Developmental Biology

Alternative Route to Male Killing

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Science  10 Oct 2008:
Vol. 322, Issue 5899, pp. 169
DOI: 10.1126/science.322.5899.169c

Wildly distorted sex ratios in certain insects—where as few as 1 male per 100 offspring are produced, dramatically altering patterns of mate competition—are caused by “male-killing” bacteria. Male killing in the parasitic wasp Nasonia vitripennis, in which males develop from unfertilized eggs by parthenogenesis, is caused by the bacterium Arsenophonus nasoniae.

Ferree et al. show that in infected Nasonia females, unfertilized eggs die during early embryogenesis because of a lack of centrosome activity and the consequent disarray of cell division. In diploid species, centrosomes are generally provided by the sperm. In Nasonia, which have haploid eggs, the centrosomes are derived from “accessory nuclei.” Accessory nuclei, vesicular organelles that are formed from the oocyte nuclear membrane that sequester centrosome components, are intact in both infected and uninfected wasps, suggesting that Arsenophonus interferes with events downstream of their formation. Indeed, haploid male eggs can be rescued by the delivery of paternal centrosomes. Thus, Arsenophonus interferes with the development of unfertilized eggs rather than targeting maleness. — GR

Curr. Biol. 18, 1409 (2008).

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