Characterization and expression analysis of an ancestor-type Pax gene in the hydrozoan jellyfish Podocoryne carnea

Abstract

We characterized a Pax gene from the hydrozoan Podocoryne carnea. It is most similar to cnidarian Pax-B genes and encodes a paired domain, a homeodomain and an octapeptide. Expression analysis demonstrates the presence of Pax-B transcripts in eggs, the ectoderm of the planula larva and in a few scattered cells in the apical polyp ectoderm. In developing and mature medusae, Pax-B is localized in particular endodermal cells, oriented toward the outside. Pax-B is not expressed in muscle cells. However, if isolated striated muscle tissue is activated for transdifferentiation, the gene is expressed within 1 h, before new cell types, such as smooth muscle and nerve cells, have formed. The expression data indicate that Pax-B is involved in nerve cell differentiation.

Direct control of neurogenesis by selector factors in the fly eye:regulation ofatonalby Ey and So

“…The association of Pax-, Six-and Ath-type factors with sensory perception is not restricted to photic sensation but extends to mechanoreception in diverse organisms including mouse, jellyfish and mollusks (Treisman, 2004;Piatigorsky and Kozmik, 2004;Fritzsch and Piatigorsky, 2005;Tessmar-Raible et al, 2005). In the jellyfish P. carnea, which lacks eyes but responds to a variety of environmental stimuli including light, expression of a putatively ancestral-like PaxB gene, Six1/2, Six3/6 and atonal-like 1 is associated with neuronal precursors found in the medusa tentacles (Groger et al, 2000;Kozmik et al, 2003;Stierwald et al, 2004;Seipel et al, 2004;Tessmar-Raible et al, 2005). Although the studies carried out in more basal metazoa consist mostly of analyses of gene expression and not function, this evidence does suggest that the association of Pax/Six/Ath-type factors and sensory organ development is ancient and may have been retained over more than 600 million years of evolutionary history.…”

Cubozoan jellyfish: an Evo/Devo model for eyes and other sensory systems

“…The Pax2/5/8 subfamily consists of a single Drosophila member, D-Pax2 (Czerny et al, 1997, Fu andNoll, 1997) and three mammalian genes, Pax2, Pax5 and Pax8, which arose by gene duplication at the onset of vertebrate lineage (Pfeffer et al, 1998) and cnidarian PaxB genes (Groger et al, 2000, Kozmik et al, 2003, Sun et al, 2001, Sun et al, 1997. D-Pax2 is required for development of ommatidial cone and pigment cells (sparkling) (Fu and Noll 1997) as well as mechanosensory bristles (shaven) (Fu et al, 1998, Kavaler et al, 1999.…”

“…The expression of PaxB has been studied in the hydrozoan Podocoryne carnea (Groger et al, 2000), which does not have eyes. The Podocoryne PaxB gene is expressed in the eggs, the ectodermal layer of larva and endoderm of the developing and adult medusa.…”

“…The Podocoryne PaxB gene is expressed in the eggs, the ectodermal layer of larva and endoderm of the developing and adult medusa. Based on the in vitro transdifferentiation assays, it has been argued that PaxB is involved in nerve cell differentiation (Groger et al, 2000).…”

“…Cnidarians suggest that PaxB, not Pax6, was the primordial gene during evolution of complex eyes A gene with a typical Pax6-like structure has not been detected in the cubozoan, Tripedalia cystophora (Kozmik et al, 2003) or in the hydrozoans, Podocoryne carnea (Groger et al, 2000) and Cladonema californicum (Sun et al, 2001), despite that Tripedalia and Cladonema have complex eyes. Even if Pax6 does exist in Tripedalia but has escaped our efforts to detect its gene or cDNA, our co-transfection tests suggest that the jellyfish Pax6 protein would neither bind nor activate the J3-crystallin promoter, as does PaxB (Kozmik et al, 2003).…”