HYDRA TROPOMYOSIN TROP1 IS EXPRESSED IN HEAD-SPECIFIC EPITHELIAL-CELLS AND IS A MAJOR COMPONENT OF THE CYTOSKELETAL STRUCTURE THAT ANCHORS NEMATOCYTES

A cDNA clone encoding a 253 amino acid tropomyosin was isolated from H ydra in a differential screen for head-specific genes. The Hydra tropo myosin gene, designated trop1, is a single copy gene, lacks introns an d is strongly expressed in tentacle-specific epithelial cells. Analysi s of protein synthesis in head and gastric tissue indicated a high rat e of tropomyosin synthesis in head tissue. Immunolocalization of tropo myosin in tentacle tissue revealed a cushion-like tropomyosin-containi ng structure within battery cells at the base of nematocytes. The stru cture appears to form part of the cytoskeletal anchor for nematocytes. Tropomyosin cushions were also observed in epithelial cells along the body column, which contain mounted stenotele nematocytes.