Physical mapping of the 5S ribosomal RNA genes in Arabidopsis thaliana by multi-color fluorescence in situ hybridization with cosmid clones

The 5S ribosomal RNA genes were mapped to mitotic chromosomes of Arabidopsis thaliana by fluorescence in situ hybridization (FISH). In the ecotype Landsberg erecta, hybridization signals appeared on three pairs of chromosomes, two of which were metacentric and the other acrocentric. Hybridization signals on one pair of metacentric chromosomes were much stronger than those on the acrocentric and the other pair of metacentric chromosomes, probably reflecting the number of copies of the genes on the chromosomes. Other ecotypes, Columbia and Wassilewskija, had similar chromosomal distribution of the genes, but the hybridization signals on one pair of metacentric chromosomes were very weak, and detectable only in chromosomes prepared from young flower buds. The chromosomes and arms carrying the 5S rDNA were identified by multi-color FISH with cosmid clones and a centromeric 180 bp repeat as co-probes. The metacentric chromosome 5 and its L arm carries the largest cluster of the genes, and the short arm of acrocentric chromosome 4 carries a small cluster in all three ecotypes. Chromosome 3 had another small cluster of 5S rRNA genes on its L arm. Chromosomes 1 and 2 had no 5S rDNA cluster, but they are morphologically distinguishable; chromosome 1 is metacentric and 2 acrocentric. Using the 5S rDNA as a probe, therefore, all chromosomes of A. thaliana could be identified by FISH. Chromosome 1 is large and metacentric; chromosome 2 is acrocentric carrying 18S-5.8S-25S rDNA clusters on its short arm; chromosome 3 is metacentric carrying a small cluster of 5S rDNA genes on its L arm; chromosome 4 is acrocentric carrying both 18S-5.8S-25S and 5S rDNAs on its short (L) arm; and chromosome 5 is metacentric carrying a large cluster of 5S rDNA on its L arm.     

Karyotypes of the most primitive catfishes (Teleostei: Siluriformas: Diplomystidae)

Karyotypes of Diplomystes composensis and Diplomystes nahuelbutaensis were the same diploid number (n= 56).The chromosome formula for D. composensis was 16 metacentric + 24 submetacentric + 8 subtelocentric + 8 telocentric chromosomes and for D. nahuelbutaensis was 14 metacentric + 26 submetacentric + 8 subtelocentric +8 telocentric chromosomes. In contrast, the differences in the chromosomal C-banding patterns between these species was large. For instance, chromosome pairs 5,6, and 7 of D. nahuelbutaensis showed heterochromatic centromeres and pairs 23, 24, 27, and 28 were entirely heterochromotic. Diplomystes composensis showed conspicuous C-banded blocks in pairs 7, 24, and 25 (chromosome pair 7 had one heterochromatic arm, chromosome pair 24 was entirely heterochromatic, and chromosome pair 25 had heterochromatin close to centromere). Comparison with other ostariophysan karyotypes (e.g. gymnotiforms, characiforms, and cypriniforms), does not allow any conclusions about the ploesiomorphic catfish condition, because the karyotypes of the outgroups are too variable. A synapomorphy shared by characiforms, gymnotiforms, and diplomystid catfishes is the presence of more metacentric to submetacentric than substelocentric to telocentric chromosomes. Cypriniforms are more primitive because they have more subtelocentric to telocentric than metacentric to submetacentric chromosomes.     

Patterns of replication in the neo-sex chromosomes ofDrosophila nasuta albomicans

Drosophila nasuta albomicans (with 2n = 6), contains a pair of metacentric neo-sex chromosomes. Phylogenetically these are products of centric fusion between ancestral sex (X, Y) chromosomes and an autosome (chromosome 3). The polytene chromosome complement of males with a neo-X- and neo-Y-chromosomes has revealed asynchrony in replication between the two arms of the neo-sex chromosomes. The arm which represents the ancestral X-chromosome is faster replicating than the arm which represents ancestral autosome. The latter arm of the neo-sex chromosome is synchronous with other autosomes of the complement. We conclude that one arm of the neo-X/Y is still mimicking the features of an autosome while the other arm has the features of a classical X/Y-chromosome. This X-autosome translocation differs from the other evolutionary X-autosome translocations known in certain species ofDrosophila.     

