The Formation of Endoplasmic Reticulum and the Shape of Plants

内质网(ER)是细胞内相互连接的小管组成的多边形网络。内质网是蛋白质和脂类生成的场所。我研究的长期目标是了解内质网是如何形成的，以及随着植物生长过程中细胞形态的变化，蛋白质和脂肪是如何在植物细胞内制造和运输的。我们最近表明，一种名为RHD3的植物蛋白在相互连接的多边ER管的生成中发挥着重要作用(Chen等人，2011年)。J.细胞科学124：2241)。 在这个方案中，我们将进一步研究RHD3和其他蛋白质如何控制相互连接的内质网的形成。我们将使用活细胞成像技术1)量化RHD3对ER小管的细胞作用；使用遗传学、生物化学和活细胞成像的组合方法2)研究另一种称为TIP1的蛋白质对RHD3的调节；3)研究RHD3与一种名为PIS2的蛋白质相互作用在相互连接的ER小管生成中的作用。在拟南芥中，RHD3的突变会影响细胞的生长方向，导致根和茎中的细胞形状异常。植物细胞被称为细胞壁的细胞外基质包围，细胞壁主要由纤维素微纤维组成。垂直于细胞生长方向的纤维微原纤维的线性分布对于植物细胞沿正确方向生长很重要。由于rhd3突变体在纤维素的积累方面存在缺陷，我们将研究纤维素和其他细胞壁材料在rhd3突变体中的运输和定位。 植物被人类用来生产食物、衣服、木材和药品。植物细胞的内质网一直是生物技术改善食品、油脂和药物积累的目标。了解ER是如何形成的，将有助于合理设计以植物为基础的材料生产。其次，利用植物细胞壁作为新的生物燃料的需求越来越大，但植物细胞如何在细胞外部组装和组织不同的细胞壁成分还不是很清楚。这项拟议的研究将阐明细胞壁材料是如何在植物细胞中适当分泌和定位的。

The endoplasmic reticulum (ER) is a polygonal network of interconnected tubules stretching inside cells. The ER is the site where proteins and lipids are made. The long term objective of my research is to understand how the ER is formed and how proteins and lipids are made and transported inside plant cells as cell morphology changes during plant growth. We recently show that a plant protein called RHD3 plays an important role in the generation of interconnected polygonal ER tubules (Chen et al., 2011. J. Cell Sci.124:2241). In this proposal, we will further investigate how RHD3, together with other proteins, controls the formation of interconnected ER network. We will use a living cell imaging technology to 1) quantify the cellular action of RHD3 on ER tubules; using a combined method of genetics, biochemistry and living cell imaging to 2) investigate the regulation of RHD3 by another protein called TIP1 and 3) to study the role of the RHD3 interaction with a protein called PIS2 in the generation of interconnected ER tubules. In Arabidopsis, mutations in RHD3 affect the direction of cell growth, resulting in abnormally-shaped cells in both roots and shoots. Plant cells are surrounded by an extracellular matrix called cell wall, composed of mainly cellulosic microfibrils. A linear distribution of cellulosic microfibrils perpendicular to the direction of cell growth is important for plant cells to grow in right direction. Because the rhd3 mutant is defective in the accumulation of cellulose, we will 4) investigate how cellulose and other cell wall materials are transported and positioned in the rhd3 mutant. Plants are used by the humans to produce food, clothes, wood and medicines. The ER of plant cells has been a target of biotechnology for improved accumulation of food, oils and pharmaceuticals. Understanding how the ER is formed will help rational design of plant-based production of materials. Secondly, there has been an increasing demand of using plant cell walls as new biofuels, but how plant cells assemble and organize the diverse components of the wall on the outside of the cell is not well understood. The proposed research will shed lights on how cell wall materials are secreted and positioned properly in plant cells.