The role of animal-vegetal interaction with respect to the determination of dorsoventral polarity in the equal-cleaving spiralian,Lymnaea palustris
The role of animal-vegetal interaction with respect to the determination of dorsoventral polarity in the equal-cleaving spiralian,Lymnaea palustris
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DOI：
10.1007/bf01152174
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发表时间：
1985-05
期刊：
影响因子：
--
通讯作者：
M. Martindale;C. Doe;J. Morrill
中科院分区：
文献类型：
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作者：
M. Martindale;C. Doe;J. Morrill
前两个卵裂产生四个大小相等的卵裂球的螺旋卵裂胚胎保持沿着其动物-植物轴径向对称，直到第三和第四四分体形成之间的间隔。此时，动物的小孢子和植物的大孢子彼此接触，因为它们伸长并堵塞中央充满液体的卵裂腔。覆盖的小单体将它们的接触集中在四个大单体中的一个上，即假定的3D大单体，因为它延伸到胚胎内的中心位置。我们测试的假设，这种动物-植物的相互作用是因果关系参与在动物和植物半球的对称性的测定可逆地抑制动物-植物接触在24细胞阶段与细胞松弛素-B。在整个处理期间，胚胎保持中空，未发生动物-植物相互作用。处理后，发生卵裂球伸长，但没有D象限大裂球出现，植物半球保持放射状。在第一个四分体衍生物的卵裂和纤毛化模式的基础上，处理过的胚胎保持完全或部分放射状，表现出强烈的倾向于发展为腹象限。这些结果表明，象限的这种平等分裂的螺旋没有明确确定，直到24细胞阶段后，动物-植物的相互作用是必要的D象限的确定。本文还讨论了等裂螺旋藻动物和植物半球对称化的机制。
Spirally cleaving embryos in which the first two cleavages generate four equal-sized blastomeres remain radially symmetrical along their animal-vegetal axis until the interval between third and fourth quartet formation. At this time animal micromeres and vegetal macromeres contact each other as they elongate and occlude the central, fluid-filled cleavage cavity. The overlying micromeres focus their contacts onto one of the four macromeres, the presumptive 3D macromere, as it elongates to a central position within the embryo. We tested the hypothesis that this animal-vegetal interaction was causally involved in the determination of the symmetry properties in both the animal and vegetal hemispheres by reversibly inhibiting animal-vegetal contact at the 24 cell stage with cytochalasin-B. Embryos remained hollow throughout the treatment period and animal-vegetal interaction did not occur. After treatment, blastomere elongation occurred but no D quadrant macromere appeared and the vegetal hemisphere remained radialized. On the basis of cleavage and ciliation patterns of first quartet derivatives, treated embryos remained fully or partially radialized, showing a strong tendancy to develop as ventral quadrants. These results show that the quadrants of this equal-cleaving spiralian are not definitively determined until after the 24 cell stage and that animal-vegetal interaction is required for D quadrant determination. The mechanisms of symmetrization in the animal and vegetal hemispheres of equal-cleaving spiralians is also discussed.