| PubMed Abstract |
Over twenty distinct families of long terminal direct repeat (LTR)-containing retrotransposons have been identified in Drosophila
melanogaster. While there have been extensive analyses of retrotransposon transcription in cultured cells, there have been
few studies of the spatial expression of retrotransposons during normal development. Here we report a detailed analysis of
the spatial expression patterns of fifteen families of retrotransposons during Drosophila melanogaster embryogenesis (17.6,
297, 412, 1731, 3S18, blood, copia, gypsy, HMS Beagle, Kermit/flea, mdg1, mdg3, opus, roo/B104 and springer). In each case,
analyses were carried out in from two to four wild-type strains. Since the chromosomal insertion sites of any particular family
of retrotransposons vary widely among wild-type strains, a spatial expression pattern that is conserved among strains is likely
to have been generated through interaction of host transcription factors with cis-regulatory elements resident in the retrotransposons
themselves. All fifteen families of retrotransposons showed conserved patterns of spatially and temporally regulated expression
during embryogenesis. These results suggest that all families of retrotransposons carry cis-acting elements that control their
spatial and temporal expression patterns. Thus, transposition of a retrotransposon into or near a particular host gene-possibly
followed by an excision event leaving behind the retrotransposon's cis-regulatory sequences-might impose novel developmental
control on such a host gene. Such a mechanism would serve to confer evolutionarily significant alterations in the spatio-temporal
control of gene expression.
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