Heterochromatin Bands Research Articles

New Cytogenetic Data for the Neottieae Tribe (Orchidaceae) in the Mediterranean Region.

This work presents a summary of cytogenetic data, including new information, on several species within the tribe Neottieae, with an update of the karyotype for 23 species belonging to the genera Cephalanthera, Limodorum, Epipactis, and Neottia (including Listera). Each of these four genera also presents distinctive chromosomal features, such as bimodal karyotypes. Our research includes insights into the distribution of constitutive heterochromatin, measured using C-banding and, in some cases, specific fluorochromes for the detection of A-T- and G-C-rich DNA. In the Epipactis group, it is noteworthy that when using the Giemsa banding technique, certain species (e.g., E. placentina, E. meridionalis) with a chromosome number of 2n = 38 were observed to exhibit a conspicuous wide band of constitutive heterochromatin on the long arm of the third pair in a subcentromeric position, resembling what has been observed in E. helleborine. These differences also have the potential to contribute to the diversification of these species. Based on the karyological results obtained, a hypothesis regarding the origin of certain species within the E. helleborine group is proposed. Additionally, karyological analyses conducted on a specimen of E. microphylla revealed chromosome counts ranging from 36 to 40. Somatic metaphases exhibited evident structural alterations in certain chromosomes, showing rearrangements probably caused by translocation phenomena. Based on the data obtained from the species within the studied genera, it is conceivable that variations in chromosomes, both structurally and in the distribution of constitutive heterochromatin, exert a significant influence on the evolution of the karyotype. Moreover, in many entities belonging to the Neottieae tribe, these processes may also contribute to the diversification of the phenotype in some instances.

Diversity of the repetitive DNA fraction in Cestrum, the genus with the largest genomes within Solanaceae.

Cestrum species present large genomes (2C = ~ 24 pg), a high occurrence of B chromosomes and great diversity in heterochromatin bands. Despite this diversity, karyotypes maintain the chromosome number 2n = 16 (except when they present B chromosomes), and a relative similarity in chromosome morphology and symmetry. To deepen our knowledge of the Cestrum genome composition, low-coverage sequencing data of C. strigilatum and C. elegans were compared, including cytogenomic analyses of seven species. Bioinformatics analyses showed retrotransposons comprising more than 70% of the repetitive fraction, followed by DNA transposons (~ 17%), but FISH assays using retrotransposon probes revealed inconspicuous and scattered signals. The four satellite DNA families here analyzed represented approximately 2.48% of the C. strigilatum dataset, andthese sequences were used as probes in FISH assays. Hybridization signals were colocalized with all AT- and GC-rich sequences associated with heterochromatin, including AT-rich Cold-Sensitive Regions (CSRs). Although satellite probes hybridized in almostall tested species, a satDNA family named CsSat49 was highlighted because it predominates in centromeric regions. Data suggest that the satDNA fraction is conserved in the genus, although there is variation in the number of FISH signals between karyotypes. Except to the absence of FISH signals with probes CsSat1 and CsSat72 in two species, the other satellites occurred in species of different phylogenetic clades. Some satDNA sequences have been detected in the B chromosomes, indicating that they are rich in preexisting sequences in the chromosomes of the A complement. This comparative study provides an important advance in the knowledge on genome organization and heterochromatin composition in Cestrum, especially on the distribution of satellite fractions between species and their importance for the B chromosome composition.

CHROMOSOMIC STUDIES IN ZEPHYRANTHES CITRINA BAKER (AMARYLLIDACEAE), A POLYPLOID ORNAMENTAL

Zephyranthes citrina is an ornamental American bulbous plant used as an ornamental garden crop for the aesthetic qualities of its yellow perigonium. The objective of this work was to characterize the species by classical chromosome staining and fluorochrome banding. A sporophytic chromosome number of 2n=8x=48 chromosomes was observed, being the karyotypic formula 20 m + 26 sm + 2 st. Satellites were detected in the short arm of metacentric chromosomes 8, 9, 11 and 12, which colocalized with constitutive heterochromatin CMA+/DAPI-/0 bands. The karyotype comprised chromosome pairs with terminal constitutive heterochromatin bands that included satellites and heteromorphic clusters indicating that it is an allooctoploid. These results will be used as a tool for monitoring genetic improvement, in interspecific crosses and its progenies and in biotechnological procedures by in vitro culture. Key words: constitutive heterochromatin, chromosome banding, bulbous, plant genetic resources, karyotype

