Karyotypic Features Research Articles

Chromosomal Karyotype Differences of the Dark-Purple Tea Cultivar ‘Ziyan’ and Its Natural Hybrid Progenies

‘Ziyan’ is a new variety of dark purple tender shoots tea tree which is rich in anthocyanins. ZY-1 and ZY-3 were two natural hybridized offspring of ‘Ziyan’, which were cultivated by single plant selection. ‘Ziyan’ is as the female parent, whereas the male parent has yet to be determined. In this study, we try to investigate cytological parameters of the three kinds of tea plants, and analyze the chromosomal karyotype differences among them. The results showed that the max arm ratio of ‘Ziyan’ was determined 2.50, and relative length was between 3.56% and 5.39%. The karyotype asymmetry index was 59.920%, and the karyotype formula was 2n=2x=30=22m (2SAT)+8sm. The max arm ratio of ZY-1 was 2.50, and relative length was between 4.80% and 8.69%. The karyotype asymmetry index was 60.307%, and the karyotype formula was 2n=2x=30=20m+10sm. The max arm ratio of ZY-3 was 2.77, and relative length was between 3.95% and 8.70%. The karyotype asymmetry index was 58.679%, which was lower than ‘Ziyan’ and ZY-3, and the karyotype formula was 2n=2x=30=24m+6sm. Although ‘Ziyan’ was significantly different from its two offspring, the karyotype characteristics of three varieties of tea plants were all type 2B. ‘Ziyan’ had a pair of satellites, but neither ZY-1 nor ZY-3 had a satellite. According to the karyotype asymmetry index and average arm ratio, the hybrid progeny ZY-3 was the most primitive, followed by the female parent ‘Ziyan’, while the hybrid progeny ZY-1 was the most evolutive.

Larval Morphology and Karyotype Structure of Chironomus sp. (Diptera, Chironomidae) from the Novaya Zemlya Archipelago (Russia)

Larval morphology and karyotype characters of Chironomus sp. from Yuzhnyi Island of the Novaya Zemlya Archipelago (70°32'N, 55°10'E) are described. This species is close to Ch. tuvanicus described from Tuva (Siberia, Russia) and belongs to the riihimakiensis group. Its chromosome set is 2n = 6: AB, CD, FEG, with the latter chromosome produced by joining of the small chromosome G with arm E. The studied Chironomus sp. has an Arctic distribution and is a primitive member of the genus.

Karyotype characteristics, chromosomal polymorphism and gene COI sequences of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the South Caucasus

The study presents data on the karyotype characteristics, features of chromosomal polymorphism and the gene COI sequences of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the South Caucasus. We found 8 banding sequences in the Caucasian population. Overall, The Caucasian population of the species can be characterized as having a low level of polymorphism. We found one new banding sequence hpiA2 in the banding sequence pool of Ch. heteropilicornis. We observed inversion polymorphism only in the arm F. The dendrogram of genetic distances by Nei criteria (1972) shows a clear separation of the Caucasian population from populations of Siberia. At the same time, the distance between populations of Siberia and the population of South Caucasus (0.379–0.445) almost reach the mean distance (0.474 ± 0.314) between subspecies (Gunderina 2001). Due to this, we can assume that the population of South Caucasus separated from Siberian populations at the level of subspecies. Constructed on data for COI gene sequences the phylogenetic tree estimated by the Bayesian inference shows that the sequences of Ch. heteropilicornis from the South Caucasus form a separate line in the general branch of Ch. heteropilicornis sequences. At the same time, calculated K2P genetic distances between Ch. heteropilicornis sequences from Norway and Caucasus (2.0–2.2%) do not exceed the 3% threshold for the genus Chironomus.

