scholarly journals Chromosome number and secondary constriction variation in 51 accessions of a citrus germplasm bank

1997 ◽  
Vol 20 (3) ◽  
pp. 489-496 ◽  
Author(s):  
Marcelo Guerra ◽  
Andrea Pedrosa ◽  
Ana Emília Barros e Silva ◽  
Maria Tereza Marquim Cornélio ◽  
Karla Santos ◽  
...  
Keyword(s):  
Secondary Constriction ◽  
Chromatin Condensation ◽  
Proximal Region ◽  
Citrus Species ◽  
Germplasm Bank ◽  
Mitotic Chromosomes ◽  
Citrus Germplasm ◽  
Numerical Variation ◽  
Subterminal Region ◽  
Secondary Constrictions

The mitotic chromosomes of 51 citrus accessions from the Centro Nacional de Pesquisa em Mandioca e Fruticultura Tropical, Cruz das Almas, BA, Brazil, were analyzed. The sample included representatives of 20 Citrus species, one of Poncirus and seven hybrids. All accessions showed 2n = 18 without any evidence of numerical variation. The most clearly variable karyotype feature was the number and position of secondary constrictions (SECs). In 19 accessions the SECs were not identified, mainly due to the degree of chromatin condensation. In the remainder they varied in number from one to three per karyotype. They were found in the proximal region of one of the three largest chromosome pairs, in the terminal/subterminal region of a smaller chromosome or, more seldom, terminally in a larger chromosome. Only in a few cases were such constrictions observed simultaneously in both homologues of the same chromosome pair. The high variability of this karyotype feature may be due to the activation of this region in the previous interphase but may also indicate a high structural variability and heterozygosity of citrus germplasms

scholarly journals Chromosomal analyses in Megalonema platanum (Siluriformes: Pimelodidae), an endangered species from South American rivers

2011 ◽  
Vol 9 (1) ◽  
pp. 177-182 ◽  
Author(s):  
Rafael Augusto de Carvalho ◽  
Sebástian Sanchez ◽  
Ana Claudia Swarça ◽  
Alberto Sergio Fenocchio ◽  
Isabel C. Martins-Santos ◽  
...  
Keyword(s):  
Diploid Number ◽  
Secondary Constriction ◽  
Centromeric Heterochromatin ◽  
Large Chromosome ◽  
South American ◽  
Terminal Position ◽  
Chromosomal Data ◽  
First Time ◽  
Secondary Constrictions ◽  
Submetacentric Pair

This study presents chromosomal data of Megalonema platanum from rio Tibagi, Paraná, Brazil and from rio Paraná, Argentina. The diploid number was equal 54 with karyotype composition of 24m+16sm+2st+12a in both populations. The AgNOR sites were detected in the terminal position of a submetacentric pair of the two analyzed populations, coinciding with secondary constrictions on the short arm of pair 15. CMA3 and FISH with 18S rDNA probe displayed fluorescent signals that correspond to the AgNOR sites and secondary constriction. The presence of a small acrocentric supernumerary chromosome can be observed in M. platanum from rio Tibagi, with centromeric heterochromatin. Others heterochromatic blocks were evidenced in the terminal position of some chromosome and one metacentric large chromosome pair, probably the first pair, showed an interstitial heterochromatin. In the population of the rio Paraná were still observed heterochromatic blocks in both ends in some chromosomes. This work brings for the first time cytogenetic date of M. platanum, which is a very rare species in the rio Paraná basin and may be endangered.

The ultrastructure of oogonia and oocytes in the foetal and neonatal rat

1962 ◽  
Vol 157 (966) ◽  
pp. 99-114 ◽  
Keyword(s):  
Meiotic Prophase ◽  
Developmental Stages ◽  
Post Partum ◽  
Chromatin Condensation ◽  
Complex Form ◽  
Neonatal Rat ◽  
Mitotic Chromosomes ◽  
Thin Sections ◽  
Cytoplasmic Organelles ◽  
Spindle Fibres

