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The Drosophila mojavensis Bari3 transposon: distribution and functional characterization.

Palazzo A, Moschetti R, Caizzi R, Marsano RM - Mob DNA (2014)

Bottom Line: The results suggest that Bari3 is transposition-competent.Our results strongly suggest that Bari3 is an independent element that has generated genomic diversity in D. mojavensis.These results will aid the studies on the Bari family of transposons, which is intriguing for its widespread diffusion in Drosophilids coupled with a structural diversity generated during the evolution of Bari-like elements in their host genomes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dipartimento di Biologia, Università degli Studi di Bari "Aldo Moro", Via Orabona 4, 70125 Bari, Italy.

ABSTRACT

Background: Bari-like transposons belong to the Tc1-mariner superfamily, and they have been identified in several genomes of the Drosophila genus. This transposon's family has been used as paradigm to investigate the complex dynamics underlying the persistence and structural evolution of transposable elements (TEs) within a genome. Three structural Bari variants have been identified so far and can be distinguished based on the organization of their terminal inverted repeats. Bari3 is the last discovered member of this family identified in Drosophila mojavensis, a recently emerged species of the Repleta group of the genus Drosophila.

Results: We studied the insertion pattern of Bari3 in different D. mojavensis populations and found evidence of recent transposition activity. Analysis of the transposase domains unveiled the presence of a functional nuclear localization signal, as well as a functional binding domain. Using luciferase-based assays, we investigated the promoter activity of Bari3 as well as the interaction of its transposase with its left terminus. The results suggest that Bari3 is transposition-competent. Finally we demonstrated transposase transcript processing when the transposase gene is overexpressed in vivo and in vitro.

Conclusions: Bari3 displays very similar structural and functional features with its close relative, Bari1. Our results strongly suggest that Bari3 is an independent element that has generated genomic diversity in D. mojavensis. It can autonomously transcribe its transposase gene, which in turn can localize in the nucleus and bind the terminal inverted repeats of the transposon. Nevertheless, the identification of an unpredicted spliced form of the Bari3 transposase transcript allows us to hypothesize a control mechanism of its mobility based on mRNA processing. These results will aid the studies on the Bari family of transposons, which is intriguing for its widespread diffusion in Drosophilids coupled with a structural diversity generated during the evolution of Bari-like elements in their host genomes.

No MeSH data available.


Related in: MedlinePlus

Bari3 distribution in the genome of Drosophila mojavensis. A) Schematic representation of the Bari3 transposon. The EcoRI site used for the genomic analyses and the position of the probe (black bar) are showed. Dashed bars represent the transposon fragments tested in this work. B) Southern blot hybridization of DNA samples extracted from ten D. mojavensis populations MWM, 1Kb DNA molecular weight marker (Promega). C) Fluorescence In Situ Hybridization (FISH) on polytene chromosomes prepared from five D. mojavensis strains. Merged images (DAPI and Cy3) are shown. Hybridization signals are pseudo-colored in red. The subspecies color code legend reported in the bottom of the figure refers to the hybridization experiments.
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Figure 2: Bari3 distribution in the genome of Drosophila mojavensis. A) Schematic representation of the Bari3 transposon. The EcoRI site used for the genomic analyses and the position of the probe (black bar) are showed. Dashed bars represent the transposon fragments tested in this work. B) Southern blot hybridization of DNA samples extracted from ten D. mojavensis populations MWM, 1Kb DNA molecular weight marker (Promega). C) Fluorescence In Situ Hybridization (FISH) on polytene chromosomes prepared from five D. mojavensis strains. Merged images (DAPI and Cy3) are shown. Hybridization signals are pseudo-colored in red. The subspecies color code legend reported in the bottom of the figure refers to the hybridization experiments.

Mentions: The DNA extracted en masse from ten D. mojavensis populations was digested with the endonuclease EcoRI and analyzed by Southern blot hybridization. We used an internal 592-bp fragment (Figure 2A) as a probe, subcloned from the full-length Bari3 element. To avoid nonspecific detection of divergent sequences related to transposon relics, we applied high-stringency conditions for our hybridization experiments. The pattern obtained is shown in Figure 2 (panel B) and clearly indicates variability in both the copy number and genomic distribution of the Bari3 elements among the populations analyzed. We estimate that the baja and wrigleyi subspecies contain from 5 to 11 copies of the transposon, while the mojavensis and sonorensis subspecies contain 1 to 3 copies of Bari3. As expected, only very faint bands can be detected in the distant species D. melanogaster and D. pseudoobscura, confirming that the Bari3 element of D. mojavensis is quite divergent from the Bari3 element of D. pseudoobscura and from the Bari1 and Bari2 elements of D. melanogaster[14].


