Identification and characterization of genes for cell polarity and asymmetric cell division in plants

不对称的细胞分裂产生两个不同的子细胞。尽管已知mRNA或蛋白质的不均匀分布在每个子细胞的特化中起着关键作用，但在植物中这种分子仍然很大程度上是未知的。该苔藓为研究细胞不对称分裂的分子机制提供了一个很好的系统。原生质体不对称分裂产生顶端干细胞和分化的原生质部非干细胞，之后顶端干细胞继续不对称分裂产生一排分化的原生质部细胞。我们已经设计了一个系统的过表达筛选，并确定了58个参与细胞不对称分裂的基因的候选基因。针对这些候选基因，我们利用基因打靶技术获得了转基因植株，研究了在天然启动子控制下的细胞不对称分裂过程中的蛋白质定位。我们发现一些融合蛋白优先聚集在顶端干细胞中，其中两个位于顶端细胞内。

Asymmetric cell division generates two different daughter cells. Although unequal distribution of mRNA or proteins has been known to play a pivotal role to specialize each daughter cell, such molecules in plants remain largely unknown. The moss, Physcomitrella patens assures a good system for the study of molecular mechanisms for asymmetric cell division. The protoplast divides asymmetrically to generate apical stem cell and differentiated protonemal, non-stem cell, thereafter the apical stem cell continues to divide asymmetrically to generate a row of differentiated protonemal cells. We have devised a systematic overexpression screening and identified 58 cDNAs as candidates for genes that are involved in asymmetric cell division. For those candidates, we made cDNA-citrine knock-in transgenic plants by using gene targeting technique to investigate protein localization during asymmetric cell division under a control of native promoters. We found several fusion proteins preferentially accumulated in apical stem cells, two of which were intracellularly localized within the apical cell.