Structure and molecular evolution of the ribosomal DNA external transcribed spacer in the cockroach genus Blattella

Genome ◽  
2011 ◽  
Vol 54 (3) ◽  
pp. 222-234 ◽  
Author(s):  
Dmitry V. Mukha ◽  
Vera Mysina ◽  
Valeria Mavropulo ◽  
Coby Schal
Keyword(s):  
Ribosomal Dna ◽  
Multigene Family ◽  
Internal Transcribed Spacers ◽  
Rrna Genes ◽  
Nucleotide Substitutions ◽  
Rdna Cluster ◽  
Nontranscribed Spacer ◽  
External Transcribed Spacer ◽  
A New Species ◽  
Nucleolus Organizers

The ribosomal DNA (rDNA) cluster of insects contains several hundred repeating structural–functional units and, therefore, is a typical example of a multigene family. Eukaryotic ribosomal RNA (rRNA) genes (18S, 5.8S, and 28S like) are arranged in tandemly repeated clusters in the nucleolus organizers, separated by several spacers, namely the nontranscribed spacer, the external transcribed spacer (ETS), and the internal transcribed spacers. The nucleotide sequences of the ETS of the three closely related Blattella cockroach species, Blattella germanica (Linnaeus, 1767), Blattella asahinai (Mizukubo, 1981), and Blattella lituricollis (Walker, 1868), were determined and compared. The three species had relatively similar ETS lengths, and sequence differences among them could be explained by two types of rearrangements, namely deletions of subrepeats and nucleotide substitutions. Minor ETS variants in B. germanica differed from the major variant in the same way that the major ETS variants of the three Blattella species differed from each other. Concerted evolution and the birth-and-death models, which are often invoked to explain the diversity and evolution of the multigene families of rDNA clusters, are discussed in the light of our data. A new model is proposed to explain the evolutionary reorganization of the ETS region: evolution of rDNA by “magnification-and-fixation” is characterized by magnification of minor subrepeats, which become adaptive in a new rapidly changed environment, and subsequent fixation of this variant type as a major component of the multigene family of a new species.

scholarly journals Clones of human ribosomal DNA containing the complete 18 S-rRNA and 28 S-rRNA genes. Characterization, a detailed map of the human ribosomal transcription unit and diversity among clones

1987 ◽  
Vol 246 (2) ◽  
pp. 519-527 ◽  
Author(s):  
B E H Maden ◽  
C L Dent ◽  
T E Farrell ◽  
J Garde ◽  
F S McCallum ◽  
...  
Keyword(s):  
Ribosomal Dna ◽  
Single Point ◽  
Transcription Unit ◽  
Internal Transcribed Spacers ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Evolutionary Divergence ◽  
Length Variation ◽  
External Transcribed Spacer ◽  
Ribosomal Transcription Unit

We have isolated several new clones of human ribosomal DNA. Each clone contains part of the external transcribed spacer, a complete 18 S-rRNA gene, the internal transcribed spacers, a complete 28 S-rRNA gene and a short downstream flanking region. We present a detailed map of the human ribosomal transcription unit with the locations of numerous useful restriction sites. In particular, a unique NheI site in the 5.8 S-rRNA gene enabled this gene to be mapped with respect to the 18 S-rRNA and 28 S-rRNA genes. The human 45 S-rRNA coding region is approx. 13,000 nucleotide residues long, of which the external transcribed spacer comprises approx. 3700 nucleotide residues and the first and second internal transcribed spacers comprise approx. 1070 and 1200 nucleotide residues respectively. A partial survey for sites of variation between clones has revealed a single point of variation among 18 S-rRNA gene sequences (a T/C variation at position 140), several sites of length variation in the regions of the transcribed spacers closely flanking the 18 S-rRNA genes, and some sites of length variation among 28 S-rRNA genes. Most of these sites of variation are associated with simple sequence tracts and are in regions that are known to undergo relatively rapid evolutionary divergence. In particular, the sites of variation among 28 S-rRNA genes occur in G + C-rich tracts whose lengths vary among vertebrates and that can be correlated with extensive hairpin structures previously observed by electron microscopy. Each of the clones so far surveyed in detail differs from the others in one or more respects.

