Repetitive Component Research Articles

Differential Spreading of Microsatellites in Holocentric Chromosomes of Chagas Disease Vectors: Genomic and Evolutionary Implications.

This study focused on analyzing the distribution of microsatellites in holocentric chromosomes of the Triatominae subfamily, insect vectors of Chagas disease. We employed a non-denaturing FISH technique to determine the chromosomal distribution of sixteen microsatellites across twenty-five triatomine species, involving five genera from the two principal tribes: Triatomini and Rhodniini. Three main hybridization patterns were identified: strong signals in specific chromosomal regions, dispersed signals dependent on microsatellite abundance and the absence of signals in certain chromosomal regions or entire chromosomes. Significant variations in hybridization patterns were observed between Rhodniini and Triatomini species. Rhodniini species displayed weak and scattered hybridization signals, indicating a low abundance of microsatellites in their genomes. In contrast, Triatomini species exhibited diverse and abundant hybridization patterns, suggesting that microsatellites are a significant repetitive component in their genomes. One particularly interesting finding was the high abundance of GATA repeats, and to a lesser extent AG repeats, in the Y chromosome of all analyzed Triatomini species. In contrast, the Y chromosome of Rhodniini species did not show enrichment in GATA and AG repeats. This suggests that the richness of GATA repeats on the Y chromosome likely represents an ancestral trait specific to the Triatomini tribe. Furthermore, this information can be used to elucidate the evolutionary relationships between Triatomini and other groups of reduviids, contributing to the understanding of the subfamily's origin. Overall, this study provides a comprehensive understanding of the composition and distribution of microsatellites within Triatominae genomes, shedding light on their significance in the evolutionary processes of these species.

Molecular insights into titin’s A-band

The thick filament-associated A-band region of titin is a highly repetitive component of the titin chain with important scaffolding properties that support thick filament assembly. It also has a demonstrated link to human disease. Despite its functional significance, it remains a largely uncharacterized part of the titin protein. Here, we have performed an analysis of sequence and structure conservation of A-band titin, with emphasis on poly-FnIII tandem components. Specifically, we have applied multi-dimensional sequence pairwise similarity analysis to FnIII domains and complemented this with the crystallographic elucidation of the 3D-structure of the FnIII-triplet A84-A86 from the fourth long super-repeat in the C-zone (C4). Structural models serve here as templates to map sequence conservation onto super-repeat C4, which we show is a prototypical representative of titin’s C-zone. This templating identifies positionally conserved residue clusters in C super-repeats with the potential of mediating interactions to thick-filament components. Conservation localizes to two super-repeat positions: Ig domains in position 1 and FnIII domains in position 7. The analysis also allows conclusions to be drawn on the conserved architecture of titin’s A-band, as well as revisiting and expanding the evolutionary model of titin’s A-band.

Cascaded iterative learning motion control of precision maglev planar motor with experimental investigation

Cascaded iterative learning control (CILC) is explored for a magnetically levitated (maglev) planar motor to achieve excellent tracking motion performance in this paper. The CILC control method is based on traditional iterative learning control (ILC) with deeper iterations. CILC solves the difficulty of ILC in constructing perfect learning filter and low-pass filter to obtain excellent accuracy. Specifically, in CILC, the traditional ILC strategy is implemented several times by the operation of feedforward signal registering and clearing in a cascaded structure, which makes the motion error reach an accuracy level superior to traditional ILC even though the filters are imperfect. The fundamental principle, convergence and stability of CILC strategy are explicitly presented and analyzed. Through the structure of CILC, the repetitive component of the convergence error can be completely eliminated in theory, while the non-repetitive component is accumulated but the sum is bounded. Simulation investigation and comparative experimental investigation on maglev planar motor are both conducted. The results consistently show that the CILC strategy is not only superior to PID and model-based feedforward control, but also obviously outperforms traditional ILC. The CILC investigations on maglev planar motor also provide a clue that CILC has appreciable application prospect for precision/ultra-precision systems requiring extreme motion accuracy.

Genome Sequence Resource of Albifimbria verrucaria Causing the Leaf Spot Disease of the Spinach Plant Spinacia oleracea.

