Department of Biology, Ghent University, Krijgslaan 281 S8, 9000 Ghent, Belgium.
VIB-UGent Center for Plant Systems Biology, Technologiepark 927, B-9052 Ghent, Belgium.
Nat Plants. 2017 Jan 23;3:16221. doi: 10.1038/nplants.2016.221.
In most complex eukaryotes, development starts with the establishment of cell polarity determining the first axis of the body plan. This polarity axis is established by the asymmetrical distribution of intrinsic factors, which breaks the symmetry in a single step. Zygotes of the brown alga Fucus, which unlike land plant and animal zygotes do not possess a maternally predetermined polarity axis, serve as models to study polarity establishment. Here, we studied this process in Dictyota, and concluded that sense and direction of the cell polarization vector are established in two mechanistically and temporally distinct phases that are under control of different life cycle stages. On egg activation, the zygote elongates rapidly according to a maternally predetermined direction expressing the first phase of cell polarization. Which of the two poles of the resulting prolate spheroidal zygote will acquire the basal cell fate is subsequently environmentally determined. The second phase is accompanied by and dependent on zygotic transcription instead of relying uniquely on maternal factors. Cell polarization, whereby determination of direction and sense of the polarization vector are temporally and mechanistically uncoupled, is unique and represents a favourable system to gain insight into the processes underlying cell polarity establishment in general.
在大多数复杂真核生物中，发育始于细胞极性的建立，从而决定了身体形态的第一个轴。这种极性轴是通过内在因素的不对称分布来建立的，这种不对称分布在一步之内打破了对称性。不同于陆地植物和动物的受精卵，褐藻的受精卵不具有母体预先确定的极性轴，因此可用作研究极性建立的模型。在这里，我们研究了 Dictyota 中的这个过程，并得出结论，细胞极化向量的意义和方向是在两个机制上和时间上不同的阶段建立的，这两个阶段受不同生命周期阶段的控制。在卵激活时，受精卵根据母体预先确定的方向快速伸长，表达细胞极化的第一阶段。由此产生的长球形受精卵的两个极中的哪一个将获得基底细胞命运，随后是由环境决定的。第二阶段伴随着并依赖于合子转录，而不是仅依赖于母体因素。细胞极化，其中极化向量的方向和意义的确定在时间和机制上是分离的，这在普遍意义上是独特的，代表了一个有利的系统，可以深入了解细胞极性建立的过程。
