Over one-half billion years of head conservation? Expression of an ems class gene in Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa)

Over one-half billion years of head conservation? Expression of an ems class gene in Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa)

^*The Institute for Nature Conservation Research, Tel Aviv University, Tel Aviv 69978, Israel; Departments of ^‡Biology and ^‖Geology and Geophysics, Yale University, P.O. Box 208104, New Haven, CT 06520-8104; ^¶Zoological Institute, J. W. Goethe University, Siesmayerstrasse 70, D-60054 Frankfurt, Germany; ^§Department of Biology, Middlebury College, Middlebury, VT 05753; and ^**Department of Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven CT 06520-8106

Communicated by James W. Valentine, University of California, Berkeley, CA (received for review September 8, 1997)

Abstract

We report the isolation of an empty spiracles class homeodomain-containing gene, Cn-ems, from the hydrozoan Hydractinia symbiolongicarpus, the first gene of this class characterized in a lower metazoan. Cn-ems was found to be expressed in the head of gastrozooids, specifically in endodermal epithelial cells of the taeniolae of the hypostome. Cn-ems is not expressed in gonozooids, which lack taeniolae. Experimental conversion of the posterior region of the planula larva into head structures up-regulates expression of the gene. These findings establish that the association of ems-class genes with head structures preceded the evolution of bilateral symmetry.

Footnotes

↵ † To whom reprint requests should be addressed. e-mail: mokady{at}post.tau.ac.il.
Data deposition: The Cn-ems sequence reported in this paper has been deposited in the GenBank database (accession no. Y11836).
ABBREVIATIONS:

MMA,

metamorphosin A;

RT,

reverse transcriptase