What is the impact of transposable elements on host genome variability?
The spread of a transposable element family through a wild population may be of astonishing rapidity. At least three families of transposable genetic elements have recently invaded Drosophila melanogaster worldwide, including the P element. The mechanism has been a process of effectively replicative transposition, and, for the P element, has occurred notwithstanding the sterility induced by unrestricted movement. This element's invasion into D. melanogaster has been accompanied by the development of heterogeneity between P sequences, most of which now have internal deletions. Increasing evidence suggests that some deleted elements can repress P transposition, thereby protecting the host from the harmful effects of complete elements. Such repressing elements may rise to high frequencies in populations as a result of selection at the level of the host. We here investigate selective sweeps invoked by the spread of P sequences in D. melanogaster populations. Numerous high-frequency sites have been identified on the X chromosome, which differ in frequency between populations, and which are associated with repression of P-element transposition. Unexpectedly, sequences adjacent to high-frequency P-element sites do not show reduced levels of genetic diversity, and DNA variability is in linkage equilibrium with the presence or absence of a P element at the adjacent selected site. This might be explained by multiple insertions or through a selection for recombination analogous to that seen in 'hitchhiking'.
Emery
P T
PT
Institute of Genetics, University of Nottingham, Queen's Medical Centre, UK.
Robinson
T E
TE
Duddington
R
R
Brookfield
J F
JF
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D004251:DNA Transposable Elements; D004331:Drosophila melanogaster / Q000235:genetics*; D017344:Genes, Insect; D014644:Genetic Variation; D008969:Molecular Sequence Data; D014960:X Chromosome
D004251:DNA Transposable Elements