How deep into the evolutionary past can we trace the history of the sensory receptor genes that mediate the Aristotelian senses? What are the relationships between the animal senses? To address these questions, I apply comparative phylogenomic methods to genome sequence data from a diversity of bilaterian animals, basal metazoans and animal outgroups such as choanoflagellates and fungi. To date I have focused mostly on animal vision and chemoreception. This work has shed light on the timing of origins of sensory receptor genes, their history of duplication and loss, and the evolution of their signal transduction pathways.
Comparative phylogenomic screens often uncover candidate sensory receptor genes in early branching animals like cnidarians, placozoans and poriferans. Another focus of my research is to understand the functional roles that these putative sensory receptors serve in cnidarian biology. We employ studies of gene expression and behavior to order to correlate gene function with an organismal response to experimental sensory cues. Much of this work is currently done in the laboratory model hydrozoan Hydra magnipapillata and we are branching into new cnidarian models and placozoa.
Cnidocytes are perhaps best known as the stinging cells of Cnidaria, but in fact they serve a range of functions from locomotion and adhesion, to defense and prey capture. They even lend structural support in a few cases. Cnidocytes are also staggeringly complex cell types, often being referred to as the most complex metazoan cell type. In addition to this functional diversity and complexity, much of cnidarian sensory biology involves the regulation of cnidocyte activity. This project seeks to identify the genes associated with specific functional classes of cnidocytes in the hydra and other cnidarians using next generation sequencing and comparative transcriptomics. This project lays the foundation for a larger phylogenetic analysis of similar data to be sampled from across the Cnidaria.
The elaboration of complex sensory systems in evolution, which allow for greater acuity in responding to environmental cues, must surely impact the character of animal diversification. However, interactions between conspecifics, which affect factors such as mating success, resource allocation (including space) and others, must also be an important factor in animal evolution. Another ongoing project investigates the genetic basis for colony fusion and rejection in the colonial hydrozoan Hydractinia symbiolongicarpus. Colonies of this species are known to undergo somatic fusion or rejection upon encountering conspecifics; a decision that correlates with relatedness. Using comparative transcriptomics, we investigate genes that underlie the morphogenetic changes that occur under fusion and rejection phenotypes. We are also interested in further circumscribing the loci involved in the initial decision to fuse or reject. This project has many shared threads with the research foci listed above. The system of allorecognition in Hydractinia relies heavily on the precise control of cnidocyte function.