Grisilda Bakiasi
Biology Department
Advisor's name: Gregory Davis

JH Regulation

In the G. Davis laboratory we study the evolution of development using the pea aphid, Acyrthosiphon pisum, as a model organism. The pea aphid is famous for its phenotypic plasticity. In one example, when exposed to short nights mothers produce embryos that will develop as asexual females, whereas when exposed to long nights mothers produce embryos that will develop as sexual females. A candidate for mediating this process is the insect hormone, Juvenile Hormone (JH). JH is best known for its role as a status quo hormone which determines the state of the aphid after each molt during development; if there are high levels of JH at molting the individual remains a nymph, and if there are low levels of JH the individual becomes an adult. In the context of reproductive fate JH is thought to induce the asexual fate: topically applied, JH can transform embryos that should have developed as sexual aphids into asexuals; additionally, JH titers inversely correlate with night length. Together this evidence suggests that JH mediates the induction of asexual fate under short night conditions. However, it remains unclear how JH titer is regulated by photoperiod.  This summer, in order to gain knowledge of how JH is regulated, I will look at the expression of pea aphid orthologues of genes known to regulate juvenile hormone. Some of these genes are JHAMTs, which catalyze the last step in the synthesis of JH. Others are JHEs which are known to degrade JH. I will examine expression of these genes in both mothers and embryonic progeny, under photoperiods promoting both sexual and asexual fates (i.e., long and short nights). Comparing the expression of these genes under these different conditions should reveal the mechanism of regulation.