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 urea‐shift gel electrophoresis. Tropomyosin isoforms included in the embryos were gradually increased after 2 cell stage and retained at a constant level after gastrula stage. To detect the tropomyosin isoforms derived from zygotic genomes, embryos cross‐fertilized between H. pulcherrimus and Pseudocentrotus depressus gametes were prepared. Since tropomyosin isoforms from H. pulcherrimus eggs and from P. depressus eggs could be distinguished from each other on a two‐dimensional electrophoretic gel, the paternal isoforms of tropomyosin in the cross‐fertilized embryos, which were not included endogenously in the egg, could be regarded as products derived from zygotic genomes. The paternal isoforms of tropomyosin were detected first at around the gastrula stage in embryos cross‐fertilized between H. pulcherrimus sperm and P. depressus eggs and also in the reverse combination of the gamete species. Muscle tropomyosins derived from H. pulcherrimus and P. depressus genomes were similarly detected in cross‐fertilized embryos at the pluteic stage when the muscle tropomyosin appeared in sea urchin embryos.