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Journal articles on the topic 'Holocentric'

Author: Grafiati

Published: 25 May 2024

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1

Guerra, Marcelo, and Miguel A. García. "Heterochromatin and rDNA sites distribution in the holocentric chromosomes of Cuscuta approximata Bab. (Convolvulaceae)." Genome 47, no. 1 (January 1, 2004): 134–40. http://dx.doi.org/10.1139/g03-098.

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Cuscuta is a widely distributed genus of holoparasitic plants. Holocentric chromosomes have been reported only in species of one of its subgenera (Cuscuta subg. Cuscuta). In this work, a representative of this subgenus, Cuscuta approximata, was investigated looking for its mitotic and meiotic chromosome behaviour and the heterochromatin distribution. The mitotic chromosomes showed neither primary constriction nor Rabl orientation whereas the meiotic ones exhibited the typical quadripartite structure characteristic of holocentrics, supporting the assumption of holocentric chromosomes as a synapomorphy of Cuscuta subg. Cuscuta. Chromosomes and interphase nuclei displayed many heterochromatic blocks that stained deeply with hematoxylin, 4',6-diamidino-2-phenylindole (DAPI), or after C banding. The banded karyotype showed terminal or subterminal bands in all chromosomes and central bands in some of them. The single pair of 45S rDNA sites was observed at the end of the largest chromosome pair, close to a DAPI band and a 5S rDNA site. Two other 5S rDNA site pairs were found, both closely associated with DAPI bands. The noteworthy giant nuclei of glandular cells of petals and ovary wall exhibited large chromocentres typical of polytenic nuclei. The chromosomal location of heterochromatin and rDNA sites and the structure of the endoreplicated nuclei of C. approximata seemed to be similar to those known in monocentric nuclei, suggesting that centromeric organization has little or no effect on chromatin organization.Key words: Cuscuta, holocentric chromosomes, heterochromatin.

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2

Mandrioli, Mauro, and Gian Carlo Manicardi. "Holocentric chromosomes." PLOS Genetics 16, no. 7 (July 30, 2020): e1008918. http://dx.doi.org/10.1371/journal.pgen.1008918.

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3

Powers, James, Debra J. Rose, Adam Saunders, Steven Dunkelbarger, Susan Strome, and William M. Saxton. "Loss of KLP-19 polar ejection force causes misorientation and missegregation of holocentric chromosomes." Journal of Cell Biology 166, no. 7 (September 27, 2004): 991–1001. http://dx.doi.org/10.1083/jcb.200403036.

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Holocentric chromosomes assemble kinetochores along their length instead of at a focused spot. The elongated expanse of an individual holocentric kinetochore and its potential flexibility heighten the risk of stable attachment to microtubules from both poles of the mitotic spindle (merotelic attachment), and hence aberrant segregation of chromosomes. Little is known about the mechanisms that holocentric species have evolved to avoid this type of error. Our studies of the influence of KLP-19, an essential microtubule motor, on the behavior of holocentric Caenorhabditis elegans chromosomes suggest that it has a major role in combating merotelic attachments. Depletion of KLP-19, which associates with nonkinetochore chromatin, allows aberrant poleward chromosome motion during prometaphase, misalignment of holocentric kinetochores, and multiple anaphase chromosome bridges in all mitotic divisions. Time-lapse movies of GFP-labeled mono- and bipolar spindles demonstrate that KLP-19 generates a force on relatively stiff holocentric chromosomes that pushes them away from poles. We hypothesize that this polar ejection force minimizes merotelic misattachment by maintaining a constant tension on pole–kinetochore connections throughout prometaphase, tension that compels sister kinetochores to face directly toward opposite poles.

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Schubert, Veit, Mateusz Zelkowski, Sonja Klemme, and Andreas Houben. "Similar Sister Chromatid Arrangement in Mono- and Holocentric Plant Chromosomes." Cytogenetic and Genome Research 149, no. 3 (2016): 218–25. http://dx.doi.org/10.1159/000447681.

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Due to the X-shape formation at somatic metaphase, the arrangement of the sister chromatids is obvious in monocentric chromosomes. In contrast, the sister chromatids of holocentric chromosomes cannot be distinguished even at mitotic metaphase. To clarify their organization, we differentially labelled the sister chromatids of holocentric Luzula and monocentric rye chromosomes by incorporating the base analogue EdU during replication. Using super-resolution structured illumination microscopy (SIM) and 3D rendering, we found that holocentric sister chromatids attach to each other at their contact surfaces similar to those of monocentrics in prometaphase. We found that sister chromatid exchanges (SCEs) are distributed homogeneously along the whole holocentric chromosomes of Luzula, and that their occurrence is increased compared to monocentric rye chromosomes. The SCE frequency of supernumerary B chromosomes, present additionally to the essential A chromosome complement of rye, does not differ from that of A chromosomes. Based on these results, models of the sister chromatid arrangement in mono- and holocentric plant chromosomes are presented.

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5

Zedek, František, Jakub Šmerda, Pavel Veselý, Lucie Horová, Jana Kocmanová, and Petr Bureš. "Elevation-dependent endopolyploid response suggests that plants with holocentric chromosomes are less stressed by UV-B." Botanical Journal of the Linnean Society 195, no. 1 (July 25, 2020): 106–13. http://dx.doi.org/10.1093/botlinnean/boaa054.

