Somatic Chromosome Complement Research Articles

Cytological details of Luffa cylindrica (L.)M.Roem. a meiotically disturbed diploid

Present work embodies cytological analysis of Luffa cylindrica (L.)M.Roem., an economically important Cucurbit. L. cylindrica is found only under cultivation and has a diploid chromosome number of 2n = 26. Ten cultivars of this species collected from different parts of Jammu province of J&K state (India) were studied for their reproductive features, meiotic behaviour and somatic chromosome complement. All of them displayed some anomalies during meiosis that resulted in low pollen viability. This undesirable trait was however compensated by bold reproductive features and efficient pollen transfer in the species leading to high fruit and seed set. Mitotic studies revealed L. cylindrica to have stable diploid chromosome number with a primitive and little evolved karyotype. Presence of multivalents and erratic anaphase segregation during meiosis however point towards some structural rearrangements in the chromosomes which are difficult to detect because of small size of chromosomes and little variation in their size.

Karyotype Analysis of Korean Lilium maximowiczii Regal Populations

Detailed karyotypes analyses were carried out in 30 populations of Korean L. maximowiczii Regel. The populations were constituted with 43 diploids (2n=2x=24) and 38 triploids (2n=3x=36). The lengths of mitotic metaphase chromosomes ranged from 13.22 µm to 25.18 µm, with a total length of 203.78 µm in diploid plants. In triploid plants, the chromosome lengths ranged from 14.28 µm to 27.75 µm, with a total length of 214.42 µm. There was only one cytotype identified by karyotype analysis in both diploid and triploid populations. The basic set of somatic chromosome complement consists of two metacentrics (chromosomes a and b), two subtelocentrics (chromosomes c and d), and eight telocentrics (chromosomes e, f, g, h, i, j, k, and l) in both diploid and triploid populations. Four loci of 45S rRNA genes were observed by FISH, and three of the four loci correspond to the secondary constrictions. One additional 45S rRNA locus was observed by FISH at the near telomere of the long arm of a set of telocentric chromosomes. There were two 5S rRNA gene loci, which were closely placed on the long arm of a set of subtelocentric chromosomes that were not the 45S rRNA loci-carrying chromosomes. In conclusion, the karyotypes in both diploid and triploid popu- lations were identical, implying that the triploid organisms are autotriploids.

FISH Karyotype and GISH Meiotic Pairing Analyses of a Stable Intergeneric Hybrid xBrassicoraphanus Line BB#5

xBrassicoraphanus line BB#5, a new synthetic intergeneric hybrid between Brassica rapa L. ssp. pekinensis and Raphanus sativus L. var. rafiphera induced by N-methyl-N-nitroso-urethane mutagenesis in microspore culture, shows high seed fertility and morphological uniformity. Dual-color fluorescence in situ hybridization (FISH) using 5S and 45S rDNA probes and genomic in situ hybridization (GISH) using B. rapa genomic DNA probe were carried out to analyze the chromosome composition and the meiosis pairing pattern compared to its parental lines. The somatic chromosome complement is 2n = 38, which consists of 17 metacentric and two submetacentric chromosomes with lengths of 2.18 to <TEX>$5.01{\mu}m$</TEX>. FISH karyotype analysis showed five and eight pairs of 5S and 45S rDNA loci. GISH meiosis pairing analysis showed that 19 complete bivalents were most frequent and accounted for 42% of the 100 pollen mother cells examined. Based on chromosome number, size, morphology, rDNA distribution, and meiosis pairing pattern, both parental genomes of B. rapa and R. sativus appear to exist in xBrassicoraphanus line BB#5, demonstrating its genome integrity. Such stable chromosome constitutions and meiotic pairing patterns in somatic and meiotic cells are very rare in natural and synthetic intergeneric hybrids. Chromosomal studies and genetic and phenotypic changes in allopolyploids a re discussed. The results p resented h erein will b e usef ul f or f urther g enomic s tudy o f xBrassicoraphanus lines and their improvement as promising new breeding varieties.

