Competence tests of early amphibian gastrula tissue containing nuclei of one species (Rana palustris) and cytoplasm of another (Rana pipiens).

Competence tests of tissue from lethal nucleocytoplasmic hybrids consisting of diploid R. palustris nuclei in R. pipiens cytoplasm were carried out by grafting pieces of early gastrulae to normal R. palustris early gastrula hosts. In the majority of cases, early gastrula ectoderm of the nucleoplasmic hybrids failed to differentiate further than if left in the intact embryo, although the grafts healed nicely and survived for several days. Grafts of the dorsal lip of the blastopore from nucleocytoplasmic hybrids to normal R. palustris hosts induced small secondary embryos with prominent suckers or sucker Anlage, a characteristic of nucleocytoplasmic hybrid development. These results indicate that the abnormal behaviour of the nucleocytoplasmic hybrids is an inherent property of the tissue, in the sense that contact with normal host does not alter its expression. Furthermore, the results with dorsal lip grafts suggest that nucleocytoplasmic hybrid tissue influences the direction in which normal tissue differentiates.