The Caenorhabditis chemoreceptor gene families

• Main Authors: Robertson Hugh M, Thomas James H
• Format: Article
• Language: English
• Published: BMC 2008-10-01
• Series: BMC Biology
• Online Access: http://www.biomedcentral.com/1741-7007/6/42

<p>Abstract</p> <p>Background</p> <p>Chemoreceptor proteins mediate the first step in the transduction of environmental chemical stimuli, defining the breadth of detection and conferring stimulus specificity. Animal genomes contain families of genes encoding chemoreceptors that mediate taste, olfaction, and pheromone responses. The size and diversity of these families reflect the biology of chemoperception in specific species.</p> <p>Results</p> <p>Based on manual curation and sequence comparisons among putative G-protein-coupled chemoreceptor genes in the nematode <it>Caenorhabditis elegans</it>, we identified approximately 1300 genes and 400 pseudogenes in the 19 largest gene families, most of which fall into larger superfamilies. In the related species <it>C. briggsae </it>and <it>C. remanei</it>, we identified most or all genes in each of the 19 families. For most families, <it>C. elegans </it>has the largest number of genes and <it>C. briggsae </it>the smallest number, suggesting changes in the importance of chemoperception among the species. Protein trees reveal family-specific and species-specific patterns of gene duplication and gene loss. The frequency of strict orthologs varies among the families, from just over 50% in two families to less than 5% in three families. Several families include large species-specific expansions, mostly in <it>C. elegans </it>and <it>C. remanei</it>.</p> <p>Conclusion</p> <p>Chemoreceptor gene families in <it>Caenorhabditis </it>species are large and evolutionarily dynamic as a result of gene duplication and gene loss. These dynamics shape the chemoreceptor gene complements in <it>Caenorhabditis </it>species and define the receptor space available for chemosensory responses. To explain these patterns, we propose the gray pawn hypothesis: individual genes are of little significance, but the aggregate of a large number of diverse genes is required to cover a large phenotype space.</p>