Updating the str and srj (stl) families of chemoreceptors in Caenorhabditis nematodes reveals frequent gene movement within and between chromosomes

The seven transmembrane receptor (str) and srj (renamed from stl) families of chemoreceptors have been updated and the genes formally named following completion di the Caenorhabditis elegans genome sequencing project. Analysi s bf gene locations revealed that 84% of the 320 genes and pseudogenes in t hese two families reside on the large chromosome V. Movements to other chro mosomes, especially chromosome IV, have nevertheless been relatively common , but only one has led to further gene family diversification. Comparisons with homologs in C. briggsae indicated that 22.5% of these genes have been newly formed by gene duplication since the species split, while also showin g that four have been lost by large deletions These patterns of gene evolut ion are similar to those revealed by analysis of the equally large srh fami ly of chemoreceptors, and are likely to reflect general features of nematod e genome dynamics: THUS large random deletions presumably balance the rapid proliferation of genes and their degeneration into pseudogenes, while gene movement within and between chromosomes keeps these nematode genomes in fl ux.