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Abstract Previous studies suggested that holocentric chromosomes may confer a selective advantage under high ionizing or UV-B radiation due to their tolerance of fragmentation, and that the first plant and animal colonizers of land in the Palaeozoic were or may have been holocentric. Holocentric chromosomes could have, therefore, aided terrestrialization of Earth’s biota half a billion years ago, because leaving water meant facing a sharp increase of UV-B. Because we cannot go back in time, the hypothesis needs to be tested with present-day species using an indicator of UV-B stress. We took advantage of the fact that UV-B intensity increases with elevation and tested whether holocentric plants (six species of Cyperaceae and Juncaceae) are less stressed with increasing elevation than monocentric plants (six species of Poaceae). Phylogenetically corrected regression showed that the proxy for UV-B stress (endopolyploidy index from 671 samples measured by flow cytometry) increased with elevation in holocentric and monocentric species, but the increase was more rapid in monocentric species. Although half a billion year elapsed since terrestrialization, holocentric Cyperaceae and Juncaceae still appear less stressed by UV-B than monocentric Poaceae, despite the other counter UV-B adaptations they both have evolved (graminoid morphology, silica bodies).

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6

Marques, André, Tiago Ribeiro, Pavel Neumann, Jiří Macas, Petr Novák, Veit Schubert, Marco Pellino, et al. "Holocentromeres in Rhynchospora are associated with genome-wide centromere-specific repeat arrays interspersed among euchromatin." Proceedings of the National Academy of Sciences 112, no. 44 (October 21, 2015): 13633–38. http://dx.doi.org/10.1073/pnas.1512255112.

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Holocentric chromosomes lack a primary constriction, in contrast to monocentrics. They form kinetochores distributed along almost the entire poleward surface of the chromatids, to which spindle fibers attach. No centromere-specific DNA sequence has been found for any holocentric organism studied so far. It was proposed that centromeric repeats, typical for many monocentric species, could not occur in holocentrics, most likely because of differences in the centromere organization. Here we show that the holokinetic centromeres of the Cyperaceae Rhynchospora pubera are highly enriched by a centromeric histone H3 variant-interacting centromere-specific satellite family designated “Tyba” and by centromeric retrotransposons (i.e., CRRh) occurring as genome-wide interspersed arrays. Centromeric arrays vary in length from 3 to 16 kb and are intermingled with gene-coding sequences and transposable elements. We show that holocentromeres of metaphase chromosomes are composed of multiple centromeric units rather than possessing a diffuse organization, thus favoring the polycentric model. A cell-cycle–dependent shuffling of multiple centromeric units results in the formation of functional (poly)centromeres during mitosis. The genome-wide distribution of centromeric repeat arrays interspersing the euchromatin provides a previously unidentified type of centromeric chromatin organization among eukaryotes. Thus, different types of holocentromeres exist in different species, namely with and without centromeric repetitive sequences.

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7

HÅKANSSON, ARTUR. "HOLOCENTRIC CHROMOSOMES IN ELEOCHARIS." Hereditas 44, no. 4 (July 9, 2010): 531–40. http://dx.doi.org/10.1111/j.1601-5223.1958.tb03498.x.

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8

Zedek, František, Klára Plačková, Pavel Veselý, Jakub Šmerda, Petr Šmarda, Lucie Horová, and Petr Bureš. "Endopolyploidy is a common response to UV-B stress in natural plant populations, but its magnitude may be affected by chromosome type." Annals of Botany 126, no. 5 (June 25, 2020): 883–89. http://dx.doi.org/10.1093/aob/mcaa109.

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Abstract Background and Aims Ultraviolet-B radiation (UV-B) radiation damages the DNA, cells and photosynthetic apparatus of plants. Plants commonly prevent this damage by synthetizing UV-B-protective compounds. Recent laboratory experiments in Arabidopsis and cucumber have indicated that plants can also respond to UV-B stress with endopolyploidy. Here we test the generality of this response in natural plant populations, considering their monocentric or holocentric chromosomal structure. Methods We measured the endopolyploidy index (flow cytometry) and the concentration of UV-B-protective compounds in leaves of 12 herbaceous species (1007 individuals) from forest interiors and neighbouring clearings where they were exposed to increased UV-B radiation (103 forest + clearing populations). We then analysed the data using phylogenetic mixed models. Key Results The concentration of UV-B protectives increased with UV-B doses estimated from hemispheric photographs of the sky above sample collection sites, but the increase was more rapid in species with monocentric chromosomes. Endopolyploidy index increased with UV-B doses and with concentrations of UV-B-absorbing compounds only in species with monocentric chromosomes, while holocentric species responded negligibly. Conclusions Endopolyploidy seems to be a common response to increased UV-B in monocentric plants. Low sensitivity to UV-B in holocentric species might relate to their success in high-UV-stressed habitats and corroborates the hypothesized role of holocentric chromosomes in plant terrestrialization.

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9

Pazy, Batia, and Uzi Plitmann. "Holocentric chromosome behaviour inCuscuta (Cuscutaceae)." Plant Systematics and Evolution 191, no. 1-2 (1994): 105–9. http://dx.doi.org/10.1007/bf00985345.

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10

Vanzela, André L. L., and Marcelo Guerra. "Heterochromatin differentiation in holocentric chromosomes of Rhynchospora (Cyperaceae)." Genetics and Molecular Biology 23, no. 2 (June 2000): 453–56. http://dx.doi.org/10.1590/s1415-47572000000200034.

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Holocentric chromosomes of six species of Rhynchospora, R. ciliata, R. pubera, R. riparia and R. barbata (2n = 10), R. nervosa (2n = 30) and R. globosa (2n = 36), were stained with CMA3/DAPI fluorochromes or treated with C-banding and sequentially stained with Giemsa or CMA3/DAPI. Variability in banding pattern was found among the species studied. Heterochromatin was observed on terminal and interstitial chromosome regions, indicating that the holocentric chromosomes of Rhynchospora show a heterochromatin distribution pattern similar to those plant monocentric chromosomes.

