Natural repressors of P-induced hybrid dysgenesis in Drosophila melanogaster: a model for repressor evolution.
Type I repressors control P element transposition and comprise full length elements and elements with small 3' deletions in the final exon. Using a sensitive assay for measuring the strength of repression of P element transposition in somatic and germline tissues, we have isolated and characterized a naturally occurring type I repressor element from a Q population of Drosophila melanogaster. We demonstrate that the almost complete repression of transposition in this population is a mixture of KP elements with intermediate levels of repression, and the strong contribution of a single 2.6 kb P element deletion derivative, which we call SR (Strong Repressor). A deletion in the final intron of SR allows for the constitutive production of a putative 75 kDa repressor protein in germline tissues in addition to the production of the 66 kDa repressor in the soma, which would result in a biparental mode of inheritance of repression. Based on the four observed classes of natural Q populations, we propose a model in which populations containing SR-like elements, capable of producing strong type I repressor constitutively, have a selective advantage over populations which rely either on maternally transmitted P cytotype or on KP-induced weak levels of repression. Such populations may subsequently spread and constitute an evolutionary stable strategy for the repression of hybrid dysgenesis in Drosophila melanogaster.
Corish
P
P
Department of Genetics, University of Leicester, UK.
Black
D M
DM
Featherston
D W
DW
Merriam
J
J
Dover
G A
GA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002875:Chromosomes; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D005127:Eye Color / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D012097:Repressor Proteins / Q000235:genetics*; D019076:Transgenes
D004251:DNA Transposable Elements; D012097:Repressor Proteins