Ovaries from eighty foetal and neonatal rats (aged 16·0 days post coitum to 4 days post partum ) were examined under the electron microscope. All the normal developmental stages (oogonia and oocytes in the leptotene, zygotene, pachytene, diplotene and dictyate phases of meiotic prophase) were identified. Patterns of degeneration (‘atretic divisions’, ‘ Z ’ cells and atresia at the diplotene phase), whose histological appearance and incidence have been recorded by Beaumont & Mandl (1962), were also recognized. The nuclei of oocytes at the leptotene phase contain single electron dense threads which become aligned in parallel pairs at the following phase (zygotene). A third finer fibril half-way between them appears at pachytene (tripartite ribbon). The longitudinal segments of threads, visible in ultra-thin sections, become shorter, presumably due to coiling. Nuclei at the diplotene phase contain single threads essentially similar to those seen at leptotene. As the oocyte enters the dictyate or resting phase, electron dense threads disappear from the nucleus. These observations suggest that the threads represent chromosomal ‘cores’. Nucleolus-like components persist throughout meiotic prophase, and at the diplotene phase regain the more complex form typical of oogonia. The cytoplasmic organelles become more numerous and complex as the oocyte approaches the dictyate phase. ‘Atretic divisions’ in oogonia are characterized by the persistence of long segments of nuclear membrane and the appearance of vesicles enveloped by a double membrane resembling the nuclear envelope. The dense masses of ‘chromatin’ (mitotic chromosomes) are more rounded than in normal cells at metaphase, and tend to coalesce. Spindle fibres have not been observed. Cytoplasmic organelles tend to increase in number and complexity. ‘ Z ’ cells (cells degenerating largely at the pachytene phase) show heavy ‘chromatin’ condensation around the tripartite ribbons. The major cytoplasmic changes consist in swelling of the endoplasmic reticulum, vacuolation of mitochondria and increase in incidence of multilamellar bodies. Atretic oocytes at the diplotene phase differ markedly from ‘ Z ’ cells in that ‘chromatin’ condensation around electron dense threads (single) is markedly less prominent. Cytoplasmic changes are similar to those of ‘ Z ’ cells, but also include a rise in the incidence of multivesicular and other complex bodies. All three types of degenerating cells are removed from the ovary by the phagocytic activity of neighbouring somatic cells.

scholarly journals Studies on Metatherian Sex Chromosomes. IX. Sex Chromosomes of the Greater Glider (Marsupialia : Petauridae)

1979 ◽  
Vol 32 (3) ◽  
pp. 375 ◽  
Author(s):  
JD Murray ◽  
GM McKay ◽  
GB Sharman
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
National Park ◽  
Secondary Constriction ◽  
X Chromosomes ◽  
Cultured Fibroblasts ◽  
Multiple Sex Chromosomes ◽  
Eastern Australia ◽  
Xy Bivalent ◽  
Secondary Constrictions

The greater glider, currently but incorrectly known as Schoinobates vo/ans, is widely distributed in forested regions in eastern Australia. All animals studied from six different localities had 20 autosomes but there were four chromosomally distinct populations. At Royal National Park, N.S.W., all female greater gliders studied had 22 chromosomes including two large submetacentric X chromosomes with subterminal secondary constrictions in their longer arms. This form of X chromosome occurred also at Bondo State Forest, Myall Lakes and Coff's Harbour, N.S.W., and at Eidsvold, Qld. At Coomooboolaroo, Qld, the X chromosome was also a large submetacentric but a secondary constriction occurred in the shorter arm. Two chromosomally distinct types apparently occur in Royal National Park, one with XY m,ales as in all other populations, and one with XY1Y2 males. Y or Yb but not Y 2, chromosomes were eliminated from the bone marrow in all populations but were present in spermatogonia, primary sperrnatocytes and cultured fibroblasts. Animals from Bondo State Forest had three or more acrocentric or metacentric supernumerary chromosomes. [Other keywords: C-banding, eytotaxonomy, multiple sex chromosomes, XY bivalent.]

Étude caryologique de trois espèces d’Hypochoeris originaires d'Argentine : H. chillensis, H. microcephala var. albiflora et H. megapotamica

1994 ◽  
Vol 72 (10) ◽  
pp. 1496-1502 ◽  
Author(s):  
S. Siljak-Yakovlev ◽  
A. Bartoli ◽  
G. Roitman ◽  
N. Barghi ◽  
C. Mugnier
Keyword(s):  
Chromosome Number ◽  
Related Species ◽  
Secondary Constriction ◽  
Nucleolar Organizer ◽  
Asymmetry Index ◽  
Evolutionary Trend ◽  
Closely Related Species ◽  
Nucleolar Organizers ◽  
Morphological Differences ◽  
Secondary Constrictions

Three Hypochoeris species from Argentina with the same chromosome number (x = 4) and similar karyotypes (typically bimodal) show significant ecological and morphological differences. Comparative cytogenetic analysis was done for these taxa, producing karyotypes with correlated idiograms. The number of secondary constrictions and nucleolar organizers varied. The results from this study are discussed in terms of the mechanisms of microevolution within this group of closely related species, and in terms of the evolutionary trend in the genus and in the tribe Cichorieae. Key words: Hypochoeris, Cichorieae, bimodal karyotype, secondary constriction, nucleolar organizer, asymmetry index.

scholarly journals High- and Low-mobility Populations of HP1 in Heterochromatin of Mammalian Cells

