scholarly journals Retrotransposable Elements R1 and R2 in the rDNA Units of Drosophila mercatorum: abnormal abdomen Revisited

Genetics ◽  
1999 ◽  
Vol 151 (2) ◽  
pp. 653-665 ◽  
Author(s):  
Harmit S Malik ◽  
Thomas H Eickbush
Keyword(s):  
Population Level ◽  
Selective Advantage ◽  
Rrna Genes ◽  
Level Shift ◽  
28S Rrna ◽  
Rdna Unit ◽  
Retrotransposable Elements ◽  
Drosophila Mercatorum ◽  
Younger Age ◽  
Type Strains

Abstract R1 and R2 retrotransposable elements are stable components of the 28S rRNA genes of arthropods. While each retrotransposition event leads to incremental losses of rDNA unit expression, little is known about the selective consequences of these elements on the host genome. Previous reports suggested that in the abnormal abdomen (aa) phenotype of Drosophila mercatorum, high levels of rDNA insertions (R1) in conjunction with the under-replication locus (ur), enable the utilization of different ecological conditions via a population level shift to younger age. We have sequenced the R1 and R2 elements of D. mercatorum and show that the levels of R1- and R2-inserted rDNA units were inaccurately scored in the original studies of aa, leading to several misinterpretations. In particular, contrary to earlier reports, aa flies differentially underreplicate R1- and R2-inserted rDNA units, like other species of Drosophila. However, aa flies do not undergo the lower level of underreplication of their functional rDNA units (general underreplication) that is seen in wild-type strains. The lack of general underreplication is expected to confer a selective advantage and, thus, can be interpreted as an adaptation to overcome high levels of R1 and R2 insertions. These results allow us to reconcile some of the apparently contradictory effects of aa and the bobbed phenotype found in other species of Drosophila.

scholarly journals Epigenetic Regulation of Retrotransposons within the Nucleolus of Drosophila

2008 ◽  
Vol 28 (20) ◽  
pp. 6452-6461 ◽  
Author(s):  
Danna G. Eickbush ◽  
Junqiang Ye ◽  
Xian Zhang ◽  
William D. Burke ◽  
Thomas H. Eickbush
Keyword(s):  
Large Scale ◽  
Transcriptional Control ◽  
Rdna Locus ◽  
Rrna Genes ◽  
28S Rrna ◽  
Nucleolar Dominance ◽  
Retrotransposable Elements ◽  
Active Line ◽  
Interspecies Hybrids ◽  
Rdna Loci

ABSTRACT R2 retrotransposable elements exclusively insert into a conserved region of the tandemly organized 28S rRNA genes. Despite inactivating a subset of these genes, R2 elements have persisted in the ribosomal DNA (rDNA) loci of insects for hundreds of millions of years. Controlling R2 proliferation was addressed in this study using lines of Drosophila simulans previously shown to have either active or inactive R2 retrotransposition. Lines with active retrotransposition were shown to have high R2 transcript levels, which nuclear run-on transcription experiments revealed were due to increased transcription of R2-inserted genes. Crosses between R2 active and inactive lines indicated that an important component of this transcriptional control is linked to or near the rDNA locus, with the R2 transcription level of the inactive parent being dominant. Pulsed-field gel analysis suggested that the R2 active and inactive states were determined by R2 distribution within the locus. Molecular and cytological analyses further suggested that the entire rDNA locus from the active line can be silenced in favor of the locus from the inactive line. This silencing of entire rDNA loci represents an example of the large-scale epigenetic control of transposable elements and shares features with the nucleolar dominance frequently seen in interspecies hybrids.

scholarly journals Turnover of R1 (type I) and R2 (type II) retrotransposable elements in the ribosomal DNA of Drosophila melanogaster.