Chromosome number, heterochromatin, and genome size support recent polyploid origin of the Epidendrum nocturnum group and reveal a new species (Laeliinae, Orchidaceae)

The Epidendrum nocturnum Jacq. group comprises about 60 species. Nine species occur in Brazil, predominantly in the Atlantic and Amazon Forests. The group is taxonomically complex because its species are morphologically similar and not easily distinguished. The main objective of this work is to characterize their chromosome evolution and how this has affected species delimitation in Brazilian representatives of the E. nocturnum group. We used chromosome numbers, heterochromatin band patterns, and genome size variation to better understand the chromosome variation, species delimitation, and the relationship among seven representatives of this group. A new species from the Cerrado/Amazon Rainforest ecotone is described based on cytological and morphological characters. The new species, Epidendrum pareciense sp. nov., is a diploid (2n = 40), Epidendrum bahiense Rchb.f., Epidendrum carpophorum Barb.Rodr., Epidendrum micronocturnum Carnevali & G.A.Romero, Epidendrum purpureocaulis Sambin & Essers, and E. nocturnum are tetraploids (2n = 80), and Epidendrum tumuc-humaciense (Veyret) Carnevali & G.A.Romero is hexaploid (2n = 120), the last a new ploidy for the group. Heterochromatin in these species is characterized by guanine-cytosine-rich regions (cromomycin A3 (CMA+) bands) on proximal and terminal regions associated with NORs. Genome size and numbers of CMA terminal bands are directly related to ploidy, suggesting that diploidization has not yet occurred and supporting the hypothesis of a recent polyploid origin for the E. nocturnum group.

Heterochromatin and polyploidy in Opuntia Mill. (Cactaceae: Opuntioideae): implications for plant breeding

ABSTRACT Despite the importance of polyploidy for the evolution of Opuntia, few researches have been focused to identify the ploidy of cultivars used in plant breeding programmes. We aimed to provide chromosome numbers, ploidy and heterochromatin band patterns of seven species and 24 cultivars from Opuntia, and investigate the relationship between phenotypic characteristics and ploidy in these species. All cultivars analyzed of Opuntia atropes, O. cochenillifera, and one cultivar of O. undulata are diploids, O. larreyi, one cultivar of O. stricta and two cultivars of O. undulata are tetraploids and all cultivars of O. ficus-indica, one cultivar of O. stricta and four cultivars of Opuntia sp. are octoploids. CMA/DAPI banding revealed the occurrence of terminal bands in all cultivars and pericentromeric bands in six cultivars. Polyploid species of Opuntia had superior mean values than diploid ones in relation to the cladode width, cladode length, cladode area, cladode thickness and plant height. Diploids had superior mean values than polyploids in relation to the number of cladodes. Polyploidy may be a useful tool for obtaining Opuntia cultivars with quantitative characteristics of interest.

Chromosome numbers and heterochromatin variation in introgressed and non-introgressed populations ofEpidendrum(Orchidaceae: Epidendroideae): interspecific transfers of heterochromatin lead to divergent variable karyotypes in the parental populations

