Hox gene expression during the development of the phoronidPhoronopsis harmeri

Abstract

Background: Phoronida is a small group of marine worm-like suspension feeders, which together with brachiopods and bryozoans form the clade Lophophorata. Although their development is well studied on the morphological level, data regarding gene expression during this process are scarce and restricted to the analysis of relatively few transcription factors. Here we present a description of the expression patterns of Hox genes during the embryonic and larval development of the phoronid Phoronopsis harmeri. Results:We identified sequences of 8 Hox genes in the transcriptome of P. harmeri and determined their expression pattern during embryonic and larval development using whole mount in situ hybridization. We found that none of the Hox genes is expressed during embryonic development. Instead their expression is initiated in the later developmental stages, when the larval body is already formed. The Hox genes are expressed in the metasomal sac, posterior mesoderm and junction between midgut and hindgut -structures that represent rudiments of the adult worm, which emerges through the process of drastic

Molecular patterning during the development of Phoronopsis harmeri reveals similarities to rhynchonelliform brachiopods

“…Interestingly, molecular studies in rhynchonelliform and craniiform brachiopods demonstrated that the early embryonic patterning is defining the mode of gastrulation as protostomic or deuterostomic [4]. However, with the exception of Hox genes [5], molecular studies on embryonic development of phoronids are still lacking and are therefore important to understand the precise timing of germ layer segregation and cell specification. Furthermore, due to their informative phylogenetic position (as sister group, together with Ectoprocta, to Brachiopoda), phoronids can shed light on whether a similar developmental mode is shaped by conserved molecular mechanisms in closely related taxa.…”