Physical mapping of rDNA sequences in four karyotypes of Ranunculus silerifolius (Ranunculaceae)

The chromosomal locations of the 18S-5.8S-26S rDNA and 5S rDNA sequences were examined in four cytotypes of Ranunculus silerifolius (the Matsuyama, Mugi, Otaru, and Karatsu types) using fluorescence in situ hybridization (FISH). Using the 18S-5.8S-26S rDNA probe, one pair of probe hybridization sites was detected by FISH in the interstitial region corresponding to the secondary constriction on the short arm of a satellite chromosome (chromosome pair 6) in all four karyotypes. FISH using 5S rDNA identified one pair of sites. The 5S rDNA locus was on different chromosomes in the four karyotypes: in the interstitial region of the short arm of the largest metacentric chromosome (chromosome pair 1) in the Matsuyama type, in the interstitial region of the short arm of the subtelocentric chromosome (pair 2) in the Mugi and Otaru types, and in the interstitial region of the short arm of the metacentric chromosome (pair 2) in the Karatsu type. This physical mapping of the 5S rDNA provides valuable information about karyotype evolution in R. silerifolius. Possible mechanisms of chromosome evolution are discussed.     

Chromosome study of Lithobius forficatus (Lithobiomorpha, Chilopoda)

The diploid number 2n = 46 and the chromosome arm number NF = 74 are described in Lithobius forficatus from Olsztyn (Poland). Analyses of silver and CMA3-stained mitotic chromosomes suggest that a single chromosome pair has active NORs which correspond to G-C-rich (CMA3-positive) chromatin. Heteromorphism of the largest metacentric chromosome pair was observed. The sex chromosomes were not identified. Size polymorphism of the first chromosome pair was found.     

Karyological observations on Turbellaria Proseriata: karyometric analysis ofMonocelis fusca,M. lineata (Monocelididae) andParotoplana macrostyla (Otoplanidae)

A karyometric analysis of the chromosome set of the marine turbellariansMonocelis fusca, M. lineata andParotoplana macrostyla has been carried out. The karyotype of the twoMonocelis species investigated (2n=6) is formed by three pairs of small and similarly sized chromosomes: InM. fusca, chromosome 1 is metacentric, chromosome 2 acrocentric and chromosome 3 is subtelocentric.M. lineata also presents one pair of metacentric chromosomes (chromosome 2), while chromosomes 1 and 3 are submetacentric.P. macrostyla (2n=12) reveals two pairs of large metacentric and four pairs of small chromosomes, three of which are metacentric, whereas the last is subtelocentric.     

Karyotype study in <Emphasis Type="Italic">Luzuriaga radicans</Emphasis> (Liliales: Luzuriagaceae)

The karyotype of Luzuriaga radicans R. & P. was quantitatively studied, assessing characters such as chromosome morphology and size, satellite location, asymmetry level and bimodality. L. radicans has an asymmetric and bimodal karyotype 2n = 20 with three metacentric pairs, followed by six submetacentric and one subtelocentric chromosome pair. One satellite was observed in the short arm of chromosome pair 6. The total haploid set length was 48.7 μm and the mean chromosome size was 4.87 ± 2.35 μm. Comparing L. radicans with other two species of the genus a high resemblance among their karyotypes was found.     

Cytogenetics in fruit breeding - localization of ribosomal RNA genes on chromosomes of apple (Malus×domestica Borkh.)

