Mentor: Dr. Greg Davis
With the recent completion of the sequencing of the Aphid (aphis pisum) genome many new areas are now open for research and exploration. One thing that has been discovered is that there are multiple versions of “one gene”. This is interesting because of the sexual polyphenism exhibited in the aphid. While it is the summer aphid populations are entirely female and reproduce asexually. They also produce young viviparously (live birth). Then when the nights start to get longer the aphids do something quite amazing. The asexual females produce viviparously sexual females and males. These sexual females and males mate producing eggs that can survive winter. In the spring these eggs hatch into asexual females and the whole cycle starts over again.
This summer we will be looking at the expression of genes in the embryos of asexual females and the ovarioles of sexual females. The genes we will be looking at are Torso-like 1, 2, and possibly 3 and Tailless 1 and 2. The Torso-like signalling pathway is important to the development of the posterior of the aphid. To do this we are replicating the DNA with primers that we designed ourselves. We will then clone the products to make our own probes for in-situ hybridization. We will also be looking at the protein expression in the two types of embryos of a protein, capicua, that is farther down in the pathway using anti-body staining.
This research is important because it will help us understand the differences between the two types of embryos. From preliminary work done we know that there is a difference in the expression levels of the torso-like gene, but that was only for torso-like 1. We are now going to look for the expression of the other versions of the gene. If one type of the gene is expressed in one type of embryo and another is expressed in the other this would then explain the earlier absence. We want to understand more about aphids because they are a good new model organism for polyphenisms in organisms.