Sm Chromosomes Research Articles

Karyological studies of four species of Lady’s Slipper Orchids (Paphiopedilum) collected in the Bogor Botanical Garden, Indonesia

Paphiopedilum is one of the most widely grown and hybridized of all orchid genera due to its distinctive flower morphology. This genus consists of 139 accepted species and is native to southern China to tropical Asia. Karyological studies on the genus Paphiopedilum have been reported by many cytologists in different countries. However, many Indonesian members of Paphiopedilum have remained comparatively limited in investigated cytologically. This study aimed to analyze karyological characters of four species of Paphiopedilum collected in the Bogor Botanical Garden, Indonesia, namely P. armeniacum, P. hirsutissimum, P. primulinum, and P. superbiens. Karyological studies were conducted by root tips squash method. The results showed that four species of Paphiopedilum have a basic chromosome number of x = 15. They are diploid with 2n=30, instead of the common diploid chromosome number of Paphiopedilum (2n = 26). Paphiopedilum hirsutissimum and P. primulinum possess 16 m + 14 sm chromosome formulae. Whereas Paphiopedilum armeniacum and P. superbiens revealed 16 m + 14 sm and 18 m + 12 sm chromosome formulae, respectively.A Robertsonian change in chromosome number generated by the fission of chromosomes would best explain the origin of the new diploid chromosome number and karyotypes of these species.

Are the chromosomal fusions that shaped the karyotype of Tetranematichthys wallacei (Siluriformes: Auchenipteridae) a shared feature among Ageneiosini species?

Abstract The genus Tetranematichthys has only three species, and none of them have undergone cytogenetic analyses. Therefore, this study brings for the first time the analysis of Tetranematichthys wallacei, collected from the Igarapé Apaú, Guamá River basin, municipality of Castanhal, Pará State, Brazil. The diploid number found was 52 chromosomes (32m+18sm+2st, NF = 104), in both sexes, with predominantly terminal and some interstitial heterochromatin. Telomeric sequences were observed exclusively in terminal regions. The 18S rDNA sites were found on pair 17sm of all specimens and in only one of the homologous of pair 7 in three specimens. The 5S rDNA sites were found in pairs 8m and 10m. Tetranematichthys wallacei exhibits characteristics worthy of attention regarding its current phylogenetic position, including a probable diploid number reduction. Additionally, it shares with Tympanopleura atronasus the 18S rDNA allocated in the long arm of a large sm chromosome (first pair) but does not share with Ageneiosus the large first m pair with evidence of fusion, as observed in Ageneiosus inermis. The chromosomal data generated for T. wallacei, along with the data from the other two previously studied Ageneiosini taxa, reinforces proposals from morphology-based studies suggesting that the tribe represents the most distinct clade within the family.

Cytogenetics of Diphysa americana (Mill.) M.Sousa (Leguminosae-Papilionoideae-dalbergioid clade), a rare species from the coast of Oaxaca, Mexico

Diphysa Jacq. is an essentially Mexican and Central American genus that includes 21 species and only one cytogenetic report. In this work, a surface spread and air-drying method was used to obtain the karyotype of Diphysa americana (Mill) M.Sousa, a rare native tree that grows in a coastal town in the State of Oaxaca, Mexico. Metaphase cells showed a 2n = 20, consistent with the predominant diploid number in the dalbergioid clade. This number contrasts with a previously reported 2n = 16. The karyotypic formula 5m + 5sm, first proposed for a species of the genus, denotes a slightly asymmetric karyotype. The presence of secondary constrictions associated with satellites on the short arms of a pair of sm chromosomes and other cytogenetic parameters require studies in other species of the genus to verify their taxonomic utility. In addition, cells in prometaphase exhibited a circular fragment of unknown origin like that observed in a species of the genus Aeschynomene, also dalbergioid. This fragment could be related to extrachromosomal circular DNA (eccDNA) observed in other plants. Diphysa is a small, cytogenetically favorable genus, and further studies will exhibit the karyotypic diversity that underlies its diversification.

