Duplication and divergence of opsins and chemoreceptors

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Gene duplication events are as common as individual nucleotide substitutions. Consequently, gene number differs to a large extent among individuals of the same species. The goal of my research program is to characterize the contribution of gene duplication to molecular and phenotypic diversity. The pattern of gene loss after duplication might have important implications for speciation (Taylor et al., 2001, Trends Genet, 17:299), however, the duplicates that are retained are the subjects of my current research. I focus on sensory receptors because this is where the link between molecular and phenotypic innovation is most clear. Project 1: Recent research in my lab shows that guppies have more Long Wavelength Sensitive opsin genes than any other vertebrate. We will test the hypothesis these 'extra' opsins improve colour vision using qPCR, in situ hybridization and, in collaboration with Dr. Kelber (University of Lund), colour discrimination tests. Guppies are colourful fish and our experiments will tell us if they also have especially good colour vision. Project 2: We were among the first to identify chemosensory genes in the purple sea urchin genome (Burke et al., 2006, Devel Biol, 300:434). We will carry out a PCR-based survey of cDNA to identify chemosensory organs (the sea urchin "nose") and in-situ hybridization to identify chemosensory cells. By expressing chemoreceptors in a cell line such as human embryonic kidney cells we will also study the responses of different chemoreceeptors to ligand stimulation by measuring changes in the levels of secondary messengers such as cAMP, IP3, or calcium. Project 3: We will study duplicated non-coding sequences upstream of chemoreceptor genes in Caenorhabditis elegans. Chemoreceptor genes make up one of the largest gene families in this species (~2000 genes), yet most are expressed in one or more of only 32 chemosensory neurons. As many genes are expressed in the same neurons, they are expected to have similarities in the non-coding DNA that regulates gene expression. We will use bioinformatics, transgenic worms, and fluorescence microscopy to characterize chemoreceptor gene regulatory modules.