2004 ◽  
Vol 15 (6) ◽  
pp. 2819-2833 ◽  
Author(s):  
Lars Schmiedeberg ◽  
Klaus Weisshart ◽  
Stephan Diekmann ◽  
Gabriele Meyer zu Hoerste ◽  
Peter Hemmerich
Keyword(s):  
Mammalian Cells ◽  
Constitutive Heterochromatin ◽  
Chromatin Condensation ◽  
Cell Types ◽  
Correlation Spectroscopy ◽  
Chromosomal Protein ◽  
Mitotic Chromosomes ◽  
Heterochromatin Protein 1 ◽  
Stable Conformation ◽  
Fluorescence Correlation

Heterochromatin protein 1 (HP1) is a conserved nonhistone chromosomal protein with functions in euchromatin and heterochromatin. Here we investigated the diffusional behaviors of HP1 isoforms in mammalian cells. Using fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP) we found that in interphase cells most HP1 molecules (50–80%) are highly mobile (recovery halftime: t1/2 ≈ 0.9 s; diffusion coefficient: D ≈ 0.6–0.7 μm2 s-1). Twenty to 40% of HP1 molecules appear to be incorporated into stable, slow-moving oligomeric complexes (t1/2 ≈ 10 s), and constitutive heterochromatin of all mammalian cell types analyzed contain 5–7% of very slow HP1 molecules. The amount of very slow HP1 molecules correlated with the chromatin condensation state, mounting to more than 44% in condensed chromatin of transcriptionally silent cells. During mitosis 8–14% of GFP-HP1α, but not the other isoforms, are very slow within pericentromeric heterochromatin, indicating an isoform-specific function of HP1α in heterochromatin of mitotic chromosomes. These data suggest that mobile as well as very slow populations of HP1 may function in concert to maintain a stable conformation of constitutive heterochromatin throughout the cell cycle.

scholarly journals (262) Screening Citrus Germplasm for Resistance to Xanthomonas axonopodis pv. Citri

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1048E-1049 ◽  
Author(s):  
Greg McCollum ◽  
Kim Bowman ◽  
Tim Gottwald
Keyword(s):  
Effective Means ◽  
Citrus Canker ◽  
Poncirus Trifoliata ◽  
Citrus Species ◽  
Citrus Industry ◽  
Xanthomonas Axonopodis ◽  
Citrus Germplasm ◽  
Citrus Bacterial Canker ◽  
Key Lime ◽  
Needle Prick

Citrus bacterial canker [causal agent Xanthomonas axonopodis pv. citri (Xac)] is a serious threat to the citrus industry. Currently, there are no effective means to control citrus canker. Our objective was to determine the resistance of selected citrus species, citrus hybrids, and citrus relatives to Xac. Our first experiment focused on determining if differences in resistance exist among 20 C. reticulata genotypes and included three other citrus species and citrus relatives (Glycosmis pentaphylla and Clausena hardimandiana). Plants were inoculated with Xac strain A either by injection infiltration or needle-prick. Our second experiment included 10 members of the genus Citrus and Poncirus trifoliata, representing a total of 31 different selections. Plants were needle-prick inoculated with both Xac strain A and Xac strain A Wellington (AW). All inoculations were done using suspensions of Xac at a concentration of 104 cfu/mL. In both experiments, there were highly significant differences among genotypes in response to inoculation with Xac. In the first experiment, regardless of inoculation method, G. pentaphylla and C. hardimandiana were found to be highly resistant to Xac, whereas C. paradisi was least resistant. In the second experiment for both Xac strain A and AW, Chinotto sour orange, Carrizo citrange, Eustis limequat, and P. trifoliata were the most resistant. Thornless key lime × Meiwa kumquat hybrids showed a range of resistance from among the most susceptible to among the most resistant. Our results expand on previous studies on resistance of citrus and citrus relatives to Xac and indicate that there may be potential for increasing resistance by breeding using selected parents.

scholarly journals Variations in heterochromatin content reveal important polymorphisms for studies of genetic improvement in garlic (Allium sativum L.)

2023 ◽  
Vol 83 ◽  
Author(s):  
P. A. A. Bacelar ◽  
L. L. Feitoza ◽  
S. E. S. Valente ◽  
R. L. F. Gomes ◽  
L. V. Martins ◽  
...  
Keyword(s):  
Allium Sativum ◽  
Chromatin Condensation ◽  
Chromosome 6 ◽  
Germplasm Bank ◽  
Chromomycin A3 ◽  
Interphase Nuclei ◽  
Karyotype Formula ◽  
Heterochromatin Content ◽  
Nutraceutical Properties ◽  
Internal Consumption