Karyomorphological Analysis and Genome Size Variation of Sixteen <i>Callicarpa</i> Taxa in China

Information on chromosomes and estimation of genome size could be applied to study the evolution and classification of a genus. In our study, the conventional pressing method was applied to prepare microscope slides for counting the chromosomes, and the chromosome numbers of all surveyed species were 2n=32, 34, 36, 38. The first-time determination of chromosome counts for 12 taxa and karyotypes for 16 taxa in Callicarpa were conducted. It exposed all the species with a higher ratio of m chromosomes and a lower ratio of sm chromosomes, and only C. macrophylla contained st chromosome pair. The minor differences between the karyotypes of all species revealed that the karyotype diversity of this genus evolved from a tiny variation of chromosome structure. Meanwhile, the genome size of 23 samples from 16 taxa of Callicarpa has been estimated by flow cytometry. The genome size ranged from 0.96 pg (C. pedunculata) to 1.26 pg (C. nudiflora), averaged out at 1.12 pg, and the variation of genome sizes was fine among the investigated species. Hence, it could also be referred from the viewpoints of cytology that Callicarpa was a group in Lamiaceae that evolved earlier and independently.

Karyotype analysis of Common Cocklebur (Xanthium strumarium L.)

Objective: The purpose of this study is to determine the mitotic chromosome number, morphometric parameters, and karyotypes of Xanthium strumarium and make contributions to other multidisciplinary studies on the genus. Material and Methods: The seeds were germinated on moist filter paper in Petri dishes at 25°C. Actively growing root tips were pre-treated with aqueous paradichlorobenzene for 4h at room temperature. Then, the root tips were fixed with acetic alcohol (1:3 glacial acetic acid–absolute ethanol) for at least 24 h at 4°C, hydrolysed in 1 N HCl at 60°C for 3 min, then rinsed in tap water for 3–5 min. Finally, they were stained in Feulgen for 1 h and mounted in 45% acetic acid. Digital microphotographs from at least five well-spread metaphase plates were taken using an Olympus BX51 microscope and were recorded with an Olympus Camedia C-4000 digital camera. Results: The chromosome number is determined as 2n = 36 for this taxon. The karyotype consists of 16 median region (m) and 2 submedian region (sm) chromosomes. The metaphase chromosome length ranges from 2.30 to 4.03 μm, longest to shortest chromosome ratio is 1.7:1.1, total karyotype length (TKL) 54.76 mm and the karyotype symmetry is type 1A. Conclusion: The results of this study showed that the chromosome number of Xanthium strumarium is 2n=36. Satellites were not observed in the karyotype of this species.Identifying the chromosome number of this species in this study provides a base for biosystematic studies.

Karyomorphology of Turkish species in Centaurea sections Centaurea and Phalolepis (Asteraceae) and implications for taxonomy

In this paper, 31 mostly endemic and locally distributed Turkish Centaurea taxa belonging to Centaurea and Phalolepis sections were examined in terms of their karyomorphology. The basic chromosome number for all of the studied species was concurringly determined as 9(x = 9) for both sections, excluding C. hierapolitana. We also determined tetraploid and hexaploid species in spite of many species having diploid chromosome numbers. Twelve chromosome counts are reported for the first time and most of the karyotyping analyses are described for the first time via the KAMERAM program. The karyotypes had a predominance of metacentric (m) chromosomes. However, in the karyotyping of six taxa, submetacentric (sm) chromosomes were dominant. Five quantitative asymmetric indices were used to evaluate karyological features of the species. A meaningful dendrogram was carried out to assess the karyotype-symmetry conditions and describe the karyotyping relationships between different taxa.

Karyotype Analysis in seven cultivars ofNarcissusspp.