 The localization of rRNA genes was studied by fluorescent in situ hybridization (FISH) on chromosomes of the cultivated apple, M.×domestica ‘Pinova’ (2n=34). The 18S/25S rRNA loci were detected in terminal positions of the short arms of two submetacentric and two metacentric chromosome pairs. One 5S rRNA gene locus was found in the proximal region of the short arm of a small metacentric chromosome pair. Received : 21 June 1996 / Accepted : 28 June 1996     

福建大头蛙的核型及带型分析

利用骨髓细胞蒸气固定法制备染色体标本,研究了福建大头蛙(Limnonectesfujianensis)黄山居群的核型、C 带和Ag NORs。结果表明,福建大头蛙核型为2n =2 2 =2 0M 2SM ,NF =44,次缢痕位于No 1 0q ;各染色体均有着丝粒C 带,3p、9q出现插入型C 带;Ag NORs位于1 0q。     

A cytogenetical study of Glossina fuscipes fuscipes including a comparison of the polytene chromosome maps with those of Glossina austeni (Diptera,Glossinidae)

The male meiotic sequence is described for the tsetse fly Glossina fuscipes fuscipes together with the polytene chromosome maps and all principal cytological markers. The diploid chromosome number is 2n=6 and includes a pair of large submetacentric autosomes (L₁), a shorter pair of metacentric autosomes (L₂), and an X and Y which constitute a heteromorphic pair. Male meiosis is normally achiasmate although evidence is presented which suggests that chiasmata do form in about 1% of males. A detailed comparison between the polytene chromosomes of this species and Glossina austeni indicates that although they must have had a common ancestor, G. austeni is genetically more closely related to morsitans group tsetses.     

The chromosome complement of the slow loris (Nycticebus coucang Boddaert, 1785)

The chromosome complements of two male and two female adult slow lorises (Nycticebus coucang) have been studied in blood cultures cultivatedin vitro for three days. We have observed basic differences in arrangement from previous results, and the existence in the complement of a dimorphic pair not described before in this species. This dimorphic pair does not fit with any known type of chromosome dimorphism or polymorphism, either in rodents or primates. The diploid chromosome number is 50. Nine of the chromosome pairs are metacentric, the remaining 15 pairs, submetacentric. The X chromosome is a long submetacentric, ranking 4 in order of decreasing size. The Y chromosome is a rather long metacentric and ranks 15 in the same order. The autosomes, 2 to 10µ long in metaphase with arm ratios ranging from 1.14 to 2.65, are paired and arranged in order of decreasing size. Chromosome pair No. 5 is dimorphic, one of the chromosomes in the pair being constantly longer than the other. An idiogram of the haploid chromosome complement is presented, incorporating measurements of 30 analyzed nuclei.     

Occurrence of macro B chromosomes in Astyanax scabripinnis paranae (Pisces,Characiformes, Characidae)

B chromosomes occur in several Neotropical fish species. Cytogenetic analysis of 27 specimens (15 females and 12 males) of Astyanax scabripinnis paranae from the Araquá river (a small headwater tributary of the Tietê river) shows that this population has 2n=50 chromosomes (4M+30 SM+4ST+12A), two chromosome pairs with NORs and conspicuous C-band positive blocks in the terminal position of the long arm of four chromosome pairs. In this population, eight females presented 2n=51 chromosomes and the extra chromosome was a large metacentric similar in size and morphology to the first chromosome pair in the karotype. This accessory chromosome is entirely heterochromatic in C-banded metaphases and shows a late replication pattern evidenced by BrdU incorporation. There was no significant correlation between the presence of B chromosomes and increased NOR activity at the P>0.05 level. Some aspects related to these B chromosomes are discussed.     

