Two distinct P element subfamilies in the genome of Drosophila bifasciata.
The genome of Drosophila bifasciata harbours two distinct subfamilies of P-homologous sequences, designated M-type and O-type elements based on similarities to P element sequences from other species. Both subfamilies have some general features in common: they are of similar length (M-type: 2935 bp, O-type: 2986 bp), are flanked by direct repeats of 8 bp (the presumptive target sequence), contain terminal inverted repeats, and have a coding region consisting of four exons. The splice sites are at homologous positions and the exons have the coding capacity for proteins of 753 amino acids (M-type) and 757 amino acids (O-type). It seems likely that both types of element represent functional transposons. The nucleotide divergence of the two P element subfamilies is high (31%). The main structural difference is observed in the terminal inverted repeats. Whereas the termini of M-type elements consists of 31 bp inverted repeats, the inverted repeats of the O-type elements are interrupted by non-complementary stretches of DNA, 12 bp at the 5' end and 14 bp at the 3' end. This peculiarity is shared by all members of the O-type subfamily. Comparison with other P element sequences indicates incongruities between the phylogenies of the species and the P transposons. M-type and O-type elements apparently have no common origin in the D. bifasciata lineage. The M-type sequence seems to be most closely related to the P element from Scaptomyza pallida and thus could be considered as a more recent invader of the D. bifasciata gene pool. The origin of the O-type elements cannot be unequivocally deduced from the present data.(ABSTRACT TRUNCATED AT 250 WORDS)
Hagemann
S
S
Institut für Allgemeine Biologie, Abt. Genetik, Medizinische Fakultät, Universität Wien, Austria.
Miller
W J
WJ
Pinsker
W
W
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000032:analysis / Q000235:genetics; D004251:DNA Transposable Elements; D004330:Drosophila / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics; D005091:Exons; D016678:Genome; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D004251:DNA Transposable Elements; D004247:DNA