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Interspecific variation in C-banded chromosomes of diploid Aegilops species

Teoh SB, Hutchinson J

Theor Appl Genet, 1983 Apr;65(1):31-40.
PMID: 24263198 DOI: 10.1007/BF00276259

Based on an improved C-banding technique, the C-banding patterns of all 11 diploid Aegilops species were described and compared. All diploid species exhibit characteristically different patterns which enable the chromosomes of any complement to be identified individually. These patterns confirm existing genome symbols and provide further evidence for the suggested changes in genome symbols of Ae. umbellulata and Ae. sharonensis, U and S(sh) respectively. Furthermore, Ae. uniaristata should be given a separate symbol, probably N. Aegilops speltoides and Ae. sharonensis could be possible donors to the B genome of wheat. Interspecific divergence in these diploid species has been accompanied by either amplification or deletion as well as massive repatterning of heterochromatin from the centromere to the telomere.

Matched MeSH terms: Centromere
Chromosomal Locations of a Non-LTR Retrotransposon, Menolird18, in Cucumis melo and Cucumis sativus, and Its Implication on Genome Evolution of Cucumis Species

Setiawan AB, Teo CH, Kikuchi S, Sassa H, Kato K, Koba T

Cytogenet Genome Res, 2020;160(9):554-564.
PMID: 33171461 DOI: 10.1159/000511119

Mobile elements are major regulators of genome evolution through their effects on genome size and chromosome structure in higher organisms. Non-long terminal repeat (non-LTR) retrotransposons, one of the subclasses of transposons, are specifically inserted into repetitive DNA sequences. While studies on the insertion of non-LTR retrotransposons into ribosomal RNA genes and other repetitive DNA sequences have been reported in the animal kingdom, studies in the plant kingdom are limited. Here, using FISH, we confirmed that Menolird18, a member of LINE (long interspersed nuclear element) in non-LTR retrotransposons and found in Cucumis melo, was inserted into ITS and ETS (internal and external transcribed spacers) regions of 18S rDNA in melon and cucumber. Beside the 18S rDNA regions, Menolird18 was also detected in all centromeric regions of melon, while it was located at pericentromeric and sub-telomeric regions in cucumber. The fact that FISH signals of Menolird18 were found in centromeric and rDNA regions of mitotic chromosomes suggests that Menolird18 is a rDNA and centromere-specific non-LTR retrotransposon in melon. Our findings are the first report on a non-LTR retrotransposon that is highly conserved in 2 different plant species, melon and cucumber. The clear distinction of chromosomal localization of Menolird18 in melon and cucumber implies that it might have been involved in the evolutionary processes of the melon (C. melo) and cucumber (C. sativus) genomes.

Matched MeSH terms: Centromere/genetics; Centromere/ultrastructure
Fulltext Centromeres of Cucumis melo L. comprise Cmcent and two novel repeats, CmSat162 and CmSat189

Setiawan AB, Teo CH, Kikuchi S, Sassa H, Kato K, Koba T

PLoS One, 2020;15(1):e0227578.
PMID: 31945109 DOI: 10.1371/journal.pone.0227578

Centromeres are prerequisite for accurate segregation and are landmarks of primary constrictions of metaphase chromosomes in eukaryotes. In melon, high-copy-number satellite DNAs (SatDNAs) were found at various chromosomal locations such as centromeric, pericentromeric, and subtelomeric regions. In the present study, utilizing the published draft genome sequence of melon, two new SatDNAs (CmSat162 and CmSat189) of melon were identified and their chromosomal distributions were confirmed using fluorescence in situ hybridization. DNA probes prepared from these SatDNAs were successfully hybridized to melon somatic and meiotic chromosomes. CmSat162 was located on 12 pairs of melon chromosomes and co-localized with the centromeric repeat, Cmcent, at the centromeric regions. In contrast, CmSat189 was found to be located not only on centromeric regions but also on specific regions of the chromosomes, allowing the characterization of individual chromosomes of melon. It was also shown that these SatDNAs were transcribed in melon. These results suggest that CmSat162 and CmSat189 might have some functions at the centromeric regions.

Matched MeSH terms: Centromere
Fulltext Activity of Plasmodium vivax promoter elements in Plasmodium knowlesi, and a centromere-containing plasmid that expresses NanoLuc throughout the parasite life cycle

Moraes Barros RR, Thawnashom K, Gibson TJ, Armistead JS, Caleon RL, Kaneko M, et al.

