Distribution of 5S and 45S rDNA sites in plants with holokinetic chromosomes and the “chromosome field” hypothesis

Sousa, Aretuza; Silva, A.E. Barros e; Cuadrado, Ángeles; Loarce, Yolanda; Alves, Marccus; Guerra, Marcelo

doi:10.1016/j.micron.2011.03.002

Cited by 31 publications

(26 citation statements)

References 34 publications

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“…Sometimes these sites are closely linked to each other as observed, for example, in different species of Brassica (Hasterok et al 2006;Berjano et al 2009;Sousa et al 2011;Barros e Silva et al 2013). Our results showed that they were located on the same chromosome in 13 species, including 12 of African and 1 of Asian origin.…”

Section: Discussionsupporting

confidence: 76%

Comparative chromosomal localization of 45S and 5S rDNAs and implications for genome evolution inCucumis

Zhang

Yang

et al. 2016

Genome

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Ribosomal DNAs are useful cytogenetic markers for chromosome analysis. Studies investigating site numbers and distributions of rDNAs have provided important information for elucidating genome organization and chromosomal relationships of many species by fluorescence in situ hybridization. But relevant studies are scarce for species of the genus Cucumis, especially in wild species. In the present study, FISH was conducted to investigate the organization of 45S and 5S rDNA among 20 Cucumis accessions, including cultivars and wild accessions. Our results showed that the number of 45S rDNA sites varied from one to five pairs in different accessions, and most of these sites are located at the terminal regions of chromosomes. Interestingly, up to five pairs of 45S rDNA sites were observed in C. sativus var. sativus, the species which has the lowest chromosome number, i.e., 2n = 14. Only one pair of 5S rDNA sites was detected in all accessions, except for C. heptadactylus, C. sp, and C. spp that had two pairs of 5S rDNA sites. The distributions of 5S rDNA sites showed more variation than 45S rDNA sites. The phylogenetic analysis in this study showed that 45S and 5S rDNA have contrasting evolutionary patterns. We find that 5S rDNA has a polyploidizationrelated tendency towards the terminal location from an interstitial location but maintains a conserved site number, whereas the 45S rDNA showed a trend of increasing site number but a relatively conserved location.

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Section: Discussionsupporting

confidence: 76%

Comparative chromosomal localization of 45S and 5S rDNAs and implications for genome evolution inCucumis

Zhang

Yang

et al. 2016

Genome

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“…2b, the 2n = 10 cytotype showed three pairs of 5S rDNA signals. One pair of 5S rDNA signals was located interstitially in both cytotypes, similar to the pattern observed in Rhynchospora (Sousa et al 2011). The other two pairs were located on the same homologous chromosome at the terminus of each arm.…”

Section: Karyotype Characterization After Dapi Stainingsupporting

confidence: 77%

Two reported cytotypes of the emergent orchid model species Erycina pusilla are two different species

et al. 2017

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Each species is characterized by a specific set of chromosomes, which is described as the chromosome portrait or karyotype. In general, such a karyotype is the same for all individuals in the population. An exception to that rule has recently been found in the orchid Erycina pusilla, which has been reported to have two cytotypes with chromosome numbers of 2n = 10 and 2n = 12. Here, we examined the karyotypes of the two cytotypes and found differences in arm ratios and heterochromatin patterns as well as in the presence of satellite chromosomes and in the number and location of rDNA and telomeric repeat sites. These differences are extensive and would have required multiple chromosome rearrangements to generate the differences between the two karyotypes. We also found that F1 hybrids between the parents with the two different chromosome numbers resulted in sterile offspring, in accordance with our previous findings. The combination of hybrid sterility and extensively rearranged chromosomes supports the hypothesis that these two reported cytotypes are, in fact, two different species.

