Distribution and structure of cloned P elements from theDrosophila melanogasterP strain π₂

Abstract

P transposable elements of Drosophila melanogaster cloned from the strong P strain ?7 2 have been analysed. The structures and chromosomal locations of 26 of the 30-50 elements estimated to be present in n 2 have been determined. At one location two elements are inserted 100 base pairs (bp) apart, and in a second location two elements are only separated by the 8 bp duplicated upon P-element insertion. In addition to 2-9 kilobasepair (kbp) elements, elements with 14 different internal deletions from 1-3 to 2-3 kbp in size have been isolated. There are 7 copies of the 2-9 kbp element, 2 copies each of 5 internally deleted elements and a single copy of 9 internally deleted elements. One of the elements found twice is the KP element, which may play a role in the regulation of hybrid dysgenesis in strains which contain many copies of this element. Apart from internal deletions the elements are extremely homogeneous in DNA sequence, with only 2 single base polymorphisms detected twice each in over 16 kbp of P-element sequence. Although transpositions are infrequent in an inbred P cytotype strain such as n 2 , the distribution of these cloned elements indicates that when the genomic library was made, the strain was polymorphic with respect to element location. The distribution and structures of the element are discussed with respect to models for regulation of P-element transposition.

The relationship between DNA structural variation and activities of P elements in P and Q strains of Drosophila melanogaster

“…the case of a strong P strain r2, in which the numbers of P elements are approximately 30-SO, seven out of 26 P elements were complete P elements (O'Hare & Rubin, 1983;O'Hare et al, 1992). The ratio of complete P elements to total P elements is lower in NP280 and WY1 13.…”

“…The number of complete P elements in a reference P strain, jr2, was estimated as one-third of the total number of P elements. Sequences of P elements from Drosophila melanogaster from diverse geographical locations are homogeneous and very similar to those of Drosophila willistoni (O'Hare & Rubin, 1983;Iwano et a!., 1984;Sakoyama etal., 1985;Black etal., 1987;Daniels eta!., 1990;O'Hare et al, 1992). Moreover, the distribution of P elements is restricted in Drosophila ,neianogaster, and other closely related species have no P element sequence (Brookfield et al, 1984).…”

DrosophilaP element: Transposition, regulation and evolution

“…Gloor, personal communication). The analysis of the P element complement of a natural P strain (7r2) has also suggested that the complete P element could play a role in the P cytotype determination of this strain, since determinants of P cytotype have been genetically located on all maj or chromosomes and the complete P element is the only type of element also present on all chromosomes (O'Hare et al, 1992). P elements derived from natural chromosomes have also been genetically isolated.…”

Copy number of P elements, KP/full-sized P element ratio and their relationships with environmental factors in Brazilian Drosophila melanogaster populations

“…P strains exhibit low to high levels of P activity potential and low levels of P susceptibility, while Q strains show extremely low levels of both P activity and P susceptibility. Both types have been shown to possess 30-50 copies of P elements per genome, of which about a third are the 2.9 kb elements and the rest are deleted derivatives (Bingham et al, 1982;Black et al, 1987;O'Hare et al, 1992). M and M 0 strains do not exhibit any significant level of P activity.…”