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11

Zhang, Bing, Camilo Ayra-Pardo, Xiaoning Liu, Meiting Song, Dandan Li, and Yunchao Kan. "siRNA-Mediated BmAurora B Depletion Impedes the Formation of Holocentric Square Spindles in Silkworm Metaphase BmN4 Cells." Insects 15, no. 1 (January 19, 2024): 72. http://dx.doi.org/10.3390/insects15010072.

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Silkworm ovary-derived BmN4 cells rely on chromatin-induced spindle assembly to form microtubule-based square mitotic spindles that ensure accurate segregation of holocentric chromosomes during cell division. The chromosome passenger protein Aurora B regulates chromosomal condensation and segregation, spindle assembly checkpoint activation, and cytokinesis; however, its role in holocentric organisms needs further clarification. This study examined the architecture and dynamics of spindle microtubules during prophase and metaphase in BmN4 cells and those with siRNA-mediated BmAurora B knockdown using immunofluorescence labeling. Anti-α-tubulin and anti-γ-tubulin antibodies revealed faint γ-tubulin signals colocalized with α-tubulin in early prophase during nuclear membrane rupture, which intensified as prophase progressed. At this stage, bright regions of α-tubulin around and on the nuclear membrane surrounding the chromatin suggested the start of microtubules assembling in the microtubule-organizing centers (MTOCs). In metaphase, fewer but larger γ-tubulin foci were detected on both sides of the chromosomes. This resulted in a distinctive multipolar square spindle with holocentric chromosomes aligned at the metaphase plate. siRNA-mediated BmAurora B knockdown significantly reduced the γ-tubulin foci during prophase, impacting microtubule nucleation and spindle structure in metaphase. Spatiotemporal BmAurora B expression analysis provided new insights into the regulation of this mitotic kinase in silkworm larval gonads during gametogenesis. Our results suggest that BmAurora B is crucial for the formation of multipolar square spindles in holocentric insects, possibly through the activation of γ-tubulin ring complexes in multiple centrosome-like MTOCs.

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Manicardi, G. C., D. C. Gautam, D. Bizzaro, E. Guicciardi, A. M. Bonvicini Pagliai, and U. Bianchi. "Chromosome banding in aphids: G, C, AluI, and HaeIII banding patterns in Megoura viciae (Homoptera, Aphididae)." Genome 34, no. 4 (August 1, 1991): 661–65. http://dx.doi.org/10.1139/g91-101.

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The holocentric mitotic chromosomes of Megoura viciae, a species that has been little studied cytogenetically to date, have been characterized by applying G, C, AluI, and HaeIII banding techniques. C bands have shown the best defined patterns, particularly on the X chromosome. This chromosome, on the other hand, behaved as the most reactive to the various treatments. Uncondensed, prometaphase X chromosomes showed a number of heterochromatic bands, interspersed among the euchromatin, which fused together during metaphase condensation. AluI and HaeIII treatments also produced reproducible banding patterns. These data permit an accurate identification of the X chromosome as well as of the autosomal pairs 1 and 2, and facilitate the construction of nonambiguous karyotypes. They will also stimulate studies on the organization of chromatin in holocentric, holokinetic chromosomes. Finally they could also promote research on chromosomal rearrangements that have occurred during the course of speciation and evolution of aphids, since these kinds of events may be significantly affected by the condition of chromosomal holocentrism.Key words: aphids, holocentric chromosomes, chromosome banding, heterochromatin.

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Manicardi, G. C., D. Bizzaro, E. Galli, and U. Bianchi. "Heterochromatin heterogeneity in the holocentric X chromatin of Megoura viciae (Homoptera, Aphididae)." Genome 39, no. 2 (April 1, 1996): 465–70. http://dx.doi.org/10.1139/g96-059.

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Holocentric chromosomes, prepared by spreading embryo cells obtained from Megoura viciae parthenogenetic females, have been C-banded, enzymatically digested in situ using the specific endonucleases DdeI (C↓TNAG), DraI (TTT↓AAA), Tru9I (TT↓AA), and CfoI (GCG↓C), and subsequently stained with Giemsa, DAPI, CMA3, and AgNO3. We observed that the X chromosome had the best defined banding patterns. In the M. viciae X chromosome there is a certain amount of heterogeneity in heterochromatic DNA composition. In fact, the GC-rich NOR-associated heterochromatin differs from other heterochromatic bands that are characterized by AT-rich DNAs. Our data also indicate that, in M. viciae holocentric chromosomes, all heterochromatic blocks are accessible to in situ enzyme attack, the only limit to the digestion being the presence or absence of recognition targets. This is an interesting point, since, in monocentric chromosomes, it is well known that in situ endonuclease digestion is heavily affected not only by DNA base composition but also by chromatin compactness that may limit enzyme accessibility to their specific targets. Key words : heterochromatin, holocentric chromosomes, aphids.

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Shanahan, Catherine M. "Cytogenetics of Australian scorpions. I. Interchange polymorphism in the family Buthidae." Genome 32, no. 5 (October 1, 1989): 882–89. http://dx.doi.org/10.1139/g89-525.

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Male scorpions from Australian species of the family Buthidae exhibit a unique combination of cytogenetic features including achiasmate meiosis, holocentric chromosomes, and extensive interchange heterozygosity. Chromosome number is highly conserved, with all species having a basic diploid number of 2n = 14. There is evidence that inbreeding has contributed to the establishment of populations with interchange heterozygotes, some exhibiting rings of up to 12 chromosomes. Although most populations contain both structural homozygotes and interchange heterozygotes, one population may exhibit fixed heterozygosity. It is argued that the interchange heterozygosity observed in buthids is of adaptive significance.Key words: interchange, chromosome polymorphism, achiasmate meiosis, holocentric chromosomes.