Genome Sequence Resource of Albifimbria verrucaria Causing the Leaf Spot Disease of the Spinach Plant Spinacia oleracea.

Efficient analysis of block circulant structures

A circulant structures has a repetitive component and the entire structure can be formed through the rotation of the repetitive component about the axis of symmetry of the structure. The analysis of such structures can be simplified through the correct understanding of the circular properties. This paper introduces different types of circulant structures and determines the problem of their eigenvalues, which play a major role in engineering applications. Our study first introduces different types of circulant models that are not exclusively designed for simple domes, but rather they include many different types of structures such as power transmission towers, diamatic domes, pyramid domes, silos, etc. In circulant structures, an entire structure can be formed through rotation of the circulant component around the structural axis. A method for calculating the eigenvalues of a circulant structure is presented. In this method the circulant structural model is decomposed and the repetitive component of the structure is identified. This component, along with its connectivity with the previous and subsequent repetitive components, is modeled and the properties of the repetitive component are included in the computations. Examples are provided to show the efficiency of the circulant structural modeling and analysis, and the computational time for analysis of circulant structures is compared to those of the standard finite element program to demonstrate the efficiency of this type of modeling. The codes utilized in this study are written in MATLAB as provided in the Appendix.

On the Trail of Tetu1: Genome-Wide Discovery of CACTA Transposable Elements in Sunflower Genome.

Much has been said about sunflower (Helianthus annuus L.) retrotransposons, representing the majority of the sunflower’s repetitive component. By contrast, class II transposons remained poorly described within this species, as they present low sequence conservation and are mostly lacking coding domains, making the identification and characterization of these transposable elements difficult. The transposable element Tetu1, is a non-autonomous CACTA-like element that has been detected in the coding region of a CYCLOIDEA (CYC) gene of a sunflower mutant, tubular ray flower (turf). Based on our knowledge of Tetu1, the publicly available genome of sunflower was fully scanned. A combination of bioinformatics analyses led to the discovery of 707 putative CACTA sequences: 84 elements with complete ends and 623 truncated elements. A detailed characterization of the identified elements allowed further classification into three subgroups of 347 elements on the base of their terminal repeat sequences. Only 39 encode a protein similar to known transposases (TPase), with 10 TPase sequences showing signals of activation. Finally, an analysis of the proximity of CACTA transposons to sunflower genes showed that the majority of CACTA elements are close to the nearest gene, whereas a relevant fraction resides within gene-encoding sequences, likely interfering with sunflower genome functionality and organization.

A computational comparative study of the repetitive DNA in the genus Quercus L

An overall picture comparing the repetitive components of the genomes of three Quercus species was obtained by genome skimming with Illumina sequence reads. Read sets of Q. lobata, Q. robur, and Q. suber species were subjected to hybrid clustering in order to assemble a repeatome of the Quercus genus and to annotate it. The repeatome was composed of 8573 clusters. The abundance of repeated sequences in the three species was assessed by mapping Illumina reads of each species onto the repeatome. The repetitive portion of the genome was similar among the three species. The most abundant repetitive sequences were long terminal repeat-retrotransposons. Copia elements were overrepresented when compared with Gypsy ones. The most abundant retrotransposon lineages were SIRE for the Copia superfamily and Ogre/TAT for the Gypsy superfamily. Some of the clusters belonging to these lineages showed different transpositional time profiles among the three species. Ribosomal DNAs accounted for 3.64–6.75% of the repetitive component. Satellite DNAs were much more abundant in Q. lobata (8.68% of the genome) than in the two other species. However, different satellite DNAs showed large variations in their abundances. Overall, the composition of the repetitive portion of the genome showed some differences among oak species, suggesting a possible role of repeats for Quercus species differentiation. In the cases of Q. lobata and Q. robur, both of which belong to the Quercus section of the Quercus genus, such differences may be related to the different geographical origins of the species.