A Cytotaxonomic study on Minuartia L. (Caryophyllaceae) in Iraq

Chromosome count, karyotypic character analysis, meiotic studies, monoploid karyograms and ideograms were performed in six taxa of Minuartia growing in Iraq (M. hamata, M. hybrida subsp. hybrida, M. intermedia, M. meyeri, M. picta and M. hybrida subsp. turcica). Species of M. hamata and M. meyeri showed 2n=2x=30 chromosome number, while M. hybrida subsp. hybrida and M. intermedia were diploid (26). The chromosome number (n=x) of six species was studied, and was found to be n=15 in M. hamata and M. meyeri, 13 in M. hybrida and M. intermedia, while in M. picta we recorded values of n= 11 and 14. Karyotype analysis of this species was first carried out in our study. Analysis of metaphases showed that the karyotype formula was mainly metacentric, submetacentric, and sub acrocentric. The sizes of the chromosomes were mainly small and very small. The course of meiosis varied from normal to abnormal. Abnormal microsporogenesis formation of two bridge chromosomes was detected in M. hamata and one bridge chromosome in M. intermedia and M. meyeri. Formation of laggard’s chromosomes was detected in M. hamata, M. meyeri and M. intermedia. As well as ring chromosome was showed in M. hybrida subsp. hybrida, also, some cells contain triad cell in metaphase stage instead four cells, as well as founded cell, contains two nuclei in same species which led to reduced pollen fertility and differences in pollen grain size.

Chromosomal study of Khawia abbottinae (Cestoda: Caryophyllidea): karyotype and localization of telomeric and ribosomal sequences after fluorescence in situ hybridization (FISH).

An original cytogenetic study combining classical karyotype analysis and modern fluorescence in situ hybridization using telomeric (TTAGGG)n and ribosomal sequences (18S rDNA) was performed in Khawia abbottinae (Cestoda, Caryophyllidea), a parasite of Chinese false gudgeon (Abbottina rivularis) from China. Analyses based on conventional Giemsa staining, DAPI, YOYO-1 dye, and silver (Ag) staining were also carried out. The karyotype is composed of eight pairs of metacentric and telocentric chromosomes (2n = 16, n=5m + 3t). Constitutive heterochromatin was mainly positioned at pericentromeric regions, and telomeric sequences (TTAGGG)n were restricted to the end of all chromosomes. In mitotic preparations stained with Giemsa, both homologues of chromosome pair 4 showed a distinct secondary constriction. FISH with rDNA probe confirmed that this secondary constriction contains a nucleolar organizer region (NOR). The process of spermatocyte meiosis and the dynamics of nucleolus degradation in dividing cell were scrutinized. The present study and its results enhance the limited knowledge on basic karyotype characteristics and 18S rDNA clusters location in caryophyllidean tapeworms.

Karyological investigation of Calotropis gigantea (L.) W. T. Aiton and Centella asiatica (L.) Urban: Two important medicinal plants of Bangladesh

Calotropis gigantea (L.) W. T. Aiton and Centella asiatica (L.) Urban have been medicinally used throughout Bangladesh. In this study, karyotypic features of these two species were studied with orcein staining and banding with two base specific fluorochromes such as chromomycine A3 (CMA) and 4´, 6 diamidino-2-phenylindole (DAPI) for authentic cytogenetical characterization. 2n = 22 and 2n = 18 somatic chromosomes were found in C. gigantea and C. asiatica, respectively. The total chromosome length of C. gigantea and C. asiatica were 45.35 ± 2.64 μm and 63.63 ± 3.19 μm, respectively. The total form percent (TF%), karyotype asymmetry index (AsK%) and karyotype symmetry index (Syi index) were 47.61, 52.39 and 90.87 in C. gigantea and 39.58, 60.42 and 65.51 in C. asiatica, respectively. Both species were found to possess 1A karyotype. In C. gigantea, 2 CMA- and 4 DAPI-bands were observed whereas C. asiatica had 16 CMA- and 6 DAPI-bands. Therefore, the compiled data generated from chromosome analysis on orcein, CMA- and DAPI-banding will be useful for cytogenetical characterization of these two species.