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Bardella, Vanessa Bellini, Diogo Milani, and Diogo Cavalcanti Cabral de Mello Cavalcanti Cabral de Mello. "Insigthts about satDNAS organization in holocentric chromosomes using Holhymenia histrio (Heteroptera) as model." Semina: Ciências Biológicas e da Saúde 38, no. 1supl (February 16, 2018): 190. http://dx.doi.org/10.5433/1679-0367.2017v38n1suplp190.

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SatDNA are organized in tandem and often distributed in heterochromatic regions, corresponding mainly to centromeres. Evolution for satDNAs is directed by “concerted evolution” that leads to sequence homogenization, frequently generating species-specific patterns. Among insects with holocentric chromosomes, organization of satellite DNAs (satDNAs) is still poorly know in comparison to species with monocentric ones. Here, using of the advantage of genome sequencing and computational analysis we characterized for the first time the entire satellitome of an insect with holocentric chromosomes, Holhymenia histrio. It was noticed 37 satDNA families (named HhisSat1 to HhisSat37) with monomer length between 46 and 487. Among the 37 satDNAs families, seven were selected based in abundance to be chromosomally mapped. HhisSat1-3 and HhisSat12 were the most abundant and showed hybridization signals, like a band pattern, forming large co-located chromosomal blocks. These sequences (HhisSat1-3 and HhisSat12) were similar suggesting that they from form a family with four subfamilies. High inter-individual polymorphism was noticed for the four sequences (HhisSat1-3 and HhisSat12), revealing similar co-spreading for the sequences, indicating that they moved together. satDNAs with lower repeatability exhibited a dispersed signal in some chromosomes (HhisSat24 and HisSat35). HhisSat35 was highlighted due to placement in euchromatic m-chromosomes, revealing information about their composition, an issue poorly knows. However, no signals were observed for HhisSat37, showing that this satellite was not arranged in large clusters. This result is similar to the observed in Locusta migratoria, showing that the non-clusterization of satellite DNAs could be a common pattern also for holocentric chromosomes. The high variability in copy number and chromosomal distribution observed for H. histrio highlights the plasticity of satDNAs in insects with holocentric chromosomes.

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de Vos, Jurriaan M., Hannah Augustijnen, Livio Bätscher, and Kay Lucek. "Speciation through chromosomal fusion and fission in Lepidoptera." Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1806 (July 13, 2020): 20190539. http://dx.doi.org/10.1098/rstb.2019.0539.

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Changes in chromosome numbers may strongly affect reproductive barriers, because individuals heterozygous for distinct karyotypes are typically expected to be at least partially sterile or to show reduced recombination. Therefore, several classic speciation models are based on chromosomal changes. One import mechanism generating variation in chromosome numbers is fusion and fission of existing chromosomes, which is particularly likely in species with holocentric chromosomes, i.e. chromosomes that lack a single centromere. Holocentric chromosomes evolved repeatedly across the tree of life, including in Lepidoptera . Although changes in chromosome numbers are hypothesized to be an important driver of the spectacular diversification of Lepidoptera, comparative studies across the order are lacking. We performed the first comprehensive literature survey of karyotypes for Lepidoptera species since the 1970s and tested if, and how, chromosomal variation might affect speciation. Even though a meta-analysis of karyological differences between closely related taxa did not reveal an effect on the degree of reproductive isolation, phylogenetic diversification rate analyses across the 16 best-covered genera indicated a strong, positive association of rates of chromosome number evolution and speciation. These findings suggest a macroevolutionary impact of varying chromosome numbers in Lepidoptera and likely apply to other taxonomic groups, especially to those with holocentric chromosomes. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

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Howe, Mary, Kent L. McDonald, Donna G. Albertson, and Barbara J. Meyer. "Him-10 Is Required for Kinetochore Structure and Function on Caenorhabditis elegans Holocentric Chromosomes." Journal of Cell Biology 153, no. 6 (June 11, 2001): 1227–38. http://dx.doi.org/10.1083/jcb.153.6.1227.

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Macromolecular structures called kinetochores attach and move chromosomes within the spindle during chromosome segregation. Using electron microscopy, we identified a structure on the holocentric mitotic and meiotic chromosomes of Caenorhabditis elegans that resembles the mammalian kinetochore. This structure faces the poles on mitotic chromosomes but encircles meiotic chromosomes. Worm kinetochores require the evolutionarily conserved HIM-10 protein for their structure and function. HIM-10 localizes to the kinetochores and mediates attachment of chromosomes to the spindle. Depletion of HIM-10 disrupts kinetochore structure, causes a failure of bipolar spindle attachment, and results in chromosome nondisjunction. HIM-10 is related to the Nuf2 kinetochore proteins conserved from yeast to humans. Thus, the extended kinetochores characteristic of C. elegans holocentric chromosomes provide a guide to the structure, molecular architecture, and function of conventional kinetochores.

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Heckmann, Stefan, Veit Schubert, and Andreas Houben. "Holocentric plant meiosis: first sisters, then homologues." Cell Cycle 13, no. 23 (December 2014): 3623–24. http://dx.doi.org/10.4161/15384101.2014.986628.

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19

Guerra, Marcelo, Tiago Ribeiro, and Leonardo P. Felix. "Monocentric chromosomes in Juncus (Juncaceae) and implications for the chromosome evolution of the family." Botanical Journal of the Linnean Society 191, no. 4 (October 10, 2019): 475–83. http://dx.doi.org/10.1093/botlinnean/boz065.