Genetics ◽  
1992 ◽  
Vol 131 (1) ◽  
pp. 129-142 ◽  
Author(s):  
J L Jakubczak ◽  
M K Zenni ◽  
R C Woodruff ◽  
T H Eickbush
Keyword(s):  
Drosophila Melanogaster ◽  
Critical Role ◽  
Rrna Genes ◽  
Type I ◽  
28S Rrna ◽  
Retrotransposable Elements ◽  
Total Percentage ◽  
Length Polymorphisms ◽  
Restriction Sites ◽  
Nucleotide Divergence

Abstract R1 and R2 are distantly related non-long terminal repeat retrotransposable elements each of which inserts into a specific site in the 28S rRNA genes of most insects. We have analyzed aspects of R1 and R2 abundance and sequence variation in 27 geographical isolates of Drosophila melanogaster. The fraction of 28S rRNA genes containing these elements varied greatly between strains, 17-67% for R1 elements and 2-28% for R2 elements. The total percentage of the rDNA repeats inserted ranged from 32 to 77%. The fraction of the rDNA repeats that contained both of these elements suggested that R1 and R2 exhibit neither an inhibition of nor preference for insertion into a 28S gene already containing the other type of element. Based on the conservation of restriction sites in the elements of all strains, and sequence analysis of individual elements from three strains, nucleotide divergence is very low for R1 and R2 elements within or between strains (less than 0.6%). This sequence uniformity is the expected result of the forces of concerted evolution (unequal crossovers and gene conversion) which act on the rRNA genes themselves. Evidence for the role of retrotransposition in the turnover of R1 and R2 was obtained by using naturally occurring 5' length polymorphisms of the elements as markers for independent transposition events. The pattern of these different length 5' truncations of R1 and R2 was found to be diverse and unique to most strains analyzed. Because recombination can only, with time, amplify or eliminate those length variants already present, the diversity found in each strain suggests that retrotransposition has played a critical role in maintaining these elements in the rDNA repeats of D. melanogaster.

Phylogeny of hymenolepidids (Cestoda: Cyclophyllidea) from mammals: sequences of 18S rRNA and COI genes confirm major clades revealed by the 28S rRNA analyses

2021 ◽  
Vol 95 ◽  
Author(s):  
B. Neov ◽  
G.P. Vasileva ◽  
G. Radoslavov ◽  
P. Hristov ◽  
D.T.J. Littlewood ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
18S Rrna ◽  
Phylogenetic Analyses ◽  
The Other ◽  
Rrna Genes ◽  
Host Switching ◽  
28S Rrna ◽  
Mitochondrial Cytochrome ◽  
Rapid Radiation ◽  
18S Rrna Genes

Abstract The aim of the study is to test a hypothesis for the phylogenetic relationships among mammalian hymenolepidid tapeworms, based on partial (D1–D3) nuclear 28S ribosomal RNA (rRNA) genes, by estimating new molecular phylogenies for the group based on partial mitochondrial cytochrome c oxidase I (COI) and nuclear 18S rRNA genes, as well as a combined analysis using all three genes. New sequences of COI and 18S rRNA genes were obtained for Coronacanthus integrus, C. magnihamatus, C. omissus, C. vassilevi, Ditestolepis diaphana, Lineolepis scutigera, Spasskylepis ovaluteri, Staphylocystis tiara, S. furcata, S. uncinata, Vaucherilepis trichophorus and Neoskrjabinolepis sp. The phylogenetic analyses confirmed the major clades identified by Haukisalmi et al. (Zoologica Scripta 39: 631–641, 2010): Ditestolepis clade, Hymenolepis clade, Rodentolepis clade and Arostrilepis clade. While the Ditestolepis clade is associated with soricids, the structure of the other three clades suggests multiple evolutionary events of host switching between shrews and rodents. Two of the present analyses (18S rRNA and COI genes) show that the basal relationships of the four mammalian clades are branching at the same polytomy with several hymenolepidids from birds (both terrestrial and aquatic). This may indicate a rapid radiation of the group, with multiple events of colonizations of mammalian hosts by avian parasites.

scholarly journals Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov., moderately halophilic bacteria isolated from a deep-sea methane cold seep

2007 ◽  
Vol 57 (6) ◽  
pp. 1243-1249 ◽  
Author(s):  
Ngoc-Phuc Hua ◽  
Atsuko Kanekiyo ◽  
Katsunori Fujikura ◽  
Hisato Yasuda ◽  
Takeshi Naganuma
Keyword(s):  
Deep Sea ◽  
Sequence Similarity ◽  
Halophilic Bacteria ◽  
Cold Seep ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
High Sequence Similarity ◽  
Moderately Halophilic ◽  
Type Strains ◽  
Moderately Halophilic Bacteria

