Formation of nucleus-like structure in the cytoplasm of λ-DNA-injected fertilized eggs and its partition into blastomeres during early embryogenesis in Xenopus laevis

The fate of bacteriophage λ-DNA was examined after injection into the fertilized eggs of Xenopus laevis. Injection of a large amount of λ-DNA (ca. 24 ng) into a fertilized Xenopus egg induced the formation around the injected DNA of a giant nucleus-like structure which was surrounded by an apparently normal bilayered nuclear membrane with nuclear pore complexes. Southern blot analysis revealed the persistence of injected λ-DNA until the blastula stage. The nucleus-like structure was partitioned into blastomeres during cleavage through a process of nuclear fission, and was maintained in a group of extraordinarily large blastomeres until the blastula stage.