Zinc Maintains Embryonic Stem Cell Pluripotency and Multilineage Differentiation Potential via AKT Activation.

Embryonic stem cells (ESCs) possess remarkable abilities, as they can differentiate into all cell types (pluripotency) and be self-renewing, giving rise to two identical cells. These characteristics make ESCs a powerful research tool in fundamental embryogenesis as well as candidates for use in regenerative medicine. Significant efforts have been devoted to developing protocols to control ESC fate, including soluble and complex cocktails of growth factors and small molecules seeking to activate/inhibit key signaling pathways for the maintenance of pluripotency states or activate differentiation. Here we describe a novel method for the effective maintenance of mouse ESCs, avoiding the supplementation of complex inhibitory cocktails or cytokines, e.g., LIF. We show that the addition of zinc to ESC cultures leads to a stable pluripotent state that shares biochemical, transcriptional and karyotypic features with the classical LIF treatment. We demonstrate for the first time that ESCs maintained in long-term cultures with added zinc, are capable of sustaining a stable ESCs pluripotent phenotype, as well as differentiating efficiently upon external stimulation. We show that zinc promotes long-term ESC self-renewal (>30 days) via activation of ZIP7 and AKT signaling pathways. Furthermore, the combination of zinc with LIF results in a synergistic effect that enhances LIF effects, increases AKT and STAT3 activity, promotes the expression of pluripotency regulators and avoids the expression of differentiation markers.

Banded karyotype of Nelore cattle (Bos taurus indicus Linnaeus, 1758).

Chromosome banding techniques were applied and standardized to obtain karyotype characteristics for the first time in Brazil of Nelore cattle – Bos taurus indicus Linnaeus, 1758 – (bovine subspecies most prominent in Brazilian livestock). Blood samples were collected from the animals of the School of Agrarian and Biological Sciences of the Pontifical Catholic University of Goiás, two males and two females of pure breed. These samples were submitted to the cell culture method to study metaphase chromosomes. Chromosome banding techniques (C, G and NOR) revealed the karyotype architecture of Nelore cattle common with that of other breeds of zebu cattle formerly karyotyped. The diploid chromosome number was invariably normal, 2n = 60. C-banding revealed C-positive heterochromatin in centromeric regions almost in all chromosomes. G-banding presented the expected band pattern in the respective chromosome pairs in correspondence with the established chromosomal patterns for the species. Ag-staining for nucleolus organizer regions (AgNOR) was identified on the telomeric end of the long arm in 7 autosomal chromosomes. In this study we found more regions in chromosomes with staining than presented in the literature for the Bos indicus group (BIN). These NOR regions were repeated on the same chromosomes for the 4 animals studied.

Genomic Organization of Repetitive DNA Elements and Extensive Karyotype Diversity of Silurid Catfishes (Teleostei: Siluriformes): A Comparative Cytogenetic Approach.

The catfish family Siluridae contains 107 described species distributed in Asia, but with some distributed in Europe. In this study, karyotypes and other chromosomal characteristics of 15 species from eight genera were examined using conventional and molecular cytogenetic protocols. Our results showed the diploid number (2n) to be highly divergent among species, ranging from 2n = 40 to 92, with the modal frequency comprising 56 to 64 chromosomes. Accordingly, the ratio of uni- and bi-armed chromosomes is also highly variable, thus suggesting extensive chromosomal rearrangements. Only one chromosome pair bearing major rDNA sites occurs in most species, except for Wallago micropogon, Ompok siluroides, and Kryptoterus giminus with two; and Silurichthys phaiosoma with five such pairs. In contrast, chromosomes bearing 5S rDNA sites range from one to as high as nine pairs among the species. Comparative genomic hybridization (CGH) experiments evidenced large genomic divergence, even between congeneric species. As a whole, we conclude that karyotype features and chromosomal diversity of the silurid catfishes are unusually extensive, but parallel some other catfish lineages and primary freshwater fish groups, thus making silurids an important model for investigating the evolutionary dynamics of fish chromosomes.