Two Gram-positive, rod-shaped, moderately halophilic bacteria were isolated from a deep-sea carbonate rock at a methane cold seep in Kuroshima Knoll, Japan. These bacteria, strains IS-Hb4T and IS-Hb7T, were spore-forming and non-motile. They were able to grow at temperatures as low as 9 °C and hydrostatic pressures up to 30 MPa. Based on high sequence similarity of their 16S rRNA genes to those of type strains of the genus Halobacillus, from 96.4 % (strain IS-Hb7T to Halobacillus halophilus NCIMB 9251T) to 99.4 % (strain IS-Hb4T to Halobacillus dabanensis D-8T), the strains were shown to belong to this genus. DNA–DNA relatedness values of 49.5 % and 1.0–33.0 %, respectively, were determined between strains IS-Hb4T and IS-Hb7T and between these strains and other Halobacillus type strains. Both strains showed the major menaquinone MK7 and l-orn–d-Asp cell-wall peptidoglycan type. Straight-chain C16 : 0, unsaturated C16 : 1 ω7c alcohol and C18 : 1 ω7c and cyclopropane C19 : 0 cyc fatty acids were predominant in both strains. The DNA G+C contents of IS-Hb4T and IS-Hb7T were respectively 43.3 and 42.1 mol%. Physiological and biochemical analyses combined with DNA–DNA hybridization results allowed us to place strains IS-Hb4T (=JCM 14154T=DSM 18394T) and IS-Hb7T (=JCM 14155T=DSM 18393T) in the genus Halobacillus as the respective type strains of the novel species Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov.

Systematic revision, diversity patterns and trophic ecology of the tropical Indo-West Pacific sea slug genus Phanerophthalmus A. Adams, 1850 (Cephalaspidea, Haminoeidae)

2018 ◽  
Vol 32 (6) ◽  
pp. 1336 ◽  
Author(s):  
Jennifer Austin ◽  
Terrence Gosliner ◽  
Manuel A. E. Malaquias
Keyword(s):  
Content Analysis ◽  
Molecular Phylogenetics ◽  
Trophic Ecology ◽  
Rrna Genes ◽  
28S Rrna ◽  
Gut Content Analysis ◽  
Gut Content ◽  
Central Pacific ◽  
Systematic Revision ◽  
West Pacific

Phanerophthalmus is a genus of Indo-West Pacific sea slugs inhabiting seagrass and coral reefs with up to now seven species currently recognised as valid. The goals of this study are to revise the systematics of Phanerophthalmus, infer its phylogeny and patterns of diversity, as well as study its diet. Morphology was combined with molecular phylogenetics based on two mitochondrial (cytochrome c oxidase subunit I, 16S rRNA) and one nuclear (28S rRNA) genes. Molecular species delimitation methods (ABGD, DISSECT) were employed to aid delimiting species. Diet was assessed by gut content analysis. Seventeen species were recognised, 10 of them new to science (P. albotriangulatum, sp. nov., P. anettae, sp. nov., P. batangas, sp. nov., P. boucheti, sp. nov., P. cerverai, sp. nov., P. lentigines, sp. nov., P. paulayi, sp. nov., P. purpura, sp. nov., P. rudmani, sp. nov., P. tibiricae, sp. nov.). Phanerophthalmus has its highest diversity in the Western Pacific where 13 species occur with a peak in the Coral Triangle (11 species; three only known from here). Diversity decreases towards the Central Pacific with five species and Indian Ocean/Red Sea with four species. Only two species are distributed across the Indo-West Pacific. Preliminary gut content analysis suggests these slugs feed on diatoms.

scholarly journals Algorithmic Methods to Infer the Evolutionary Trajectories in Cancer Progression

2015 ◽  
Author(s):  
Giulio Caravagna ◽  
Alex Graudenzi ◽  
DANIELE RAMAZZOTTI ◽  
Rebeca Sanz-Pamplona ◽  
Luca De Sano ◽  
...  
Keyword(s):  
Cancer Progression ◽  
Current Knowledge ◽  
Population Level ◽  
Selective Advantage ◽  
Explanatory Models ◽  
Driver Mutations ◽  
Cross Sectional ◽  
Progression Model ◽  
Colorectal Cancer Progression ◽  
Ngs Data

