Meeting Abstract

70.1  Sunday, Jan. 6  Molecular Characterization of Parthenogenetic Meiosis in Acyrthosiphon pisum SRINIVASAN, D.G.*; DAVIS, G.K.; STERN, D.L.; Princeton University; Princeton University; Princeton University dsriniva@princeton.edu

Meiosis is a highly conserved process in which a diploid genome is recombined and assorted into haploid gametes. The pea aphid Acyrthosiphon pisum exhibits a reproductive polyphenism whereby environmental signals trigger a switch between apomixis (parthenogenetic reproduction) and meiosis (sexual reproduction). This important adaptation allows aphid populations to rapidly expand and cope with fleeting resources. How aphids have evolved this ability to switch between parthenogenesis and sexual meiosis is unknown. To arrive at a mechanistic explanation for this plasticity, I examined the proximal molecular differences between sexual meiosis and parthenogenesis in aphids. First, I first identified homologs of fourteen genes that act in different aspects on meiosis from the pea aphid genome. Next, I determined if these core meiosis genes are expressed in asexuals by performing RT-PCR spanning across least one intron from mRNA isolated from asexual ovaries. Surprisingly, meiosis specific genes (e.g., Msh4, Msh5, Hop2 and Mnd1) are expressed in asexual ovaries. Additionally, the Spo11 PCR product contained intronic sequence, thus representing unspliced mRNA. An A. pisum strain (Tucson) that no longer cycles through sexual forms also fails to express Spo11. Thus, Spo11 may be a crucial point in the control of this reproductive polyphenism. Experiments looking at mRNA and protein localization will help to distinguish among several possible explanations for these results. Further molecular characterization of this example of phenotypic plasticity will be helpful in understanding how multiple interacting pathways can evolve to create alternate adaptive phenotypes.