A genome-wide survey of genetic instability by transposition in Drosophila hybrids

Abstract

Hybridization between species is a genomic instability factor involved in increasing mutation rate and new chromosomal rearrangements. Evidence of a relationship between interspecific hybridization and transposable element mobilization has been reported in different organisms, but most studies are usually performed with particular TEs and do not discuss the real effect of hybridization on the whole genome. We have therefore studied whole genome instability of Drosophila interspecific hybrids, looking for the presence of new AFLP markers in hybrids. A high percentage (27-90%) of the instability markers detected corresponds to TEs belonging to classes I and II. Moreover, three transposable elements (Osvaldo, Helena and Galileo) representative of different families, showed an overall increase of transposition rate in hybrids compared to parental species. This research confirms the hypothesis that hybridization induces genomic instability by transposition bursts and suggests that genomic stress by transposition could contribute to a relaxation of mechanisms controlling TEs in the Drosophila genome.

Figure 1. Hybrid crosses and an example of AFLP gel showing bands of parental species and hybrids.

A) Interspecific cross and backcrosses used in experiments B) Selective PCR AFLP band patterns using primers with selective nucleotides GG (EcoRI) and CTG (MseI). The arrows indicate two instability markers detected in hybrids from backcross 1 as an example. MWM, molecular weight marker; Dk, D. koepferae; Db, D. buzzatii; HF1, F1 hybrids; BC1, backcross 1.

Figure 2. Markers in hybrids and parental species.

Figure 3. Percentage of transposition markers in hybrid.