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At least 235 records · Page 13Linked to original sources
PubMed1999

Aberrant splicing of the Drosophila melanogaster phenylalanine hydroxylase pre-mRNA caused by the insertion of a B104/roo transposable element in the Henna locus.

We report the insertion of the transposable element B104 in the Phenylalanine hydroxylase gene of the Drosophila mutant Henna-recessive 3. Its presence alters the Phenylalanine hydroxylase splicing pattern, producing at least two aberrant mRNAs which contain part of the B104 sequence interrupting the coding region. This aberrant splicing is provoked by the use of a cryptic donor site encoded by the B104 3' long terminal repeat in combination with either the gene intron 3 acceptor site or a novel acceptor site generated by the target duplication caused by transposition. One of them, referred as mRNA type 1, encodes a truncated protein that could be predictably non-functional. In mRNA type 2, in spite of a 42 nt insertion, the Phenylalanine hydroxylase reading frame is not altered and it would encode for a protein with 14 extra amino acids which would be able to account for the low enzyme activity detected in this mutant. These results demonstrated that Henna locus encodes the enzyme phenylalanine hydroxylase providing direct evidence of its participation in pteridine synthesis. Moreover, it constitutes an example of the ability of transposable elements to generate protein variation in populations with the evolutionary consequences that this implies.

Alternative Splicing↗
PubMed2002

Characterization of transposable elements in the genome of rice (Oryza sativa L.) using Representational Difference Analysis (RDA).

Representational Difference Analysis was applied to characterize genomic differentiations between rice ( Oryza sativa) and foxtail millet ( Setaria italica) and subsequently to identify rice transposable elements. Rice was used as the tester and millet as the driver. A total of eleven, non-redundant, positive clones were isolated from the library. Their analysis revealed that they all represent dispersed repetitive DNA sequences. In addition, homology searches using the BLAST procedure showed that they correspond to seven distinct rice transposable elements. Three had been previously identified as gypsy-like retroelements ( Retrosat1, RIRE3 and RIRE8). The remaining four are novel: we named them hipa (a CACTA-like transposon), houba (a copia-like retroelement), hopi and dagul (two gypsy-like retroelements). The RDA clones were used as probes in Southern hybridization experiments with genomic DNAs of several species from the family Poaceae. The results suggest that the genomic differentiations associated with the activity of these transposable elements are of relatively recent origin. In addition, comparison of the hybridization patterns obtained for several Oryza species suggests that several independent amplifications of these transposable elements might have occurred within the genus.

Base Sequence↗
PubMed1994

The strange phylogenies of transposable elements: are horizontal transfers the only explantation?

Analyses of the evolution of transposable elements reveal some inconsistencies when the phylogenies of such elements are compared to conventional phylogenies of the host species. Such discrepancies are generally interpreted as resulting from occasional horizontal transfers of transposable elements across species boundaries. This phenomenon has been clearly demonstrated for only a few elements and both its frequency and the mechanism by which it occurs remain unknown. Moreover, in many cases, the hypothesis of horizontal transfer must be compared with alternative evolutionary scenarios.

Animals↗
PubMedDate not supplied

[Thermosensitive vector derived from RP1 plasmid for detection of transposable elements].

The involvement of the transposable DNA element of E. coli K12 chromosome in integrative recombination of RP1 plasmid was studied. Using temperature sensitive for replication plasmid RP1ts12--the derivative of RP1 which contains mutated transposon Tnl, it was shown that integration of RP1 into host chromosome and Hfr formation may occur according to a mechanism mediated by chromosome IS-elements. Plasmids that are desintegrated from the chromosome of these Hfrs contain discrete DNA segments (IS-elements) and possess elevated frequency of integration into chromosome of rec+ cells. The latter was used for selection of RP1ts12 recombinants carrying chromosome IS. For identification of IS involved in RP1 integration the number of independent RP1ts 12 recombinants was subjected to restriction and heteroduplex analysis. By analysing recombinants integrated into bacterial chromosome with frequency 5 X 10(-3), a new IS-element of E. coli K12 designated IS111 was discovered. IS111-element is about 1500bp of length, contains Smal, Pst1 and BamH1 restriction endonuclease sites and was found in the same position on the plasmid RP1 in two different orientations. IS-elements that have been revealed in a number of other RP1ts12 recombinants were preliminary identified as IS1-like elements. One recombinants plasmid was found to have an IS5-like elements. The activity of IS-elements inserted into RP1ts12 in recA-dependent integrative recombination was estimated. From the data of absolute and relative RP1ts12 integration frequencies mediated by IS111, IS1- and IS5-like elements a conclusion was made about the absence of E. coli K12 chromosome IS-elements in RP1 plasmid. The Hfr-formation and chromosomal gene transfer by recombinant plasmids RP1ts12: IS111 were studied. The possibility to use insertion RP1ts12 derivatives for the estimation of copies number, mapping and definition of orientation of IS-elements in bacterial chromosome and the possibilities for detection of transposable DNA elements using RP1ts12 in a wide range of gram-negative bacteria are discussed.