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Abstract Holocentric chromosomes are rare among angiosperms, but have been suggested to be shared by all or most of the species of Cyperaceae and Juncaceae. However, no clear demonstration of the centromere type in Juncus, the largest genus of Juncaceae, has so far been published. Thus, we conducted a detailed chromosomal investigation of four Juncus spp. aiming to identify their centromere type. Mitotic chromosomes were analysed using the fluorochromes CMA and DAPI, fluorescent in situ hybridization (FISH) with rDNA probes and immunodetection of histones H3 phosphorylated at serine 10 (H3-S10ph) and H2A phosphorylated at threonine 133 (H2A-T133ph). DAPI-stained chromosomes of all species displayed typical primary constrictions, which were not related to AT-poor CMA+ heterochromatin or rDNA sites (usually negatively stained with DAPI). Immunodetection with H3-S10ph and H2A-T133ph revealed hyperphosphorylation of pericentromeric and centromeric regions, respectively, in a restricted area, as observed in monocentric chromosomes. Meiotic analyses in J. microcephalus showed no indication of inverted meiosis, commonly found in plants with holocentric chromosomes. Since the species investigated here belong to four different sections of Juncus and all of them display typical monocentric chromosomes, it seems that this kind of centromere is common in the genus and may represent the standard centromere organization for Juncus. If Juncus has monocentric chromosomes, there is no reason to hypothesize that other genera of Juncaceae for which centromeres have not been carefully investigated have holocentric chromosomes.

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Bowen, B. A., D. Lee, G. P. Creissen, G. E. Marks, and C. A. Cullis. "The ribosomal DNA of Luzula pilosa (L.) Willd, a plant with holocentric chromosomes." Genome 30, no. 6 (December 1, 1988): 915–23. http://dx.doi.org/10.1139/g88-147.

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The ribosomal DNA (rDNA) of Luzula pilosa (L.) Willd, a plant with holocentric chromosomes, has been cloned and characterized by restriction mapping. The major variant is present in about 730 tandemly arranged copies per haploid genome which occupy nearly an entire chromosome. We propose that much of the rDNA is flanked or interspersed by kinetochores, so that reciprocal interchromatid exchanges in this region would lead to chromosome breakage. Homogenization and amplification of rDNA spacer length variants may occur largely by intrachromatid exchanges and gene conversion. By trying to isolate rDNA junction fragments which might be closely linked to centromeric DNA, we have isolated three minor rDNA variants whose spacer regions do not cross-hybridize with one another or with the major variant. The possibility that these minor variants may be rRNA pseudogenes is discussed.Key words: centromere, holocentric, Luzula, rDNA, recombination.

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Jonika, Michelle, Johnathan Lo, and Heath Blackmon. "Mode and Tempo of Microsatellite Evolution across 300 Million Years of Insect Evolution." Genes 11, no. 8 (August 16, 2020): 945. http://dx.doi.org/10.3390/genes11080945.

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Microsatellites are short, repetitive DNA sequences that can rapidly expand and contract due to slippage during DNA replication. Despite their impacts on transcription, genome structure, and disease, relatively little is known about the evolutionary dynamics of these short sequences across long evolutionary periods. To address this gap in our knowledge, we performed comparative analyses of 304 available insect genomes. We investigated the impact of sequence assembly methods and assembly quality on the inference of microsatellite content, and we explored the influence of chromosome type and number on the tempo and mode of microsatellite evolution across one of the most speciose clades on the planet. Diploid chromosome number had no impact on the rate of microsatellite evolution or the amount of microsatellite content in genomes. We found that centromere type (holocentric or monocentric) is not associated with a difference in the amount of microsatellite content; however, in those species with monocentric chromosomes, microsatellite content tends to evolve faster than in species with holocentric chromosomes.

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Camacho, J. P. M., J. Belda, and J. Cabrero. "Meiotic behaviour of the holocentric chromosomes of Nezara viridula (Insecta, Heteroptera) analysed by C-banding and silver impregnation." Canadian Journal of Genetics and Cytology 27, no. 5 (October 1, 1985): 491–97. http://dx.doi.org/10.1139/g85-073.

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While silver impregnation reveals the presence of kinetochores in monocentric chromosomes, it does not do so in the holocentric system of Nezara viridula. Here, C-banding and silver impregnation techniques reveal that C-heterochromatin is present in the greater part of the Y chromosome and at the nucleolus organizer region (NOR) of the largest autosome (A 1) and in the extra NOR located in the X chromosome of a single exceptional male. Furthermore, one telomere of each autosome appeared lightly C-banded. The largest, A1, bivalent shows chiasmata almost always located at the chromosome ends. This bivalent may orient axially or equatorially in metaphase I cells depending on whether it carries a single chiasma or two chiasmata, respectively. From our cytological analysis we deduce that centromeric activity is preferentially located at the two telomeric ends and that the presence of chiasmata at an end excludes such activity.Key words: diffuse centromere, C-banding, holocentric, insect chromosomes.

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Luceño, Modesto, André LL Vanzela, and Marcelo Guerra. "Cytotaxonomic studies in Brazilian Rhynchospora (Cyperaceae), a genus exhibiting holocentric chromosomes." Canadian Journal of Botany 76, no. 3 (March 1, 1998): 440–49. http://dx.doi.org/10.1139/b98-013.