Karyological traits related to phylogenetic signal and environmental conditions within the Hymenaea clade (Leguminosae, Detarioideae)

The Hymenaea clade is a lineage of the subfamily Detarioideae of Leguminosae. The clade is currently composed of three genera: Guibourtia, Hymenaea, and Peltogyne. The genera Guibourtia and Hymenaea present an Amphi-Atlantic distribution, whereas Peltogyne is exclusively found in the Neotropics. Previous studies have focused on the phylogeny of the group but there are no studies that demonstrate mechanisms that could be involved in the evolution of this Amphi-Atlantic clade. The present work is the largest cytogenetic analysis for the group published so far. We aimed to provide a study of karyotypic characteristics of the Hymenaea clade, interpreted using the plastidial trnK phylogenetic reconstruction as background. We analyzed karyological characteristics such as chromosome number, chromosome size, centromeric position, CMA/DAPI patterns, and banding for 5S and 45S rDNA. With the present data available, multivariate analyses (PCA) and Phylogenetic Eigenvector Regression (PVR) demonstrated that centromeric asymmetry and number of 5S rDNA sites may present a strong phylogenetic signal, whereas number of CMA+ sites is associated with geography/climate characteristics. The association of CMA bands and geography has been reported for other legumes of the Caesalpinia group. This study demonstrates that the use of statistical tools for analyzing karyotypic characteristics can result in more precise interpretation of evolutionary processes related to structural changes in chromosomes and how these changes can also be related to environmental conditions.

Clinical Significance of Monosomal Karyotype in MDS

To investigate the frequency, karyotype characteristics and prognosis significance of monosomal karyotype (MK) in newly diagnosed MDS patients. The clinical, laboratorial and follow-up data of 202 MDS patients received the chromosome karyotype test in Department of Hematology, Ningbo Hospital of Zhejiang University from 2009 to 2018 were analyzed retrospectively, the monosomal karyotype features, clinical characteristics and their effects on the prognosis of MDS patients also were analyzed. Among 202 cases of MDS, 25 (12.38%) confirmed to be the MK. The abnormality of chromosome 5 (60.00%), 7 (56.00%), 17 (56.00%), 15 (56.00%), 13 (40.00%) and 20（40.00%）were common in monosomal karyotype. MK+-MDS (MDS with monosomal karyotype) patients had higher bone marrow blast percentage than MK--MDS (MDS without monosomal karyotype) patients, the median are 6.25% and 3.00% (P＜0.01) respectively, but there were no difference in age, sex, hemoglobin level, white blood cell count, neutrophile granulocyte percentage, platelet count, blood blast percentage, serum ferritin, folic acid and vitaminB12 between MK+-MDS and MK--MDS. The overall survival time of MK+-MDS and MK--MDS patiens with chromosome 3, 5, 7, 13, 15, 17 abnormalities was significantly shorter than MK--MDS and AK+MK--MDS patients (MDS with abnormal karyotype but without monosomal karyotype) , the MK+-MDS patients had a median survival time of 7.33 months, but the median survival time had not been reached in MK--MDS and AK+MK--MDS patients had not been reached by the end of the follow-up, and could not be assessed (P＜0.01). The monosomal karyotype is a poor prognosis factor for newly-diagnosed MDS patients. The poor prognosis suggested by monosomal karyotype may be related with the abnormality of 3, 5, 7, 13, 15 and 17 chromosome.

Cytogeography and chromosomal variation of the endemic East Asian herb Lycoris radiata.