Bacterial Proteins↗
PubMed1996

Insertion mutagenesis and study of transposable elements using a new unstable virescent seedling allele for isolation of haploid petunia lines.

The new unstable virescent seedling (vis) allele of a petunia mutant, that has green leaves but white cotyledons with green revertant spots, was used to identify spontaneously occurring haploid petunia lines with active transposable elements. Endogenous transposons were trapped into the single petunia nitrate reductase structural gene (nia) using chlorate selection on haploid protoplasts. In two mutant lines, the dTph1-like transposable element dTph1-3 was inserted at almost the same position but in opposite orientations in the first exon of the nia gene. In a third mutant, a different transposable element was integrated into the fourth exon. This element, called dTph4, is 787 bp long and has 13 bp terminal inverted repeats of which 12 bp are identical to those of dTph1. Insertion of dTph1-3 and dTph4 results in an 8 bp duplication of the target site, as already described for dTph1. In contrast to dTph1-like elements, dTph4 is present at low copy number in the petunia genome. This can facilitate its use for gene tagging in petunia. The dTph1-3 and dTph4 elements excise frequently, as transposon footprints were found in most of the insertion mutants. The data demonstrate that haploid petunia is an excellent system for gene tagging and for the study of transposable elements.

Alleles↗
PubMed1987

The maize transposable element Ds is spliced from RNA.

In some instances, insertion of maize transposable elements into exons does not result in the total loss of enzymatic activity. In other instances, messenger RNAs of wild-type size are encoded by genes known to contain the maize transposable element Dissociation (Ds) in exons. To understand how Ds is processed from RNA, a study was made of transcripts encoded by two alleles of the maize waxy (wx) gene containing Ds insertions in exon sequences. The analysis was carried out in strains where the Ds element could not excise from the wx gene. Despite insertions of 4.3- and 1.5-Ds elements, the predominant transcripts encoded by these two genes were wild type in size. For both alleles, DNA sequencing of complementary DNAs revealed that the Ds elements had been spliced in a similar manner. Splicing was accomplished by the utilization of multiple 5' donor splice sites in the Ds termini and a 3' acceptor site within the wx gene adjacent to the Ds element. The net effect in both cases was the removal of most of the Ds element from the messenger RNA.

Base Sequence↗
PubMed1992

Excision of a transposable element from a viral vector introduced into maize plants by agroinfection.

The geminivirus maize streak virus (MSV) was used as a vector to introduce the maize transposable element Dissociation (Ds) and to study its excision in maize plants. MSV carrying Ds1 in its genome was introduced into maize plants by agroinfection. Excision of the Ds1 element from the MSV genome was detected only when functions from the transposable element Activator (Ac) were supplied in trans, either endogenously by the recipient maize plant or by co-transformation with Agrobacterium carrying a genomic Ac clone. The excision of Ds1 could easily be visualized by the appearance of viral symptoms induced by the revertant virus. The junction sequences left on the MSV genome after excision revealed 'footprints' typical of transposition as described for maize. From these results, we conclude that transposition functions in our system and that the use of the MSV replicon provides a rapid and simple tool for the investigation of the excision of transposable elements in maize plants.

Agrobacterium tumefaciens↗
PubMed2005

Transposable elements as artisans of the heterochromatic genome in Drosophila melanogaster.

Over 50 years ago Barbara McClintock discovered that maize contains mobile genetic elements, but her findings were at first considered nothing more than anomalies. Today it is widely recognized that transposable elements have colonized all eukaryotic genomes and represent a major force driving evolution of organisms. Our contribution to this special issue deals with the theme of transposable element-host genome interactions. We bring together published and unpublished work to provide a picture of the contribution of transposable elements to the evolution of the heterochromatic genome in Drosophila melanogaster. In particular, we discuss data on 1) colonization of constitutive heterochromatin by transposable elements, 2) instability of constitutive heterochromatin induced by the I factor, and 3) evolution of constitutive heterochromatin and heterochromatic genes driven by transposable elements. Drawing attention to these topics may have direct implications on important aspects of genome organization and gene expression.

Animals↗
PubMed1985

Plant transposable elements generate the DNA sequence diversity needed in evolution.

Two germinal and 16 somatic reversion events induced by the Enhancer (En) transposable element system at the wx-8::Spm-I8 allele of Zea mays were cloned and studied by sequence analysis. Excision of the Spm-I8 receptor element from the wx gene results in various mutant DNA sequences. This leads to altered gene products, some of which are still capable of restoring the wild-type phenotype. Possible 'foot-print' sequences that may have arisen by the excision of transposable elements were observed when intron sequences of the wild-type (wx+) and mutant (wx-m8) alleles of the wx gene were compared. The sequence divergence generated by visitation of a locus by plant transposable elements is discussed with respect to the molecular evolution of the new gene functions.

