Fruit flies diversify their offspring in response to parasite infection

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Science  14 Aug 2015:
Vol. 349, Issue 6249, pp. 747-750
DOI: 10.1126/science.aab1768

Helping the next generation diversify

Parasitism, including infections, can negatively affect fitness. Parents can help the next generation by increasing genetic diversity so that offspring can avoid or fight off these deleterious interactions more easily. For fruit flies, Singh et al. observed that in response to bacterial infection or predation by a parasitic wasp, the next generation showed increased recombination. However, this increase in genetic diversity was not due to increased recombination rates, but rather an unequal allocation of gametes that have undergone recombination. Infection therefore drives plasticity in the parental gametes, resulting in more diverse offspring.

Science, this issue p. 747


The evolution of sexual reproduction is often explained by Red Queen dynamics: Organisms must continually evolve to maintain fitness relative to interacting organisms, such as parasites. Recombination accompanies sexual reproduction and helps diversify an organism’s offspring, so that parasites cannot exploit static host genotypes. Here we show that Drosophila melanogaster plastically increases the production of recombinant offspring after infection. The response is consistent across genetic backgrounds, developmental stages, and parasite types but is not induced after sterile wounding. Furthermore, the response appears to be driven by transmission distortion rather than increased recombination. Our study extends the Red Queen model to include the increased production of recombinant offspring and uncovers a remarkable ability of hosts to actively distort their recombination fraction in rapid response to environmental cues.

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