Information on the spatial distribution of cytotypes and karyotype variation in plants is critical for studies of the origin and evolution of polyploid complexes. Here, the spatial distribution of cytological races and intraspecific variation in the karyotype of Lycoris radiata, an endemic species to East Asia, is investigated. Conventional karyotype analysis methods were used to determine ploidy level and karyotypical characteristics in 2,420 individuals from 114 populations of L. radiata nearly covering the whole distribution areas in China. Of 114 populations studied, 52 (45.61%), 58 (50.88%), and 4 (3.51%) are diploid, triploid, and mixoploid populations, respectively, with 1,224, 1,195, and 1 individuals being diploid, triploid, and tetraploid, respectively. The triploid possesses a much wider distribution range than the diploid, with the former almost occupying the entire range of this complex species in East Asia and the latter distributing in the middle and east regions of China. Triploids tend to occur at high altitudes, and the relationship between the ploidy and altitude is significantly positive but low (r 2 = 0.103, p < 0.01). About 98.6% of examined bulbs have a common karyotype consisting of 22 or 33 acrocentric (A) chromosomes. Some aberrant chromosomes which should be generated from A‐type chromosome have been found including metacentrics (m), small metacentrics (m′), and B‐type chromosome. The results can provide a fundamental cytogeographic data for further studies on the evolutionary origins and adaptive divergences of polyploids, especially the triploid, within L. radiata using molecular and/or ecological methods in the future.

Evolutionary Insights of the ZW Sex Chromosomesin Snakes: A New Chapter Added by the AmazonianPuffing Snakes of the Genus Spilotes.

Amazonian puffing snakes (Spilotes; Colubridae) are snakes widely distributed in the Neotropical region. However, chromosomal data are scarce in this group and, when available, are only limited to karyotype description using conventional staining. In this paper, we focused on the process of karyotype evolution and trends for sex chromosomes in two Amazonian Puffer Snakes (S. pulllatus and S. sulphureus). We performed an extensive karyotype characterization using conventional and molecular cytogenetic approaches. The karyotype of S. sulphureus (presented here for the first time) exhibits a 2n = 36, similar to that previously described in S. pullatus. Both species have highly differentiated ZZ/ZW sex chromosomes, where the W chromosome is highly heterochromatic in S. pullatus but euchromatic in S. sulphureus. Both W chromosomes are homologous between these species as revealed by cross-species comparative genomic hybridization, even with heterogeneous distributions of several repetitive sequences across their genomes, including on the Z and on the W chromosomes. Our study provides evidence that W chromosomes in these two species have shared ancestry.

Karyotype Analysis of Three Varieties of Red Leaf Beet

Red leaf beet was one of the most important leaf vegetables and an ornamental with rich pigment. However, there is a lack of information on genetic variability. In this study, cytological parameters on three varieties of red leaf beet were obtained. The results displayed that the average arm ratio of RR1 was determined 1.52 and relative length was ranged from 9.26% to 13.10%. The karyotype asymmetry index was 59.93%, and the karyotype formula was 2n=2x=18=14m+4sm (2SAT). The average arm ratio of RR2 was determined 1.50 and relative length was ranged from 8.57% to 13.11%. The karyotype asymmetry index was mensurated as 59.60%, and the karyotype formula was 2n=2x=18=14m (2SAT) +4sm. The average arm ratio of RR3 was determined 1.33 and relative length was ranged from 9.44% to 12.56%. The karyotype asymmetry index was 56.85%, which was much lower than RR1 and RR2, and the karyotype formula was 2n=2x=18=18m (2SAT). Although RR3 had an obvious difference with RR1 and RR2, the karyotype characteristics of three varieties of red leaf beet were all type 1A. This research revealed the karyotypic characteristics of red leaf beet. The results indicated that there was an obvious difference among the three varieties of red leaf beet in karyotypic characteristics, and the evolution of red leaf beet was relatively primitive.