Base Sequence↗
PubMed1989

The splicing of maize transposable elements from pre-mRNA--a minireview.

There are six examples of maize transposable elements that are spliced from pre-mRNA. These represent the first introns that have been added to nuclear genes in recent years. All six are members of the Ac/Ds or Spm/dSpm family of elements and all have been inserted into exons of active genes within the last twenty-five years. The structure of these element-introns and the sequences involved in their splicing are presented. These examples illustrate how active transposable elements can also function as introns and how they may evolve into stable introns.

Alleles↗
PubMed1990

Genomic organization of the transposable element Tdd-3 from Dictyostelium discoideum.

The transposable element Tdd-3 from D. discoideum has been described originally in 1984 (Poole and Firtel, 1984). Additional copies of this element were discovered in the course of a recent study on tRNA gene organization in D. discoideum. Five out of 24 independently isolated tRNA genes proved to be associated with Tdd-3 elements. The surprising observation that all the elements always occurred within the 3'-flanking sequences of the Dictyostelium tRNA genes suggested the possibility of a general position specific integration of Tdd-3 elements upon transposition. Therefore we isolated additional Tdd-3 elements from various genomic D. discoideum libraries in order to test this hypothesis. Several new Tdd-3 elements were found associated with various tRNA genes. Additionally we identified Tdd-3 elements organized in tandem array or in association with RED (Repetitive Element of Dictyostelium), another repetitive element recently identified by our laboratory. In all cases a B-box equivalent of the eukaryotic gene-internal RNA polymerase III promoter was identified upstream of all Tdd-3 elements.

Base Sequence↗
PubMed1995

Mu1-related transposable elements of maize preferentially insert into low copy number DNA.

The Mutator transposable element system of maize was originally identified through its induction of mutations at an exceptionally high frequency and at a wide variety of loci. The Mu1 subfamily of transposable elements within this system are responsible for the majority of Mutator-induced mutations. Mu 1-related elements were isolated from active Mutator plants and their flanking DNA was characterized. Sequence analyses revealed perfect nine base target duplications directly flanking the insert for 13 of the 14 elements studied. Hybridizational studies indicated that Mu1-like elements insert primarily into regions of the maize genome that are of low copy number. This preferential selection of low copy number DNA as targets for Mu element insertion was not directed by any specific secondary structure(s) that could be detected in this study, but the 9-bp target duplications exhibited a discernibly higher than random match with the consensus sequence 5'-G-T-T-G-G/C-A-G-G/A-G-3'.

Chromosome Mapping↗
PubMed2003

Pearl, a novel family of putative transposable elements in bivalve mollusks.

While genome sequencing projects have discovered numerous types of transposable elements in diverse eukaryotes, there are many taxa of ecological and evolutionary significance that have received little attention, such as the molluscan class Bivalvia. Examination of a 0.7-MB genomic sequence database from the cupped oyster Crassostrea virginica revealed the presence of a common interspersed element, CvA. CvA possesses subterminal inverted repeats, a tandemly repeated core element, a tetranucleotide microsatellite region, and the ability to form stable secondary structures. Three other less abundant repetitive elements with a similar structure but little sequence similarity were also found in C. virginica. Ana-1, a repetitive element with similar features, was discovered in the blood ark Anadara trapezia by probing a genomic library with a dimeric repeat element contained in intron 2 of a minor globin gene in that species. All of these elements are flanked by the dinucleotide AA, a putative target-site duplication. They exhibit structural similarity to the sea urchin Tsp family and Drosophila SGM insertion sequences; in addition, they possess regions of sequence similarity to satellite DNA from several bivalve species. We suggest that the Crassostrea repetitive elements and Ana-1 are members of a new MITE-like family of nonautonomous transposable elements, named pearl. Pearl is the first putative nonautonomous DNA transposon to be identified in the phylum Mollusca.

Animals↗
PubMed1996

Germline transformation of Drosophila virilis with the transposable element mariner.

An important goal in molecular genetics has been to identify a transposable element that might serve as an efficient transformation vector in diverse species of insects. The transposable element mariner occurs naturally in a wide variety of insects. Although virtually all mariner elements are nonfunctional, the Mos1 element isolated from Drosophila mauritiana is functional. Mos1 was injected into the pole-cell region of embryos of D. virilis, which last shared a common ancestor with D. mauritiana 40 million years ago. Mos1 PCR fragments were detected in several pools of DNA from progeny of injected animals, and backcross lines were established. Because G0 lines were pooled, possibly only one transformation event was actually obtained, yielding a minimum frequency of 4%. Mos1 segregated in a Mendelian fashion, demonstrating chromosomal integration. The copy number increased by spontaneous mobilization. In situ hybridization confirmed multiple polymorphic locations of Mos1. Integration results in a characteristic 2-bp TA duplication. One Mos1 element integrated into a tandem array of 370-bp repeats. Some copies may have integrated into heterochromatin, as evidenced by their ability to support PCR amplification despite absence of a signal in Southern and in situ hybridization.

