Regulation of the asymmetric division of the Arabidopsis thaliana zygote by the WRKY2 pathway

拟南芥胚胎沿着顶基轴的极性可以追溯到合子的极性和不对称分裂。这种分裂产生两个不同命运的子细胞：小的顶端子细胞将形成大部分胚胎，而大的基部子细胞产生额外的胚柄，其后代有助于胚根。然而，不同的细胞命运如何从极化合子产生的机制是未知的。在这个项目中，我们将解决受精卵的分子组织，以及如何作为一个结果，不同的子细胞的命运产生。我们已经确定了两个同源异型盒基因，ZOX1和ZOX3，其mRNA定位反映了受精卵的不对称分裂，并可能在其女儿中建立不同的基因表达程序。因此，ZOX1和ZOX3可用作研究合子极性以及这种极性如何转化为不同胚胎细胞命运的机制的工具。这两种mRNA都存在于卵细胞和受精卵中。细胞分裂后，ZOX1 mRNA仅位于合子的顶端，ZOX3 mRNA仅位于合子的基部。我们的初步结果表明，这种不对称的ZOX mRNA的定位已经建立在受精卵的水平。我们的工作假设，在这个项目中进行测试，是受精卵包含顶端和基底细胞的命运决定因素，其不对称的本地化有助于其女儿的不同命运的一代。

The polarity of the Arabidopsis embryo along the apical-basal axis can be traced back to the polarity and the asymmetric division of the zygote. This division gives rise to two daughter cells of different fates: the small apical daughter will form most of the embryo, whereas the large basal daughter generates the extra embryonic suspensor and its progeny contributes to the embryonic root. However, the mechanisms of how different cell fates arise from the polarized zygote are unknown. In this project we will address the molecular organization of the zygote and how as a consequence different daughter cell fates are generated. We have identified two homeobox genes, ZOX1 and ZOX3, whose mRNA localization reflects the asymmetric division of the zygote and are likely to establish different gene expression programs in their daughters. ZOX1 and ZOX3 thus can be used as tools to study zygote polarity and the mechanisms of how this polarity is translated into different embryonic cell fates. Both mRNAs are present in the egg cell and the zygote. After cell division, ZOX1 mRNA is located only in the apical and ZOX3 mRNA only in the basal daughter of the zygote. Our preliminary results indicate that this asymmetric localization of ZOX mRNAs is established at the level of the zygote already. Our working hypothesis, to be tested in this project, is that the zygote contains both apical and basal cell fate determinants, the asymmetric localization of which contributes to the generation of the different fates of its daughters.