AbstractSome groups in Epidendrum have stable chromosome numbers, whereas the species of Epidendrum subgenus Amphiglottium exhibit high levels of chromosome number variability and other genomic alterations. Polyploidy and dysploidy have both been invoked to explain chromosome number variation in the subgenus, but little is known about what is driving the high frequency of chromosome modification within some species in this group. To test whether hybridization and introgression are involved, we use fluorochrome staining to evaluate the chromosome numbers and heterochromatin bands in E. subgenus Amphiglottium, including individual parental genotypes from introgressed and non-introgressed populations. Two main types of heterochromatin were observed forming CMA and DAPI bands in Epidendrum spp. B chromosomes were identified in some individuals. In non-introgressed populations, E. secundum has three cytotypes, 2n = 28, 56 and 84, found in different parts of its geographical range and a small number of DAPI bands. In introgressed populations of E. secundum, there was dysploid variation among individuals that were morphologically typical parental plants, and in one introgressed population a high number of DAPI bands was observed in what appeared on morphological grounds to be pure parental individuals. Our data corroborate the hypothesis that hybridization and introgression play a role in generating chromosome variation (number and form) and heterochromatin diversification in E. subgenus Amphiglottium.

Long-term retainment of some chromosomal inversions in a local population of Belgica antarctica Jacobs (Diptera, Chironomidae)

Genome of antarctic endemic Belgica antarctica Jacobs has been sequenced. However, no set of inversion diagnostic markers has ever been assigned for the species. Using the classical method of polytene chromosome squash preparation, we found three heterozygous inversions located on the second (two heterozygous inversions) and third chromosomes (one heterozygous inversion) in the Belgica antarctica population of a cape of Wiencke Island, 500 m to SW from Port Lockroy. The chromosome set and chromosome variability did not differ from those described in the literature (Atchley and Davis 1979). Every salivary gland chromosome had its own markers by which it can be determined. However, we did not find a sex-linked inversion on chromosome III and heterozygous inversion on chromosome I, reported in earlier studies. For the first time, we observed a strong heterochromatin band in chromosome III at the telomere of one arm. Our data show not only the stability of the described inversions in the population but also the usefulness of the squash preparation technique in the studies of genetic variability of Belgica antarctica in present time.

A Study of Constitutive Heterochromatin and NOR Banding in Three Species of Puntius from the State of Haryana, India

The purpose of the present study was to investigate and compare the karyotypes of three species of Puntius viz. Puntius sarana (Hamilton, 1822), Puntius sophore (Hamilton, 1822) and Puntius ticto (Hamilton, 1822) belonging to family Cyprinidae in terms of chromosomal architecture, banding pattern and number of chromosomes from aquatic ecosystems of Haryana, India. Diploid chromosome no. 50 was observed in all 3 species of Puntius. The chromosomes of 3 species of Puntius showed constitutive heterochromatin at telomeric and centromeric regions of chromosomes.The Ag-NOR (Argyrophilic-Nucleolus Organizer Region) bands were observed on homologous chromosome pair nos. 2, 8 and 14 in P. sophore, pair nos. 2, 9 and 14 in P. ticto. The diploid chromosome number in P. sarana was found to be 2n = 50, 2 pairs of metacentric chromosomes, 3 pairs of subtelocentric and 20 pairs of acrocentric chromosomes. Chromosomal studies on the P. sophore revealed the diploid chromosome number to be 2n = 50, showed 16 pairs of metacentric chromosomes, 5 pairs of submetacentric, 2 pairs of subtelocentric and 2 pairs of acrocentric chromosomes. The diploid chromosome number in P. ticto was found to be 2n = 50, with 15 pairs of metacentric chromosomes, 6 pairs of submetacentric, 2 pairs of subtelocentric and 2 pairs of acrocentric chromosomes. No heteromorphic sex chromosomes were cytologically detected. Variations in chromosomes are observed with respect to earlier studies which may be due to variation in habitat conditions as a result of anthropogenic activities.

Chromosome analysis in Saccodon wagneri (Characiformes) and insights into the karyotype evolution of Parodontidae

ABSTRACT Parodontidae is a relatively small group of Neotropical characiform fishes consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid species. A vast cytogenetic literature is available on Apareiodon and Parodon, but to date, there is no cytogenetic data about Saccodon, a genus that contains only three species with a trans-Andean distribution. In the present study the karyotype of S. wagneri was described, based on both conventional (Giemsa staining, Ag-NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ hybridization) methods. A diploid chromosome number of 2n = 54 was observed in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/ZW type was detected. The W chromosome has a terminal heterochromatin band that occupies approximately half of the long arm, being this band approximately half the size of the Z chromosome. The FISH assay showed a synteny of the 18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative karyotype structure in Parodontidae and suggest an ancient origin of the sex chromosomes in the fishes of this family.