A Fast Signal Estimation Method Based on Probability Density Functions for Fault Feature Extraction of Rolling Bearings

Fault diagnosis of rolling bearings is essential to ensure the efficient and safe operation of mechanical equipment. The extraction of fault features of the repetitive transient component from noisy vibration signals is key to bearing fault diagnosis. However, the bearing fault-induced transients are often submerged by strong background noise and interference. To effectively detect such fault-related transient components, this paper proposes a probability- and statistics-based method. The maximum-a-posteriori (MAP) estimator combined with probability density functions (pdfs) of the repetitive transient component, which is modeled by a mixture of two Laplace pdfs and noise, were used to derive the fast estimation model of the transient component. Subsequently, the LapGauss pdf was adopted to model the noisy coefficients. The parameters of the model derived could then be estimated quickly using the iterative expectation–maximization (EM) algorithm. The main contributions of the proposed statistic-based method are that: (1) transients and their wavelet coefficients are modeled as mixed Laplace pdfs; (2) LapGauss pdf is used to model noisy signals and their wavelet coefficients, facilitating the computation of the proposed method; and (3) computational complexity changes linearly with the size of the dataset and thus contributing to the fast estimation, indicated by analysis of the computational performance of the proposed method. The simulation and experimental vibration signals of faulty bearings were applied to test the effectiveness of the proposed method for fast fault feature extraction. Comparisons of computational complexity between the proposed method and other transient extraction methods were also conducted, showing that the computational complexity of the proposed method is proportional to the size of the dataset, leading to a high computational efficiency.

Characterization of the satellitome in lower vascular plants: the case of the endangered fern Vandenboschia speciosa.

Vandenboschia speciosa is a highly vulnerable fern species, with a large genome (10.5 Gb). Haploid gametophytes and diploid sporophytes are perennial, can reproduce vegetatively, and certain populations are composed only of independent gametophytes. These features make this fern a good model: (1) for high-throughput analysis of satellite DNA (satDNA) to investigate possible evolutionary trends in satDNA sequence features; (2) to determine the relative contribution of satDNA and other repetitive DNAs to its large genome; and (3) to analyse whether the reproduction mode or phase alternation between long-lasting haploid and diploid stages influences satDNA abundance or divergence. We analysed the repetitive fraction of the genome of this species in three different populations (one comprised only of independent gametophytes) using Illumina sequencing and bioinformatic analysis with RepeatExplorer and satMiner. The satellitome of V. speciosa is composed of 11 satDNA families, most of them showing a short repeat length and being A + T rich. Some satDNAs had complex repeats composed of sub-repeats, showing high similarity to shorter satDNAs. Three families had particular structural features and highly conserved motifs. SatDNA only amounts to approx. 0.4 % of its genome. Likewise, microsatellites do not represent more than 2 %, but transposable elements (TEs) represent approx. 50 % of the sporophytic genomes. We found high resemblance in satDNA abundance and divergence between both gametophyte and sporophyte samples from the same population and between populations. (1) Longer (and older) satellites in V. speciosa have a higher A + T content and evolve from shorter ones and, in some cases, microsatellites were a source of new satDNAs; (2) the satellitome does not explain the huge genome size in this species while TEs are the major repetitive component of the V. speciosa genome and mostly contribute to its large genome; and (3) reproduction mode or phase alternation between gametophytes and sporophytes does not entail accumulation or divergence of satellites.

Specific LTR-Retrotransposons Show Copy Number Variations between Wild and Cultivated Sunflowers

The relationship between variation of the repetitive component of the genome and domestication in plant species is not fully understood. In previous work, variations in the abundance and proximity to genes of long terminal repeats (LTR)-retrotransposons of sunflower (Helianthus annuus L.) were investigated by Illumina DNA sequencingtocompare cultivars and wild accessions. In this study, we annotated and characterized 22 specific retrotransposon families whose abundance varies between domesticated and wild genotypes. These families mostly belonged to the Chromovirus lineage of the Gypsy superfamily and were distributed overall chromosomes. They were also analyzed in respect to their proximity to genes. Genes close to retrotransposon were classified according to biochemical pathways, and differences between domesticated and wild genotypes are shown. These data suggest that structural variations related to retrotransposons might have occurred to produce phenotypic variation between wild and domesticated genotypes, possibly by affecting the expression of genes that lie close to inserted or deleted retrotransposons and belong to specific biochemical pathways as those involved in plant stress responses.