Genotype-specific changes associated to early synthesis of autotetraploids in wild potato species

Polyploidy is an important factor in plant evolution that may trigger drastic genome reorganization and phenotypic differentiation. In the last decade, extensive studies have been carried to understand the consequences of allopolyploidization, where the effects of ploidy change may be confounded by interspecific hybridization. By contrast, less is known on autopolyploidization, which only involves doubling of homologous chromosomes. This study was undertaken to assess leaf anatomical modifications and gene expression changes occurring after doubling the somatic chromosome complement of diploid (2n = 2x = 24) potato species Solanum commersonii Dunal and S. bulbocastanum Dunal. Polyploidization did not induce qualitative changes in leaf structure and, for several leaf traits, anatomic modifications were stochastic. In addition, in both species a diploid superiority was generally observed, suggesting the occurrence of a high-ploidy syndrome. Expression change study was carried out on eight important cell cycle-regulatory genes in plant. It revealed a strong alteration of the expression patterns in the 4x genotypes with respect to the 2x parents. Changes often exceed the twofold, with no consistent trend towards up- or down regulation when comparing 2x vis-a-vis 4x. We discuss the possible relevance of epigenetic changes in controlling the expression of duplicated genes.

Karyomorphotypic variation in Eriospermum abyssinicum Baker

The karyomorphology of the cotton seed lily, Eriospermum abyssinicum Baker (family Eriospermaceae) was investigated through mitotic and meiotic studies. The chromosome complement was karyotypically analysed based on chromosome arm ratio and centromeric indices. The somatic chromosome complement of 2n = 24 recorded at metaphase I and the 12 bivalents at prophase I of meiosis suggested x = 6 basic chromosome number and paleopolyploidization process in the evolution of this species. There was no evidence of B chromosome or nucleolar-organizer in the complements. Variation in position of centromere ranged from the median to sub-median and sub-terminal. We found slight variation between some homologues in terms of lengths which suggest hybrid origin (allopolyploidy) of the genome. The microspore mother cell had normal meiosis with subsequent formation of 4 daughter nuclei and normal spores suggesting that the changes in chromosome behaviour occurred at very low frequency and these changes were transient with no evidence of phenotypic and genomic instability (aneuploidy) consequences. It was therefore inferred that the population of E. abyssinicum studied might have evolved through changes in chromosome structure or through natural hybridisation between closely related populations. Key words: Eriospermum abyssinicum, lily, chromosome, karyotype.

Karyotype analysis of Panax ginseng C.A.Meyer, 1843 (Araliaceae) based on rDNA loci and DAPI band distribution

Ginseng has long been considered a valuable plant owing to its medicinal properties; however, genomic information based on chromosome characterization and physical mapping of cytogenetic markers has been very limited. Dual-color FISH karyotype and DAPI banding analyses of Panax ginseng C. A. Meyer, 1843 were conducted using 5S and 45S rDNA probes. The somatic chromosome complement was 2n=48 with lengths from 3.3 μm to 6.3 μm. The karyotype was composed of 12 metacentric, 9 submetacentric, and 3 subtelocentric pairs. The 5S rDNA probe localized to the intercalary region of the short arm of pair 11, while the 45S rDNA was located at the secondary constriction of the subtelocentric satellited chromosome 14. DAPI bands were clearly observed for most chromosomes, with various signal intensities and chromosomal distributions that consequently improved chromosome identification. As a result, all 24 chromosomes could be distinguished and numbers were assigned to each chromosome for the first time. The results presented here will be useful for the on-going ginseng genome sequencing and further molecular-cytogenetic studies and breeding programs of ginseng.

Derivation of embryonic germ cells and male gametes from embryonic stem cells.

Egg and sperm cells (gametes) of the mouse are derived from a founder population of primordial germ cells that are set aside early in embryogenesis. Primordial germ cells arise from the proximal epiblast, a region of the early mouse embryo that also contributes to the first blood lineages of the embryonic yolk sac. Embryonic stem cells differentiate in vitro into cystic structures called embryoid bodies consisting of tissue lineages typical of the early mouse embryo. Because embryoid bodies sustain blood development, we reasoned that they might also support primordial germ cell formation. Here we isolate primordial germ cells from embryoid bodies, and derive continuously growing lines of embryonic germ cells. Embryonic germ cells show erasure of the methylation markers (imprints) of the Igf2r and H19 genes, a property characteristic of the germ lineage. We show that embryoid bodies support maturation of the primordial germ cells into haploid male gametes, which when injected into oocytes restore the somatic diploid chromosome complement and develop into blastocysts. Our ability to derive germ cells from embryonic stem cells provides an accessible in vitro model system for studies of germline epigenetic modification and mammalian gametogenesis.