The genomic evolution inherent to cancer relates directly to a renewed focus on the voluminous next generation sequencing (NGS) data, and machine learning for the inference of explanatory models of how the (epi)genomic events are choreographed in cancer initiation and development. However, despite the increasing availability of multiple additional -omics data, this quest has been frustrated by various theoretical and technical hurdles, mostly stemming from the dramatic heterogeneity of the disease. In this paper, we build on our recent works on "selective advantage" relation among driver mutations in cancer progression and investigate its applicability to the modeling problem at the population level. Here, we introduce PiCnIc (Pipeline for Cancer Inference), a versatile, modular and customizable pipeline to extract ensemble-level progression models from cross-sectional sequenced cancer genomes. The pipeline has many translational implications as it combines state-of-the-art techniques for sample stratification, driver selection, identification of fitness-equivalent exclusive alterations and progression model inference. We demonstrate PiCnIc's ability to reproduce much of the current knowledge on colorectal cancer progression, as well as to suggest novel experimentally verifiable hypotheses.

scholarly journals Rhizobium azibense sp. nov., a nitrogen fixing bacterium isolated from root-nodules of Phaseolus vulgaris

2014 ◽  
Vol 64 (Pt_5) ◽  
pp. 1501-1506 ◽  
Author(s):  
Bacem Mnasri ◽  
Tian Yan Liu ◽  
Sabrine Saidi ◽  
Wen Feng Chen ◽  
Wen Xin Chen ◽  
...  
Keyword(s):  
Type Species ◽  
Root Nodules ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
The Novel ◽  
Content Type ◽  
Link Type ◽  
Physiological Properties ◽  
Microbial Strains ◽  
Type Strains

Three microbial strains isolated from common beans, 23C2T (Tunisia), Gr42 (Spain) and IE4868 (Mexico), which have been identified previously as representing a genomic group closely related to Rhizobium gallicum , are further studied here. Their 16S rRNA genes showed 98.5–99 % similarity with Rhizobium loessense CCBAU 7190BT, R. gallicum R602spT, Rhizobium mongolense USDA 1844T and Rhizobium yanglingense CCBAU 71623T. Phylogenetic analysis based on recA, atpD, dnaK and thrC sequences showed that the novel strains were closely related and could be distinguished from the four type strains of the closely related species. Strains 23C2T, Gr42 and IE4868 could be also differentiated from their closest phylogenetic neighbours by their phenotypic and physiological properties and their fatty acid contents. All three strains harboured symbiotic genes specific to biovar gallicum. Levels of DNA–DNA relatedness between strain 23C2T and the type strains of R. loessense , R. mongolense , R. gallicum and R. yanglingense ranged from 58.1 to 61.5 %. The DNA G+C content of the genomic DNA of strain 23C2T was 59.52 %. On the basis of these data, strains 23C2T, Gr42 and IE4868 were considered to represent a novel species of the genus Rhizobium for which the name Rhizobium azibense is proposed. Strain 23C2T ( = CCBAU 101087T = HAMBI3541T) was designated as the type strain.

scholarly journals The differential expression of ribosomal 18S RNA paralog genes from the chaetognath Spadella cephaloptera

2007 ◽  
Vol 12 (4) ◽  
Author(s):  
Roxane-Marie Barthélémy ◽  
Michel Grino ◽  
Pierre Pontarotti ◽  
Jean-Paul Casanova ◽  
Eric Faure
Keyword(s):  
Physiological Role ◽  
Class Ii ◽  
Class I ◽  
Rrna Genes ◽  
Whole Body ◽  
Rrna Gene ◽  
28S Rrna ◽  
Cellular Functions ◽  
Intraindividual Variation ◽  
Spadella Cephaloptera

AbstractChaetognaths constitute a small marine phylum of approximately 120 species. Two classes of both 18S and 28S rRNA gene sequences have been evidenced in this phylum, even though significant intraindividual variation in the sequences of rRNA genes is unusual in animal genomes. These observations led to the hypothesis that this unusual genetic characteristic could play one or more physiological role(s). Using in situ hybridization on the frontal sections of the chaetognath Spadella cephaloptera, we found that the 18S Class I genes are expressed in the whole body, with a strong expression throughout the gut epithelium, whereas the expression of the 18S Class II genes is restricted to the oocytes. Our results could suggest that the paralog products of the 18S Class I genes are probably the “housekeeping” 18S rRNAs, whereas those of class II would only be essential in specific tissues. These results provide support for the idea that each type of 18S paralog is important for specific cellular functions and is under the control of selective factors.