Initiation and termination of DNA replication in human rRNA genes

1993 ◽  
Vol 13 (10) ◽  
pp. 6600-6613
Author(s):  
R D Little ◽  
T H Platt ◽  
C L Schildkraut
Keyword(s):  
Dna Replication ◽  
Ribosomal Dna ◽  
Regulatory Elements ◽  
Transcription Unit ◽  
Replication Initiation ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Replication Forks ◽  
Nontranscribed Spacer ◽  
Dna Repeat

We have used the multicopy human rRNA genes as a model system to study replication initiation and termination in mammalian chromosomes. Enrichment for replicating molecules was achieved by isolating S-phase enriched populations of cells by centrifugal elutriation, purification of DNA associated with the nuclear matrix, and a chromatographic procedure that enriches for molecules containing single-stranded regions, a characteristic of replication forks. Two-dimensional agarose gel electrophoresis techniques were used to demonstrate that replication appears to initiate at multiple sites throughout most of the 31-kb nontranscribed spacer (NTS) of human ribosomal DNA but not within the 13-kb transcription unit or adjacent regulatory elements. Although initiation events were detected throughout the majority of the NTS, some regions may initiate more frequently than others. Termination of replication, the convergence of opposing replication forks, was found throughout the ribosomal DNA repeat units, and, in some repeats, specifically at the junction of the 3' end of the transcription unit and the NTS. This site-specific termination of replication is the result of pausing of replication forks near the sites of transcription termination. The naturally occurring multicopy rRNA gene family offers a unique system to study mammalian DNA replication without the use of chemical synchronization agents.

Gyrodactylus species (Monogenea) infecting alpine bullhead (Cottus poecilopus Heckel, 1837) in Norway and Slovakia, including the description of Gyrodactylus mariannae sp. nov.

2008 ◽  
Vol 53 (3) ◽  
Author(s):  
Anja Winger ◽  
Haakon Hansen ◽  
Lutz Bachmann ◽  
Tor Bakke
Keyword(s):  
New Species ◽  
Nucleotide Sequences ◽  
Internal Transcribed Spacers ◽  
Type Material ◽  
Nuclear Rdna ◽  
Rdna Cluster ◽  
Cottus Gobio ◽  
Cottus Poecilopus ◽  
A New Species ◽  
North Norway

AbstractGyrodactylus specimens infecting the skin and fins of two alpine bullhead (Cottus poecilopus) populations from the rivers Signaldalselva (North Norway) and Rena (South-East Norway) were characterized by both morphological and molecular means. Morphometrical differences were minor and the nucleotide sequences of the internal transcribed spacers (ITS) of the nuclear rDNA cluster were identical for parasites from both localities. Based on earlier descriptions, the relatively closest species are Gyrodactylus hrabei Ergens, 1957, described from common bullhead (Cottus gobio) in Slovakia and G. sp. Malmberg, 1973, from alpine bullhead in Sweden. The Norwegian Gyrodactylus specimens from the two alpine bullhead populations were morphometrically different from both the type material of G. hrabei from Slovakia and newly collected Gyrodactylus specimens from alpine bullhead in two Slovakian localities. The Slovakian Gyrodactylus specimens were found to be identical with type material of G. hrabei. The nucleotide sequences of the ITS of the Norwegian Gyrodactylus species were different from the Slovakian material. Hence, the Norwegian Gyrodactylus specimens from the alpine bullhead represent a new species, G. mariannae sp. nov.

scholarly journals Initiation and termination of DNA replication in human rRNA genes.

