Transcription Sites Are Not Correlated with Chromosome Territories in Wheat Nuclei

Abranches, Rita; Beven, Alison F.; Aragón-Alcaide, Luis; Shaw, Peter

doi:10.1083/jcb.143.1.5

Cited by 133 publications

(127 citation statements)

References 39 publications

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“…Previous studies have shown that the nucleus is organized into chromosome territorial domains and interchromosomal channels Lichter et al, 1988;Abranches et al, 1998). It will be instructive to investigate whether coiled bodies move through interchromosomal channels, or along an underlying nuclear matrix, and whether specific motor proteins are required.…”

Section: Discussionmentioning

confidence: 99%

The Movement of Coiled Bodies Visualized in Living Plant Cells by the Green Fluorescent Protein

Boudonck

Dolan

Shaw

1999

MBoC

Self Cite

131

119

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Coiled bodies are nuclear organelles that contain components of at least three RNAprocessing pathways: pre-mRNA splicing, histone mRNA 3Ј-maturation, and pre-rRNA processing. Their function remains unknown. However, it has been speculated that coiled bodies may be sites of splicing factor assembly and/or recycling, play a role in histone mRNA 3Ј-processing, or act as nuclear transport or sorting structures. To study the dynamics of coiled bodies in living cells, we have stably expressed a U2BЉ-green fluorescent protein fusion in tobacco BY-2 cells and in Arabidopsis plants. Time-lapse confocal microscopy has shown that coiled bodies are mobile organelles in plant cells. We have observed movements of coiled bodies in the nucleolus, in the nucleoplasm, and from the periphery of the nucleus into the nucleolus, which suggests a transport function for coiled bodies. Furthermore, we have observed coalescence of coiled bodies, which suggests a mechanism for the decrease in coiled body number during the cell cycle. Deletion analysis of the U2BЉ gene construct has shown that the first RNP-80 motif is sufficient for localization to the coiled body. INTRODUCTIONThe coiled body was first described by Ramon y Cajal (1903), who called it the "nucleolar accessory body" because of its association with the nucleolus. This nuclear organelle was later reidentified by electron microscopy and renamed the "coiled body" because of its appearance as loosely packed coiled fibrils (Monneron and Bernhard, 1969). Subsequent studies detected coiled bodies in animal and plant nuclei, showing that it is a conserved structure (Moreno Diaz de la Espina et al., 1980;Seite et al., 1982;Schultz, 1990).Coiled bodies have been shown to contain splicing small nuclear ribonucleoproteins (snRNPs) and small nuclear RNAs (snRNAs), a subset of nucleolar components -including fibrillarin, Nopp140, NAP57, and U3 small nucleolar ribonucleoprotein (U3 snoRNP) -and the protein p80 coilin, which has been widely used as a marker for coiled bodies (Lamond and Earnshaw, 1998;Matera, 1998). The function of coiled bodies is still under debate, but several hypotheses have been proposed that are not necessarily mutually exclusive. Because coiled bodies do not contain DNA, nascent pre-mRNA, heterogeneous nuclear RNPs (hnRNPs), or the SC-35 splicing factor, which is required for splicing in vitro, it has been argued that they are not directly involved in transcription and pre-mRNA splicing . However, it has been speculated that coiled bodies may be sites of splicing factor assembly or recycling, may play a role in histone mRNA 3Ј processing (Gall et al., 1995;Lamond and Earnshaw, 1998), or may be involved in all these activities. As coiled bodies are frequently observed at the nucleolar periphery and also in the nucleoplasm and within nucleoli (Malatesta et al. 1994;Ochs et al., 1994), they may also act as nuclear transport or sorting structures. It has been shown recently that coiled bodies are also involved in processing or transport of small nucleolar RNA (snoRNA) pr...

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Section: Discussionmentioning

confidence: 99%

The Movement of Coiled Bodies Visualized in Living Plant Cells by the Green Fluorescent Protein

Boudonck

Dolan

Shaw

1999

MBoC

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131

119

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“…Persistently anisotropic distributions of telomeres and centromeres have been described in interphase nuclei (Abranches et al, 1998;Dong and Jiang, 1998; reviewed by Franklin and Cande, 1999). This may be a consequence of constraints on chromosomal diffusion within the nuclei or of specific interactions of different chromosomal structures with the nuclear membrane (Franklin and Cande, 1999) and is presumably related to nuclear function.…”

Section: Nuclear Dynamics In Arabidopsis Thalianamentioning

confidence: 99%

“…In terms of the gross changes in nuclear morphology observed in the root hairs, these might represent means whereby different chromosomal regions could contribute appropriately to the metabolic and developmental activities of the cell. Persistently anisotropic distributions of telomeres and centromeres have been described in interphase nuclei (Abranches et al, 1998;Dong and Jiang, 1998; reviewed by Franklin and Cande, 1999). This may be a consequence of constraints on chromosomal diffusion within the nuclei or of specific interactions of different chromosomal structures with the nuclear membrane (Franklin and Cande, 1999) and is presumably related to nuclear function.…”

