Ectopic expression of Xenopus noggin RNA induces complete secondary body axes in embryos of the direct developing frog Eleutherodactylus coqui

被引:17
|
作者
Fang, H [1 ]
Marikawa, Y [1 ]
Elinson, RP [1 ]
机构
[1] Univ Toronto, Dept Zool, Toronto, ON M5S 3G5, Canada
基金
美国国家科学基金会; 加拿大自然科学与工程研究理事会;
关键词
noggin; direct development; egg evolution; head development; body axis;
D O I
10.1007/PL00008184
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
We rested the effects of noggin RNA from Xenopus laevis on axis induction in embryos of a direct developing frog, Eleutherodactylus coqui. We microinjected noggin RNA into one blastomere of 4-cell embryos at the site close to the animal pole, and found that overexpression of noggin RNA is not only sufficient to induce additional axes but also induces heads with eyes. We also injected noggin RNA into 8-cell or 16-cell embryos in various sites, including the marginal zone, above the marginal zone, and the vegetal pole, and found the formation of a complete secondary axis in all three types of injection. These effects of X, laevis noggin RNA on the E. coqui embryo are remarkably different from those found in the X. laevis embryo itself. It has been shown previously that overexpression of noggin RNA on the ventral side of the normal X, laevis embryo induces only a partial axis, with no head structures. We show here that the failure of noggin induction of a complete axis when overexpressed on the ventral side of the X. laevis embryos is not due to an insufficient amount of RNA injected. Also, the failure is unlikely due to inhibition from the primary axis since noggin RNA can induce duplicated head structures on opposite sides of UV-irradiated X. laevis embryos. There appear to be fundamental differences in the responses of E. coqui and X. laevis embryos to exogenous noggin RNA. We propose that these differences stem from an alteration in cytoplasmic arrangements that occurred during evolution of this large egg.
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页码:21 / 27
页数:7
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