Abstract Allium sativum L. is an herb of the Alliaceae family with a specific taste and aroma and medicinal and nutraceutical properties that are widely marketed in several countries. Brazil is one of the largest importers of garlic in the world, despite of its production is restricted and limited to internal consumption. Thus, explore the genetic diversity of commercial garlic conserved at germplasm banks is essential to generate additional genetic information about its economically important crop. A suitable tool for this purpose is the cytogenetic characterisation of these accessions. This study aimed to characterise the cytogenetic diversity among seven accessions of garlic from a Germplasm Bank in Brazil. The karyotypes were obtained by conventional staining and with chromomycin A3 (CMA) and 4,6-diamidino-2-phenylindole (DAPI) fluorochromes. All accessions analysed showed chromosome number 2n = 16, karyotype formula 6M+2SM, symmetrical karyotypes, reticulate interphase nuclei, and chromosomes with uniform chromatin condensation from prophase to metaphase. The fluorochromes staining showed differences in the amount and distribution of heterochromatin along the chromosomes and between accessions studied. Based on the distribution pattern of these small polymorphisms, it was possible to separate the seven accessions into three groups. It was also possible to differentiate some of the accessions individually. One of the results obtained showed a heteromorphic distension of the nucleolar organiser region observed on the chromosome pairs 6 or 7 with peculiar characteristics. It was suggested for example, that the heteromorphic block of heterochromatin (CMA+++/DAPI-) on chromosome 6 of the “Branco Mineiro Piauí” accession can be used as a marker to identify this genotype or may be associated with some character of economic interest.

scholarly journals Locations of 18S and 28S ribosomal genes on the chromosomes of the Indian muntjac.

1975 ◽  
Vol 64 (1) ◽  
pp. 251-254 ◽  
Author(s):  
M L Pardue ◽  
T C Hsu
Keyword(s):  
In Situ Hybridization ◽  
Ribosomal Rna ◽  
Secondary Constriction ◽  
Ribosomal Genes ◽  
Metaphase Chromosomes ◽  
Indian Muntjac ◽  
Secondary Constrictions

The locations of genes coding for 18S and 28S ribosomal RNA have been mapped on metaphase chromosomes of the Indian muntjac M. muntjak by in situ hybridization with (3H)rRNA from the toad X. laevis. The results show that, in the muntjac, rDNA clusters are associated with the prominent secondary constrictions on the X and the Y1 chromos. In addition a cluster of rDNA is found near the tip of one arm on the longest pair of autosomes. The autosomal cluster of rDNAs usually does not express as a secondary constriction at metaphase.

Banding in mitotic chromosomes of Brassica campestris var. pekinensis with a trypsin–Giemsa method

Genome ◽  
1992 ◽  
Vol 35 (5) ◽  
pp. 899-901 ◽  
Author(s):  
Soryu Nishibayasahi
Keyword(s):  
Banding Pattern ◽  
Brassica Campestris ◽  
Chromosome Size ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Secondary Constrictions

In Brassica campestris var. pekinensis cv. CR-strong, the karyotype comprised 12 median, 6 submedian, and 2 sub-terminal chromosomes. Secondary constrictions were observed in the two subterminal chromosomes. Banding pattern appeared very clearly in metaphase chromosomes with a trypsin–Giemsa method. It was possible to classify the chromosomes into 10 types (C1–C10), based on the chromosome size, shape, and banding pattern.Key words: Brassica campestris var. pekinensis, mitotic chromosomes, G-banding.

scholarly journals Mitotic Transcription Repression in Vivo in the Absence of Nucleosomal Chromatin Condensation

2000 ◽  
Vol 150 (1) ◽  
pp. 13-26 ◽  
Author(s):  
Charlotte A. Spencer ◽  
Michael J. Kruhlak ◽  
Heather L. Jenkins ◽  
Xuejun Sun ◽  
David P. Bazett-Jones
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase Ii ◽  
Chromatin Condensation ◽  
Mitotic Chromosomes ◽  
Viral Dna ◽  
Transcription Repression ◽  
Cellular Genes ◽  
Rnap Ii ◽  
Simplex Virus

All nuclear RNA synthesis is repressed during the mitotic phase of the cell cycle. In addition, RNA polymerase II (RNAP II), nascent RNA and many transcription factors disengage from DNA during mitosis. It has been proposed that mitotic transcription repression and disengagement of factors are due to either mitotic chromatin condensation or biochemical modifications to the transcription machinery. In this study, we investigate the requirement for chromatin condensation in establishing mitotic transcription repression and factor loss, by analyzing transcription and RNAP II localization in mitotic cells infected with herpes simplex virus type 1. We find that virus-infected cells enter mitosis and that mitotic viral DNA is maintained in a nucleosome-free and noncondensed state. Our data show that RNAP II transcription is repressed on cellular genes that are condensed into mitotic chromosomes and on viral genes that remain nucleosome free and noncondensed. Although RNAP II may interact indirectly with viral DNA during mitosis, it remains transcriptionally unengaged. This study demonstrates that mitotic repression of transcription and loss of transcription factors from mitotic DNA can occur independently of nucleosomal chromatin condensation.

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