Satellite DNA in Paphiopedilum subgenus Parvisepalum as revealed by high-throughput sequencing and fluorescent in situ hybridization

BackgroundSatellite DNA is a rapidly diverging, largely repetitive DNA component of many eukaryotic genomes. Here we analyse the evolutionary dynamics of a satellite DNA repeat in the genomes of a group of Asian subtropical lady slipper orchids (Paphiopedilum subgenus Parvisepalum and representative species in the other subgenera/sections across the genus). A new satellite repeat in Paphiopedilum subgenus Parvisepalum, SatA, was identified and characterized using the RepeatExplorer pipeline in HiSeq Illumina reads from P. armeniacum (2n = 26). Reconstructed monomers were used to design a satellite-specific fluorescent in situ hybridization (FISH) probe. The data were also analysed within a phylogenetic framework built using the internal transcribed spacer (ITS) sequences of 45S nuclear ribosomal DNA.ResultsSatA comprises c. 14.5% of the P. armeniacum genome and is specific to subgenus Parvisepalum. It is composed of four primary monomers that range from 230 to 359 bp and contains multiple inverted repeat regions with hairpin-loop motifs. A new karyotype of P. vietnamense (2n = 28) is presented and shows that the chromosome number in subgenus Parvisepalum is not conserved at 2n = 26, as previously reported. The physical locations of SatA sequences were visualised on the chromosomes of all seven Paphiopedilum species of subgenus Parvisepalum (2n = 26–28), together with the 5S and 45S rDNA loci using FISH. The SatA repeats were predominantly localisedin the centromeric, peri-centromeric and sub-telocentric chromosome regions, but the exact distribution pattern was species-specific.ConclusionsWe conclude that the newly discovered, highly abundant and rapidly evolving satellite sequence SatA is specific to Paphiopedilum subgenus Parvisepalum. SatA and rDNA chromosomal distributions are characteristic of species, and comparisons between species reveal that the distribution patterns generate a strong phylogenetic signal. We also conclude that the ancestral chromosome number of subgenus Parvisepalum and indeed of all Paphiopedilum could be either 2n = 26 or 28, if P. vietnamense is sister to all species in the subgenus as suggested by the ITS data.

Highly GC-rich heterochromatin in chili peppers ( Capsicum -Solanaceae): A cytogenetic and molecular characterization

Abstract Capsicum comprises 35 species of chili peppers and five of them are cultivated worldwide as spices or vegetables. Diploid karyotypes based in x = 12 and x = 13 are common in Capsicum and the constitutive heterochromatin (cHet) is of particular interest in the genus since it is largely variable, particularly its highly GC-rich fraction. However, the repetitive DNA components of this heterochromatic regions are unknown. Given the co-localization of rDNA loci with the CMA+DAPI– heterochromatic bands, we tested the hypothesis that the highly GC-rich cHet fraction is composed of the whole 18S-25S ribosomal DNA (rDNA) unit or some of its components. Here we report on a novel satellite for Capsicum and Solanaceae composed of the complete rDNA unit. We physically mapped six Capsicum derived specific 18S-25S rDNA probes that covered the entire span of the rDNA unit and analysed a DraI restriction product on eight chromosomally different taxa of Capsicum, representative of the major phylogenetic clades of chili peppers. The co-localization of every gene and spacer probes of the 18S-25S rDNA unit suggest their structural function as a major repetitive component of the highly GC-rich cHet in Capsicum species with x = 12. In addition, analyses of the clones derived from restriction assays in C. pubescens suggested that the differential functional status of 18S-25S rDNA loci (nucleolar organizer regions -NORs- or cHet) in this species is related to a divergence in a short sequence upstream the regulatory transcription initiation site (TIS) of the intergenic spacer (IGS). The results here provided evidence that an rDNA mega satellite played a significant role in the evolution of the karyotype features of x = 12 Capsicum species. The finding of a mega satellite family derived from the whole rDNA unit is a novelty for plant genomes.

Dating the Species Network: Allopolyploidy and Repetitive DNA Evolution in American Daisies (Melampodium sect. Melampodium, Asteraceae).