We investigated the chromosome number and karyotype in seven cultivars of Narcissus spp. using the traditional squash method. The result indicated that all seven cultivars were diploid and the basic chromosome numbers in these seven cultivars were n = 12 and 14. The karyotype was 2B for all seven cultivars. Six of seven cultivars consisted of m and sm chromosome, and only one cultivar contains st chromosome. The detailed karyotypes of the seven cultivars are as follows: Arkle: 2n = 2x = 28 = 3m + 11sm, index of the karyotypic asymmetry (As·k) = 66.57 %; Fortissimo: 2n = 2x = 28 = 4m + 10sm, As·k = 66.60 %; Pink Charm: 2n = 2x = 28 = 3m + 10sm + 1st, As·k = 66.62 %; Mary Bcharmon: 2n = 2x = 24 = 5m + 7sm, As·k = 64.56 %; Barret Browing: 2n = 2x = 24 = 6m + 6sm, As·k = 65.73 %; Romance: 2n = 2x = 24 = 2m + 10sm, As·k = 65.64 %; Dutch Master: 2n = 2x =24 = 3m + 9sm, As·k = 65.95 %. Our results indicated that the karyotype analysis combined with morphological characters could assist to classify the taxonomic ...

Karyomorphology and GC-rich heterochromatin pattern in Passiflora (Passifloraceae) wild species from Decaloba and Passiflora subgenera

Thirteen wild species of Passiflora were analyzed using conventional and CMA/DA/DAPI staining to evaluate the karyotype diversity between and within the subgenus Decaloba and Passiflora. The karyotypic features indicate that both subgenera have a conserved chromosome number, as reported before for several species. Submetacentric (sm) chromosomes were found in species from both subgenera, suggesting that sm chromosomes are not restricted to a particular subgenus. The analysis of the karyotypic heterogeneity enabled to distribute the species in three groups, but with no support to phylogenetic and taxonomic levels. The application of fluorochromes allowed for the visualization of CMA+/DAPI− blocks, which in our studies always correlated with the occurrence of satellites, showing that occurrence of two chromosome pairs with satellites per cell is a characteristic shared by some species from both subgenera. This feature does not always have relationship with the basic chromosome number. The data found in this study will help to understand the phylogeny, cytotaxonomy, and evolution of the genus Passiflora showing that karyotypic variation can be seen between and within the subgenus Decaloba and Passiflora.

Cytotaxonomy of two species of genus Chrysolaena H. Robinson, 1988 (Vernonieae, Asteraceae) fromNortheast Paraguay.

Chromosome counts and karyotypes of two species of Chrysolaena H. Robinson 1988 are presented in this paper. Mitotic analysis revealed that both taxa have x=10, a basic chromosome number considered characteristic of the genus. The chromosome number and the karyotype of Chrysolaena cristobaliana are reported for the first time, as well as a new cytotype and the karyotype of Chrysolaena sceptrum. Chrysolaena cristobaliana showed heptaploid cytotype with 2n=7x=70 and a karyotype composed of 46 m + 24 sm chromosomes. On the other hand, Chrysolaena sceptrum presented tetraploid cytotype with 2n=4x=40 and a karyotype with 30 m + 10 sm chromosomes. Accessory chromosomes were observed in cells of both species. The chromosome analysis showed that these species differ in the chromosome number and the total chromosome length, although they showed similar chromosome morphology and asymmetry indexes. The results support the use of chromosome data in taxonomic treatments of the American members of the tribe Vernonieae.

Chromosomal Studies and Quantitative Karyotypic Analysis of Rohu, Labeo rohita

Chromosomal and karyotypic studies are required for genetic improvement of any organisms. This study was performed to identify individual chromosomes on morphological basis and to characterize a standard karyotype using the fish, Rohu (Labeo rohita, Hamilton, 1822). Colchicine (0.05%) treated (2, 2.5 and 3 h) tissues of two day-old larvae were used for slide preparations and selected plates were photomicrographed under high resolution research microscope. Slide preparations were done following hydrolysis (10% HCl), mordanting (2% iron alum) and staining with haematoxylin. Colchicine treatment for 2 h gave satisfactory results in respect of degree of contraction of the chromosomes. Chromosome number 2n = 50 was counted at metaphase stage. Measurements of the chromosomes were taken from the selected plates based on morphologically distinct condition. Standard haploid karyotype was formulated following the combined scatter diagram technique. Six individually identifiable and 19 not individually identifiable chromosomes consisted of the haploid complement. The six individually identifiable ones consisted of 2 m+3 sm+1st and not individually identifiable ones consisted of 16 m+3 sm chromosomes. This study report may provide complete report on chromosomal and karyotype knowledge in L. rohita and suggest the genetic purity of L. rohita may contributes to sustainable aquaculture production.

