Abstract
A highly repetitive DNA element, homologous to the mariner transposon of Drosophila mauritiana was found in the intron of the gene for cecropin A, an antibacterial peptide from the Cecropia moth. The mariner-like elements (MLE) represent a homogeneous population with a copy number of about 1000/genome. Sequencing analysis showed it to be 1255 base pairs long, including 38-base pair terminal inverted repeats. The MLE contains a defective reading frame. Nevertheless, the putative product is clearly homologous to the predicted translation product encoded by mariner. In consonance is also the fact that the inverted repeats are highly conserved between the two elements and that the overall DNA homology is 48%. Since the mariner element is present in several Drosophila species closely related to Drosophila melanogaster and since MLE is present in the lepidopteran Cecropia, a route of horizontal transfer is indicated rather than vertical transmission from a common ancestor. This suggests the possible use of mariner for the construction of an interspecies vector.
Highlights
A highly repetitive DNA element, homologous to the 1986; Bryan et al, 1987; Bryan and Hartl, 1988; Medhora et mariner transposon of Drosophilamauritianawas al., 1988;Hartl, 1989).The element, named mariner, has been found in the intron of the gene for cecropin A, an found in several Drosophila species but surprisingly not in D
Mariner-like elements (MLE) represent a homogene- The discovery of mariner has introduced a novel class of ous population with a copy numberofabout lOOO/ transposable elements that represent some of the smallest genome
We here report that during our analysis of the gene for preprocecropin A, a precursor to an antibacterial peptide from the lepidopteran H. cecropia,we found a highly repetitive DNA element homologous to the mariner element of D. mauritiana
Summary
Gaster and since MLE is present in the lepidopteran For procedures,see accompanyingpaper(Gudmundsson et al., Cecropia, a route of horizontal transfer is indicated 1991) and figure legends. Some of these elements have been detected by their ability to cause puter analysis of the intron sequence lead first to thediscovery of two almost perfect inverted repeats Many of the transposable elements found in D. melanocomplete DNA sequence of the MLE, including the inverted repeats. The inverted repeats of the gaster can be detected in related species In D. mauritiana, which is closely related ing these extra nucleotides, Fig. 3 shows that positions 7-35 to D. melanogaster, an insertion of a transposable element of the inverted repeat of the MLE are68% homologousto the has been shown to be the cause of somatic instability in the corresponding 28-bp repeat of mariner. Using isolated MLE DNA as a probe, genomic Southern analyses
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