Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Plant J. 2011 May;66(4):629-41. doi: 10.1111/j.1365-313X.2011.04523.x. Epub 2011 Mar 21.
The nuclear envelope (NE) is a highly active structure with a specific set of nuclear envelope proteins acting in diverse cellular events. SUN proteins are conserved NE proteins among eukaryotes. Although they form nucleocytoplasmic linkage complexes in metazoan cells, their functions in the plant kingdom are unknown. To understand the function of plant SUN proteins, in this study we first investigated the dynamics of Arabidopsis SUN proteins during mitosis in Arabidopsis roots and cultured cells. For this purpose, we performed dual and triple visualization of these proteins, microtubules, chromosomes, and endoplasmic reticulum (ER) in cultured cells, and observed their dynamics during mitosis using a high-speed spinning disk confocal microscope. The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics. Moreover, NE re-formation marked with SUN proteins is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts. Finally, the analysis with gene knockdowns of AtSUN1 and AtSUN2 indicated that they are necessary for the maintenance and/or formation of polarized nuclear shape in root hairs. These results suggest that Arabidopsis SUN proteins function in the maintenance or formation of nuclear shape as components of the nucleocytoskeletal complex.
核膜（NE）是一种高度活跃的结构，具有一组特定的核膜蛋白，在多种细胞事件中发挥作用。SUN 蛋白是真核生物中保守的核膜蛋白。尽管它们在后生动物细胞中形成核质连接复合物，但它们在植物界的功能尚不清楚。为了了解植物 SUN 蛋白的功能，本研究首先在拟南芥根和培养细胞中研究了 SUN 蛋白在有丝分裂过程中的动态变化。为此，我们在培养细胞中对这些蛋白、微管、染色体和内质网（ER）进行了双重和三重可视化，并使用高速旋转盘共聚焦显微镜观察了它们在有丝分裂过程中的动态变化。SUN 蛋白的定位在有丝分裂过程中动态变化，与 NE 动力学紧密相关。此外，用 SUN 蛋白标记的 NE 再形成与植物特异性微管结构（如成膜体）在时间和空间上协调一致。最后，对 AtSUN1 和 AtSUN2 的基因敲低分析表明，它们对于根毛中极性核形状的维持和/或形成是必需的。这些结果表明，拟南芥 SUN 蛋白作为核质骨架复合物的组成部分，在核形状的维持或形成中发挥作用。