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“…Since the 45S ribosomal DNA (rDNA) clusters are located terminally on three chromosome pairs of R. pubera (Sousa et al 2011), we performed FISH with a 45S rDNA probe. The presence of the FISH signals always at the pole sides (n = 27) ( Figure 6J) supports the finding of Cabral et al (2014), that preferentially the non-rDNA telomeres of the homologous nonsister chromatids associate.…”

Section: Resultsmentioning

confidence: 99%

“…FISH after immunostaining was performed as described by Ishii et al (2015). 45S rDNA FISH was performed as described in Sousa et al (2011).…”

Section: Fishmentioning

confidence: 99%

“…FISH after immunostaining was performed as described by Ishii et al (2015). 45S rDNA FISH was performed as described in Sousa et al (2011).Wide-field and super-resolution fluorescence microscopy Wide-field fluorescence images were recorded using a Leica DM5500B microscope equipped with a Leica DFC FX camera and a deconvolution system. To analyze the substructures and spatial arrangement of immunosignals and chromatin beyond the classical Abbe/Raleigh limit (super-resolution), spatial structured illumination microscopy (3D-SIM) was applied using a Plan-Apochromat 633/1.4 oil objective of an Elyra PS.1 microscope system and the software ZEN (Carl Zeiss, Thornwood, NY).…”

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confidence: 99%

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Restructuring of Holocentric Centromeres During Meiosis in the Plant Rhynchospora pubera

et al. 2016

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Centromeres are responsible for the correct segregation of chromosomes during mitosis and meiosis. Holocentric chromosomes, characterized by multiple centromere units along each chromatid, have particular adaptations to ensure regular disjunction during meiosis. Here we show by detecting CENH3, CENP-C, tubulin, and centromeric repeats that holocentromeres may be organized differently in mitosis and meiosis of Rhynchospora pubera. Contrasting to the mitotic linear holocentromere organization, meiotic centromeres show several clusters of centromere units (cluster-holocentromeres) during meiosis I. They accumulate along the poleward surface of bivalents where spindle fibers perpendicularly attach. During meiosis II, the cluster-holocentromeres are mostly present in the midregion of each chromatid. A linear holocentromere organization is restored after meiosis during pollen mitosis. Thus, a not yet described case of a cluster-holocentromere organization, showing a clear centromere restructuration between mitosis and meiosis, was identified in a holocentric organism.KEYWORDS holocentric chromosomes; CENH3; CENP-C; centromere structure/organization; inverted meiosis T HE centromere is the chromosome site responsible for spindle fiber attachment and faithful chromosome segregation during mitosis and meiosis. In general, every eukaryotic chromosome has a centromere on which the kinetochore complex assembles (Cleveland et al. 2003;Burrack and Berman 2012). In most eukaryotes, centromeric nucleosomes contain CENH3 (also known as CENP-A, a histone H3 variant that replaces canonical H3 at the centromere), and usually spans several hundred kilobase pairs often in association with centromere-specific repeats (Steiner and Henikoff 2015).Centromere organization and dynamics vary between mitosis and meiosis (Duro and Marston 2015;Ohkura 2015). During mitosis, sister chromatids are held together by centromere cohesion until metaphase. Simultaneous with the disruption of cohesion, sister chromatids are pulled to opposite poles during anaphase. In contrast, during meiosis, sister centromere cohesion is ensured until metaphase II (Ishiguro and Watanabe 2007). The stepwise regulation of cohesion release during meiosis I (MI) and II (MII) is well studied in organisms with one primary constriction per chromosome (monocentric), ensuring the segregation of homologs at MI followed by the segregation of sister chromatids at MII (Duro and Marston 2015).Contrary to monocentrics, the centromeres of holocentric chromosomes are distributed almost over the entire chromosome length and cohesion occurs along the entire associated sister chromatids (Maddox et al. 2004). Although this does not imply much difference during mitotic divisions, the presence of a holokinetic centromere (holocentromere) imposes obstacles to the dynamics of chromosome segregation in meiosis. Due to their alternative chromosome organization, species with holocentric chromosomes cannot perform the two-step cohesion loss during meiosis typical for monocentric species...

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Distribution of 5S and 45S rDNA sites in plants with holokinetic chromosomes and the “chromosome field” hypothesis

Cited by 31 publications

References 34 publications

Comparative chromosomal localization of 45S and 5S rDNAs and implications for genome evolution inCucumis

Comparative chromosomal localization of 45S and 5S rDNAs and implications for genome evolution inCucumis

Two reported cytotypes of the emergent orchid model species Erycina pusilla are two different species

Restructuring of Holocentric Centromeres During Meiosis in the Plant Rhynchospora pubera

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