How diverse is heterochromatin in the Caesalpinia group? Cytogenomic characterization of Erythrostemon hughesii Gagnon & G.P. Lewis (Leguminosae: Caesalpinioideae).

Cytogenomic characterization of Erythrostemon hughesii reveals a heterogeneity of repeats in its subtelomeric heterochromatin. Comparative analyses with other Caesalpinia group species reveal a significant reduction in the abundance of Ty3-gypsy/Chromovirus Tekay retrotransposons during its evolution. In numerically stable karyotypes, repetitive DNA variability is one of the main causes of genome and chromosome variation and evolution. Species from the Caesalpinia group (Leguminosae) are karyotypically characterized by 2n = 24, with small chromosomes and highly variable CMA+ heterochromatin banding patterns that correlate with environmental variables. Erythrostemon hughesii differs from other species of the group examined to date for having subtelomeric CMA+ bands; this contrasts with most species in the group which have proximal bands. Here we analyse the repeatome of E.hughesii using genome skimming and chromosomal mapping approaches to characterize the identity of the most abundant repetitive elements and their physical location. The repetitive fraction of E. hughesii comprises 28.73% of the genome. The most abundant elements were retrotransposons (RT) with long terminal repeats (LTR-RT; 9.76%) and satellite DNAs (7.83%). Within the LTR-RTs, the most abundant lineages were: Ty1/copia-Ale (1%), Ty3/gypsy CRM (0.88%) and Ty3/gypsy Athila (0.75%). Using fluorescent in situ hybridization four satellite DNAs and several LTR-RT elements were shown to be present in most subtelomeric CMA+ bands. These results highlight how the repeatome in E. hughesii, a species from Oaxaca state in Mexico, is clearly distinct from Northeast Brazilian species of the Caesalpinia group, mainly due to its high diversity of repeats in its subtelomeric heterochromatic bands and low amount of LTR-RT Ty3/gypsy-Tekay elements. Comparative sequence analysis of Tekay elements from different species is congruent with a clade-specific origin of this LTR-RT after the divergence of the Caesalpinia group. We hypothesize that repeat-rich heterochromatin may play a role in leading to faster genomic divergence between individuals, increasing speciation and diversification.

Heterochromatin banding and rDNA physical mapping in 22Epimediumspecies and twoVancouveriaspecies: implications for evolution inEpimedium

AbstractHeterochromatin banding patterns and the physical locations of 45S and 5S rDNA loci in mitotic metaphase chromosomes in 22 Epimedium spp. and two Vancouveria spp. species were studied using orcein staining and double-colour fluorescent in situ hybridization, respectively. Four types of chromosomal heterochromatin bands (satellite, centromeric, intercalary and terminal) were detected in all species, and there was clear variation in the number of bands and total length. In all species examined, at least one pair each of 45S and 5S rDNA signals was detected. The position of 5S rDNA is more conserved than that of 45S rDNA. The chromosomal distribution of 45S rDNA loci detected in Epimedium can be divided into three types. The chromosomal distributions of heterochromatin bands and 45S and 5S rDNA loci were closely related to the geographical distribution and may provide important evidence concerning the classification and systematics of Epimedium. Finally, based on results of the present study and pervious research, the centre of origin and formation of modern geographical distribution of Epimedium are discussed.