1993 ◽  
Vol 13 (10) ◽  
pp. 6600-6613 ◽  
Author(s):  
R D Little ◽  
T H Platt ◽  
C L Schildkraut
Keyword(s):  
Dna Replication ◽  
Ribosomal Dna ◽  
Regulatory Elements ◽  
Transcription Unit ◽  
Replication Initiation ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Replication Forks ◽  
Nontranscribed Spacer ◽  
Dna Repeat

We have used the multicopy human rRNA genes as a model system to study replication initiation and termination in mammalian chromosomes. Enrichment for replicating molecules was achieved by isolating S-phase enriched populations of cells by centrifugal elutriation, purification of DNA associated with the nuclear matrix, and a chromatographic procedure that enriches for molecules containing single-stranded regions, a characteristic of replication forks. Two-dimensional agarose gel electrophoresis techniques were used to demonstrate that replication appears to initiate at multiple sites throughout most of the 31-kb nontranscribed spacer (NTS) of human ribosomal DNA but not within the 13-kb transcription unit or adjacent regulatory elements. Although initiation events were detected throughout the majority of the NTS, some regions may initiate more frequently than others. Termination of replication, the convergence of opposing replication forks, was found throughout the ribosomal DNA repeat units, and, in some repeats, specifically at the junction of the 3' end of the transcription unit and the NTS. This site-specific termination of replication is the result of pausing of replication forks near the sites of transcription termination. The naturally occurring multicopy rRNA gene family offers a unique system to study mammalian DNA replication without the use of chemical synchronization agents.

scholarly journals A new species of Balansia (Clavicipitaceae) associated with a cyperaceous plant in Brazil

2021 ◽  
Author(s):  
Debora Guterres ◽  
Roberto Ramos-Sobrinho ◽  
Danilo B. Pinho ◽  
Iraildes P. Assunção ◽  
Gaus S.A. Lima
Keyword(s):  
New Species ◽  
Rna Polymerase Ii ◽  
Ribosomal Dna ◽  
Elongation Factor ◽  
Molecular Data ◽  
Fungal Species ◽  
Internal Transcribed Spacers ◽  
Translation Elongation ◽  
Elongation Factor 1 ◽  
A New Species

Abstract Fungal species belonging to the genus Balansia (Clavicipitaceae) are well known as endophytic and epibiotic species commonly found on grasses or sedges. Among the 36 species of Balansia described worldwide, ten have been reported in Brazil. While most species of balansoid fungi were described on graminaceous plants, only four were characterized on cyperaceous hosts. To correctly identify the species of balansoid fungi associated with Scleria bracteata (Cyperaceae), specimens were collected in the state of Alagoas, Brazil, in 2014 and 2016. Nucleotide partial sequences of the second-largest subunit of RNA polymerase II (RPB2), translation elongation factor 1-α (TEF1), 18S subunit ribosomal DNA (SSU), 28S subunit ribosomal DNA (LSU), and internal transcribed spacers (ITS) were obtained from each balansoid specimen. Based on morphology and molecular data, the specimens were identified as a putative new species of Balansia, herein referred to as Balansia scleriae sp. nov.

Xanthagaricus thailandensis sp. nov. (Agaricales, Basidiomycota), from northern Thailand

Phytotaxa ◽  
2018 ◽  
Vol 348 (2) ◽  
pp. 109 ◽  
Author(s):  
JATURONG KUMLA ◽  
NAKARIN SUWANNARACH ◽  
KRIANGSAK SRI-NGERNYUANG ◽  
SAISAMORN LUMYONG
Keyword(s):  
New Species ◽  
Ribosomal Dna ◽  
Phylogenetic Analyses ◽  
Large Subunit ◽  
Internal Transcribed Spacers ◽  
Nuclear Ribosomal Dna ◽  
Full Description ◽  
Northern Thailand ◽  
Molecular Phylogenetic ◽  
A New Species