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The genus Rhynchospora (Cyperaceae) is a widely distributed Brazilian group, with approximately 150 species. We have studied mitosis and (or) meiosis of 16 species of four sections (Dichromena, Longirostres, Polycephalae, and Pluriflorae). The results showed high frequencies of chromosome number multiples of x = 5, which is the probable basic number. Polyploidy, in contrast to agmatoploidy and (or) symploidy, seems to be the predominant cytogenetic mechanism in the evolution of the karyotype. Primary constrictions were not visible in the chromosomes, suggesting a holocentric condition, as observed in other genera of this family. Karyotype interspecific differences were useful in the cytotaxonomic analysis in three sections. Our data propose (i) the separation of Rhynchospora ciliata (Vahl.) Kükenth. from Rhynchospora nervosa (Vahl.) Böckeler (section Dichromena), (ii) the inclusion of Rhynchospora legrandii Kükenth. ex Barros as a subspecies of Rhynchospora corymbosa (L.) Britton (section Longirostres), and (iii) a suggestion for the organization of section Pluriflorae.Key words: Rhynchospora, Cyperaceae, holocentric chromosomes, polyploidy.

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Kolodin, Pavel, Hana Cempírková, Petr Bureš, Lucie Horová, Adam Veleba, Jana Francová, Lubomír Adamec, and František Zedek. "Holocentric chromosomes may be an apomorphy of Droseraceae." Plant Systematics and Evolution 304, no. 10 (September 28, 2018): 1289–96. http://dx.doi.org/10.1007/s00606-018-1546-8.

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25

Manicardi, G. C., D. Bizzaro, P. Azzoni, and U. Bianchi. "Cytological and electrophoretic analysis of DNA methylation in the holocentric chromosomes of Megoura viciae (Homoptera, Aphididae)." Genome 37, no. 4 (August 1, 1994): 625–30. http://dx.doi.org/10.1139/g94-089.

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Chromosomal and purified DNA methylation patterns were determined in the holocentric chromosomes of Megoura viciae by treatment with MspI and HpaII. Both enzymes produced a clear C-like banding pattern but widely digested one telomere of the X chromosome, which appeared as heterochromatic after C-banding treatment and brightly fluorescent after chromomycin A3 staining. Quantitative microfluorometric evaluations of DNA extraction performed on cytological preparations showed that both isoschizomers resulted in the same DNA extraction (about 30%). Contrary to what was found by in situ endonuclease treatment, the electrophoretic patterns of purified and digested DNA showed that digestion with MspI was slightly more extensive than that with HpaII in a zone of fragments ranging from 23 to 9 kb. This result indicates that aphid chromatin is not wholly unmethylated. The discrepancy between electrophoretic and cytological data has been explained by taking into consideration that DNA fragments with high molecular weights could be cleaved in situ by the enzymes but not extracted from the chromatin.Key words: aphids, DNA methylation, holocentric chromosomes, heterochromatin, restriction enzyme bandings.

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26

Manicardi, Gian Carlo, Mauro Mandrioli, Davide Bizzaro, and Umberto Bianchi. "Patterns of DNase I sensitivity in the holocentric chromosomes of the aphid Megoura viciae." Genome 41, no. 2 (April 1, 1998): 169–72. http://dx.doi.org/10.1139/g97-112.

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Using the in situ nick translation technique, we looked for the presence of DNase I sensitive sites in Megoura viciae chromosomes, to study the distribution of active or potentially active genes in aphids, a group of insects possessing holocentric chromosomes. Cytological preparations obtained by the spreading of embryo cells were treated in situ with increasing concentrations (ranging from 5 to 200 ng/mL) of DNase I. At DNase I concentrations below 50 ng/mL, only one hypersensitive site was observed, and this was located on a telomeric region of the X chromosome that contains transcriptionally active nucleolar organizing regions, as assayed by silver staining. Interestingly, at intermediate concentrations of DNase, the incorporation of biotinylated nucleotide occurred uniformly throughout all chromosomes, whereas at concentrations above 100 ng/mL, a C-like banding pattern was produced. Our data differ from results obtained with mammalian, frog, and grasshopper chromosomes, where it was found that DNase I nicking is concentrated at the distal regions of all chromosomes.Key words: aphids, holocentric chromosomes, DNase I sensitivity, nick translation.

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27

Schubert, Veit, Pavel Neumann, André Marques, Stefan Heckmann, Jiri Macas, Andrea Pedrosa-Harand, Ingo Schubert, Tae-Soo Jang, and Andreas Houben. "Super-Resolution Microscopy Reveals Diversity of Plant Centromere Architecture." International Journal of Molecular Sciences 21, no. 10 (May 15, 2020): 3488. http://dx.doi.org/10.3390/ijms21103488.

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Centromeres are essential for proper chromosome segregation to the daughter cells during mitosis and meiosis. Chromosomes of most eukaryotes studied so far have regional centromeres that form primary constrictions on metaphase chromosomes. These monocentric chromosomes vary from point centromeres to so-called “meta-polycentromeres”, with multiple centromere domains in an extended primary constriction, as identified in Pisum and Lathyrus species. However, in various animal and plant lineages centromeres are distributed along almost the entire chromosome length. Therefore, they are called holocentromeres. In holocentric plants, centromere-specific proteins, at which spindle fibers usually attach, are arranged contiguously (line-like), in clusters along the chromosomes or in bands. Here, we summarize findings of ultrastructural investigations using immunolabeling with centromere-specific antibodies and super-resolution microscopy to demonstrate the structural diversity of plant centromeres. A classification of the different centromere types has been suggested based on the distribution of spindle attachment sites. Based on these findings we discuss the possible evolution and advantages of holocentricity, and potential strategies to segregate holocentric chromosomes correctly.

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28

Escudero, Marcial, J. Ignacio Márquez-Corro, and Andrew L. Hipp. "The Phylogenetic Origins and Evolutionary History of Holocentric Chromosomes." Systematic Botany 41, no. 3 (September 1, 2016): 580–85. http://dx.doi.org/10.1600/036364416x692442.

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29

Subirana, Juan A., and Xavier Messeguer. "A Satellite Explosion in the Genome of Holocentric Nematodes." PLoS ONE 8, no. 4 (April 24, 2013): e62221. http://dx.doi.org/10.1371/journal.pone.0062221.