Structural Variation of the X Chromosome Heterochromatin in the Anopheles gambiae Complex

Heterochromatin is identified as a potential factor driving diversification of species. To understand the magnitude of heterochromatin variation within the Anopheles gambiae complex of malaria mosquitoes, we analyzed metaphase chromosomes in An. arabiensis, An. coluzzii, An. gambiae, An. merus, and An. quadriannulatus. Using fluorescence in situ hybridization (FISH) with ribosomal DNA (rDNA), a highly repetitive fraction of DNA, and heterochromatic Bacterial Artificial Chromosome (BAC) clones, we established the correspondence of pericentric heterochromatin between the metaphase and polytene X chromosomes of An. gambiae. We then developed chromosome idiograms and demonstrated that the X chromosomes exhibit qualitative differences in their pattern of heterochromatic bands and position of satellite DNA (satDNA) repeats among the sibling species with postzygotic isolation, An. arabiensis, An. merus, An. quadriannulatus, and An. coluzzii or An. gambiae. The identified differences in the size and structure of the X chromosome heterochromatin point to a possible role of repetitive DNA in speciation of mosquitoes. We found that An. coluzzii and An. gambiae, incipient species with prezygotic isolation, share variations in the relative positions of the satDNA repeats and the proximal heterochromatin band on the X chromosomes. This previously unknown genetic polymorphism in malaria mosquitoes may be caused by a differential amplification of DNA repeats or an inversion in the sex chromosome heterochromatin.

Heterochromatin and numeric chromosome evolution in Bignoniaceae, with emphasis on the Neotropical clade Tabebuia alliance.

Bignoniaceae is a diverse family composed of 840 species with Pantropical distribution. The chromosome number 2n = 40 is predominant in most species of the family, with n = 20 formerly being considered the haploid base number. We discuss here the haploid base number of Bignoniaceae and examine heterochromatin distributions revealed by CMA/DAPI fluorochromes in the Tabebuia alliance, as well as in some species of the Bignonieae, Tecomeae, and Jacarandeae tribes. When comparing the chromosome records and the phylogenies of Bignoniaceae it can be deduced that the base number of Bignoniaceae is probably n = 18, followed by an ascendant dysploidy (n = 18 → n = 20) in the most derived and diverse clades. The predominant heterochromatin banding patterns in the Tabebuia alliance were found to be two terminal CMA+ bands or two terminal and two proximal CMA+ bands. The banding pattern in the Tabebuia alliance clade was more variable than seen in Jacarandeae, but less variable than Bignonieae. Despite the intermediate level of variation observed, heterochromatin banding patterns offer a promising tool for distinguishing species, especially in the morphologically complex genus Handroanthus.

How to become a successful invasive tapeworm: a case study of abandoned sexuality and exceptional chromosome diversification in the triploid carp parasite Atractolytocestus huronensis Anthony, 1958 (Caryophyllidea: Lytocestidae)

BackgroundA cytogenetic analysis of the new local triploid population of the caryophyllidean tapeworm Atractolytocestus huronensis, a unique parthenogenetic species with the ability to colonise new regions, was performed to understand the inner structure of its chromosome complement.MethodsA karyotype analysis was carried out using classical Giemsa staining and C-banding combined with fluorescent DAPI staining. A hypothesis that triplets are composed from three homologue chromosomes of approximately the same length and same centromere position was tested statistically for multiple dependent variables using a non-parametric Friedman’s ANOVA. The chromosomal location of ribosomal DNA clusters within the nucleolar organization region (NORs) and telomeric (TTAGGG)n sequences were detected by fluorescent in situ hybridization (FISH). Chromosomes were subjected to AgNO3 staining in order to determine whether the rDNA sites represent active NORs.ResultsThe cytogenetic analysis confirmed the karyotype composed from eight chromosome triplets (3n = 24) as well as the existence of a pair of NORs located on each chromosome of the second triplet. Six NORs varied their activity from cell to cell, and it was reflected in the numbers of nucleoli (from 1 to 5). A huge morphological diversification of homologue chromosomes was originally detected in six out of eight triplets; the homologue elements differed significantly either in length and/or morphology, and some of them carried discernible interstitial telomeric sequences (ITSs), while the end telomeres were minute. The heterochromatin bands with high AT content varied irregularly, and the course of aberrant spermatogenesis was evident.ConclusionsDiversification of homologues is a unique phenomenon very likely caused by the long-term absence of a recombination and consequential accumulation of chromosome rearrangements in the genome of A. huronensis during species evolution. Unalterable asexual reproduction of the tapeworm, along with international trade in its host (carp), is facilitating its ongoing spread.

