Figure 3.

Homologous recombination of two Mutators caused a genomic inversion. An autonomous MuLE should have a terminal invert repeat (TIR) and 9–11 bp target site duplication (TSD). However, the TSDs of these two MuLEs (MU1 and MU2) are completely different. Sequence comparison between MU1 and MU2 indicated that two elements exchanged one side of TIR and TSD. Therefore, we propose that homologous recombination caused this inversion: Two identical MuLEs inserted into each side of these three genes (Gene 51, 52 and 53) independently. Subsequently, homologous recombination took place between the transposed enzyme coding sequences of these two MuLEs, finally leading to an inversion. MU1 and MU2 contain MuLE elements and MU1′ and MU2′ contain the original elements that were present prior to the recombination event.