Brian Eads, PhD

My work in the field of ecological and evolutionary genomics centers around characterizing adaptive transcriptional responses of animals to their environment. I study the small crustacean Daphnia pulex, a cyclical parthenogen (it alternate rounds of sexual and asexual reproduction). Typically females reproduce clonally under benign environmental conditions, but as autumn approaches, they begin to produce either male offspring or haploid eggs which require fertilization. Once fertilized, sexual eggs are laid in a state of endogenous dormancy (diapause) so they can overwinter as ponds freeze. I am interested in how the genes and gene networks responsible for these processes respond in a mechanistic sense to evolutionary and ecological pressures. Specifically, my research involves the following questions:

1. Obligate asexuality. Some lineages have evidently lost the ability to undergo meiosis; I compare these obligate asexuals to their sexual counterparts with the aim of understanding at a mechanistic level how oogenesis works in these two kinds of animals. We are using microarray analysis of oogenesis, and immunohistochemistry and sequencing of meiosis-specific proteins in sexual and obligate asexual lineages to answer these questions.
2. Environmental sex determination. I am especially interested in deciphering the architecture of transcriptional regulatory networks in this process using microarrays. Epigenetic effects play a major role (males are genetically identical to their mothers), and steroid hormone receptors are also suspected to be important in this process.
3. Diapause and subitaneous (parthenogenetic) egg production. From the standpoint of comparative biochemistry and physiology, how does maternal provisioning differ in these two kinds of eggs at the molecular level? Also, how different are signalling pathways in sexuals and obligate asexuals during diapause and subitaneous egg production?