Karyotype Analysis of Wild Rosa Species in Xinjiang, Northwestern China

Wild Rosa species, which are highly variable and locally adapted, are widely distributed in the Xinjiang Uygur autonomous region of China. These species possess many important horticultural traits that are not found in the gene pool of modern cultivated roses. However, little is known about their cytological characteristics, because few of them have been karyologically analyzed. Karyological data of 13 samples of seven wild Rosa taxa, including R. berberifolia, two botanical varieties of R. spinosissima, R. platyacantha, R. beggeriana, R. acicularis, and R. laxa, were investigated by means of squashes of shoot tips. The results showed that seven samples were diploid (2n = 2x = 14), whereas the other six samples were tetraploid (2n = 4x = 28). The karyotypes of all the test samples were composed of m and sm chromosomes, which include 1A, 2A, 1B, and 2B. There were differences in asymmetry index, centromere index, and distribution of relative lengths. The karyotype of the tetraploid R. laxa var. laxa sample from Aksu easily distinguished from the other R. laxa var. laxa samples tested in having the highest asymmetry index and the most evolved karyotype. This Aksu population merits recognition as a new botanical variety of R. laxa. The karyological data, most of which are first reports for their taxa, provide a comprehensive cytogenetic resource that can be used to better understand the taxonomy, evolution, and speciation in the genus Rosa and to identify candidate species for breeding programs.

First karyological report in Larnax and Deprea (Solanaceae)

Somatic chromosomes of 12 samples belonging to seven Larnax Miers species and three Deprea Raf. species are studied. Chromosome number and karyotype analysis of both genera are reported for the first time. All taxa have 2n = 24. The most frequent haploid karyotype formula (8 of 12 samples) is 9 metacentric (m) + 3 submetacentric (sm) chromosomes, whereas L. glabra (Standl.) N.W. Sawyer and Larnax sp. display 10 m + 2 sm. Karyotypes of L. nieva S. Leiva & N.W. Sawyer and D. cuyacensis (N.W. Sawyer & S. Leiva) S. Leiva & Lezama are remarkable for the highest number of sm chromosome pairs, with 7 m + 5 sm and 5 m + 7 sm, respectively, presenting the highest intrachromosomal asymmetry index (A1), whereas Larnax sp. and L. glabra show the lowest A1. Most samples (9 of 12) examined have only one pair of chromosomes with nucleolar organiser regions (NOR), whereas L. glabra, Larnax sp., and D. cuyacensis possess two pairs of NOR. Systematic considerations about the monophyly of Larnax and Deprea are provided. The different karyotype parameters obtained, together with morphological characters, are discussed to single out the species.

Karyotypes of South American species of the Morelloid and Dulcamaroid clades (Solanum, Solanaceae)

A karyotypic study on South American representatives of the Morelloid and Dulcamaroid clades of Solanum was conducted to contribute to a better understanding of their relationships. Mitotic chromosomes of 26 species were examined (13 of which were previously unknown). All taxa presented 2n = 2x = 24 and had small chromosomes (less than 4 μm long) with the exception of S. crispum. Most species displayed symmetrical karyotypes, being 78% and 69% m, 19% and 25% sm and 3% and 6% st for the Morelloid and Dulcamaroid clades, respectively. Solanum crispum (Dulcamaroid clade) was unique by having mostly sm chromosomes and S. sinuatirecurvum (Morelloid clade) stood out with four st pairs and an exclusive pair of satellites in long arms. Solanum tripartitum was the sole entity exhibiting an sm pair with satellites. Most examined species of these clades resulted karyologically indistinguishable, based on conventionally stained mitotic chromosomes. Molecular analyses are needed to gain a better knowledge of the possible karyoevolutionary trends of both clades.

