Differential expression of primary pair-rule genes during bidirectional regeneration in Perionyx excavatus.

The earthworm Perionyx excavatus is a species highly capable of bidirectional regeneration. Pair-rule genes are thought to have an ancestral function in arthropod segmentation. However, orthologs in annelids (i.e. Capitella teleta) do not exhibit segmental expression in the ectoderm or mesoderm. Their role in regeneration is currently unclear. Here, we report the expression profile of primary pair-rule genes (Pex-EvxA, Pex-EvxB, Pex-RuntA, Pex-RuntB, Pex-Hes1A, Pex-Hes1B, Pex-Hes4A, and Pex-Hey) found in P. excavatus using semi-quantitative reverse transcription-polymerase chain reaction. Our results indicated these genes showed variable expression during bidirectional regeneration. Six of these genes might play diverse and potentially critical roles in head and/or tail regeneration.