Structure and evolution of the intergenic region in a ribosomal DNA repeat unit of wheat

Barker, R. F.; Harberd, Nicholas P.; Jarvis, Mark; Flavell, R. B.

doi:10.1016/0022-2836(88)90434-2

Cited by 162 publications

(149 citation statements)

References 35 publications

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“…Consistent with this hypothesis that all eukaryotes form a 5' ETS processing complex on their nascent rRNA, molecular analysis of the pre-rRNA of numerous species has revealed more than one 5' end location, with the downstream end shown to result from rRNA processing [Neurospora (Tyler and Giles 1985); yeast (Hughes and Ares 1991)] or inferred to derive in this manner [Physarum (Blum et al 1986); Tetrahymena (Sutiphong et al 1984); Bombyx (Fujiwara and Ishikawa 1987); maize (McMullen et al 1986); wheat (Barker et al 1988); pea (Piller et al 1990)]. The 5' processing in yeast is also known to require the U3 snRNP (Hughes and Ares 1991).…”

Section: Ea293~13' Which Is the Same As Ea2933'mentioning

confidence: 79%

The terminal balls characteristic of eukaryotic rRNA transcription units in chromatin spreads are rRNA processing complexes.

Mougey¹,

O'Reilly²,

Osheim³

et al. 1993

Genes Dev.

167

131

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When spread chromatin is visualized by electron microscopy, active rRNA genes have a characteristic Christmas tree appearance: From a DNA "trunk" extend closely packed "branches" of nascent transcripts whose ends are decorated with terminal "balls." These terminal balls have been known for more than two decades, are shown in most biology textbooks, and are reported in hundreds of papers, yet their nature has remained elusive. Here, we show that a rRNA-processing signal in the 5'-external transcribed spacer (ETS) of the Xenopus laevis ribosomal primary transcript forms a large, processing-related complex with factors of the Xenopus oocyte, analogous to 5' ETS processing complexes found in other vertebrate cell types. Using mutant rRNA genes, we find that the same rRNA residues are required for this biochemically defined complex formation and for terminal ball formation, analyzed electron microscopically after injection of these cloned genes into Xenopus oocytes. This, plus other presented evidence, implies that rRNA terminal balls in Xenopus, and by inference, also in the multitude of other species where they have been observed, are the uhrastructural visualization of an evolutionarily conserved 5' ETS processing complex that forms on the nascent rRNA.[Key Words: rRNA processing complex; terminal balls; eukaryotic rRNA transcription units; chromatin spreads; X. laevis] Received February 5, 1993; revised version accepted May 21, 1993.One of the earliest, yet still highly informative and much used methods of studying eukaryotic gene expression, is by direct electron microscopic visualization of the transcribing chromatin (Miller and Beatty 1969a). This technique of native chromatin visualization (forming socalled Miller spreads) has facilitated numerous advances in the analysis of gene expression. These include (1) the finding that eukaryotic rRNA genes are organized typically in tandem head-to-tail arrays separated by "nontranscribed spacers" (Miller and Beatty 1969a); (2) the demonstration that the polarity of ribosomal transcription is from 18S to 28S (Reeder et al. 1976), (3) the first analyses of the synchrony of rRNA transcriptional turnon during development Foe 1978;Franke et al. 1979); (4) the first indication of transcription of cloned rRNA genes (Trendelenburg and Gutdon 1978); and (5) the ability to visualize spliceosome complexes on nascent RNA polymerase II-driven transcripts Beyer and Osheim 1988).

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Section: Ea293~13' Which Is the Same As Ea2933'mentioning

confidence: 79%

The terminal balls characteristic of eukaryotic rRNA transcription units in chromatin spreads are rRNA processing complexes.

Mougey¹,

O'Reilly²,

Osheim³

et al. 1993

Genes Dev.

167

131

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“…In wheat (Triticum aestivum), a 10 000-year-old allohexapolyploid, subrepeats are found in the IGS (Barker et al, 1988) as in tobacco (Volkov et al, 1999). In wheat, the structure of the A-type subrepeat varies little, but their copy number differs among loci and cultivars (Flavell, 1990).…”

Section: Discussionmentioning

confidence: 99%

Ribosomal DNA evolution and gene conversion in Nicotiana rustica

et al. 2003

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Genomic in situ hybridisation was used to confirm that Nicotiana rustica (2n ¼ 4x ¼ 48) is an allotetraploid between N. paniculata (2n ¼ 2x ¼ 24, maternal P-genome donor) and N. undulata (2n ¼ 2x ¼ 24, paternal U-genome donor), their progenitors or species closely related to them. Fluorescent in situ hybridisation showed that N. paniculata has one 5S and two 18-5.8-26S rDNA loci whereas N. undulata has an additional 18-5.8-26S rDNA locus. N. rustica has the sum of the loci found in these putative parents. The sizes of the 18-5.8-26S rDNA loci indicate that the number of rDNA units on the U-genome chromosomes has amplified; perhaps this is associated with a concomitant reduction in the number of units on P-genome chromosomes. Restriction fragment length polymorphism analysis of the intergenic spacer (IGS) of the 18-5.8-26S rDNA units in N. rustica and the two progenitor diploids revealed that about 80% of IGS sequences in N. rustica are of an N. undulata type and 20% of N. paniculata type. These data indicate that interlocus sequence homogenisation has caused the replacement of many N. paniculata-type IGSs in N. rustica with an N. undulata-type of sequence. It is probable that subsequent to this replacement there has been sequence divergence at the 5 0 end of the IGS. As in tobacco, an allotetraploid between N. sylvestris and N. tomentosiformis, the direction of the IGS interlocus conversion is towards the paternal genome donor.

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“…(Rayburn and Gill 1986;Nagaki et al 1995), X76300 (Vershinin et al 1994) 3 pAs1-2 6-FAM-TCAGAGTTCATTTGAAATGCTTTTCA 4 NOR 6-FAM-TGGCGCGCGTCAACTTCCGTC 100 X07841 (pTa71) (Barker et al 1988) 5 pTa71…”

Section: Al 4al 3blmentioning

confidence: 99%

Single-copy gene fluorescence in situ hybridization and genome analysis: Acc-2 loci mark evolutionary chromosomal rearrangements in wheat

2012

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Structure and evolution of the intergenic region in a ribosomal DNA repeat unit of wheat

Cited by 162 publications

References 35 publications

The terminal balls characteristic of eukaryotic rRNA transcription units in chromatin spreads are rRNA processing complexes.

The terminal balls characteristic of eukaryotic rRNA transcription units in chromatin spreads are rRNA processing complexes.

Ribosomal DNA evolution and gene conversion in Nicotiana rustica

Single-copy gene fluorescence in situ hybridization and genome analysis: Acc-2 loci mark evolutionary chromosomal rearrangements in wheat

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