Karyotypic characterization of melon accessions

Cucumis melo (melon) is a species from the Iberian Peninsula and is included in the family Cucurbitaceae. Despite the knowledge about the physical structure of melon chromosomes, little is known about the intraspecific karyotype diversity of the species. To study karyotype diversity in eight melon accessions, the following methods were used: Giemsa 3% staining; application of CMA 3 /DAPI fluorochromes; and location of 45S and 5S rDNA sequences by fluorescence in situ hybridization. Conventional staining analysis revealed stability in the chromo­some number, with accessions presenting 2 n = 24. There were significant variations in the mean chromosome size between accessions, ranging from 0.98 μm to 1.46 μm for accessions A26 and A18, respectively. Scott-Knott clustering distributed the accessions into two groups. GC-rich heterochromatic blocks (CMA 3 + /DAPI - ) were observed in pericentromeric regions of all chromosomes in the complement. CMA 3 + /DAPI - blocks were also lo­cated in terminal regions, being specific to satellite regions. Hybridization sites of 45S rDNA probes revealed the presence of a chromosome pair with this locus . In addition, 5S rDNA sites revealed a labeled chromosome pair. No quantitative variation was observed in rDNA sites between the accessions analyzed, indicating these markers as ideal for the verification of karyotypic stability in C . melo .

Analysis of chromosome karyotype and genome size in echiuran Urechisunicinctus Drasche, 1880 (Polychaeta, Urechidae).

Karyotype and genome size are two primary cytogenetic characteristics of species, which are of great significance to the study of cytogenetics, taxonomy, phylogenesis, evolution as well as molecular biology. However, this basic cytogenetic information in echiurans is lacking. Therefore, we analyzed characteristics of karyotype and genome size in the echiuran worm Urechisunicinctus Drasche, 1880. In this study, coelomic cells of U.unicinctus were used for analyzing the genome size by a flow cytometry with chicken erythrocytes as DNA standard, and the 2C DNA content was determined to be 1.85 pg, which was corresponded to the genome size of 904.58 Mbp approximately. Furthermore, trochophores of U.unicinctus were dissociated and cells were utilized for preparing the chromosomes stained with DAPI, and the karyotype was determined as 2n = 30 (10m + 6sm + 6st + 8t), FN=52. Our data provided the basic cytogenetic information of U.unicinctus, which could be utilized in taxonomic study and whole-genome sequencing in future.

Evolutionary history of the Pasque-flowers (Pulsatilla, Ranunculaceae): Molecular phylogenetics, systematics and rDNA evolution

Pulsatilla (Anemoneae, Ranunculaceae) is sister to Anemone s.s. and contains ca 40 perennial species of considerable horticultural and medical importance. We sequenced 31 of those species, plus nine subspecies, two cultivars and six outgroups, for two nuclear regions (high-copy nrITS and low-copy MLH1) and three plastid regions (rbcL, accD–psaI, trnL intron) in order to generate the first comprehensive species-level phylogeny of the genus. Phylogenetic trees were constructed using both concatenation-based (maximum likelihood and Bayesian inference) and coalescence methods. The better supported among the internal nodes were subjected to molecular clock dating and ancestral area reconstruction, and karyotypic characters identified by us using Fluorescence In Situ Hybridization were mapped across the tree. The preferred species tree from the coalescence analysis formed the basis of a new infrageneric classification based on monophyly plus degree of divergence. The earliest divergent of the three subgenera, Kostyczewianae, is represented by only a single species that is morphologically intermediate between Anemone s.s. and ‘core’ Pulsatilla. Subgenus Pulsatilla is considerably richer in species than its sister subgenus Preonanthus and contains three monophyletic sections. Species possessing nodding flowers and pectinately dissected leaves are phylogenetically derived compared with groups possessing erect flowers and palmately lobed leaves. Pulsatilla separated from Anemone s.s. at ca 25 Ma. Our results indicate a central Asian mountain origin of the genus and an initial diversification correlated with late Tertiary global cooling plus regional mountain uplift, aridification and consequent expansion of grasslands. The more rapid and extensive diversification within subgenus Pulsatilla began at ca 3 Ma and continued throughout the Quaternary, driven not only by major perturbations in global climate but also by well-documented polyploidy.

