Small Metacentric Chromosome Research Articles

Karyotype analysis and nucleolar organizer regions (NORs) of Sundaic yellow catfish, Hemibagrus capitulum (Siluriformes, Siluridae) in Thailand

This is the first report on karyo-morphological details and characteristic of nucleolar organizer regions (NORs) of Sundaic yellow catfish, Hemibagrus capitulum (Siluriformes, Siluridae), from Sirindhorn Peat Swamp Forest, Narathiwat Province, Thailand.The mitotic chromosome preparations were prepared from kidney cells of ten male and eight female specimens. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of H. capitulum was 2n = 56 and the fundamental number of both sexes was 108. The karyotype consists of 2 large metacentric, 8 large submetacentric, 2 large acrocentric, 18 medium metacentric, 12 medium submetacentric, 6 medium acrocentric, 4 medium telocentric, and 4 small metacentric chromosomes. None of strange size chromosomes related to sex was found. In addition, the telomeric NORs were clearly observed in the short arm of the submetacentric chromosome pair 16. The karyotype formula for H. capitulum is as follows: 2n = 56 = L2m + L8sm + L2a + M18m + M12sm + M6a + M4t + S4m.

FISH analysis of Zanthoxylum armatum based on oligonucleotides for 5S rDNA and (GAA)6.

Fluorescence in situ hybridization (FISH) using oligonucleotide probes for (GAA)6 (18 bp) and ribosomal DNA (rDNA) (5S rDNA, 41 bp) was applied to analyse Zanthoxylum armatum. (GAA)6 loci were detected on the pericentromeric regions of five chromosome pairs, and 5S rDNA loci were also detected on the pericentromeric regions of another two chromosome pairs. The densities and locations of (GAA)6 and 5S rDNA signals varied between individual chromosomes. High-intensity (GAA)6 signals were detected at the centromeres of two large and two smaller metacentric chromosomes. Relatively strong (GAA)6 signals were detected at the centromeres of two relatively small metacentric chromosomes, although strong 5S rDNA signals were detected at the centromeres of two additional smaller metacentric chromosomes. Weak (GAA)6 signals were detected at the centromeres of four large metacentric chromosomes, whereas weak 5S rDNA signals were detected at the centromeres of two smaller metacentric chromosomes. The remaining chromosomes exhibited no signals. Zanthoxylum armatum had 2n = ∼128. The lengths of the mitotic metaphase chromosomes ranged from 1.22 to 2.34 μm. Our results provide information that may be beneficial for future cytogenetic studies and could contribute to the physical assembly of the Zanthoxylum genome.

Karyotype of the Neotropical mangrove speciesPelliciera RhizophoraeTriana and Planchon (Tetrameristaceae)

AbstractPelliciera rhizophorae is the sole survivor of the Eocene mangroves inhabiting the Isthmus of Panama. Two populations of Pelliciera rhizophorae, a small morphotype at the Pacific coast and a tall morphotype at the Caribbean coast, display significant morphological and molecular differences. The patterns of differentiation between these two morphotypes were not determined by the isthmus itself, but are probably due to a process of adaptation in response to the climate that resulted in specific traits for the two populations. Aiming to verify if the ecological isolation also caused changes in the karyotype of the two morphotypes, we investigated the number of chromosomes, size, morphology, distribution of CMA, DAPI bands and nuclear DNA content of the Atlantic and Pacific populations of P. rhizophorae. A diploid chromosome number of 2n = 34 was found in both morphotypes, exhibiting small metacentric, submetacentric and acrocentric chromosomes. The acrocentric chromosomes presented the largest CMA+ba...

Chromosome Evolution in the Free-Living Flatworms: First Evidence of Intrachromosomal Rearrangements in Karyotype Evolution of Macrostomum lignano (Platyhelminthes, Macrostomida).