Cytogenetic characterization of Rhamdia quelen (Siluriformes, Heptapteridae) from the Bodoquena Plateau, Mato Grosso do Sul, Brazil

We made a cytogenetic study of the fish Rhamdia quelen collected from the Bodoquena Plateau, an isolated national park region in Mato Grosso do Sul State, Brazil. The diploid number was 2n = 58, with 36 metacentric + 16 submetacentric + 6 subtelocentric chromosomes. We found one to three B chromosomes, which were metacentric and submetacentric and of medium size, showing both intra- and interindividual variation. The nucleolus organizer region (NOR) was located in the terminal region of the short arm of submetacentric pair 20. Staining with CMA3 fluorochrome revealed the NOR location, while there was no evidence of fluorescent staining with DAPI. C banding revealed heterochromatin mainly in the terminal regions of the chromosome arms, including the NOR pair. In addition, metacentric pair 2 showed three heterochromatic blocks in the terminal portions and in the pericentromeric region. The B chromosomes appeared euchromatic. The CB + CMA3 staining combination demonstrated only one chromosome pair with fluorescence, probably the NOR-bearing one, while CB + DAPI gave various fluorescent signals, including metacentric pair 2, indicating that these heterochromatic regions are AT-rich in this population of R. quelen. The R. quelen population in this isolated region of Brazil is chromosomally distinct from that of other populations that have been studied.     

Karyotypes of Cerastoderma glaucum (Bivalvia) from Baltic and Mediterranean populations

Chromosomes of C. glaucum from Baltic (Gdansk Bay) and Mediterranean (Thau lagoon, Sète) populations were studied using karyometric analysis and silver-staining. The karyotype of the Gdansk population consists of three metacentric, ten submetacentric and six subtelocentric chromosome pairs. The karyotype of the Thau population shows four metacentric, nine submetacentric and six subtelocentric pairs. Nucleolus organizer regions were found terminally on the second largest submetacentric chromosome pair of the Gdansk population and on the second largest metacentric chromosome pair of the Thau population. This suggests a cytotaxomomic difference between these two geographically isolated populations. Striking differences exist between C. glaucum and C. edule karyotypes, probably resulting from a long divergence time.     

Cytogenetics of Amaryllidaceae species: heterochromatin evolution in different ploidy levels

Species belonging to the Amaryllidaceae (Zephyranthes and Habranthus) were analyzed by banding with chromomycin A3 (CMA)/4,6-diamidino-2-phenylindole (DAPI) fluorochromes. The patterns of bands were studied in seven species of Zephyranthes Herb. and one of Habranthus Herb. Subterminal and interstitial DAPI+ bands were observed in Z. robusta 2n?=?12 and Z. brachyandra 2n?=?24. Other species showed no AT-rich heterochromatin. In species with 2n?=?12, CMA+ bands were observed on one chromosome pair of Z. robusta and Zephyranthes sp., while in Z. sylvatica an additional small terminal band in the fifth chromosome pair was observed. Z. rosea and Z. grandiflora presented with 2n?=?24 and had four CMA+ bands, while in Z. brachyandra, with 2n?=?24?+?1B, there were eight interstitial dot bands and a larger terminal band in the short arm of the B chromosome. Z. candida with 2n?=?38 presented CMA+ heterochromatin blocks on the long arms of five metacentric pairs and in the short arm of one of the submetacentric pairs; in addition a terminal band was observed on the long arm of one of the homologues of a larger submetacentric pair. H. itaobinus showed a heterozygous pair revealing a strong CMA+ band in only one of the homologues, likely a nucleolus organizing region. Taxonomic implications and karyotype evolution of this group are discussed and correlated with previous data from the literature.     

Chromosomes of lemuriformes. I. A chromosome complement of Lepilemur mustelinus (I. Geoffroy 1851)

The diploid chromosome number of two specimens of Lepilemur mustelinus (I. Geoffroy 1851) is 2N = 20. All of the chromosomes, except the Y chromosome, are metacentric or submetacentric; the Y chromosome is acrocentric and is the shortest chromosome in the complement. Satellites on autosomal pair 5 provide marked chromosomes for the animals studied and may be a marked pair for the species.     

