A laterally transferred viral gene modifies aphid wing plasticity

Organisms often respond to changing environments by altering development of particular traits. These plastic traits exhibit genetic variation, i.e., genotypes respond differently to the same environmental cues. Theoretical studies have demonstrated the importance of this variation, which is targeted by natural selection, in adapting plastic responses to maximize fitness. However, little is known about the underlying genetic mechanisms. We identify two laterally transferred genes that contribute to variation in a classic example of phenotypic plasticity: the pea aphid’s ability to produce winged offspring in response to crowding. We discovered that aphid genotypes vary extensively for this trait, and that aphid genes of viral origin are upregulated in response to crowding solely in highly-inducible genotypes. We knocked-down expression of these genes to demonstrate their functional role in wing plasticity. Through phylogenetic analysis we found that these genes likely originated from a v...