Malar J, 2021 Jun 05;20(1):247.
PMID: 34090438 DOI: 10.1186/s12936-021-03773-4

BACKGROUND: Plasmodium knowlesi is now the major cause of human malaria in Malaysia, complicating malaria control efforts that must attend to the elimination of multiple Plasmodium species. Recent advances in the cultivation of P. knowlesi erythrocytic-stage parasites in vitro, transformation with exogenous DNA, and infection of mosquitoes with gametocytes from culture have opened up studies of this pathogen without the need for resource-intensive and costly non-human primate (NHP) models. For further understanding and development of methods for parasite transformation in malaria research, this study examined the activity of various trans-species transcriptional control sequences and the influence of Plasmodium vivax centromeric (pvcen) repeats in plasmid-transfected P. knowlesi parasites.
METHODS: In vitro cultivated P. knowlesi parasites were transfected with plasmid constructs that incorporated Plasmodium vivax or Plasmodium falciparum 5' UTRs driving the expression of bioluminescence markers (firefly luciferase or Nanoluc). Promoter activities were assessed by bioluminescence, and parasites transformed with human resistant allele dihydrofolate reductase-expressing plasmids were selected using antifolates. The stability of transformants carrying pvcen-stabilized episomes was assessed by bioluminescence over a complete parasite life cycle through a rhesus macaque monkey, mosquitoes, and a second rhesus monkey.
RESULTS: Luciferase expression assessments show that certain P. vivax promoter regions, not functional in the more evolutionarily-distant P. falciparum, can drive transgene expression in P. knowlesi. Further, pvcen repeats may improve the stability of episomal plasmids in P. knowlesi and support detection of NanoLuc-expressing elements over the full parasite life cycle from rhesus macaque monkeys to Anopheles dirus mosquitoes and back again to monkeys. In assays of drug responses to chloroquine, G418 and WR9910, anti-malarial half-inhibitory concentration (IC50) values of blood stages measured by NanoLuc activity proved comparable to IC50 values measured by the standard SYBR Green method.
CONCLUSION: All three P. vivax promoters tested in this study functioned in P. knowlesi, whereas two of the three were inactive in P. falciparum. NanoLuc-expressing, centromere-stabilized plasmids may support high-throughput screenings of P. knowlesi for new anti-malarial agents, including compounds that can block the development of mosquito- and/or liver-stage parasites.

Matched MeSH terms: Centromere/metabolism
Fulltext Identification of a BET family bromodomain/casein kinase II/TAF-containing complex as a regulator of mitotic condensin function

Kim HS, Mukhopadhyay R, Rothbart SB, Silva AC, Vanoosthuyse V, Radovani E, et al.

Cell Rep, 2014 Mar 13;6(5):892-905.
PMID: 24565511 DOI: 10.1016/j.celrep.2014.01.029

Condensin is a central regulator of mitotic genome structure with mutants showing poorly condensed chromosomes and profound segregation defects. Here, we identify NCT, a complex comprising the Nrc1 BET-family tandem bromodomain protein (SPAC631.02), casein kinase II (CKII), and several TAFs, as a regulator of condensin function. We show that NCT and condensin bind similar genomic regions but only briefly colocalize during the periods of chromosome condensation and decondensation. This pattern of NCT binding at the core centromere, the region of maximal condensin enrichment, tracks the abundance of acetylated histone H4, as regulated by the Hat1-Mis16 acetyltransferase complex and recognized by the first Nrc1 bromodomain. Strikingly, mutants in NCT or Hat1-Mis16 restore the formation of segregation-competent chromosomes in cells containing defective condensin. These results are consistent with a model where NCT targets CKII to chromatin in a cell-cycle-directed manner in order to modulate the activity of condensin during chromosome condensation and decondensation.

Matched MeSH terms: Centromere/metabolism
Down syndrome as a result of de novo robertsonian translocation involving chromosome 14 and 21: a case report

Norhasimah, M.M., Ahmad Tarmizi, A.B., Azman, B.A., Zilfalil, B.A., Ankathil, R.

Malaysian Journal of Paediatrics and Child Health, 2007;15(1):46-49.
MyJurnal

Generally, the karyotype profile of Down Syndrome has been reported to be full trisomy 21 in 92% of patients, mosaic trisomy 21 in 4% of patients and translocation involving chromosome 21 in 4% of patients in most of the population groups worldwide. But, karyotype analysis of 149 DS patients at the Human Genome Center, USM, during the past five years revealed that free trisomy accounted for 94.6%, mosaic trisomy 21 for 4.7% and translocation involving chromosome 21 in 0.7% of the Down Syndrome etiology in North East Malaysian population, indicating a low frequency of translocation DS in this region. Here, we report one case of translocation Down Syndrome encountered during karyotype analysis of 149 DS cases. Karyotype showed a robertsonian translocation where an entire extra chromosome 21 was attached to the centromere of one of the chromosome 14, resulting in a derivative chromosome 14 with attached chromosome 21. Karyotype analysis of the parents revealed a normal 46,XY pattern for father and 46,XX pattern for mother indicating that this robertsonian translocation had arisen de novo either prior to or at conception.

Matched MeSH terms: Centromere