Border Structure of Intercalary Heterochromatin Bands of Drosophila melanogaster Polytene Chromosomes.

The precise genomic localization of the borders of 62 intercalary heterochromatin bands in Drosophila polytene chromosomes was determined. A new type of bands containing chromatin of different states was identified. This type is a combination of the gray band and the intercalary heterochromatin band, creating a genetic structure that with a light microscope is identified as a continuous band. The border structure of such bands includes the coding regions of genes with ubiquitous activity.

Karyotype analysis in Bignonieae (Bignoniaceae): chromosome numbers and heterochromatin.

Chromosome numbers and heterochromatin banding pattern variability have been shown to be useful for taxonomic and evolutionary studies of different plant taxa. Bignonieae is the largest tribe of Bignoniaceae, composed mostly by woody climber species whose taxonomies are quite complicated. We reviewed and added new data concerning chromosome numbers in Bignonieae and performed the first analyses of heterochromatin banding patterns in that tribe based on the fluorochromes chromomycin A3 (CMA) and 4'-6-diamidino-2-phenylindole (DAPI). We confirmed the predominant diploid number 2n = 40, as well as variations reported in the literature (dysploidy in Mansoa [2n = 38] and polyploidy in Dolichandra ungis-cati [2n = 80] and Pyrostegia venusta [2n = 80]). We also found a new cytotype for the genus Anemopaegma (Anemopaegma citrinum, 2n = 60) and provide the first chromosome counts for five species (Adenocalymma divaricatum, Amphilophium scabriusculum, Fridericia limae, F. subverticillata, and Xylophragma myrianthum). Heterochromatin analyses revealed only GC-rich regions, with six different arrangements of those bands. The A-type (one large and distal telomeric band) were the most common, although the presence and combinations of the other types appear to be the most promising for taxonomic studies.

Cytogenetic evidences on the evolutionary relationships between the tetraploids of the section Rhizomatosae and related diploid species (Arachis, Leguminosae).

Rhizomatosae is a taxonomic section of the South American genus Arachis, whose diagnostic character is the presence of rhizomes in all its species. This section is of particular evolutionary interest because it has three polyploid (A. pseudovillosa, A. nitida and A. glabrata, 2n = 4x = 40) and only one diploid (A. burkartii, 2n = 2x = 20) species. The phylogenetic relationships of these species as well as the polyploidy nature and the origin of the tetraploids are still controversial. The present study provides an exhaustive analysis of the karyotypes of all rhizomatous species and six closely related diploid species of the sections Erectoides and Procumbentes by cytogenetic mapping of DAPI/CMA heterochromatin bands and 5S and 18-26S rDNA loci. Chromosome banding showed variation in the DAPI heterochromatin distribution pattern, which, together with the number and distribution of rDNA loci, allowed the characterization of all species studied here. The bulk of chromosomal markers suggest that the three rhizomatous tetraploid species constitute a natural group and may have at least one common diploid ancestor. The cytogenetic data of the diploid species analyzed evidenced that the only rhizomatous diploid species-A. burkartii-has a karyotype pattern different from those of the rhizomatous tetraploids, showing that it is not likely the genome donor of the tetraploids and the non-monophyletic nature of the section Rhizomatosae. Thus, the tetraploid species should be excluded from the R genome, which should remain exclusively for A. burkartii. Instead, the karyotype features of these tetraploids are compatible with those of different species of the sections Erectoides and Procumbentes (E genome species), suggesting the hypothesis of multiple origins of these tetraploids. In addition, the polyploid nature and the group of diploid species closer to the tetraploids are discussed.

