Abstract：
Oriented cell divisions establish plant tissue and organ patterning and produce different cell types; this is particularly true of the highly organized Arabidopsis (Arabidopsis thaliana) root meristem. Mutant alleles of INFLORESCENCE AND ROOT APICES RECEPTOR KINASE (IRK) exhibit excess cell divisions in the root endodermis. IRK is a transmembrane receptor kinase that localizes to the outer polar domain of these cells, suggesting that directional signal perception is necessary to repress endodermal cell division. Here, a detailed examination revealed many of the excess endodermal divisions in irk have division planes that specifically skew towards the outer lateral side. Therefore, we termed them \'outward askew\' divisions. Expression of an IRK truncation lacking the kinase domain retains polar localization and prevents outward askew divisions in irk; however, the roots exhibit excess periclinal endodermal divisions. Using cell identity markers, we show that the daughters of outward askew divisions transition from endodermal to cortical identity similar to those of periclinal divisions. These results extend the requirement for IRK beyond repression of cell division activity to include cell division plane positioning. Based on its polarity, we propose that IRK at the outer lateral endodermal cell face participates in division plane positioning to ensure normal root ground tissue patterning.
摘要：
定向细胞分裂建立植物组织和器官模式并产生不同的细胞类型;对于高度组织的拟南芥(拟南芥)根分生组织尤其如此。在根内皮层表现出过度的细胞分裂。IRK是一种跨膜受体激酶，位于这些细胞的外极性结构域，这表明定向信号感知是抑制内胚层细胞分裂所必需的。这里,详细的检查显示，irk中许多多余的内胚层分裂具有向外侧倾斜的分裂平面。因此,我们称之为“向外歪斜”的部门。缺乏激酶结构域的IRK截短的表达保留了极性定位，并防止了irk中的向外歪斜分裂；然而，根部表现出过度的外缘内胚层分裂。使用细胞身份标记，我们表明，向外歪斜分裂的子体从内胚层过渡到皮质身份，类似于外围分裂。这些结果扩展了对IRK的需求，不仅抑制了细胞分裂活性，还包括细胞分裂平面定位。基于它的极性，我们建议外外侧内胚层细胞面的IRK参与分裂平面定位，以确保正常的根底组织图案。
