Regulation of mariner transposition: the peculiar case of Mos1.

BACKGROUND: Mariner elements represent the most successful family of autonomous DNA transposons, being present in various plant and animal genomes, including humans. The introduction and co-evolution of mariners within host genomes imply a strict regulation of the transposon activity. Biochemical data accumulated during the past decade have led to a convergent picture of the transposition cycle of mariner elements, suggesting that mariner transposition does not rely on host-specific factors. This model does not account for differences of transposition efficiency in human cells between mariners. We thus wondered whether apparent similarities in transposition cycle could hide differences in the intrinsic parameters that control mariner transposition. PRINCIPAL FINDINGS: We find that Mos1 transposase concentrations in excess to the Mos1 ends prevent the paired-end complex assembly. However, we observe that Mos1 transposition is not impaired by transposase high concentration, dismissing the idea that transposase over production plays an obligatory role in the down-regulation of mariner transposition. Our main finding is that the paired-end complex is formed in a cooperative way, regardless of the transposase concentration. We also show that an element framed by two identical ITRs (Inverted Terminal Repeats) is more efficient in driving transposition than an element framed by two different ITRs (i.e. the natural Mos1 copy), the latter being more sensitive to transposase concentration variations. Finally, we show that the current Mos1 ITRs correspond to the ancestral ones. CONCLUSIONS: We provide new insights on intrinsic properties supporting the self-regulation of the Mos1 element. These properties (transposase specific activity, aggregation, ITR sequences, transposase concentration/transposon copy number ratio...) could have played a role in the dynamics of host-genomes invasion by Mos1, accounting (at least in part) for the current low copy number of Mos1 within host genomes

Quantitative Trait Loci for Cuticular Hydrocarbons Associated With Sexual Isolation Between Drosophila simulans and D. sechellia

The identification of genes with large effects on sexual isolation and speciation is an important link between classic evolutionary genetics and molecular biology. Few genes that affect sexual isolation and speciation have been identified, perhaps because many traits influencing sexual isolation are complex behaviors. Cuticular hydrocarbons (CHs) of species of the Drosophila melanogaster group play a large role in sexual isolation by functioning as contact pheromones influencing mate recognition. Some of the genes that play key roles in determining species-specific CHs have been identified. We have performed separate quantitative trait locus (QTL) analyses of 7-tricosene (7-T) and 7,11-heptacosadiene (7,11-HD), the two major female CHs differing between D. simulans and D. sechellia. We find that ∼40% of the phenotypic variance in each CH is associated with two to four chromosomal regions. A region on the right arm of chromosome 3 contains QTL that affect both traits, but other QTL are in distinct chromosomal regions. Epistatic interactions were detected between two pairs of QTL for 7,11-HD such that if either were homozygous for the D. simulans allele, the fly was similar to D. simulans in phenotype, with a low level of 7,11-HD. We discuss the location of these regions with regard to candidate genes for CH production, including those for desaturases

Additional file 1: Table S1. of Mariner transposons are sailing in the genome of the blood-sucking bug Rhodnius prolixus

Transposases sequences used as queries in the TBLASTN search (GI, family and subfamily) with the number of clusters obtained by a reciprocal BLASTX using the longest element of each cluster (PDF 30 kb

Diversity and evolution of mariner-like elements in aphid genomes

Abstract Background Although transposons have been identified in almost all organisms, genome-wide information on mariner elements in Aphididae remains unknown. Genomes of Acyrthosiphon pisum, Diuraphis noxia and Myzus persicae belonging to the Macrosiphini tribe, actually available in databases, have been investigated. Results A total of 22 lineages were identified. Classification and phylogenetic analysis indicated that they were subdivided into three monophyletic groups, each of them containing at least one putative complete sequence, and several non-autonomous sublineages corresponding to Miniature Inverted-Repeat Transposable Elements (MITE), probably generated by internal deletions. A high proportion of truncated and dead copies was also detected. The three clusters can be defined from their catalytic site: (i) mariner DD34D, including three subgroups of the irritans subfamily (Macrosiphinimar, Batmar-like elements and Dnomar-like elements); (ii) rosa DD41D, found in A. pisum and D. noxia; (iii) a new clade which differs from rosa through long TIRs and thus designated LTIR-like elements. Based on its catalytic domain, this new clade is subdivided into DD40D and DD41D subgroups. Compared to other Tc1/mariner superfamily sequences, rosa DD41D and LTIR DD40-41D seem more related to maT DD37D family. Conclusion Overall, our results reveal three clades belonging to the irritans subfamily, rosa and new LTIR-like elements. Data on structure and specific distribution of these transposable elements in the Macrosiphini tribe contribute to the understanding of their evolutionary history and to that of their hosts

The PEC contains two ITRs and two transposases. A.

