Based on previous estimates, we expect 63/100 of these elements to be active, with 54/100 exhibiting particularly high levels of activity [ 31].
To confirm the absence of the 412 element, known to be active in some populations of D. simulans (Vieira and Biémont 1997), we performed a de novo assembly of the TEs directly from the reads of the 2012 D. simulans genome project.
Previous work has identified only a subset of elements likely to be active, due to genomic position, sequence mutation, or methylation status [ 13].
The internal K1-4GC' arrays do not appear to affect mobilization efficiency, as all SVA elements reported to be active in the literature (H2D, H11D [ 8], H19_27 and H10_1 [ 7]) differ with respect to their presence and number (Additional file 2).
In contrast, only two conifer-specific LTR retroelements in the BACs (PtGypsyX1 and PtCopiaX1) may be still active after 140 million years, and the IFG7 family of gypsy-like elements appears to be active in both subgenera of Pinus [ 34], which diverged approximately 110 million years ago [ 2].
In M. perniciosa, transposable elements were reported to be active elements that may contribute to genetic variability of this pathogen [ 20].
Hence, it is not surprising that studies have shown the elements most likely to be active are those that have most recently inserted and therefore may not have become fixed in the population [ 11- 13].
Recently, the miniature inverted-repeat transposable element mPing was shown to be active in the japonica strain Gimbozu EG4 where it had accumulated more than 1000 copies.
Taken together, these data indicate an individual genome may contain upwards of 90 non-reference full length L1 elements with the potential to be active.
Ty1-copia elements have been found to be active in several gymnosperm species, potentially facilitating the creation of retrogenes [ 32]. hAT-like genes, closely related to SLEEPERs contain at least one intron in their coding sequence.