Animals↗
PubMed2002

Transposable elements and the evolution of genome size in eukaryotes.

It is generally accepted that the wide variation in genome size observed among eukaryotic species is more closely correlated with the amount of repetitive DNA than with the number of coding genes. Major types of repetitive DNA include transposable elements, satellite DNAs, simple sequences and tandem repeats, but reliable estimates of the relative contributions of these various types to total genome size have been hard to obtain. With the advent of genome sequencing, such information is starting to become available, but no firm conclusions can yet be made from the limited data currently available. Here, the ways in which transposable elements contribute both directly and indirectly to genome size variation are explored. Limited evidence is provided to support the existence of an approximately linear relationship between total transposable element DNA and genome size. Copy numbers per family are low and globally constrained in small genomes, but vary widely in large genomes. Thus, the partial release of transposable element copy number constraints appears to be a major characteristic of large genomes.

DNA Transposable Elements↗
PubMed1995

Recent horizontal transfer of a mariner transposable element among and between Diptera and Neuroptera.

Transposable elements of the mariner family are widespread among insects and other invertebrates, and initial analyses of their relationships indicated frequent occurrence of horizontal transfers between hosts. A specific PCR assay was used to screen for additional members of the irritans subfamily of mariners in more than 400 arthropod species. Phylogenetic analysis of cloned PCR fragments indicated that relatively recent horizontal transfers had occurred into the lineages of a fruit fly Drosophila ananassae, the horn fly Haematobia irritans, the African malaria vector mosquito Anopheles gambiae, and a green lacewing Chrysoperla plorabunda. Genomic dot-blot analysis revealed that the copy number in these species varies widely, from about 17,000 copies in the horn fly to three copies in D. ananassae. Multiple copies were sequenced from genomic clones from each of these species and four others with related elements. These sequences confirmed the PCR results, revealing extremely similar elements in each of these four species (greater than 88% DNA and 95% amino acid identity). In particular, the consensus sequence of the transposase gene of the horn fly elements differs by just two base pairs out of 1,044 from that of the lacewing elements. The mosquito lineage has diverged from the other Diptera for over 200 Myr, and the neuropteran last shared a common ancestor with them more than 265 Myr ago, so this high similarity implies that these transposons recently transferred horizontally into each lineage. Their presence in only the closest relatives in at least the lacewing lineage supports this hypothesis. Such horizontal transfers provide an explanation for the evolutionary persistence and widespread distribution of mariner transposons. We propose that the ability to transfer horizontally to new hosts before extinction by mutation in the current host constitutes the primary selective constraint maintaining the sequence conservation of mariners and perhaps other DNA-mediated elements.

Amino Acid Sequence↗
PubMed2001

The genome of the Queensland fruit fly Bactrocera tryoni contains multiple representatives of the mariner family of transposable elements.

Representatives of five distinct types of transposable elements of the mariner family were detected in the genomes of the Queensland fruit fly Bactrocera tryoni and its sibling species Bactrocera neohumeralis by phylogenetic analysis of transposase gene fragments. Three mariner types were also found in an additional tephritid, Bactrocera jarvisi. Using genomic library screening and inverse PCR, full-length elements representing the mellifera subfamily (B. tryoni.mar1) and the irritans subfamily (B. tryoni.mar2) were isolated from the B. tryoni genome. Nucleotide consensus sequences for each type were derived from multiple defective copies. Predicted transposase sequences share approximately 23% amino acid identity. B. tryoni.mar1 elements have an estimated copy number of about 900 in the B. tryoni genome, whereas B. tryoni.mar2 element types appear to be present in low copy number.

Amino Acid Sequence↗
PubMed1986

On the evolution and population genetics of hybrid-dysgenesis-causing transposable elements in Drosophila.

Much has been learned about transposable genetic elements in Drosophila, but questions still remain, especially concerning their evolutionary significance. Three such questions are considered here. Has the behaviour of transposable elements been most influenced by natural selection at the level of the organism, the population, or the elements themselves? How did the elements originate in the genome of the species? Why are laboratory stocks different from natural populations with respect to their transposable element composition? No final answers to these questions are yet available, but by focusing on the two families of hybrid dysgenesis-causing elements, the P and I factors, we can draw some tentative conclusions.

Animals↗