Expression of the pair-rule gene homologs <it>runt</it>, <it>Pax3/7, even-skipped-1 </it>and <it>even-skipped-2 </it>during larval and juvenile development of the polychaete annelid <it>Capitella teleta </it>does not support a role in segmentation

• Main Authors: Seaver Elaine C, Yamaguchi Emi, Richards Gemma S, Meyer Néva P
• Format: Article
• Language: English
• Published: BMC 2012-04-01
• Series: EvoDevo
• Subjects: <it>Capitella</it>; <it>Eve</it>; <it>Pax3/7</it>; polychaete; <it>Runt</it>; Segmentation
• Online Access: http://www.evodevojournal.com/content/3/1/8

<p>Abstract</p> <p>Background</p> <p>Annelids and arthropods each possess a segmented body. Whether this similarity represents an evolutionary convergence or inheritance from a common segmented ancestor is the subject of ongoing investigation.</p> <p>Methods</p> <p>To investigate whether annelids and arthropods share molecular components that control segmentation, we isolated orthologs of the <it>Drosophila melanogaster </it>pair-rule genes, <it>runt</it>, <it>paired </it>(<it>Pax3/7</it>) and <it>eve</it>, from the polychaete annelid <it>Capitella teleta </it>and used whole mount <it>in situ </it>hybridization to characterize their expression patterns.</p> <p>Results</p> <p>When segments first appear, expression of the single <it>C. teleta runt </it>ortholog is only detected in the brain. Later, <it>Ct-runt </it>is expressed in the ventral nerve cord, foregut and hindgut. Analysis of <it>Pax </it>genes in the <it>C. teleta </it>genome reveals the presence of a single <it>Pax3/7 </it>ortholog. <it>Ct-Pax3/7 </it>is initially detected in the mid-body prior to segmentation, but is restricted to two longitudinal bands in the ventral ectoderm. Each of the two <it>C. teleta eve </it>orthologs has a unique and complex expression pattern, although there is partial overlap in several tissues. Prior to and during segment formation, <it>Ct-eve1 </it>and <it>Ct-eve2 </it>are both expressed in the bilaterial pair of mesoteloblasts, while <it>Ct-eve1 </it>is expressed in the descendant mesodermal band cells. At later stages, <it>Ct-eve2 </it>is expressed in the central and peripheral nervous system, and in mesoderm along the dorsal midline. In late stage larvae and adults, <it>Ct-eve1 </it>and <it>Ct-eve2 </it>are expressed in the posterior growth zone.</p> <p>Conclusions</p> <p><it>C. teleta eve, Pax3/7 </it>and <it>runt </it>homologs all have distinct expression patterns and share expression domains with homologs from other bilaterians. None of the pair-rule orthologs examined in <it>C. teleta </it>exhibit segmental or pair-rule stripes of expression in the ectoderm or mesoderm, consistent with an independent origin of segmentation between annelids and arthropods.</p>