The role of Actin dynamics in auxin-dependent oriented cell division

植物细胞被坚硬的壁包围，限制了它们的运动，因此定向细胞分裂是决定生长发育过程中形状的核心机制。定向分裂是胚胎和胚胎后发育过程中形成事件的基础，以产生细胞多样性。尽管对固有的细胞分裂机制有详细的了解，但细胞分裂的方向是如何由发育调节因子控制的还完全不清楚。19世纪的经典模型预测，细胞几何通过一个简单的物理规则来约束划分平面。最近的研究表明，这一几何缺省规则确实可以解释拟南芥早期胚胎在3D中的许多分裂。然而，所有不对称的划分都违反了这一规则。结果表明，抑制缺省分裂需要对生长素激素的转录反应。对这种抑制的分子调控的进一步分析揭示了多个肌动蛋白调节因子。在这个项目中，我将使用遗传学、细胞生物学、分子和计算相结合的方法来解决1)肌动蛋白模式在胚胎发育过程中如何变化，以及它们是否与定向细胞分裂相关，以及2)哪些蛋白质调节早期胚胎中的肌动蛋白动态。此外，我将探索肌动蛋白调节是否在控制定向细胞分裂中调节生长素的作用。我期待这个项目的成果将把发育调节器与细胞分裂机制联系起来，从而填补我们在如何将超细胞发育落实到个体细胞行为方面的一个重大空白。

Plant cells are surrounded by rigid walls restricting their movement, and therefore oriented cell division is a central mechanism in defining shape during growth and development. Oriented divisions underlie formative events during embryonic and post-embryonic development to generate cell diversity. Despite detailed knowledge of the intrinsic cell division machinery, it is entirely unclear how orientation of cell divisions is controlled by developmental regulators. Classical models in the 19th century predicted that cell geometry constrains division plane through a simple physical rule. It was recently demonstrated that this geometric default rule can indeed explain many divisions in the early Arabidopsis embryo in 3D. However, all asymmetric divisions disobeyed this rule. It was shown that transcriptional response to the auxin hormone is required to suppress default division. Further analysis on the molecular regulation for this suppression revealed multiple Actin regulators. In this project, I will use a combined genetic, cell biological, molecular and computational approach to address 1) how Actin patterns change during embryo development, and do they correlate with oriented cell division, and 2) which proteins regulate Actin dynamics in the early embryo. Furthermore, I will 3) explore whether Actin regulation mediates auxin action in controlling oriented cell division. I expect the outcomes of this project to connect developmental regulators to the cell division machinery and thus to fill a major gap in our knowledge on how supracellular development is implemented into individual cell behaviour.