Ultrastructural and immunophenotype distribution of Telocytes in female genital tract of adult albino rats

Background: Few information was given about Telocyte (TC) which was recently discovered in the lastfew years.Aim of the work: This study was designed to give full histological, immunohistochemichal andultrastructural preview on TCs distribution in the female genital tract.Material and method: After vaginal smear examination, thirty rats in diestrus phase were subjected forthis study. Uterine, fallopian tube and vaginal specimens were taken and processed for both light andelectron microscopic examination.Results: TCs showed weak positive ER-α and marked immunoexpression of PR-A and CD34 in theendometrial stroma and around the glands, in stratum vascular and outer longitudinal smooth muscle layersof the uterus, serosa of the fallopian tube and in the lamina propria in addition to the connective tissueunder vaginal epithelium and around and within the bundles of the vagina. Ultrastructurally, the uterus,fallopian tube and vagina showed triangular or stellate- shaped TCs that contained elongated nucleusoccupying the whole cell body with thin band of marginal heterochromatin and prominent nucleolus andhad one or more telopodes (TPs) with dichotomous pattern of branching. TPs had thin podomere andthick podom. Podom contains many mitochondria, rough endoplasmic reticulum (RER), many caveolaeand pinchedout vesicles. TCs had either homocellular junction between them or heterocellular junctionwith adjacent smooth muscle cells. TCs were surrounded by collagen fibers.Conclusion:TCs are new type of cells with special ultrastructure and immunophenotype characters thatare detected in the female genital tract ,therefore further studies on their distribution in the female genitaltract during different stages of estrus cycle, and trying to correlate between their distribution and theirrole in controlling infertility or myometrial contraction during pregnancy should be considered.

Cytogenetic characteristic of the Caucasian pygmy shrew (Sorex volnuchini) and Levant mole (Talpa levantis) (Mammalia: Eulipotyphla) in northern Anatolia, Turkey

The karyotype of the Caucasian pygmy shrew (Sorex volnuchini) consists of 2n = 40 NFa = 54. The X chromosome is metacentric and the Y chromosome is large acrocentric. In the chromosome set, there are six metacentric/submetacentric, one large subtelocentric, one small metacentric, and 11 acrocentric autosomal chromosome pairs. C-negative and C-positive heterochromatin band regions are determined in the karyotype. NORs were localized in the secondary constriction in autosomal pair no. 17 of Sorex volnuchini. The diploid number of the Levant mole (Talpa levantis) is 2n = 34, NFa = 64. The X chromosome is medium size and metacentric. The Y chromosome is the smallest chromosome in the karyotype. There are 10 pairs of metacentric, three submetacentric, and three subtelocentric chromosomes in the chromosome set and X is metacentric and Y is acrocentric. In the karyotype, NOR is located in the secondary constriction region of chromosome no. 8.

The ancestral chromosomes of Dromiciops gliroides (Microbiotheridae), and its bearings on the karyotypic evolution of American marsupials.

BackgroundThe low-numbered 14-chromosome karyotype of marsupials has falsified the fusion hypothesis claiming ancestrality from a 22-chromosome karyotype. Since the 14-chromosome condition of the relict Dromiciops gliroides is reminecent of ancestrality, its interstitial traces of past putative fusions and heterochromatin banding patterns were studied and added to available marsupials’ cytogenetic data. Fluorescent in situ hybridization (FISH) and self-genomic in situ hybridization (self-GISH) were used to detect telomeric and repetitive sequences, respectively. These were complemented with C-, fluorescent banding, and centromere immunodetection over mitotic spreads. The presence of interstitial telomeric sequences (ITS) and diploid numbers were reconstructed and mapped onto the marsupial phylogenetic tree.ResultsNo interstitial, fluorescent signals, but clearly stained telomeric regions were detected by FISH and self-GISH. Heterochromatin distribution was sparse in the telomeric/subtelomeric regions of large submetacentric chromosomes. Large AT-rich blocks were detected in the long arm of four submetacentrics and CG-rich block in the telomeric regions of all chromosomes. The ancestral reconstructions both ITS presence and diploid numbers suggested that ITS are unrelated to fusion events.ConclusionAlthough the lack of interstitial signals in D. gliroides’ karyotype does not prove absence of past fusions, our data suggests its non-rearranged plesiomorphic condition.Electronic supplementary materialThe online version of this article (doi:10.1186/s13039-016-0270-8) contains supplementary material, which is available to authorized users.