomal Location and Nucleotide Sequences of 5S Ribosomal DNA of Two Cyprinid Species (Osteichthyes, Pisces)

5S ribosomal DNAs (rDNAs) from two cyprinid species, Acheilognathus tabira subsp. 1 and Cyprinus carpio, were isolated and sequenced. Tandemly arranged rDNAs were 179 bp in A. tabira and 204 bp in C. carpio. The non-transcribed spacer region elucidates the size difference of 5S rDNA between the two species. Fluorescence in-situ hybridization (FISH) localized 5S rDNAs to the short arms of two pairs of chromosomes in A. tabira and two to four pairs in C. carpio. Subsequent analysis demonstrated NORs in one pair of chromosomes in both species. Both the NOR and 5S rDNA are carried by a chromosome pair in A. tabira, but they are located on different chromosomes separately in C. carpio. Karyotype evolution by tetraploidy seems complex in cyprinid species. This revised version was published online in August 2006 with corrections to the Cover Date.     

Possible autosomal origin of macro B chromosomes in two grasshopper species

The acrocentric macro B chromosomes of Rhammatocerus brasiliensis (Acrididae, Gomphocerinae) and Xyleus discoideus angulatus (Romaleidae, Romaleinae) are highly similar to the X chromosome in each species in terms of morphology, size, and pycnosis. However, the results of FISH experiments using 45S and 5S rDNA probes suggest that in both species the B chromosomes are most likely of autosomal origin. In R. brasiliensis, the B chromosome presented 5S rDNA but not 45S rDNA, in resemblance to the L₂, L₃, M₅ and S₁₁ autosomes, but the X chromosome lacks both rDNA families. In X. d. angulatus, 45S rDNAs is absent from the B chromosome, whereas the X chromosome contains one of the two 45S rDNA clusters in the genome. The occurrence of B chromosomes in all nine R. brasiliensis populations analyzed indicates that they are widely distributed in Northeastern Brazil, and the small amount of interpopulation variation found for B chromosome prevalence suggests the existence of high gene flow, presumably due to the abundance of this grasshopper species on several types of vegetation and its relatively high flight capability.     

Establishment of high-resolution FISH mapping system and its application for molecular cytogenetic characterization of chromosomes in newt, <Emphasis Type="Italic">Cynops pyrrhogaster</Emphasis> (Urodela,Amphibia)

Urodele amphibians (newts and salamanders) are important animal models for understanding regeneration mechanisms and genome evolution. We constructed ideograms of BrdU/dT- and C-banded karyotypes in the Japanese fire-belly newt, Cynops pyrrhogaster, which is useful as a model animal with extremely high ability of regeneration. We also established a high-resolution FISH mapping system for newts, and localized satellite DNA sequences, 18S rDNAs, telomeric (TTAGGG)n repeats and seven functional genes, including genes associated with lens regeneration, tyrosinase and two types of gamma crystallins, to chromosomes of the newt. The 18S rDNAs were localized to three chromosomal pairs in males, whereas the chromosomal locations were highly variable in females. No hybridization signals were detected for the telomeric (TTAGGG)n sequence. All three lens regeneration-related genes were mapped on the short arm of chromosome 7, suggesting that the location of the genes in the same linkage group may be correlated with the regulation of gene expression associated with chromatin dynamics in interphase nuclei during regeneration. The chromosomal distribution and nucleotide sequences of pericentric satellite DNA sequences were well conserved between C. pyrrhogaster and European newts; in contrast, there was species specificity of nucleotide sequences for centromere-specific satellite DNAs.