Molecular cytogenetic analysis of DNA sequences with flanking telomeric repeats inTriticum aestivumcv. Begra

A cloned genomic DNA fragment (pTa241) formerly derived from a DNA fraction obtained from isolated nuclei of embryos of a Polish cultivar of wheat (Triticum aestivum cv. Begra) comprises a tandem repeat of the telomeric array CCCTAAA, and hybridizes in situ exclusively to the telomeres of all chromosome arms of the somatic chromosome complement of wheat. A second cloned fragment (pTa637) derived from the same fraction is 637 bp long, flanked by 28 bp of the same telomeric repeat unit, and hybridizes in situ to the entire lengths of all the chromosomes of the complement. The same pattern of hybridization was observed when the flanking telomeric sequences were removed. A third DNA fragment (pTa1439), derived from unfractionated genomic DNA and flanked with 62 bp of the same telomeric unit, showed the same patterns of distribution. Together with additional evidence from Southern analysis, these observations were interpreted to mean that these sequences are associated with mobile DNA elements and are distributed widely throughout the genome. The chromosomal distribution of the non-telomeric parts of the clones is consistent with the dispersed genomic distribution characteristic of transposons and retroelements.Key words: wheat, Triticum aestivum cv. Begra, mobile elements, telomeric DNA sequence, FISH.

Molecular cytogenetic analysis of DNA sequences with flanking telomeric repeats in Triticum aestivum cv. Begra.

A cloned genomic DNA fragment (pTa241) formerly derived from a DNA fraction obtained from isolated nuclei of embryos of a Polish cultivar of wheat (Triticum aestivum cv. Begra) comprises a tandem repeat of the telomeric array CCCTAAA, and hybridizes in situ exclusively to the telomeres of all chromosome arms of the somatic chromosome complement of wheat. A second cloned fragment (pTa637) derived from the same fraction is 637 bp long, flanked by 28 bp of the same telomeric repeat unit, and hybridizes in situ to the entire lengths of all the chromosomes of the complement. The same pattern of hybridization was observed when the flanking telomeric sequences were removed. A third DNA fragment (pTa1439), derived from unfractionated genomic DNA and flanked with 62 bp of the same telomeric unit, showed the same patterns of distribution. Together with additional evidence from Southern analysis, these observations were interpreted to mean that these sequences are associated with mobile DNA elements and are distributed widely throughout the genome. The chromosomal distribution of the non-telomeric parts of the clones is consistent with the dispersed genomic distribution characteristic of transposons and retroelements.

Colchiploid Induction in Anthephora ampulacea Stapf and Hubb.

A tetraploid variety of A. ampulacea was produced through colchiploidization by treatments in 0.15% and 0.20% colchicine for 7 to 20hr. The cytogenetics of the diploid and induced tetraploid were studied in order to determine the chromosome numbers and observe the meiotic behaviour. A. ampulacea diploid had a somatic chromosome complement of 18 chromosomes and regular 9 bivalents. The induced tetraploid had 36 somatic chromosomes and showed irregular meiosis characterized by the presence of quadrivalents and univalents at diakinesis and metaphase I with laggards and bridges at anaphse I. These differences in chromosomes numbers were reflected in plant size, length of spikes, number of spikelets and total seed production.

ネギ (&lt;I&gt;Allium fistulosum&lt;/I&gt;) と&lt;I&gt;A. altaicum&lt;/I&gt;のC-バンド核型分析および類縁関係の検討

C-banded karyotypes and their variations were studied in Allium fistulosum and A. altaicum, and the phylogenetic relationship between the two species was verified.1. All plants of cultivars and strains examined in A. fistulosum had the same karyotypes except for a variation of satellites [K(2n) =14V+2JT, 14V+1JT+1Jt, 14V+1JT+1J]. The telomeric and centromeric regions in all chromosomes, satellites and proximal regions to the nucleolar organizer in No. 6 chromosome, and five intercalary regions in No. 6, 7, 8 chromosomes were differentially stained as the fundamental C-banding pattern of A. fistulosum.2. Two strains of A. altaicum were, in whole, similar to A. fistulosum in the karyotype, including the variation of satellites. The C-banding patterns differed between the two species by the presence or absence of three intercalary bands.3. In F1 hybrid plants between A. fistulosum and A. altaicum, the somatic chromosome complement consisted of eight pairs of chromosomes after C-banded karyotype analysis. Almost homologous meioses in PMCs were observed in F1 hybrid plants. Moreover, F1 hybrid plants showed high seed fertility. Consequently, these results suggest that A. fistulosum and A. altaicum have homologous genomes, and indicate the degree of their close relationship.

