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Main Menu - Block
- Overview
- Anatomy and Histology
- Cryo-Electron Microscopy
- Electron Microscopy
- Flow Cytometry
- Gene Targeting and Transgenics
- Immortalized Cell Line Culture
- Integrative Imaging
- Invertebrate Shared Resource
- Janelia Experimental Technology
- Mass Spectrometry
- Media Prep
- Molecular Genomics
- Primary & iPS Cell Culture
- Project Pipeline Support
- Project Technical Resources
- Quantitative Genomics
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- Scientific Computing Systems
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- Vivarium
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Note: Research in this publication was not performed at Janelia.
Abstract
Phenotypic plasticity allows organisms to quickly adapt in response to changing environments. Little is known of the genetic, environmental and epigenetic contribution to the expression of alternative adaptive developmental outcomes. We study aphid polyphenisms, which offer a unique, compelling opportunity to study multiple levels of biological organization, especially insect epigenetics. The pea aphid, Acyrthosiphon pisum, exhibits an adaptive reproductive polyphenism whereby genetically identical individuals reproduce either sexually (meiosis) or asexually (parthenogenesis) depending on environmental conditions during maternal development (short or long photoperiod, respectively). To understand how facultative asexuality evolved in aphids, we first determined meiosis gene activity in sexuals and asexuals. I determined that the pea aphid genome encodes single copies of homologs for the majority of the core meiotic machinery, suggesting that meiotic plasticity is not due simply to gene loss or expansion. Next, we determined if these core meiosis genes are expressed using PCR spanning across at least one intron from cDNA isolated from asexual and sexual ovaries. Surprisingly, meiosis specific genes (e.g., Spo11, Msh4, Msh5, Hop2 and Mnd1) are expressed in not only in asexual ovaries but also in somatic tissue and an obligately asexual aphid strain. Interestingly, the Spo11 PCR product contained intronic sequence, thus representing unspliced mRNA. Germline expression of Spo11, Mnd1 and Hop2 was confirmed by in situ analysis. Preliminary results identified candidate methylation sites in the Spo11 locus, indicating an epigenetic basis for this expression difference. Further characterization will help us better understand the molecular and epigenetic mechanisms underlying this adaptive facultative plasticity.