Allopolyploidy has played an important role in the evolution of the flowering plants. Genome mergers are often accompanied by significant and rapid alterations of genome size and structure via chromosomal rearrangements and altered dynamics of tandem and dispersed repetitive DNA families. Recent developments in sequencing technologies and bioinformatic methods allow for a comprehensive investigation of the repetitive component of plant genomes. Interpretation of evolutionary dynamics following allopolyploidization requires both the knowledge of parentage and the age of origin of an allopolyploid. Whereas parentage is typically inferred from cytogenetic and phylogenetic data, age inference is hampered by the reticulate nature of the phylogenetic relationships. Treating subgenomes of allopolyploids as if they belonged to different species (i.e., no recombination among subgenomes) and applying cross-bracing (i.e., putting a constraint on the age difference of nodes pertaining to the same event), we can infer the age of allopolyploids within the framework of the multispecies coalescent within BEAST2. Together with a comprehensive characterization of the repetitive DNA fraction using the RepeatExplorer pipeline, we apply the dating approach in a group of closely related allopolyploids and their progenitor species in the plant genus Melampodium (Asteraceae). We dated the origin of both the allotetraploid, Melampodium strigosum, and its two allohexaploid derivatives, Melampodium pringlei and Melampodium sericeum, which share both parentage and the direction of the cross, to the Pleistocene (n}{}<1.4 Ma). Thus, Pleistocene climatic fluctuations may have triggered formation of allopolyploids possibly in short intervals, contributing to difficulties in inferring the precise temporal order of allopolyploid species divergence of M. sericeum and M. pringlei. The relatively recent origin of the allopolyploids likely played a role in the near-absence of major changes in the repetitive fraction of the polyploids’ genomes. The repetitive elements most affected by the postpolyploidization changes represented retrotransposons of the Ty1-copia lineage Maximus and, to a lesser extent, also Athila elements of Ty3-gypsy family.

Comparative genome-wide analysis of repetitive DNA in the genus Populus L.

Genome skimming was performed, using Illumina sequence reads, in order to obtain a detailed comparative picture of the repetitive component of the genome of Populus species. Read sets of seven Populus and two Salix species (as outgroups) were subjected to clustering using RepeatExplorer (Novak et al. BMC Bioinformatics 11:378 2010). The repetitive portion of the genome ranged from 33.8 in Populus nigra to 46.5% in Populus tremuloides. The large majority of repetitive sequences were long terminal repeat-retrotransposons. Gypsy elements were over-represented compared to Copia ones, with a mean ratio Gypsy to Copia of 6.7:1. Satellite DNAs showed a mean genome proportion of 2.2%. DNA transposons and ribosomal DNA showed genome proportions of 1.8 and 1.9%, respectively. The other repeat types accounted for less of 1% each. Long terminal repeat-retrotransposons were further characterized, identifying the lineage to which they belong and studying the proliferation times of each lineage in the different species. The most abundant lineage was Athila, which showed large differences among species. Concerning Copia lineages, similar transpositional profiles were observed among all the analysed species; by contrast, differences in transpositional peaks of Gypsy lineages were found. The genome proportions of repeats were compared in the seven species, and a phylogenetic tree was built, showing species separation according to the botanical section to which the species belongs, although significant differences could be found within sections, possibly related to the different geographical origin of the species. Overall, the data indicate that the repetitive component of the genome in the poplar genus is still rapidly evolving.

Genome-wide analysis of LTR-retrotransposon diversity and its impact on the evolution of the genus Helianthus (L.)

