Meeting Abstract
Genome evolution has shaped the remarkable diversity exhibited in the animal body plans of today’s animals. Changes in Hox genes and other homeobox genes, in particular, have made considerable contributions to major transitions in animal morphology. Vertebrate genomes have undergone several rounds of whole-genome duplication giving rise to multiple clusters of Hox genes. These duplications, especially to developmental patterning genes like the Hox genes, have contributed to the vertebrate body plan. Genomic evidence from the annelids Helobdella robusta (class Clitellata) and Capitella teleta (class Polychaeta) suggest that large-scale duplications also occurred in the lineage leading to H. robusta. To better understand the nature of these duplications, we have sequenced and assembled the genome of the earthworm Eisenia fetida (class Clitellata). We have identified 250 homeobox genes and 33 Hox genes in the E. fetida genome. These numbers represent the largest number of Hox genes reported in an annelid (e.g., C. teleta has 11 Hox and H. robusta has 19 Hox genes). These data suggest a series of evolutionary expansions in the Clitellata, in particular along the lineage leading to E. fetida. Besides providing an important genomic resource for the community, these analyses provide timing information for important genomic duplication and loss events that undoubtedly have contributed to the evolution of annelid body plans.