Chromosomes of European cyprinid fishes: comparative cytogenetics and chromosomal characteristics of ribosomal DNAs in nine Iberian chondrostomine species (Leuciscinae)

Karyotypes and chromosomal features of both minor and major ribosomal RNA genes (rDNA) were investigated in nine Iberian chondrostomine species by fluorescent in situ hybridization (FISH) with 5S and 45S rDNA probes. All species presented invariably diploid values of 2n = 50 and the characteristic leuciscin karyotype pattern with 6-7 metacentric (m), 15-16 submetacentric (sm) and 3-4 subtelo- to acrocentric (st/a) chromosome pairs. The largest chromosome pair of the set was st/a as typical of Leuciscinae and no heteromorphic chromosomes could be unequivocally associated to sex determination. Achondrostoma occidentale and Pseudochondrostoma willkommii were cytogenetically characterized for the first time while Achondrostoma arcasii and Iberochondrostoma lemmingii were revisited regarding previous karyotype descriptions. Remarkable variability in number and location was observed for both molecular chromosome markers, especially within Achondrostoma and Iberochondrostoma genera. Clusters of 5S rDNA were mostly terminally associated to st/a chromosomes varying from four to eight positive signals, whilst NOR sites directly detected by the 45S rDNA probe were identified in sm chromosomes varying from three to six independent clusters. Frequent population bottlenecks in Mediterranean-type semiarid habitats were hypothesized to explain not only such extensive polymorphism which seems unique among leuciscin cyprinids but also the increased probability of fixation of rDNA translocation events.

Karyotypes of four bird species of the order Passeriformes.

The karyotypes of four bird species in the order Passeriformes have been studied. The results further confirm that in birds, the karyotypes of closely related species are only slightly different. One of the species investigated, Chloris chloris, shows a special feature. Chromosome No. I can be either an st chromosome or an sm chromosome probably due to a pericentric inversion.

Cytogenetic studies inHerbertiaSw. (Iridaceae)

Fil: Moreno, Natalia Cecilia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto Multidisciplinario de Biologia Vegetal. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Instituto Multidisciplinario de Biologia Vegetal; Argentina

Cytogenetic Characterization and Nuclear DNA Content of Diploid and Tetraploid Forms of Stokes Aster

Stokesia laevis (J. Hill) Greene is a herbaceous perennial native to the southeastern United States. Most cultivars of Stokesia are diploid (2n = 2x = 14) except for ‘Omega Skyrocket’, a tetraploid (2n = 4x = 28) form selected from a natural population. A comparative study of the karyotypes and meiotic behavior of diploid cultivars, seed-derived accessions of ‘Omega Skyrocket’, synthetically derived autotetraploids, and triploid progeny from these taxa strongly suggest that ‘Omega Skyrocket’ is an autotetraploid form of Stokesia. Total karyotype length, 161 μm and 293 μm, and average chromosome length, 11.5 μm and 10.5 μm, of the diploid cultivars and tetraploid accessions of ‘Omega Skyrocket’, respectively, were determined. The karyotype of the diploid cultivars consisted of eight metacentric (m) and six submetacentric (sm) chromosomes with average arm ratio values ranging from 1.12 to 2.06. The karyotype of ‘Omega Skyrocket’ consisted of 23 m chromosomes and 5 sm chromosomes with average arm ratio values ranging from 1.22 to 2.02. Meiotic pairing in the diploids was normal. No meiotic irregularities such as laggards or bridges were observed and disjunction was balanced (7:7). Accessions of ‘Omega Skyrocket’ demonstrated a high frequency (60%) of quadrivalent formation; however, later stages of meiosis were regular with balanced disjunction (14:14) occurring in 95% of the cells. Meiotic configurations in synthetically derived autotetraploids and triploid hybrids from crosses of diploid cultivars × ‘Omega Skyrocket’ consisted of univalents, bivalents, trivalents, quadrivalents, and pentavalents. Abnormalities, including laggards, unequal and/or premature disjunction, chromosome bridges, and chromosome stickiness were observed. Average nuclear 2C DNA content was 20.3 pg for the diploid cultivars and 39.9 pg for the newly synthesized autotetraploids. Average nuclear 2C DNA content for ‘Omega Skyrocket’ was 37.3 pg, which was 8.2% less than twice the average 2C DNA content of the diploid accessions and 6.4% less than the newly synthesized autotetraploids, suggesting that genomic downsizing in ‘Omega Skyrocket’ has occurred. Similarity of the karyotypes of the diploids and ‘Omega Skyrocket’ and the slight reduction in nuclear DNA content suggest that ‘Omega Skyrocket’ has diverged little from its original diploid progenitor.