The free-living flatworm Macrostomum lignano is a hidden tetraploid. Its genome was formed by a recent whole genome duplication followed by chromosome fusions. Its karyotype (2n = 8) consists of a pair of large chromosomes (MLI1), which contain regions of all other chromosomes, and three pairs of small metacentric chromosomes. Comparison of MLI1 with metacentrics was performed by painting with microdissected DNA probes and fluorescent in situ hybridization of unique DNA fragments. Regions of MLI1 homologous to small metacentrics appeared to be contiguous. Besides the loss of DNA repeat clusters (pericentromeric and telomeric repeats and the 5S rDNA cluster) from MLI1, the difference between small metacentrics MLI2 and MLI4 and regions homologous to them in MLI1 were revealed. Abnormal karyotypes found in the inbred DV1/10 subline were analyzed, and structurally rearranged chromosomes were described with the painting technique, suggesting the mechanism of their origin. The revealed chromosomal rearrangements generate additional diversity, opening the way toward massive loss of duplicated genes from a duplicated genome. Our findings suggest that the karyotype of M. lignano is in the early stage of genome diploidization after whole genome duplication, and further studies on M. lignano and closely related species can address many questions about karyotype evolution in animals.

Comparative morphological and cytogenetic study of five Asparagus (Asparagaceae) species from Algeria including the endemic A. altissimus Munby

Forty wild populations belonging to five Asparagus species including the endemic A. altissimus were sampled in an east-west bioclimatic gradient of North Algeria. More than 250 individuals were taxonomically examined and karyologically investigated. Meiotic behavior was analyzed for each species. New chromosome numbers were consistent with the base number x = 10 for the genus Asparagus, and two cytotypes, diploid and hexaploid, were observed. Four species were found to have 2n = 20 chromosomes, highlighting the prominence of diploidy in North Africa. One polyploid with 2n = 60 is reported here as the first karyological information on the endemic A. altissimus. Karyotype parameters were established and compared for diploid species. New data provided for A. acutifolius and A. albus indicate differences in the number of submetacentric chromosomes and genome size estimated by total chromosome length. A. acutifolius is distinguished by the largest genome, the smallest being that of A. horridus. The hexaploid cytotype consists of very small metacentric chromosomes. All diploid species displayed regular meiotic behavior with mostly bivalent pairing. Abnormalities, including univalents, multivalents, laggards, and bridges, were sometimes observed in A. horridus and A. officinalis. The new cytogenetic information provided in this study is discussed in the biogeographic context of the North African flora.

The karyotype of the great sculpin, Myoxocephalus polyacanthocephalus (Pallas, 1814) (Pisces: Cottidae), from the Russian part of the species range

The karyotype of the great sculpin, Myoxocephalus polyacanthocephalus (Pallas, 1814) (Pisces: Cottidae) from the Sea of Okhotsk and the Sea of Japan has been studied for the first time. The karyotype is stable; it consists of 40 chromosomes (4 metacentric, 2 submeta-subtelocentric, 20 subtelocentric, and 14 acrocentric chromosomes); the number of chromosomal arms is 44 + 2. Nucleolar organizer regions (NOR) are found in the telomeric region of the arm in one homologue of a pair of small metacentric chromosomes, using the Ag-NOR banding technique. A comparative analysis of the karyotype of M. polyacanthocephalus and the karyotypes of other Myoxocephalus species (M. stelleri, M. brandtii, M. jaok, M. ochotensis, and M. scorpius) has been carried out based on the main karyotype characters, as well as on the number and localization of NORs. The identified differences make it possible to differentiate the studied species, whereas the general traits indicate their taxonomic proximity.

Unraveling the karyotype structure of the spurges Euphorbia hirta Linnaeus, 1753 and E. hyssopifolia Linnaeus, 1753 (Euphorbiaceae) using genome size estimation and heterochromatin differentiation.

Euphorbia Linnaeus, 1753 (Euphorbiaceae) is one of the most diverse and complex genera among the angiosperms, showing a huge diversity in morphologic traits and ecologic patterns. In order to improve the knowledge of the karyotype organization of Euphorbia hirta (2n = 18) and Euphorbia hyssopifolia (2n = 12), cytogenetic studies were performed by means of conventional staining with Giemsa, genome size estimations with flow cytometry, heterochromatin differentiation with chromomycin A3 (CMA) and 4’,6-diamidino-2-phenylindole (DAPI) and Giemsa C-banding, fluorescent in situ hybridization (FISH) with 45S and 5S rDNA probes, and impregnation with silver nitrate (AgNO3). Our results revealed small metacentric chromosomes, CMA+/DAPI0 heterochromatin in the pericentromeric regions of all chromosomes and CMA+/DAPI− in the distal part of chromosome arms carriers of nucleolar organizing regions (NORs). The DNA content measurements revealed small genomes for both species: Euphorbia hirta with 2C = 0.77 pg and Euphorbia hyssopifolia with 2C = 1.41 pg. After FISH procedures, Euphorbia hirta, and Euphorbia hyssopifolia presented three and four pairs of terminal 45S rDNA sites, respectively, colocalizing with CMA+ heterochromatic blocks, besides only one interstitial pair of 5S rDNA signals. Additionally, the maximum number of active NORs agreed with the total number of observed 45S rDNA sites. This work represents the first analysis using FISH in the subfamily Euphorbioideae, revealing a significant number of chromosomal markers, which may be very helpful to understand evolutionary patterns among Euphorbia species.