A new species of agaricomycetes, Xanthagaricus thailandensis, is described based on collections from northern Thailand. This species is characterized by its medium-sized basidiomata, pale orange pileus, a pseudoparenchymatous structure of the squamules on the pileal surface, subcylindrical to clavate caulocystidia and brownish yellow basidiospores. It is clearly distinguished from the previously described Xanthagaricus species by narrow caulocystidia. Molecular phylogenetic analyses, based on a combination of the internal transcribed spacers (ITS) and the large subunit (LSU) of the nuclear ribosomal DNA, also support the finding that X. thailandensis is distinct from other known species within the genus Xanthagaricus. A full description, color photographs, illustrations and a phylogenetic tree showing the position of X. thailandensis are provided.

Theileria parva ribosomal internal transcribed spacer sequences exhibit extensive polymorphism and mosaic evolution: application to the characterization of parasites from cattle and buffalo

Parasitology ◽  
1999 ◽  
Vol 118 (6) ◽  
pp. 541-551 ◽  
Author(s):  
N. E. COLLINS ◽  
B. A. ALLSOPP
Keyword(s):  
Genetic Recombination ◽  
Large Subunit ◽  
Small Subunit ◽  
Internal Transcribed Spacers ◽  
Rrna Genes ◽  
Gene Pools ◽  
Theileria Parva ◽  
Causative Agents ◽  
Internal Transcribed Spacer Sequences

We sequenced the rRNA genes and internal transcribed spacers (ITS) of several Theileria parva isolates in an attempt to distinguish between the causative agents of East coast fever and Corridor disease. The small subunit (SSU) and large subunit (LSU) rRNA genes from a cloned T. p. lawrencei parasite were sequenced; the former was identical to that of T. p. parva Muguga, and there were minor heterogeneities in the latter. The 5·8S gene sequences of 11 T. parva isolates were identical, but major differences were found in the ITS. Six characterization oligonucleotides were designed to hybridize within the variable ITS1 region; 93·5% of T. p. parva isolates examined were detected by probe TPP1 and 81·8% of T. p. lawrencei isolates were detected by TPL2 and/or TPL3a. There was no absolute distinction between T. p. parva and T. p. lawrencei and the former hybridized with fewer of the probes than did the latter. It therefore seems that a relatively homogenous subpopulation of T. parva has been selected in cattle from a more diverse gene pool in buffalo. The ITSs of both T. p. parva and T. p. lawrencei contained different combinations of identifiable sequence segments, resulting in a mosaic of segments in any one isolate, suggesting that the two populations undergo genetic recombination and that their gene pools are not completely separate.

Pilaira australis sp. nov. (Mucorales, Mucoromycota) isolated from emu faeces in Australia

Phytotaxa ◽  
2017 ◽  
Vol 329 (3) ◽  
pp. 277 ◽  
Author(s):  
ANDREW S. URQUHART ◽  
PAULINE M. L. COULON ◽  
ALEXANDER IDNURM
Keyword(s):  
Phylogenetic Analysis ◽  
New Species ◽  
Species Identification ◽  
Internal Transcribed Spacers ◽  
Molecular Phylogenetic Analysis ◽  
Unique Combination ◽  
Dromaius Novaehollandiae ◽  
Molecular Phylogenetic ◽  
Carbon Utilisation ◽  
A New Species

Pilaira australis, a new species of fungus in the coprophilous genus Pilaira, was isolated from emu (Dromaius novaehollandiae) faeces and is described. Morphologically, the species resembles other species in the genus, particularly P. moreaui, except differs in its unique combination of sporangiophore height and sporangiospore length. Molecular phylogenetic analysis indicates that P. australis is distinct from other species in the genus with two regions, the internal transcribed spacers (ITS) and a fragment of the pyrG gene, showing 91% and 90% identity to the nearest species, respectively. Ultrastructure features and carbon utilisation were determined for P. australis, and may provide characteristics for species identification in this genus.

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