The Drosophila mojavensis Bari3 transposon: distribution and functional characterization.

Palazzo A, Moschetti R, Caizzi R, Marsano RM - Mob DNA (2014)

Bari3 distribution in the genome of Drosophila mojavensis. A) Schematic representation of the Bari3 transposon. The EcoRI site used for the genomic analyses and the position of the probe (black bar) are showed. Dashed bars represent the transposon fragments tested in this work. B) Southern blot hybridization of DNA samples extracted from ten D. mojavensis populations MWM, 1Kb DNA molecular weight marker (Promega). C) Fluorescence In Situ Hybridization (FISH) on polytene chromosomes prepared from five D. mojavensis strains. Merged images (DAPI and Cy3) are shown. Hybridization signals are pseudo-colored in red. The subspecies color code legend reported in the bottom of the figure refers to the hybridization experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4120734&req=5

Figure 2: Bari3 distribution in the genome of Drosophila mojavensis. A) Schematic representation of the Bari3 transposon. The EcoRI site used for the genomic analyses and the position of the probe (black bar) are showed. Dashed bars represent the transposon fragments tested in this work. B) Southern blot hybridization of DNA samples extracted from ten D. mojavensis populations MWM, 1Kb DNA molecular weight marker (Promega). C) Fluorescence In Situ Hybridization (FISH) on polytene chromosomes prepared from five D. mojavensis strains. Merged images (DAPI and Cy3) are shown. Hybridization signals are pseudo-colored in red. The subspecies color code legend reported in the bottom of the figure refers to the hybridization experiments.
Mentions: The DNA extracted en masse from ten D. mojavensis populations was digested with the endonuclease EcoRI and analyzed by Southern blot hybridization. We used an internal 592-bp fragment (Figure 2A) as a probe, subcloned from the full-length Bari3 element. To avoid nonspecific detection of divergent sequences related to transposon relics, we applied high-stringency conditions for our hybridization experiments. The pattern obtained is shown in Figure 2 (panel B) and clearly indicates variability in both the copy number and genomic distribution of the Bari3 elements among the populations analyzed. We estimate that the baja and wrigleyi subspecies contain from 5 to 11 copies of the transposon, while the mojavensis and sonorensis subspecies contain 1 to 3 copies of Bari3. As expected, only very faint bands can be detected in the distant species D. melanogaster and D. pseudoobscura, confirming that the Bari3 element of D. mojavensis is quite divergent from the Bari3 element of D. pseudoobscura and from the Bari1 and Bari2 elements of D. melanogaster[14].

Bottom Line: The results suggest that Bari3 is transposition-competent.Our results strongly suggest that Bari3 is an independent element that has generated genomic diversity in D. mojavensis.These results will aid the studies on the Bari family of transposons, which is intriguing for its widespread diffusion in Drosophilids coupled with a structural diversity generated during the evolution of Bari-like elements in their host genomes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dipartimento di Biologia, Università degli Studi di Bari "Aldo Moro", Via Orabona 4, 70125 Bari, Italy.

ABSTRACT

Background: Bari-like transposons belong to the Tc1-mariner superfamily, and they have been identified in several genomes of the Drosophila genus. This transposon's family has been used as paradigm to investigate the complex dynamics underlying the persistence and structural evolution of transposable elements (TEs) within a genome. Three structural Bari variants have been identified so far and can be distinguished based on the organization of their terminal inverted repeats. Bari3 is the last discovered member of this family identified in Drosophila mojavensis, a recently emerged species of the Repleta group of the genus Drosophila.

Results: We studied the insertion pattern of Bari3 in different D. mojavensis populations and found evidence of recent transposition activity. Analysis of the transposase domains unveiled the presence of a functional nuclear localization signal, as well as a functional binding domain. Using luciferase-based assays, we investigated the promoter activity of Bari3 as well as the interaction of its transposase with its left terminus. The results suggest that Bari3 is transposition-competent. Finally we demonstrated transposase transcript processing when the transposase gene is overexpressed in vivo and in vitro.

Conclusions: Bari3 displays very similar structural and functional features with its close relative, Bari1. Our results strongly suggest that Bari3 is an independent element that has generated genomic diversity in D. mojavensis. It can autonomously transcribe its transposase gene, which in turn can localize in the nucleus and bind the terminal inverted repeats of the transposon. Nevertheless, the identification of an unpredicted spliced form of the Bari3 transposase transcript allows us to hypothesize a control mechanism of its mobility based on mRNA processing. These results will aid the studies on the Bari family of transposons, which is intriguing for its widespread diffusion in Drosophilids coupled with a structural diversity generated during the evolution of Bari-like elements in their host genomes.

No MeSH data available.


Related in: MedlinePlus