<p>Sequence of the double-strand oligonucleotide (short-PC: short pre-cleaved ITR) used in EMSAs. TS: transferred strand; NTS: non-transferred strand. The 3′ITR is shown in bold, with a 3-bases overhang in 3′ of the TS <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043365#pone.0043365-Dawson1" target="_blank">[14]</a>. Inner sequence: narrow letters. The long-PC oligonucleotide (long pre-cleaved ITR) has the same sequence, with a longer inner sequence. An asterisk marks the position of the ³²P labeling. <b>B.</b> Short/long transposase analyses. EMSAs were performed with 250 nM of short-PC (short pre-cleaved) labeled ITR (as a probe), and 250 nM of purified MBP-MOS1. Lane 1: probe alone, Lane 2: complexes assembly without factor-Xa treatment. Lanes 3 to 5, complexes were subjected to factor-Xa cleavage (1H, 2H and 5H respectively) before electrophoresis. The MOS1 dimer in the PEC was assayed here. We have taken advantage of the fact that the MBP-MOS1 fusion protein contains a cleavage site for factor-Xa between MBP and MOS1. If the PEC contains MBP-MOS1 dimer, then a three-band pattern is expected after cleavage of factor-Xa: one band containing uncleaved MBP-MOS1 (in native PEC, as seen at T = 0), one band containing one cleaved and one uncleaved MOS1 in the complex, and one band containing two cleaved MOS1s in the complex. SEC2 disappears as a result of the factor-Xa cleavage, since it contains two MBP-MOS1 molecules that are converted into MOS1 molecules by the release of the MBP moiety, giving bands with faster mobility in electrophoresis. The proteins present in the various PECs are drawn on the right. <b>C.</b> Short/long ITR analyses. EMSAs were performed with 250 nM of purified MBP-MOS1 and 250 nM of short/long ITR combinations (as indicated). The number of ITRs in the PEC is assayed here. The ITRs present in the complexes are drawn on the right. Short-PC: short pre-cleaved ITR. Long-PC: long pre-cleaved ITR. S*: labeled short-PC. L*: labeled long-PC.</p

5′ ITR sequences of the <i>Mos1</i>-tribe elements.

<p>The accession numbers are given on the right. The host species is given in brackets. Ds: <i>Drosophila simulans</i>; Md: <i>Musca domestica</i>; Zt: <i>Zaprionus tuberculatus</i>; Dm: <i>Drosophila mauritiana</i>; Dse: <i>Drosophila sechelia</i>; Dt: <i>Drosophila tsacasi</i>; Bg: <i>Blattella germanica.</i> The differences between the consensus and the element are in underlined lower cases letters. The Mos1 sequence and accession number are in bold.</p

ITR sequence analyses.

<p>Sequences of the <i>Mos1-</i>tribe ITRs (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043365#pone-0043365-t001" target="_blank">Tables 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043365#pone-0043365-t002" target="_blank">2</a>) were aligned to obtain 5′ and 3′ITRs logos and consensus. The majority rule was used to define variable positions, which are 1, 2, 3, 14, 18, and 26 in the 5′ITR and 1, 2, 3, and 14 in the 3′ITR. Doing so, the 24 conserved positions in <i>Mos1</i> ITRs are conserved in the consensus ITRs (black letters). When compared to each other, 5′ and 3′ consensus ITRs contain three clear differences at positions 1, 18, and 26, which are the same as that found in <i>Mos1</i> ITRs (blue letters). Position 16 (purple letter) in the 5′ consensus remains ambiguous, being either a G (as in the 5′ <i>Mos1</i> ITR) or a T (as in the 3′ <i>Mos1</i> ITR).</p