BackgroundGenome divergence by mobile elements activity and recombination is a continuous process that plays a key role in the evolution of species. Nevertheless, knowledge on retrotransposon-related variability among species belonging to the same genus is still limited. Considering the importance of the genus Helianthus, a model system for studying the ecological genetics of speciation and adaptation, we performed a comparative analysis of the repetitive genome fraction across ten species and one subspecies of sunflower, focusing on long terminal repeat retrotransposons at superfamily, lineage and sublineage levels.ResultsAfter determining the relative genome size of each species, genomic DNA was isolated and subjected to Illumina sequencing. Then, different assembling and clustering approaches allowed exploring the repetitive component of all genomes. On average, repetitive DNA in Helianthus species represented more than 75% of the genome, being composed mostly by long terminal repeat retrotransposons. Also, the prevalence of Gypsy over Copia superfamily was observed and, among lineages, Chromovirus was by far the most represented. Although nearly all the same sublineages are present in all species, we found considerable variability in the abundance of diverse retrotransposon lineages and sublineages, especially between annual and perennial species.ConclusionsThis large variability should indicate that different events of amplification or loss related to these elements occurred following species separation and should have been involved in species differentiation. Our data allowed us inferring on the extent of interspecific repetitive DNA variation related to LTR-RE abundance, investigating the relationship between changes of LTR-RE abundance and the evolution of the genus, and determining the degree of coevolution of different LTR-RE lineages or sublineages between and within species. Moreover, the data suggested that LTR-RE abundance in a species was affected by the annual or perennial habit of that species.

Identification and characterization of abundant repetitive sequences in Eragrostis tef cv. Enatite genome.

BackgroundEragrostis tef is an allotetraploid (2n = 4 × = 40) annual, C4 grass with an estimated nuclear genome size of 730 Mbp. It is widely grown in Ethiopia, where it provides basic nutrition for more than half of the population.Although a draft assembly of the E. tef genome was made available in 2014, characterization of the repetitive portion of the E. tef genome has not been a subject of a detailed analysis.Repetitive sequences constitute most of the DNA in eukaryotic genomes. Transposable elements are usually the most abundant repetitive component in plant genomes. They contribute to genome size variation, cause mutations, can result in chromosomal rearrangements, and influence gene regulation. An extensive and in depth characterization of the repetitive component is essential in understanding the evolution and function of the genome.ResultsUsing new paired-end sequence data and a de novo repeat identification strategy, we identified the most repetitive elements in the E. tef genome. Putative repeat sequences were annotated based on similarity to known repeat groups in other grasses.Altogether we identified 1,389 medium/highly repetitive sequences that collectively represent about 27 % of the teff genome. Phylogenetic analyses of the most important classes of TEs were carried out in a comparative framework including paralog elements from rice and maize. Finally, an abundant tandem repeat accounting for more than 4 % of the whole genome was identified and partially characterized.ConclusionsAnalyzing a large sample of randomly sheared reads we obtained a library of the repetitive sequences of E. tef. The approach we used was designed to avoid underestimation of repeat contribution; such underestimation is characteristic of whole genome assembly projects. The data collected represent a valuable resource for further analysis of the genome of this important orphan crop.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0725-4) contains supplementary material, which is available to authorized users.

Analysis of the repetitive component and retrotransposon population in the genome of a marine angiosperm, Posidonia oceanica (L.) Delile

Posidonia oceanica is a monocotyledonous marine plant that plays a crucial role in maintaining the Mediterranean environment. Despite its ecological importance, basic knowledge of the functional and structural genomics of this species is still limited, as it is for the other seagrasses. Here, for the first time, we report data on the repetitive component of the genome of this seagrass using a low coverage of Illumina sequences and different assembly approaches. A dataset of 19,760 assembled sequences, mostly belonging to the repetitive fraction of the genome, was produced and annotated. Based on mapping Illumina reads onto this dataset, the genome structure of P. oceanica and its repetitive component was inferred. A very large proportion of the genome is represented by long-terminal-repeat (LTR) retrotransposons of both the Copia and Gypsy superfamilies. Posidonia LTR-retrotransposons were classified and their sequences analysed. Gypsy elements belong to three main lineages, while Copia ones belong to seven lineages. Gypsy elements were more represented than Copia ones in the set of assembled sequences and in the genome. Analysis of sequence variability indicated that Gypsy lineages have experienced amplification in more recent times compared to Copia ones.

LTR retrotransposon dynamics in the evolution of the olive (Olea europaea) genome.