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30

Tartarotti, Ester, and Maria Tercilia Vilela de Azeredo-Oliveira. "Meiosis Patterns of Holocentric Chromosomes in Triatomines Genus Panstrongylus." CYTOLOGIA 64, no. 3 (1999): 235–40. http://dx.doi.org/10.1508/cytologia.64.235.

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31

MANDRIOLI, MAURO, and GIAN CARLO MANICARDI. "Analysis of insect holocentric chromosomes by atomic force microscopy." Hereditas 138, no. 2 (June 2003): 129–32. http://dx.doi.org/10.1034/j.1601-5223.2003.01661.x.

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32

Melters, Daniël P., Leocadia V. Paliulis, Ian F. Korf, and Simon W. L. Chan. "Holocentric chromosomes: convergent evolution, meiotic adaptations, and genomic analysis." Chromosome Research 20, no. 5 (July 2012): 579–93. http://dx.doi.org/10.1007/s10577-012-9292-1.

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33

Moore, Landon L., Mike Morrison, and Mark B. Roth. "Hcp-1, a Protein Involved in Chromosome Segregation, Is Localized to the Centromere of Mitotic Chromosomes in Caenorhabditis elegans." Journal of Cell Biology 147, no. 3 (November 1, 1999): 471–80. http://dx.doi.org/10.1083/jcb.147.3.471.

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To learn more about holocentric chromosome structure and function, we generated a monoclonal antibody (mAb), 6C4, that recognizes the poleward face of mitotic chromosomes in Caenorhabditis elegans. Early in mitosis, mAb 6C4 stains dots throughout the nucleoplasm. Later in prophase, mAb 6C4 stains structures on opposing faces of chromosomes which orient towards the centrosomes at metaphase. Colocalization with an antibody against a centromeric histone H3–like protein and the MPM-2 antibody, which identifies a kinetochore-associated phosphoepitope present in a variety of organisms, shows that the mAb 6C4 staining is present adjacent to the centromere. Expression screening using mAb 6C4 identified a protein in C. elegans that we named HCP-1 (for holocentric protein 1). We also identified a second protein from the C. elegans genome sequence database, HCP-2, that is 54% similar to HCP-1. When expression of HCP-1 is reduced by RNA interference (RNAi), staining with mAb 6C4 is eliminated, indicating that hcp-1 encodes the major mAb 6C4 antigen. RNAi with hcp-1 and hcp-2 together results in aberrant anaphases and embryonic arrest at ∼100 cells with different amounts of DNA in individual nuclei. These results suggest that HCP-1 is a centromere-associated protein that is involved in the fidelity of chromosome segregation.

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34

Li, Bingqian, Zhiqing Li, Chenchen Lu, Li Chang, Dongchao Zhao, Guanwang Shen, Takahiro Kusakabe, Qingyou Xia, and Ping Zhao. "Heat Shock Cognate 70 Functions as A Chaperone for the Stability of Kinetochore Protein CENP-N in Holocentric Insect Silkworms." International Journal of Molecular Sciences 20, no. 23 (November 20, 2019): 5823. http://dx.doi.org/10.3390/ijms20235823.

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The centromere, in which kinetochore proteins are assembled, plays an important role in the accurate congression and segregation of chromosomes during cell mitosis. Although the function of the centromere and kinetochore is conserved from monocentric to holocentric, the DNA sequences of the centromere and components of the kinetochore are varied among different species. Given the lack of core centromere protein A (CENP-A) and CENP-C in the lepidopteran silkworm Bombyx mori, which possesses holocentric chromosomes, here we investigated the role of CENP-N, another important member of the centromere protein family essential for kinetochore assembly. For the first time, cellular localization and RNA interference against CENP-N have confirmed its kinetochore function in silkworms. To gain further insights into the regulation of CENP-N in the centromere, we analyzed the affinity-purified complex of CENP-N by mass spectrometry and identified 142 interacting proteins. Among these factors, we found that the chaperone protein heat shock cognate 70 (HSC70) is able to regulate the stability of CENP-N by prohibiting ubiquitin–proteasome pathway, indicating that HSC70 could control cell cycle-regulated degradation of CENP-N at centromeres. Altogether, the present work will provide a novel clue to understand the regulatory mechanism for the kinetochore activity of CENP-N during the cell cycle.

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35

Padhy, K. B. "Chromosome aberrations in the holocentric chromosomes of Philosamia ricini (Saturniidae)." Journal of Research on the Lepidoptera 25, no. 1 (1986): 63–66. http://dx.doi.org/10.5962/p.266731.

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36

Mandrioli, Mauro, and Gian Carlo Manicardi. "Unlocking Holocentric Chromosomes: New Perspectives from Comparative and Functional Genomics?" Current Genomics 13, no. 5 (July 1, 2012): 343–49. http://dx.doi.org/10.2174/138920212801619250.

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37

Zedek, František, and Petr Bureš. "Evidence for Centromere Drive in the Holocentric Chromosomes of Caenorhabditis." PLoS ONE 7, no. 1 (January 23, 2012): e30496. http://dx.doi.org/10.1371/journal.pone.0030496.

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38

Luceño, Modesto, and Marcelo Guerra. "Numerical variations in species exhibiting holocentric chromosomes: a nomenclatural proposal." Caryologia 49, no. 3-4 (January 1996): 301–9. http://dx.doi.org/10.1080/00087114.1996.10797374.

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39

Haizel, T., Y. K. Lim, A. R. Leitch, and G. Moore. "Molecular analysis of holocentric centromeres of Luzula species." Cytogenetic and Genome Research 109, no. 1-3 (2005): 134–43. http://dx.doi.org/10.1159/000082392.