Karyotypes and chromosome association in aneuploid varieties of Japanese garden iris, Iris ensata Thunb

Karyotypes, chromosome association and pollen fertility of aneuploid varieties (2n=25), ‘Ochibagoromo’, ‘Matsusakatsukasa’ and ‘Isehomare’ in Iris ensata were analysed and compared with those of eu-diploid varieties (2n=24), ‘Shishinden’, ‘Kacho’ and ‘Asahimaru’. The somatic chromosome complement of the aneuploid varieties consisted of 11 pairs and 3 singles of chromosomes and that of the eu-diploid varieties 12 pairs of chromosomes. The singles of chromosomes in the aneuploid varieties had similarity with one another and with a pair of chromosomes in the eu-diploid varieties. The high frequency of normal association was present in the eu-diploid varieties, and this indicated that 12 pairs of chromosomes had full homology between each other. In contrast, the mean chromosome association per cell in an aneuploid variety ‘Ochibagoromo’ was 4.615I+10.067II+0.077III+0.005IV, indicating that the chromosome complement of this variety consisted of 11 pairs and 3 singles and that these singles had partial homology among them. The eu-diploid varieties exhibited high pollen fertility due to their regularity of chromosome association; the aneuploid varieties considerably lower fertility, i.e. 28.2% for ‘Ochibagoromo’, 31.8% for ‘Isehomare’ and 43.8% for ‘Matsusakatsukasa’. The primary cause for the low fertility of these varieties seemes to be the partial homology among 3 single chromosomes. Finally, the origin and the development of the aneuploid varieties were discussed.

Maternal haploids of Petunia axillaris (Lam.) B.S.P. via culture of placenta attached ovules

Hybridization of Petunia axillaris and P. parodii with Nicotiana tabacum was attempted using the method of in vitro pollination and fertilization. Seedlings were produced when the Petunia species and N. tabacum were used as the maternal parents; however, most of these had the identical somatic chromosome complement of the maternal parent. With crosses involving P. axillaris as the maternal parent, a low frequency of haploids was also produced. Due to the potential of haploids in basic and applied genetic research, additional experiments were carried out to determine whether in vitro pollination was necessary to stimulate haploid production and to more closely define the optimal time for ovule excision and culture. Four treatments were applied to accomplish these objectives. They were: placentas cultured prior to the time of anthesis, with and without pollination, and placentas cultured after the time of anthesis, with and without pollination. In vitro pollination had no effect on the frequency of haploids produced. Placenta attached ovules cultured prior to the time of anthesis produced significantly more haploids than those cultured after anthesis. The preanthesis treatment produced a frequency of 6.5 haploids per 100 ovaries cultured. The culture of placenta attached ovules provides an alternative to anther culture as a means for haploid production.

4倍性ワケギと複2倍体 (シャロット&amp;times;ネギ) との雑種の核型, 減数分裂及び稔性

In the somatic chromosome complement of the hybrid between the tetraploid Allium wakegi and the amphidiploid (A. ascalonicum×A. fistulosum) 16 pairs of chromosomescould be morphologically distinguished, and the karyotype was expressed by the following formula: K (2n) =2(14V+J(t)1+JT2). At meiotic metaphase-I in the pollen mother cells of the hybrid 16 bivalents were regularly formed. At metaphase of pollen grain mitosis most of the pollen grains possessed the chromosome complements (K (n) =14V+J(t)1+JT2) equivalent to the exact half of the somatic chromosome complement of thehybrid. Moreover, the hybrid was pollen fertile and had a good seed set. Therefore, it became clear that A. wakegi has the same genome constitution as that of the hybrid between A. ascalonicum and A. fistulosum. This indicates incontestably that A. wakegi is the synthetic species of these two species.

Somatic chromosomes of Bubulcus ibis (L.) (Cattle-Egret): A case of reciprocal translocation

The somatic chromosome complement of Bubulcus ibis consists of six pairs of macrochromosomes, twenty-three pairs of microchromosomes and a pair of sex chromosomes. The Z-chromosome is comparable in size to autosome pairs 3 and 4, from which it is difficult to distinguish, and the W-chromosome is indistinguishable from the larger microchromosomes. The chromosome complement of one individual was found to deviate from the normal because of structural heterozygosity involving a member of chromosome pair 1 and a microchromosome.

