Effects of the injection of exogenous DNAs on gene expression in early embryos and coenocytic egg cells ofXenopus laevis

  • Koichiro Shiokawa
  • Yuchang Fu
  • Norihiko Nakakura
  • Kosuke Tashiro
  • Munefumi Sameshima
  • Keiichi Hosokawa


InXenopus laevis embryogenesis, the synthesis of heterogeneous mRNA-like RNA starts at the cleavage stage, whereas that of low-molecular-mass RNAs and rRNA occurs at the early blastula and late blastula stages, respectively. In coenocytic fertilizedXenopus egg cells, which fail to cleave, an excess of exogenously injected DNA (pBR322) induces ‘premature’ expression of previously injected exogenous genes (yeast tRNA genes). We have carried out experiments to discover whether the injection of excess exogenous DNAs of various origins modifies the expression of endogenous genes and previously injected exogenous genes inXenopus embryogenesis. We found that injection of a relatively large amount of exogenous DNA (Xenopus rDNA clone) induces the premature expression, or enhanced expression, of previously injected bacterial chloramphenicol acetyltransferase genes in coenocytic cells. In embryos, however, the injection of exogenous DNAs of various origins did not appreciably modify the expression of either endogenous or previously injected CAT genes. The DNAs injected into fertilized eggs were not degraded and were partitioned into the nuclei of most (at least 80%) of the descendant blastomeres at least during early stages of development. Therefore, we concluded that the program of gene expression in normally developing embryos cannot easily be altered by the introduction of excess exogenous DNAs.

Key words

DNA injection CAT gene expression Midblastula transition Xenopus embryogenesis Coenocytic egg cells 


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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Koichiro Shiokawa
    • 1
  • Yuchang Fu
    • 1
  • Norihiko Nakakura
    • 1
  • Kosuke Tashiro
    • 1
  • Munefumi Sameshima
    • 2
  • Keiichi Hosokawa
    • 3
  1. 1.Laboratory of Embryology, Department of Biology, Faculty of Science 33Kyushu UniversityFukuokaJapan
  2. 2.Department of Ophthalmology, Faculty of MedicineKagoshima UniversityKagoshimaJapan
  3. 3.Department of BiochemistryKawasaki Medical CollegeKurashikiJapan

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