CHANGES OF TROPOMYOSIN ISOFORMS DURING DEVELOPMENT OF CROSS-FERTILIZED SEA-URCHIN EMBRYOS

Changes of tropomyosin isoforms during development of the sea urchin, Hemicentrotus pulcherrimus, were investigated using two-dimensional ur ea-shift gel electrophoresis. Tropomyosin isoforms included in the emb ryos were gradually increased after 2 cell stage and retained at a con stant level after gastrula stage. To detect the tropomyosin isoforms d erived from zygotic genomes, embryos cross-fertilized between H. pulch errimus and Pseudocentrotus depressus gametes were prepared. Since tro pomyosin isoforms from H. pulcherrimus eggs and from P. depressus eggs could be distinguished from each other on a two-dimensional electroph oretic gel, the paternal isoforms of tropomyosin in the cross-fertiliz ed embryos, which were not included endogenously in the egg, could be regarded as products derived from zygotic genomes. The paternal isofor ms of tropomyosin were detected first at around the gastrula stage in embryos cross-fertilized between H. pulcherrimus sperm and P. depressu s eggs and also in the reverse combination of the gamete species. Musc le tropomyosins derived from H. pulcherrimus and P. depressus genomes were similarly detected in cross-fertilized embryos at the pluteic sta ge when the muscle tropomyosin appeared in sea urchin embryos.