The maternal-effect, selfish genetic element Medea is associated with a composite Tc1 transposon

Maternal-Effect Dominant Embryonic Arrest (“ Medea ”) factors are selfish nuclear elements that combine maternal-lethal and zygotic-rescue activities to gain a postzygotic survival advantage. We show that Medea 1 activity in Tribolium castaneum is associated with a composite Tc1 transposon inserted just downstream of the neurotransmitter reuptake symporter bloated tubules ( blot ), whose Drosophila ortholog has both maternal and zygotic functions. The 21.5-kb insertion contains defective copies of elongation initiation factor-3 , ATP synthase subunit C , and an RNaseD -related gene, as well as a potentially intact copy of a prokaryotic DUF1703 gene. Sequence comparisons suggest that the current distribution of Medea 1 reflects global emanation after a single transpositional event in recent evolutionary time. The Medea system in Tribolium represents an unusual type of intragenomic conflict and could provide a useful vehicle for driving desirable genes into populations.