Int. J. Dev. Biol. 54: 795 - 802 (2010)
doi: 10.1387/ijdb.082738ms
© UPV/EHU Press

An organizing region in metamorphosing hydrozoan planula larvae - stimulation of axis formation in both larval and in adult tissue

Melanie Stumpf1,2, Britta Will1,3, Karola Wittig1,4, Jennifer Kasper1,5, Benjamin Fischer1,6, Jürgen Schmich1,7, Stefanie Seipp1,8 and Thomas Leitz*,1

1Entwicklungsbiologie der Tiere, Fachbereich Biologie, Technische Universität, Kaiserslautern, Germany, 2Bluestone Laboratory, UCSF Diabetes Center, San Francisco, USA, 3Harvard Institutes of Medicine, Tenen Lab, Boston, USA, 4Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät Mannheim der Universität Heidelberg, Mannheim, Germany, 5Klinikum der Johannes Gutenberg-Universität Mainz, Institut für Pathologie, Germany, 6Affenstein 6, Dirmstein, Germany, 7R.O.S.E. Europe GmbH, Frankfurt am Main, Germany and 8Carl Roth GmbH + Co. KG, Karlsruhe, Germany

ABSTRACT A novel wingless gene was isolated from the marine colonial hydroid Hydractinia echinata. Alignments and Bayesian inference analysis clearly assign the gene to the Wnt5A group. In line with data found for the brachyury ortholog of Hydractinia, He-wnt5A is expressed during metamorphosis in the posterior tip of the spindle-shaped planula larva, suggesting that the tip functions as a putative organizer during metamorphosis. Additionally, the outermost cells of the posterior tip are omitted from apoptosis during metamorphosis. In order to investigate this putative organizer function, we transplanted the posterior tip of metamorphosing animals into non-induced larvae and into primary polyps 24 h and 48 h of age. In larvae, the tip induced formation of a secondary axis. In polyps the building of ectopic head structures was induced. Based on our data on axis formation, on gene expression similar to the organizers of other species, and the absence of regular apoptosis, we conclude that the posterior tip of the Hydractinia larva has organizing activity during metamorphosis.

Keywords:

Hydractinia echinata, planula larva, wnt, brachyury, organizer

*Corresponding author e-mail: leitz@biologie.uni-kl.de