Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.
Department of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
Gene. 2014 Jul 10;544(2):241-7. doi: 10.1016/j.gene.2014.04.057. Epub 2014 Apr 25.
Cell polarity is fundamentally important to growth and development in higher plants, from pollen tubes to root hairs. Basal land plants (mosses and ferns) also have cell polarity, developing protonemal apical cells that show polar tip growth. Flowering plants have a distinct group of Rho GTPases that regulate polarity in polarized cell growth. Rop/RAC signaling module components have been identified in non-flowering plants, but their roles remain unclear. To understand the importance and evolution of Rop/RAC signaling in polarity regulation in land plants, we examined the functions of PpRop and PpRopGEF in protonemal apical cells of the moss Physcomitrella patens. Inducible overexpression of PpRop2 or PpRopGEF3 caused depolarized growth of tip-growing apical cells. PpRop2 overexpression also caused aberrant cross wall formation. Fluorescent protein-tagged PpRop2 localized to the plasma membrane, including the cross wall membrane, and fluorescent-tagged PpRopGEF3 showed polarized localization to the tip region in apical cells. Thus, our results suggest common functions of PpRop and PpRopGEF in the tip-growing apical cells and the importance of a conserved Rop/RAC signaling module in the control of cell polarity in land plants.
细胞极性对于高等植物的生长和发育至关重要，从花粉管到根毛。基生陆地植物（苔藓和蕨类植物）也具有细胞极性，它们会发育出原丝体顶端细胞，这些细胞表现出极性尖端生长。开花植物具有一组独特的 Rho GTPases，它们可以调节极性细胞生长中的极性。已经在非开花植物中鉴定出 Rop/RAC 信号模块的组成部分，但它们的作用仍不清楚。为了了解 Rop/RAC 信号在陆地植物极性调控中的重要性和进化，我们研究了苔藓植物Physcomitrella patens 原丝体顶端细胞中 PpRop 和 PpRopGEF 的功能。PpRop2 或 PpRopGEF3 的诱导过表达导致尖端生长的顶端细胞去极化生长。PpRop2 的过表达也导致异常的交叉壁形成。荧光蛋白标记的 PpRop2 定位于质膜，包括交叉壁膜，而荧光标记的 PpRopGEF3 在顶端细胞的顶端区域表现出极化定位。因此，我们的结果表明 PpRop 和 PpRopGEF 在尖端生长的顶端细胞中具有共同的功能，并且保守的 Rop/RAC 信号模块在控制陆地植物细胞极性方面非常重要。