Major cytogenetic landmarks and karyotype analysis inDaucus carota and other Apiaceae

Karyotype analysis provides insights into genome organization at the chromosome level and into chromosome evolution. Chromosomes were marked for comparative karyotype analysis using FISH localization of rDNA genes for the first time in Apioideae species including taxa of economic importance and several wild Daucus relatives. Interestingly, Daucus species did not vary in number of rDNA loci despite variation in chromosome number (2n = 18, 20, 22, and 44) and previous publications suggesting multiple loci. All had single loci for both 5S and 18S-25S (nucleolar organizing region) rDNA, located on two different chromosome pairs. The 5S rDNA was on the short arm of a metacentric chromosome pair in D. crinitus (2n = 22) and D. glochidiatus (2n = 44) and on the long arm of a metacentric pair in other Daucus species, suggesting possible rearrangement of this chromosome. For other Apiaceae, from two (Apium graveolens), to three (Orlaya grandiflora), to four (Cuminum cyminum) chromosomes had 18S-25S rDNA sites. Variability for number and position of the 5S rDNA was also observed. FISH signals enabled us to identify 20-40% of the chromosome complement among species examined. Comparative karyotype analysis provides insights into the fundamental aspects of chromosome evolution in Daucus.     

Unequal X Chromosomes in Bradysia Hygida (Diptera:Sciaridae) Females: Karyotype Assembly and Morphometric Analysis

The mitotic chromosomes of Bradysia hygida(Diptera:Sciaridae) neuroblast cells are described together with their morphometric data. Giemsa-stained neuroblast chromosomes from female and male larvae confirm the chromosome number of this species, 2n=8 (XX) and 2n=7 (XO), respectively. The karyotype assembly reveals two metacentric autosomic pairs, the A and B chromosome; a subtelocentric, the C chromosome, the smallest one; and a sexual unequal metacentric pair, X chromosome, in female karyotype and a one sexual metacentric X chromosome in male. The implications of the unequal X chromosome pair are discussed.     

A population analysis of Robertsonian and Ag-NOR polymorphisms in brown trout (Salmo trutta)

An analysis of Robertsonian polymorphism and variation in the number of active NORs has been carried out in several populations of brown trout (Salmo trutta) from Northwestern Spain. The karyotype of this species appears to be soundly established, and essentially no variation has been found in chromosome number. Interindividual and interpopulation variation in arm number was detected, with figures ranging between 100 and 102 among individuals, and between 100.10 and 100.80 among populations. This variation in arm number is solely attributable to the polymorphism of the short arm of the main NOR-bearing pair 11, which can appear from acrocentric to metacentric in different individuals. Most populations analyzed showed the standard distribution of active NORs previously observed in this species. The Miño drainage basin, and specially the Chamoso population, showed a multi-chromosomal distribution of active NORs, with several new locations, always telomeric. In most cases no concordance was observed between previously detected rDNA sites in S. trutta and the new Ag-NOR locations. This fact suggests a transposition mechanism rather than an activation of silent rDNA sites to explain this multichromosomal NOR pattern.     

不同地理区域鲫鱼染色体银染核仁组织者的比较研究

本文对不同地理区域的鲫鱼(Carassius auratus)—滇池高背鲫、低背鲫、方正银鲫(C.auratusgibelio)的核型及核仁组织者NORs进行了比较研究,并对高背鲫来源作些初步探讨,结果如下: 1.低背鲫Carassius auratus (back low type):2n=100,22m+30sm+48t.st,NORs=4,出现于第5—6对亚中着丝粒染色体短臂。 2.滇池高背鲫Carassius auratus(back high type):2n=156,30m+46sm+80t.st,NORs=6,出现于第5—7对亚中着丝粒染色体短臂。 3.方正银鲫C.auratus gibelio:2n=162,32m+52sm+78t.st NORs=4,出现于第5—6对亚中着粒染色体短臂。