Evidence for Karyotype Polymorphism in the Free-Living Flatworm, Macrostomum lignano, a Model Organism for Evolutionary and Developmental Biology.

Over the past decade, the free-living flatworm Macrostomum lignano has been successfully used in many areas of biology, including embryology, stem cells, sexual selection, bioadhesion and aging. The increased use of this powerful laboratory model, including the establishment of genomic resources and tools, makes it essential to have a detailed description of the chromosome organization of this species, previously suggested to have a karyotype with 2n = 8 and one pair of large and three pairs of small metacentric chromosomes. We performed cytogenetic analyses for chromosomes of one commonly used inbred line of M. lignano (called DV1) and uncovered unexpected chromosome number variation in the form of aneuploidies of the largest chromosomes. These results prompted us to perform karyotypic studies in individual specimens of this and other lines of M. lignano reared under laboratory conditions, as well as in freshly field-collected specimens from different natural populations. Our analyses revealed a high frequency of aneuploids and in some cases other numerical and structural chromosome abnormalities in laboratory-reared lines of M. lignano, and some cases of aneuploidy were also found in freshly field-collected specimens. Moreover, karyological analyses were performed in specimens of three further species: Macrostomum sp. 8 (a close relative of M. lignano), M. spirale and M. hystrix. Macrostomum sp. 8 showed a karyotype that was similar to that of M. lignano, with tetrasomy for its largest chromosome being the most common karyotype, while the other two species showed a simpler karyotype that is more typical of the genus Macrostomum. These findings suggest that M. lignano and Macrostomum sp. 8 can be used as new models for studying processes of partial genome duplication in genome evolution.

Contributions to cytogenetics of Plectranthusbarbatus Andr. (Lamiaceae): a medicinal plant.

Accessions of Plectranthus barbatus (Lamiaceae), a medicinal plant, were investigated using a cytogenetic approach and flow cytometry (FCM). Here, we describe for the first time details of the karyotype including chromosome morphology, physical mapping of GC rich bands (CMA3 banding), as well as the mapping of 45S and 5S rDNA sites. All accessions studied showed karyotypes with 2n = 30 small metacentric and submetacentric chromosomes. The CMA3 banding and fluorescent in situ hybridization techniques revealed coincidence between CMA3 bands and 45S rDNA sites (6 terminal marks) while for the 5S rDNA were observed 4 subterminal marks no coincident with CMA3 marks. For nuclear genome size measurement, the FCM procedure provided histograms with G0/G1 peaks exhibiting CV between 2.0–4.9 and the mean values obtained for the species was 2C = 2.78 pg, with AT% = 61.08 and GC% = 38.92. The cytogenetic data obtained here present new and important information which enables the characterization of Plectranthus barbatus.

Co-occurrence of mosaic supernumerary isochromosome 18p and intermittent 2q13 deletions in a child with multiple congenital anomalies

The present study deals with karyotpye–phenotype correlations in a six month old child with multiple congenital abnormalities. Cytogenetic analysis revealed mosaicism of a small metacentric supernumerary marker chromosome with a karyotype mos 47,XY+mar[34]/46,XY[31]. Cytogenetic microarray result showed three copies of chromosome 18p (15,400kb in size). Moreover, 255kbp intermittent deletion of chromosome 2q13 involving RGPD5, RGPD6, LIMS3, and LIMS3-LOC440895 was also observed. Correlating microarray data with the mosaic karyotype, the marker chromosome was identified as mosaic isochromosome 18p and was found to be 32,600kbp in size. Baby resembled clinical characteristics of trisomy chromosome 18p, isochromosome 18p and trisomy chromosome 18. The present study suggested that deletion of evolutionarily conserved developmental genes (RGPD5, RGPD and LIMS3) in the 2q13 region might have contributed to more severity in phenotype as compared to so far such reported cases of 18p trisomy's, as these are involved in nuclear-cytoplasm trafficking, signaling for tissue patterning and differentiation.