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40

Panzera, Fco, F. Alvarez, J. Sanchez-Rufas, R. Pérez, J. A. Suja, E. Scvortzoff, J. P. Dujardin, E. Estramil, and R. Salvatella. "C-heterochromatin polymorphism in holocentric chromosomes of Triatoma infestans (Hemiptera: Reduviidae)." Genome 35, no. 6 (December 1, 1992): 1068–74. http://dx.doi.org/10.1139/g92-164.

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This is the first report of intraspecific variation of C-bands in Heteroptera, described in natural populations of Triatoma infestans (Hemiptera: Reduviidae), the main vector of Chagas disease in Uruguay. Marked variation in number, position, and size of C-heterochromatic bands was found in the three large autosomal pairs. A geographical pattern of this chromosomal polymorphism was observed. Evolutionary importance and epidemiological relevance are discussed.Key words: Triatoma infestans, cytogenetics, C-band polymorphism, holocentric chromosomes, Chagas disease.

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41

Lukhtanov, Vladimir A., Vlad Dincă, Magne Friberg, Jindra Šíchová, Martin Olofsson, Roger Vila, František Marec, and Christer Wiklund. "Versatility of multivalent orientation, inverted meiosis, and rescued fitness in holocentric chromosomal hybrids." Proceedings of the National Academy of Sciences 115, no. 41 (September 28, 2018): E9610—E9619. http://dx.doi.org/10.1073/pnas.1802610115.

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Chromosomal rearrangements (e.g., fusions/fissions) have the potential to drive speciation. However, their accumulation in a population is generally viewed as unlikely, because chromosomal heterozygosity should lead to meiotic problems and aneuploid gametes. Canonical meiosis involves segregation of homologous chromosomes in meiosis I and sister chromatid segregation during meiosis II. In organisms with holocentric chromosomes, which are characterized by kinetic activity distributed along almost the entire chromosome length, this order may be inverted depending on their metaphase I orientation. Here we analyzed the evolutionary role of this intrinsic versatility of holocentric chromosomes, which is not available to monocentric ones, by studying F1 to F4 hybrids between two chromosomal races of the Wood White butterfly (Leptidea sinapis), separated by at least 24 chromosomal fusions/fissions. We found that these chromosomal rearrangements resulted in multiple meiotic multivalents, and, contrary to the theoretical prediction, the hybrids displayed relatively high reproductive fitness (42% of that of the control lines) and regular behavior of meiotic chromosomes. In the hybrids, we also discovered inverted meiosis, in which the first and critical stage of chromosome number reduction was replaced by the less risky stage of sister chromatid separation. We hypothesize that the ability to invert the order of the main meiotic events facilitates proper chromosome segregation and hence rescues fertility and viability in chromosomal hybrids, potentially promoting dynamic karyotype evolution and chromosomal speciation.

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42

Márquez-Corro, José Ignacio, Marcial Escudero, and Modesto Luceño. "Do holocentric chromosomes represent an evolutionary advantage? A study of paired analyses of diversification rates of lineages with holocentric chromosomes and their monocentric closest relatives." Chromosome Research 26, no. 3 (October 17, 2017): 139–52. http://dx.doi.org/10.1007/s10577-017-9566-8.

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43

Marques, A., V. Schubert, A. Houben, and A. Pedrosa-Harand. "Restructuring of Holocentric Centromeres During Meiosis in the Plant Rhynchospora pubera." Genetics 204, no. 2 (August 3, 2016): 555–68. http://dx.doi.org/10.1534/genetics.116.191213.

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44

Zedek, František, and Petr Bureš. "Holocentric chromosomes: from tolerance to fragmentation to colonization of the land." Annals of Botany 121, no. 1 (October 20, 2017): 9–16. http://dx.doi.org/10.1093/aob/mcx118.

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45

Ruckman, Sarah N., Michelle M. Jonika, Claudio Casola, and Heath Blackmon. "Chromosome number evolves at equal rates in holocentric and monocentric clades." PLOS Genetics 16, no. 10 (October 13, 2020): e1009076. http://dx.doi.org/10.1371/journal.pgen.1009076.

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46

Dey, S. K., and T. Wangdi. "Banding patterns of the holocentric chromosomes in some species of Heteroptera." CYTOLOGIA 55, no. 2 (1990): 181–86. http://dx.doi.org/10.1508/cytologia.55.181.

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47

Albertson, Donna G., and J. Nichol Thomson. "Segregation of holocentric chromosomes at meiosis in the nematode,Caenorhabditis elegans." Chromosome Research 1, no. 1 (May 1993): 15–26. http://dx.doi.org/10.1007/bf00710603.

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48

Manicardi, G. C., and D. C. Gautam. "Cytogenetic investigations on the holocentric chromosomes ofTetraneurella akinire(Sasaki) (Homoptera, Pemphigidae)." Caryologia 47, no. 2 (January 1994): 159–65. http://dx.doi.org/10.1080/00087114.1994.10797293.

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49

Zedek, František, and Petr Bureš. "Correction: Evidence for Centromere Drive in the Holocentric Chromosomes of Caenorhabditis." PLOS ONE 11, no. 1 (January 26, 2016): e0147889. http://dx.doi.org/10.1371/journal.pone.0147889.

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50

Mandrioli, M., S. Ganassi, D. Bizzaro, and G. C. Manicardi. "Cytogenetic Analysis of the Holocentric Chromosomes of the Aphid Schizaphis Graminum." Hereditas 131, no. 3 (May 6, 2004): 185–90. http://dx.doi.org/10.1111/j.1601-5223.1999.t01-1-00185.x.

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