Meeting Abstract
The remarkable level of morphological diversity in Syngnathidae (pipefish, seahorses, and seadragons) makes this clade of fish excellent territory to explore developmental genetic processes underlying extreme morphological diversification. Conserved hox cluster genes are responsible for positional information in many early developmental processes, including specification of the anterior-posterior body axis in metazoans. Changes in these genes are hypothesized to underlie a significant amount of animal body plan diversity. We hypothesize that changes in hox genes organization, content or regulation in the syngnathid lineage may have contributed to the evolution of their elongated body axis. To test this hypothesis we sequenced, annotated and confirmed the orthology of 45 hox genes in the Gulf pipefish genome – the first syngnathid reference genome. We searched for cis-regulatory elements and miRNAs near hox genes by identifying conserved-noncoding elements co-localized within the hox clusters. Our results indicate that Gulf pipefish have the typical number of hox genes for teleost fish and have conserved coding sequences, but some intergenic noncoding elements missing in pipefish suggest regulatory regions may be altered. HoxA7a, which has been hypothesized to be associated with absence of ribs when lost, appears to have deteriorated independently in the tetraodontid pufferfish and the pipefish lineages. We conclude that although hox genes may be involved with the body axis diversification through differential regulation, a significant causative factor may be other downstream developmental genetic pathways.