Comparative cytogenetics of Physalaemusalbifrons and Physalaemus cuvieri species groups (Anura,Leptodactylidae).

Recently, Physalaemus albifrons (Spix, 1824) was relocated from the Physalaemus cuvieri group to the same group as Physalaemus biligonigerus (Cope, 1861), Physalaemus marmoratus (Reinhardt & Lütken, 1862) and Physalaemus santafecinus Barrio, 1965. To contribute to the analysis of this proposition, we studied the karyotypes of Physalaemus albifrons, Physalaemus santafecinus and three species of the Physalaemus cuvieri group. The karyotype of Physalaemus santafecinus was found to be very similar to those of Physalaemus biligonigerus and Physalaemus marmoratus, which were previously described. A remarkable characteristic that these three species share is a conspicuous C-band that extends from the pericentromeric region almost to the telomere in the short arm of chromosome 3. This characteristic is not present in the Physalaemus albifrons karyotype and could be a synapomorphy of Physalaemus biligonigerus, Physalaemus marmoratus and Physalaemus santafecinus. The karyotype of Physalaemus santafecinus is also similar to those of Physalaemus marmoratus and Physalaemus biligonigerus owing to the presence of several terminal C-bands and the distal localization of the NOR in a small metacentric chromosome. In contrast, the Physalaemus albifrons karyotype has no terminal C-bands and its NOR is located interstitially in the long arm of submetacentric chromosome 8. The NOR-bearing chromosome of Physalaemus albifrons very closely resembles those found in Physalaemus albonotatus (Steindachner, 1864), Physalaemus cuqui Lobo, 1993 and some populations of Physalaemus cuvieri Fitzinger, 1826. Additionally, the Physalaemus albifrons karyotype has an interstitial C-band in chromosome 5 that has been exclusively observed in species of the Physalaemus cuvieri group. Therefore, we were not able to identify any chromosomal feature that supports the reallocation of Physalaemus albifrons.

First Cytogenetic Study of Puff-Faced Water Snake, <i>Homalopsis buccata</i> (Squamata, Colubridae) by Conventional Staining, Ag-NOR Banding and GTG-Banding Techniques

Summary The first cytogenetics of the puff-faced water snake (Homalopsis buccata) from Khon Kaen Province, Thailand was obtained from the present study. Mitotic chromosome was prepared directly from the spleens of specimens after in vivo colchicines treatment. The metaphase spreads were performed on microscopic slides and air-dried. Conventional staining, Ag-NOR banding, and GTG-banding techniques were applied to stain the chromosome with Giemsas solution. Results showed that the number of diploid chromosome was 2n=36, while the fundamental number (NF) was 52 in both males and females. The types of macrochromosome were four large metacentric, two medium metacentric, six small metacentric, and two small acrocentric chromosome, and 20 micro- chromosomes. It was found that nucleolar organizer regions (NORs, the representative of chromo- some marker) locate on the long arms near centromeres of a pair of microchromosomes, pair 15. The Z chromosome was a small metacentric chromosome, while the W chromosome was a small sub- metacentric chromosome. From the GTG-banding technique, it was found that each chromosome pairs could be clearly differentiated and the numbers of bands in the H. buccata was 109. The karyo- type formula is as follows: 2n (36)=L m 4 +M m 2 +S m 6 +S a +20 microchromosomes+sex chromosomes (ZW)

Polyploidy, B chromosomes, and heterochromatin characterization of Mimosa caesalpiniifolia Benth. (Fabaceae-Mimosoideae)