Cytological characterization of three closely related pines - Pinus mugo, P. uliginosa and P. \xd7 rhaetica from the Pinus mugo complex (Pinaceae)

The Pinus mugo complex comprises closely related pines in different taxonomic ranks, which commonly occur in major European mountain chains. This large and polymorphic complex has been, and still is, a considerable challenge for taxonomists due to highly variable phenotypical characteristics within particular taxa, ongoing hybridization in sympatric populations, lack of distinct morphological species-specific determinants, and the absence of distinct genetic differentiation among them. Moreover, cytogenetic data on pines from this complex are very scarce. Therefore, in this study, we used C-banding methods and flow cytometric analysis in order to provide new data on karyotypical features and DNA content of three closely-related pines from the Pinus mugo complex, i.e., Pinus mugo (Turra), Pinus uliginosa (Neumann), and Pinus × rhaetica (Brügger) and to gain more insight into the taxonomic relationships between these pines. Our results confirmed that the basic number of chromosome is the same amongst the analyzed taxa (2n = 2x = 24), and that the karyotypes have a similar morphology. The number of secondary constrictions (SCs) and C-banding patterns differed slightly between P. mugo, P. uliginosa and P. × rhaetica. The nuclear DNA content (2C/pg) among analyzed taxa is from 46.41 pg for P. mugo and P. × rhaetica to 46.48 pg for P. uliginosa. For each of these pines, certain taxa-specific cytogenetic determinants were identified. Our results indicate that they may represent two different taxa, and so their names should not be used interchangeably in scientific literature.

Distribution and amplification of interstitial telomeric sequences (ITSs) in Australian dragon lizards support frequent chromosome fusions in Iguania.

Telomeric sequences are generally located at the ends of chromosomes; however, they can also be found in non-terminal chromosomal regions when they are known as interstitial telomeric sequences (ITSs). Distribution of ITSs across closely related and divergent species elucidates karyotype evolution and speciation as ITSs provide evolutionary evidence for chromosome fusion. In this study, we performed physical mapping of telomeric repeats by fluorescence in situ hybridisation (FISH) in seven Australian dragon lizards thought to represent derived karyotypes of squamate reptiles and a gecko lizard with considerably different karyotypic feature. Telomeric repeats were present at both ends of all chromosomes in all species, while varying numbers of ITSs were also found on microchromosomes and in pericentromeric or centromeric regions on macrochromosomes in five lizard species examined. This suggests that chromosomal rearrangements from ancestral squamate reptiles to Iguania occurred mainly by fusion between ancestral types of acrocentric chromosomes and/or between microchromosomes, leading to appearance of bi-armed macrochromosomes, and in the reduction of microchromosome numbers. These results support the previously proposed hypothesis of karyotype evolution in squamate reptiles. In addition, we observed the presence of telomeric sequences in the similar regions to heterochromatin of the W microchromosome in Pogona barbata and Doporiphora nobbi, while sex chromosomes for the two species contained part of the nucleolar organiser regions (NORs). This likely implies that these ITSs are a part of the satellite DNA and not relics of chromosome fusions. Amplification of telomeric repeats may have involved heterochromatinisation of sex-specific W chromosomes and play a role in the organisation of the nucleolus.

Revision of Polygonatum (Asparagaceae, Nolinoideae, Polygonateae) of Taiwan.

Polygonatum is widely distributed in the northern hemisphere, especially in eastern Asia. There has been no comprehensive taxonomic study of Taiwanese taxa for some time, and researchers could not agree on a consistent treatment of the genus. Therefore, we revised the genus by literature review and type specimen examination along with comparison of morphology, karyotype and pollen characteristics. Only one species P.arisanense Hayata was recognized in this study. P.chingshuishanianum Ying and P.formosanum (Hayata) Masamune & Simada are regarded as varieties of P.arisanense and are here presented as two new combinations, P.arisanensevar.chingshuishanianum and P.arisanensevar.formosanum.