Low incidence of polyploids and high uniformity of karyotypes displayed byDelphinium(Ranunculaceae) in the Hengduan Mountains region of south-west China

The chromosome numbers and morphology in 92 populations belonging to 49 species and three varieties in the genus Delphinium L. (Ranunculaceae), mostly from the Hengduan Mountains region of south-west China, were studied. Forty seven species and three varieties were diploid, with 2n = 16, one species was tetraploid, with 2n = 32, and one species had diploid and tetraploid cytotypes. Three species had B chromosomes, representing the first time the occurrence of B chromosomes has been reported in the genus. The karyotypes of all the diploid species were quite uniform, commonly bimodal, and usually consisted of one pair of large median-centromeric (m), one pair of large submedian-centromeric (sm), five pairs of medium-sized subterminal-centromeric (st), and one pair of smaller sm (rarely st) chromosomes. The low incidence of polyploids in Delphinium from the Hengduan Mountains region indicates that polyploidy has played a minor role in the speciation of this highly diversified genus in the region. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158, 172–188.

Supernumerary chromosomes in the pufferfish Sphoeroides spengleri: first occurrence in marine Teleostean Tetraodontiformes fish

Cytogenetic analyses carried out in eight specimens of Sphoeroides spengleri revealed the presence of 2n = 46 chromosomes (20 M/SM and 26 ST/A). Besides the standard karyotypical set, the presence of B microchromosomes was observed in two individuals, ranging from 0 to 2 microchromosomes per cell. A karyotype composed by 2n = 46 chromosomes with occurrence of M and SM chromosomes is considered basal for the species from the clade comprising the families Tetraodontidae, Balistidae, and Diodontidae, although it represents a derived condition for the order Tetraodontiformes, whose basal karyotype would be composed by 2n = 48 acrocentric chromosomes. The occurrence of B microchromosomes in marine Tetraodontiformes fish was not known, and this represents the first report of such a chromosomal type.

Comparative cytogenetics of Carnegiella marthae and Carnegiella strigata (Characiformes, Gasteropelecidae) and description of a ZZ/ZW sex chromosome system

Comparative cytogenetic analyses of hatchetfishes Carnegiella marthae and Carnegiella strigata (Gasteropelecidae) from the Rio Negro basin were performed using conventional Giemsa staining, silver (Ag) -staining and C-banding. The diploid chromosome numbers of both species equaled 2n = 50 but their karyotypes were distinct. We found evidence for sex chromosomes in C. marthae since karyotype of males presented 20 M + 12 SM + 4 ST + 14 A and ZZ ST chromosomes while the females presented 20 M + 12 SM + 4 ST + 14 A and ZW ST chromosomes of distinct size. Conversely, C. strigata presented 4 M + 4 SM + 2 ST + 40 A chromosomes without sex chromosome heteromorphism. Karyotypes of both species had two NOR-bearing SM chromosomes of distinct size indicating the presence of multiple NOR phenotypes. The sex chromosome pair had specific C-banding pattern allowing identification of both Z and W. This heteromorphic system has previously been described for the gasteropelecids.