Eight populations of Mimosa caesalpiniifolia Benth. were investigated using a cytogenetic approach. Here, we describe for the first time details of the karyotype including chromosome morphology, physical mapping of chromomycin A3 (CMA) 4′,6-diamidino-2-phenylindole (DAPI) and silver staining of nucleolar organizer regions (Ag-NOR banding), as well as 45S rDNA sites. All populations studied showed karyotypes with 2n = 2x = 26 small metacentric and submetacentric chromosomes, although some individuals exhibited 2n = 4x = 52 chromosomes. Moreover, we observed putative additional B chromosomes in some populations. The CMA banding and fluorescent in situ hybridization techniques revealed NOR heteromorphism on the unique pair containing 45 rDNA site (chromosome 12) while the Ag-NOR banding indicated NORs on both cytotypes. Up to two and four nucleoli were observed, respectively, on individuals with 2n = 2x = 26 and 2n = 4x = 52 chromosomes and the differences in nucleolar size seems to be directly related to NOR heteromorphism in some individuals. The data present new and important information to understand karyotypic evolution of Mimosa and Fabaceae.

Morphokaryological variability and divergence of stargazers (Uranoscopus, perciformes) from the Mediterranean Sea basin: I. Divergence and taxonomic state of the Black Sea Stargazer

Based on museum collections, the variability of morphological characters of stargazers (Uranoscopus, Uranoscopidae) from different seas of the Mediterranean Sea basin have been studied. On the basis of the obtained results and data on the karyological divergence of the previously studied populations, stargazers of the Black Sea are regarded as an independent subspecies, Uranoscopus scaber anostomus, differing from the Mediterranean Sea populations in relatively long ventral fins, whose length usually exceeds half of the head length, the presence in most individuals of not less than 12 pyloric caeca, chromosome polymorphism with 2n = 28–32, NF = 50, and the presence in the karyotype of a pair of marker small metacentric chromosomes. Morphological characters suitable for analysis of morphological divergence of populations of the Mediterranean region have been revealed.

Robertsonian Translocation [56,XX and 57,XY,rob(1;29)] in Captive Thai Gaur (Bos gaurus readei) by Conventional, GTG-Banding, CBG-Banding and Ag-NOR Banding Techniques

Robertsonian translocation, or centric fusion, which is known to be the most common mechanism in karyotype evolution of bovid species, was observed and described in captive Thai gaur (Bos gaurus readei). Blood samples were taken from 2 male and 2 female captive Thai gaur. After the standard whole blood lymphocyte culture in the presence of colchicine, the metaphase spreads were performed on microscopic slides and air-dried. Conventional staining, GTG-banding, CBG-banding and Ag-NOR banding techniques were applied to stain the chromosomes. The number of diploid chromosomes (2n) were 57 in 2 males and 56 in 2 females instead of the normal 2n=58. The fundamental number (NF) was 62 in both the 2 males and 2 females. The autosome consists of 3 submetacentric and 52 telocentric chromosomes in males, and 4 submetacentric and 50 telocentric chromosomes in females. The X chromosome was a large submetacentric chromosome and the Y chromosome was the smallest metacentric chromosome. Eight telocentric chromosomes and 2 submetacentric chromosomes (5 autosome pairs) were identified as satellite chromosomes which showed clearly observable nucleolar organizer regions (NORs). The presence of an extra submetacentric chromosome and the loss of 2 telocentric chromosomes [57,XY,rob(1;29)] were observed in both males. Also, the presence of 2 extra submetacentric chromosomes and the loss of 4 telocentric chromosomes [56,XX,rob(1;29)] were observed in both females. Results from the GTG-banding and CBG-banding techniques analyses confirmed that the 2 autosomes of male (2n=57) and 4 autosomes of female (2n=56) involved in the translocation are the chromosome pairs 1 and 29, which are common in translocation of the bovid species.

First report of GTG-banded nomenclature of Pakistani Lohi sheep (Ovis aries)

The present study was planned to generate the G-band nomenclature of the commonly occurring Lohi sheep breed in the Punjab province of Pakistan. Whole blood samples were collected through jugular venepuncture in heparinised vacutainers. The metaphase slides were prepared using standard protocols. The results from microscopic screening of 50 good quality metaphase cells from each animal were studied and they revealed a chromosome complement of 54, XX and XY in Lohi sheep. The first 3 pairs were sub/metacentric whereas the other autosomes, including X, were classed as acro/subacrocentric. The Y chromosome was the smallest metacentric chromosome and had a star-like presentation. The trypsinisation time for optimal G-bands was highly variable, and individual chromosomes were identified by G-positive and negative band markers. The identification of chromosomes 4 & 6, 8 & 9, and 19-26 was difficult because these chromosomes were indistinct and small. The X chromosome was the largest sub/acrocentric, with a prominent G-positive band along the lower middle length. Complete G-band homology was noticed between Lohi and other reported sheep breeds from different parts of the world. The G-band ideogram of Lohi was also constructed based upon the G-band organisation observed in the Lohi genome. None of the 350 metaphase cells studied revealed chromosomal abnormalities.

