开花植物的胚胎发生起始于合子不对称分裂，产生的两个子细胞将按照固定的模式分别发育为胚体和胚柄，植物的顶基轴也在此步开始建立。合子不对称分裂的机理是一个备受关注的生物学问题，但目前仅有少量的调控因子被鉴定出。我们的前期工作发现玉米SUMO家族成员diSUMO-like（DSUL）是合子不对称分裂必需的，它在细胞核的极性迁移过程中具有重要作用。拟南芥合子细胞核的极性迁移和不对称分裂依赖于微丝骨架，而Actin是我们鉴定出的DSUL主要修饰底物之一，暗示DSUL很可能通过调控微丝骨架排布来控制细胞核极性迁移和合子不对称分裂。本项目拟通过对与细胞分裂和极性分布相关的DSUL靶蛋白、相互作用蛋白和特异结合酶在合子不对称分裂中的作用及其调控网络进行研究，解析DSUL调控合子不对称分裂过程的分子机理，完善对胚对胚胎发生起始这一重要发育过程的理解，为认识不对称分裂的复杂调控机制提供新的视角。

In most flowering plants, embryogenesis is initiated by an asymmetric zygote division, generating two daughter cells that are precursors of different cell lineages. The apical-basal axis of the embryo as well as the mature plant is also defined in this step. Despite its importance, little is known about the molecular mechanism regulating the establishment of zygote polarity, and the process of the first asymmetrical division. In our previous work, we found that a diSUMO-like protein called DSUL plays an important role in polar nuclei migration, and is required for the first asymmetric zygote division in maize. In Arabidopsis, F-actin is required to position the nucleus to the apical region of the zygote, setting the plane of the first asymmetrical division. We have recently identified Actin as a main substrate of DSUL, implying that DSUL may regulate polar nuclear migration and thus the first asymmetric zygote division through modulating F-Actin patterns. In this study, we will adopt cell and molecular biology, genetics and chemical cytology approaches to investigate DSUL targets, interacting proteins as well as specific conjugating enzymes that are related to cell division and polar localization. We intend to elucidate their activity, subcellular localization and the genetic network in which they function. Knowledge gained from this study will not only facilitate understanding of the molecular mechanisms by which DSUL regulates asymmetric zygote division but also provide insights about the involvement of SUMO family protein in controlling asymmetry in plants.