Morphological and molecular characterisation of Helicotylenchus ciceri n. sp. and H. scoticus Boag & Jairajpuri, 1985 (Nematoda: Hoplolaimidae) from Iran

Nematology ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 611-626
Author(s):  
Fariba Mohammadi Zameleh ◽  
Akbar Karegar ◽  
Reza Ghaderi ◽  
Abbas Mokaram Hesar
Keyword(s):  
New Species ◽  
Excretory Pore ◽  
18S Rrna ◽  
Phylogenetic Analyses ◽  
Rrna Genes ◽  
28S Rrna ◽  
Molecular Characterisation ◽  
Closely Related Species ◽  
Partial 18S ◽  
Molecular Characters

Summary Helicotylenchus ciceri n. sp. and H. scoticus are described and illustrated based on morphological, morphometric and molecular characters. The new species is characterised by a conical and truncated lip region with five or six distinct annuli, stylet 32-37 μm long with anteriorly concave knobs, secretory-excretory pore posterior to the pharyngo-intestinal valve, dorsally convex-conoid tail with a terminal projection, phasmids 14 (7-20) annuli anterior to the level of anus, empty spermatheca and absence of males. Intraspecific variation of 16 populations of H. scoticus, collected from chickpea and lentil fields in Kermanshah province, western Iran, is discussed. The results of the phylogenetic analyses based on the sequences of the partial 18S rRNA, D2-D3 expansion segments of 28S rRNA and ITS rRNA genes are provided for the studied species, confirming their differences from each other and determining the position of them and their relationships with closely related species.

Description and phylogenetic analyses of ribosomal transcription units from species of Fasciolidae (Platyhelminthes: Digenea)

2020 ◽  
Vol 94 ◽  
Author(s):  
T.H. Le ◽  
K.L.T. Pham ◽  
H.T.T. Doan ◽  
T.K. Xuyen Le ◽  
K.T. Nguyen ◽  
...  
Keyword(s):  
Fasciola Hepatica ◽  
Phylogenetic Analyses ◽  
Intergenic Spacer ◽  
Transcription Unit ◽  
Rrna Genes ◽  
28S Rrna ◽  
Intergenic Spacer Region ◽  
Repeat Units ◽  
Complete Sequences ◽  
Fasciolopsis Buski

Abstract Many members of Fasciolidae are common trematodes in cattle, buffaloes, sheep, elephants, pigs, with some capable of infecting humans also. In this study, the complete or near-complete sequences of ribosomal transcription unit (rTU or rDNA), each of Fasciola hepatica (Australia), Fascioloides jacksoni (Sri Lanka), Fasciolopsis buski (Vietnam) and three isolates of F. gigantica (Vietnam), were obtained and characterized. The full length of rDNA for each F. hepatica, ‘hybrid’ Fasciola sp., Fas. jacksoni and Fa. Buski, was 7657 bp, 7966 bp, 7781 bp and 8361 bp, with the complete intergenic spacer region (IGS) (862 bp, 1170 bp, 987 bp and 561 bp), respectively. The rDNA of two ‘pure’ F. gigantica isolates from Vietnam was 6794 bp with unsequenced IGS. For 28S rRNA genes the Fasciola spp. are equal, 1958 bp for 18S, 160 bp for 5.8S, 3863 bp and 454 bp for ITS1 but ITS2 differ by one nucleotide (Thymine) (359 or 360 bp). The ITS1 of the sensu lato Fa. buski has some distinguishable features, 286 bp for ITS2, 3862 bp for 28S and four repeat units of 356–361 bp each found in ITS1. The 28S rDNA analysis showed the lowest level of divergence (0–0.57%) between F. hepatica and F. gigantica and higher (2.23–2.62%) and highest (6–6.42%) for Fas. jacksoni and Fasciolopsis, respectively. The tree of 43 strains/species clearly produced a well-supported phylogeny, where 18 fasciolids consistently grouped, forming a discrete Fasciolidae clade, distinct from Philophthalmidae, Echinostomatidae and Echinochasmidae in Echinostomatoidea. Fascioloides jacksoni is outside Fasciola spp.: basal with Fas. magna, as previously demonstrated.

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