School of Biological Sciences, Macleay Building A12, University of Sydney, NSW 2006, Australia.
Plant J. 2011 Jun;66(5):806-17. doi: 10.1111/j.1365-313X.2011.04545.x. Epub 2011 Apr 4.
Plasmodesmata are plasma membrane-lined channels through which cytoplasmic molecules move from cell-to-cell in plants. Most plasmodesmata contain a desmotubule, a central tube of endoplasmic reticulum (ER), that connects the ER of adjacent cells. Here we demonstrate that molecules of up to 10.4 kDa in size can move between the ER lumen of neighbouring leaf trichome or epidermal cells via the desmotubule lumen. Fluorescent molecules of up to 10 kDa, microinjected into the ER of Nicotiana trichome cells, consistently moved into the ER and nuclei of neighbouring trichome cells. This movement occurred more rapidly than movement via the cytoplasmic pathway. A fluorescent 3-kDa dextran microinjected into the ER of a basal trichome cell moved into the ER and nuclei of epidermal cells across a barrier to cytoplasmic movement. We constructed a 10.4-kDa recombinant ER-lumenal reporter protein (LRP) from a fragment of the endogenous ER-lumenal binding protein AtBIP1. Following transient expression of the LRP in the ER of Tradescantia leaf epidermal cells, it often moved into the nuclear envelopes of neighbouring cells. However, green fluorescent protein targeted to the ER lumen (ER-GFP) did not move from cell to cell. We propose that the ER lumen of plant cells is continuous with that of their neighbours, and allows movement of small ER-lumenal molecules between cells.
胞间连丝是植物细胞之间细胞质分子运动的质膜通道。大多数胞间连丝包含一个中央内质网（ER）小管，将相邻细胞的 ER 连接起来。在这里，我们证明了大小可达 10.4 kDa 的分子可以通过中央小管腔在相邻的叶毛状体或表皮细胞的 ER 腔之间移动。荧光分子大小可达 10 kDa，微注射到烟草原生质体细胞的 ER 中，一致地进入相邻毛状体细胞的 ER 和核。这种运动比通过细胞质途径的运动更快。荧光 3 kDa 葡聚糖微注射到一个基础毛状体细胞的 ER 中，穿过细胞质运动的屏障进入表皮细胞的 ER 和核。我们从内源性 ER 腔结合蛋白 AtBIP1 的片段构建了一个 10.4 kDa 的重组 ER 腔报告蛋白（LRP）。LRP 在 Tradescantia 叶表皮细胞的 ER 中瞬时表达后，它经常进入邻近细胞的核膜。然而，靶向 ER 腔的绿色荧光蛋白（ER-GFP）不会从一个细胞移动到另一个细胞。我们提出，植物细胞的 ER 腔与其相邻细胞的 ER 腔是连续的，并允许小分子 ER 腔分子在细胞之间移动。