Section: Nuclear Dynamics In Arabidopsis Thalianamentioning

confidence: 99%

Nuclear Dynamics inArabidopsis thaliana

Chytilová

Macas

Śliwińska

et al. 2000

MBoC

117

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The nucleus is a definitive feature of eukaryotic cells, comprising twin bilamellar membranes, the inner and outer nuclear membranes, which separate the nucleoplasmic and cytoplasmic compartments. Nuclear pores, complex macromolecular assemblies that connect the two membranes, mediate communication between these compartments. To explore the morphology, topology, and dynamics of nuclei within living plant cells, we have developed a novel method of confocal laser scanning fluorescence microscopy under time-lapse conditions. This is used for the examination of the transgenic expression in Arabidopsis thaliana of a chimeric protein, comprising the GFP (Green-Fluorescent Protein of Aequorea victoria) translationally fused to an effective nuclear localization signal (NLS) and to ␤-glucuronidase (GUS) from E. coli. This large protein is targeted to the nucleus and accumulates exclusively within the nucleoplasm.This article provides online access to movies that illustrate the remarkable and unusual properties displayed by the nuclei, including polymorphic shape changes and rapid, longdistance, intracellular movement. Movement is mediated by actin but not by tubulin; it therefore appears distinct from mechanisms of nuclear positioning and migration that have been reported for eukaryotes. The GFP-based assay is simple and of general applicability. It will be interesting to establish whether the novel type of dynamic behavior reported here, for higher plants, is observed in other eukaryotic organisms. INTRODUCTIONA definitive feature of eukaryotic cells is the nucleus, first described in stamen cells of Tradescantia by Robert Brown in 1831, which is found in all cell types at some stage of their development. The nucleus comprises twin bilamellar membranes, the inner and outer nuclear membranes, which serve to separate the nuclear contents, the nucleoplasm, from the cytoplasm. Communication between these compartments is mediated by nuclear pores, complex macromolecular assemblies that connect the two membranes.All of our information concerning nuclear morphology, topology, and dynamics comes from the use of various forms of microscopy. The major components of the nucleoplasm, including proteins, RNA, and DNA, do not absorb in the visible part of the spectrum. Thus, nuclei are nearly translucent and nonfluorescent. This impedes the observation of nuclei within living cells with standard bright-field or fluorescence microscopy. Although other forms of light microscopy can be used to examine nuclei, particularly phase contrast and differential interference contrast microscopy, which rely on optical properties other than absorbance and fluorescence, this is practical only in nonpigmented cells and in tissues having simple three-dimensional organization.We have developed an alternative method for observation of nuclei in living plant cells that uses confocal laser scanning fluorescence microscopy (Chytilova et al., 1999). Based on the transgenic expression of the Green Fluorescent Protein (GFP) of Aequorea victoria, it involves ...

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“…Although local distributions of genes may tend toward gene-rich or gene-poor, there is no evidence for a systematically skewed distribution of retroelements in maize. In wheat, in situ hybridization used to visualize transcription foci in interphase nuclei showed a distribution consistent with evenly distributed genes on the chromosome (Abranches et al 1998). Maize and other Gramineae genomes may have similar distributions of genes and retroelements.…”

Section: Genome Research 1671mentioning

confidence: 99%

Abundance, Distribution, and Transcriptional Activity of Repetitive Elements in the Maize Genome

Meyers

Tingey²,

Morgante³

2001

Genome Res.

372

313

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Long terminal repeat (LTR) retrotransposons have been shown to make up much of the maize genome. Although these elements are known to be prevalent in plant genomes of a middle-to-large size, little information is available on the relative proportions composed by specific families of elements in a single genome. We sequenced a library of randomly sheared genomic DNA from maize to characterize this genome. BLAST analysis of these sequences demonstrated that the maize genome is composed of diverse sequences that represent numerous families of retrotransposons. The largest families contain the previously described elements Huck, Ji, and Opie. Approximately 5% of the sequences are predicted to encode proteins. The genomic abundance of 16 families of elements was estimated by hybridization to an array of 10,752 maize bacterial artificial chromosome (BAC) clones. Comparisons of the number of elements present on individual BACs indicated that retrotransposons are in general randomly distributed across the maize genome. A second library was constructed that was selected to contain sequences hypomethylated in the maize genome. Sequence analysis of this library indicated that retroelements abundant in the genome are poorly represented in hypomethylated regions. Fifty-six retroelement sequences corresponding to the integrase and reverse transcriptase domains were isolated from ∼407,000 maize expressed sequence tags (ESTs). Phylogenetic analysis of these and the genomic retroelement sequences indicated that elements most abundant in the genome are less abundant at the transcript level than are more rare retrotransposons. Additional phylogenies also demonstrated that rice and maize retrotransposon families are frequently more closely related to each other than to families within the same species. An analysis of the GC content of the maize genomic library and that of maize ESTs did not support recently published data that the gene space in maize is found within a narrow GC range, but does indicate that genic sequences have a higher GC content than intergenic sequences (52% vs. 47% GC).

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Transcription Sites Are Not Correlated with Chromosome Territories in Wheat Nuclei

Cited by 133 publications

References 39 publications

The Movement of Coiled Bodies Visualized in Living Plant Cells by the Green Fluorescent Protein

The Movement of Coiled Bodies Visualized in Living Plant Cells by the Green Fluorescent Protein

Nuclear Dynamics inArabidopsis thaliana

Abundance, Distribution, and Transcriptional Activity of Repetitive Elements in the Maize Genome

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