Improved knowledge of genome composition, especially of its repetitive component, generates important information for both theoretical and applied research. The olive repetitive component is made up of two main classes of sequences: tandem repeats and retrotransposons (REs). In this study, we provide characterization of a sample of 254 unique full-length long terminal repeat (LTR) REs. In the sample, Ty1-Copia elements were more numerous than Ty3-Gypsy elements. Mapping a large set of Illumina whole-genome shotgun reads onto the identified retroelement set revealed that Gypsy elements are more redundant than Copia elements. The insertion time of intact retroelements was estimated based on sister LTR’s divergence. Although some elements inserted relatively recently, the mean insertion age of the isolated retroelements is around 18 million yrs. Gypsy and Copia retroelements showed different waves of transposition, with Gypsy elements especially active between 10 and 25 million yrs ago and nearly inactive in the last 7 million yrs. The occurrence of numerous solo-LTRs related to isolated full-length retroelements was ascertained for two Gypsy elements and one Copia element. Overall, the results reported in this study show that RE activity (both retrotransposition and DNA loss) has impacted the olive genome structure in more ancient times than in other angiosperms.

Matrin 3 Augments the Transcriptional Activity of an SV40 Promoter-Mediated Luciferase Gene with a Highly Repetitive DNA Component

We examined the transcriptional augmentation of matrin 3, a nuclear matrix protein, of the SV40 promotermediated luciferase gene (pGL3) following transient transfection of recombinant plasmids into cells. It has been reported that the interaction of the Xmn I fragment, a highly repetitive DNA component as one of a typical matrix- or scaffold-attachment regions (MAR/SAR) tethered upstream from the SV40 promoter (pGL3-Xmn I) with matrin 3 appeared to be required for augmentation of luciferase gene transcription. In this study, we investigated the levels of induction in cells overexpressing the wild type and several deletion mutants of matrin 3. It appeared that pGL3-Xmn I augmented luciferase production to 4-times the control level in Ac2F cells, but 23-fold in cells overexpressing matrin 3. Electrophoretic mobility shift assay showed that the Xmn I fragment augmented luciferase gene transcription through interaction with matrin 3. Furthermore, our findings suggest that all of the functional domains tested in matrin 3 were necessary for transcriptional augmentation. We aim not only to describe the transcriptional augmentation of matrin 3 with MAR/SAR, but also to strengthen interest in their use to mediate the expression of therapeutic transgenes.

The repetitive component of the A genome of peanut (Arachis hypogaea) and its role in remodelling intergenic sequence space since its evolutionary divergence from the B genome

Peanut (Arachis hypogaea) is an allotetraploid (AABB-type genome) of recent origin, with a genome of about 2·8 Gb and a high repetitive content. This study reports an analysis of the repetitive component of the peanut A genome using bacterial artificial chromosome (BAC) clones from A. duranensis, the most probable A genome donor, and the probable consequences of the activity of these elements since the divergence of the peanut A and B genomes. The repetitive content of the A genome was analysed by using A. duranensis BAC clones as probes for fluorescence in situ hybridization (BAC-FISH), and by sequencing and characterization of 12 genomic regions. For the analysis of the evolutionary dynamics, two A genome regions are compared with their B genome homeologues. BAC-FISH using 27 A. duranensis BAC clones as probes gave dispersed and repetitive DNA characteristic signals, predominantly in interstitial regions of the peanut A chromosomes. The sequences of 14 BAC clones showed complete and truncated copies of ten abundant long terminal repeat (LTR) retrotransposons, characterized here. Almost all dateable transposition events occurred <3·5 million years ago, the estimated date of the divergence of A and B genomes. The most abundant retrotransposon is Feral, apparently parasitic on the retrotransposon FIDEL, followed by Pipa, also non-autonomous and probably parasitic on a retrotransposon we named Pipoka. The comparison of the A and B genome homeologous regions showed conserved segments of high sequence identity, punctuated by predominantly indel regions without significant similarity. A substantial proportion of the highly repetitive component of the peanut A genome appears to be accounted for by relatively few LTR retrotransposons and their truncated copies or solo LTRs. The most abundant of the retrotransposons are non-autonomous. The activity of these retrotransposons has been a very significant driver of genome evolution since the evolutionary divergence of the A and B genomes.