Evidence for a gene involved in multiple and diverse rearrangements in the Drosophila genus.

In Drosophila, chromosomes have been extensively reorganized during evolution, with most rearrangements affecting the gene order in chromosomal elements but not their gene content. The level of reorganization and the evidence for breakpoint reuse vary both between and within elements. The subito gene stands out as a gene involved in multiple rearrangements both because of its active single-gene transposition and because it is the nearest gene to diverse rearrangements breakpoints. Indeed, subito has undergone three single-gene transpositions and it is the nearest gene to the breakpoints of other single-gene transpositions and of two chromosomal inversions. Given that subito is involved in meiosis and therefore active in the female germ line, the high number of nearby fixed breakages might be related among others to the presumed high accessibility of the subito region to the machinery associated with double-strand breaks repair. A second important contributor would be the reduced and simple regulatory region of subito, which would imply that a fraction of the rearrangements originating from subito nearby breakages would have not affected either its pattern or timing of expression and would have, thus, not resulted in reduced fitness.