Meeting Abstract
The pea aphid, Acyrthosiphon pisum, exhibits several environmentally cued, discrete, alternate phenotypes (polyphenisms) during its life cycle. In the reproductive polyphenism, differences in day length determine whether mothers will produce daughters that reproduce either sexually by laying fertilized eggs (oviparous sexual reproduction), or asexually by allowing oocytes to complete embryogenesis within the mother without fertilization (viviparous parthenogenesis). Among other aspects of the polyphenism, we are interested in the process that specifies sexual versus asexual fate during embryonic development. Two lines of evidence implicate juvenile hormone (JH) in this process: titers of JH correlate with day length (Ishikawa et al. 2012) and topical application of JH can alter reproductive fate (Corbit and Hardie 1985). Together these observations suggest that high titers of JH are responsible for specifying asexual fate. We have confirmed the sufficiency of JH to specify asexual fate and have explored this JH hypothesis further by 1) testing whether JH is also required for the specification of asexual fate during embryonic development and 2) attempting to discriminate among competing models for the role JH plays in the process. As a complementary approach we have used RNAseq to identify genes that are differentially expressed in sexually versus asexually fated embryos, both during the periods of specification and subsequent differentiation. Finally, with an eye toward understanding how this response to photoperiod might evolve, we have begun to characterize a population reported to have lost the ability to produce sexuals in response to shortened day length. Corbit TS and Hardie J. 1985. Entomologia Experimentalis et Applicata 38: 131-135. Ishikawa et al. 2012. Insect Mol Biol 21: 49-60.
