Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2008
Publication Date: 7/15/2008
Citation: Lorenzen, M.D., Gnirke, A., Margolis, J., Campbell, M., Garnes, J., Stuart, J.J., Aggarwal, R., Richards, S., Park, Y., Beeman, R.W. 2008. The maternal-effect, selfish genetic element Medea in Tribolium is a Tc1 transposon. Proceedings of the National Academy of Sciences 105: 10085-10089. Interpretive Summary: Selfish genetic elements are naturally occurring agents that can impose limits on insect population growth and viability. We discovered a new type of selfish gene in flour beetles that causes the death of hatchlings, and depends both on the susceptibility of progeny larvae and on the selective lethal influence of the mother. We have now determined the molecular basis for this unusual larvicidal mechanism, namely the insertion of a large segment of DNA next to a beetle gene required for nervous system function. The inserted segment of DNA contains another gene normally found only in bacteria. A better understanding of how insect populations are regulated in nature could suggest new ways to control pest populations in mills and warehouses.
Technical Abstract: Previously characterized selfish genes act prezygotically and are independent of cytotype. Selfish “Medea” (M) elements are unique in combining maternal and zygotic components to gain a postzygotic survival advantage. We show that Medea1 activity in Tribolium castaneum is associated with a composite Tc1 transposon inserted just downstream of a neurotransmitter reuptake symporter with both maternal and zygotic functions. The insertion contains defective copies of elongation initiation factor-3, ATP synthase subunit C, RnaseD, and a prokayrotic DUF1703 gene. Sequence comparisons suggest that the current distribution of M1 reflects global emanation following a single transpositional event in recent evolutionary time. The Medea system in Tribolium represents an unusual type of intra-genomic conflict, and could provide a vehicle for driving desirable genes into populations.