Different evolutionary behaviour of P element subfamilies: M-type and O-type elements in Drosophila bifasciata and D. imaii.
Distribution and variation of two P-element subfamilies designated M-type and O-type elements were investigated in Drosophila bifasciata (Db) and its relatives. PCR screening revealed that full-sized and internally deleted elements of both types occur in three geographic Db strains and in the related species, D. imaii (Di). Molecular analyses indicate differences in the evolutionary behaviour of the two P-element types. Internally deleted M-type elements fall into two size classes present in all three Db strains. In contrast, internally deleted O-type elements vary between the strains in number and length. With respect to genomic location, M-type elements seem to be restricted to conserved euchromatic sites, whereas the positions of O-type elements appear to be geographically variable. In one strain of Db (Italy), O-type elements seem to accumulate in the heterochromatin. Sequencing of a 397-bp segment shows intra- and interspecific divergence of M-type elements. In a 452-bp segment of the O-type elements, no substitutions were found, neither within nor between species. This finding suggests recent introgression of O-type elements via hybridization between Db and Di. Sequence identity and variation in chromosomal locations among different copies imply that O-type elements are transpositionally active. For M-type elements, genomic mobility cannot be proved. In a survey of several other taxa, no O-type-related sequences were detected so far. Therefore, the origin of the O-type subfamily remains unknown, whereas the source of M-type elements can be traced back to the genus Scaptomyza.
Haring
E
E
Institut für Allgemeine Biologie, Abteilung Genetik, Medizinische Fakultät, Universität Wien, Austria.
Hagemann
S
S
Pinsker
W
W
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002874:Chromosome Mapping; D004251:DNA Transposable Elements / Q000235:genetics*; D004330:Drosophila / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction
D004251:DNA Transposable Elements