Cytogenetic studies of Poecilia (Pisces). I. Chromosome numbers of naturally occurring poeciliid species and their hybrids from Eastern Mexico.

Cytological studies of fish from the subgenus Poecilia (Pisces) including members of an all-female species, P. formosa, have clearly shown diploid, somatic chromosome complements and Robertsonian arm numbers of 46. A triploid somatic chromosome complement of 3N = 69 was demonstrated for members of a naturally occurring variant clone of P. formosa, a form whose general body morphology closely resembles that of its sympatric species P. mexicana. Chromosomes of the different poeciliid species studied are remarkably similar in size, shape and structure, being mostly short acrocentrics, 2 μ long or less.The presence of a chromosome bearing a sub-terminal centromere within the complement of the Amazon molly provides the only direct evidence to date of centric shifts within the chromosome complement of the subgenus Poecilia. This finding also provides the first plausible cytogenetic basis for concluding that P. formosa is of relatively recent origin. Comparisons of relative chromosome lengths from both mitotic and meiotic configurations of related species indicate that the heteromorphic chromosome pair of P. formosa probably was derived by hybridization between P. latipinna and P. mexicana. Finally, as suggested by the numbers and forms of chromosomes in atypical, triploid specimens of P. formosa, their complements apparently contain both a maternal diploid set of chromosomes from the all-female species, and a paternal haploid set of chromosomes from P. mexicana.

Somatic Chromosomes ofClarius Batrachus(L.) (Clariidae: Teleostomi)

SUMMARYThe somatic chromosome complement of Clarius batrachus consists of (1) a pair of large metacentrics, (2) two pairs of small metacentrics, (3) 21 pairs of medium-size telocentrics and (4) two pairs of very small telocentrics.

Meiosis in a male with Down's syndrome.

The chromosomes in mitotic and meiotic phases were investigated in a male Down's syndrome case, aged 45. Information was obtained that based on blood and tunica vaginalis cultures, the somatic chromosome complement was found to possess 47 chromosomes with the standard 21-trisomy, and further that the majority of cells from biopsied testicular specimens examined showed the chromosome number 47 in spermatogonia, and 22 autosomal elements consisting of 21 bivalents and a trivalent, together with an X-Y bivalent in the first spermatocytes. The seminiferous tubules contained no mature spermatozoa.

Cytogenetics of Polyploids

Two cytological races having 2n=32 and 48 and designated as tetraploid and hexaploid, respectively were found in C. reflexa. While somatic chromosome complement of tetraploid race comprises of 28 metacentric and 4 submetacentric chromosomes, the complement of hexaploid races consists of 36 chromosomes with median and 12 chromosomes with submedian centromere. On the basis of general chromosome morphology and shape, the somatic chromosomes of the complement could be grouped into 8 sets, each set comprising of 4 chromosomes in the tetraploid and of 6 chromosomes in the hexaploid race. The differences observed in these parameters within the chromosomes of each set are statistically insignificant but those between the sets are significant. Meiosis in the tetraploid race is normal leading to the formation of viable pollen grains. In the hexaploid race, meiosis is highly abnormal and is arrested before heterotypic division is completed. Immediately after the pollen mother cells degenerate, branched fibrilous attachments projecting out from the degenerated PMCs are observed. When the young immature anthers were clipped off and the flowers bagged, parthenocarpic seeds are produced in the hexaploid material, However, the seed set is poor. A gene controlled suppression of homeologous pairing in the tetraploid race has been postulated. This type of control is not operative in the two hexaploid races of the species. The implications of karyotype morphology and chromosome pairing behaviour in polyploids are critically discussed in general and the role of polyploidy in the species in particular.

Plasma level of growth hormone and chromosome complement in four patients with gonadal dysgenesis (Turner's syndrome).

ABSTRACT Elevated levels of growth hormone (GH) were found in the plasma of four patients with Turner's syndrome. The somatic chromosome complement of these patients was determined by using a cell culture method. Bone marrow cells from three patients had 45 chromosomes instead of the normal number of 46. The missing chromosome is all probability one of the two X chromosomes. These subjects have therefore a sex chromosome constitution of the XO type. The fourth patient had a complement of 45 chromosomes in the skin cells but in bone marrow cultures cells with 45 and 46 chromosomes were found. During successive transfers in vitro the cells with 46 chromosomes outnumbered those with 45. It is assumed that in these patients the production of growth hormone by the pituitary gland is normal but a target system, as yet unidentified, is defective or absent.