Characterisation of a GC-Rich Telomeric Satellite DNA in Eumeces schneideri Daudin (Reptilia, Scincidae)

A hitherto undescribed satellite DNA family (AvaII satDNA) has been isolated and characterised in Eumeces schneideri, a squamate reptile belonging to the family Scincidae. AvaII satDNA is characterised by a monomer length of 208 bp, a GC content of 59% and exhibits a certain degree of CpG methylation. FISH experiments with AvaII satDNA probe produced bright signals (i) at the end of the short arms of all subtelocentric chromosomes except for pair 14, in which the signal was at the end of the long arms, (ii) at the ends of both arms of the small metacentric chromosomes 12, and (iii) in a terminal position on the acrocentric chromosomes 11 and 13. AvaII satDNA repeats were not found in the metacentric pair 3, whereas only a weak interstitial signal occurred in the metacentric pairs 1 and 2. C-banding showed that this satellite represents most of the constitutive heterochromatin in the genome of this skink, and chromomycin A₃ staining produced a clear signal overlapping with the satellite, except for NOR-associated heterochromatin. In addition, quantitative dot blot analysis showed that these repetitive sequences constitute about 3% of the genomic DNA of this lizard. AvaII satDNA sequence analysis revealed the occurrence of short guanine residue stretches for which a function in structural stability of these sequences and a role in recombination with telomeric sequences can be hypothesised. Fibre FISH experiments showed that on some chromatin fibres telomeric sequences and AvaII satellite DNA repeats are intermingled or overlapping.

Extra marker chromosome in newborn children.

A total of 6 children with an extra, small metacentric chromosome have been found in a population study of 11,148 newborn children. No deleterious phenotypic effect was found in the carriers. The derivation and possible effect of the marker chromosomes are discussed.

The G- and Q-band karyotype of Böhm's or Grant's zebra (Equus burchelli böhmi).

The modal chromosome number of Bohm's zebra (Equus burchelli bohmi) is 44. One female and one male were investigated. The autosomes were constituted by 12 pairs of metacentric, four pairs of submetacentric, one pair of subtelocentric and four pairs of acrocentric chromosomes. All the chromosomes were identified by the G- and Q-banding patterns, except two small acrocentric pairs which did not show bands. The smallest metacentric pair had indefinite satellites. In pair No. 18 one of the chromosomes had a short arm, the homologue was acrocentric. The X chromosome was submetacentric. It was the fifth longest chromosome and constituted 5.8 % of the female chromosome complement. The Y chromosome was the smallest metacentric chromosome and constituted about 1 % of the female chromosome complement. The G- and Q-banding patterns of the chromosomes were identical. A G-band diagram, an idiogram and G- and Q-band karyotypes are presented.

Genome size, base composition and karyotype of Jatropha curcas L., an important biofuel plant

In this report, we present the genome size, the base composition and the karyotype of Jatropha curcas L., which is becoming an important oleaginous crop in tropical areas for biofuel production. The genome size and the base composition were obtained by flow cytometry of G 0/G 1 nuclei stained with propidium iodide (for genome size), DAPI (for AT) and chromomycin A3 (for GC), respectively. The karyotype was obtained by root-tip (i) incubation with amiprophos-methyl (microtubule inhibitor), (ii) digestion in enzymatic solution, (iii) squashing on glass slides, (iv) fixation and (v) coloration in Giemsa solution. We found that the genome of J. curcas is relatively small and in the same size range as that of rice. The flow cytometry indicates an average 2 C value of 0.85 pg and an average base composition of 38.7% GC. The karyotype of J. curcas is made up of 22 relatively small metacentric and submetacentric chromosomes whose size range from 1.71 to 1.24 μm. The possibility of a polyploidization event in the evolutionary history of J. curcas is discussed.