Programmed cell death in plant development

程序性细胞死亡（PCD）是一种遗传激活的过程，其中选择的细胞组织自己的破坏。PCD在所有真核生物界中普遍存在，并且被单细胞和多细胞生物体用作正常发育的一部分或响应于外部刺激。在植物中，PCD是生长和存活所必需的，可以是发育调节的或环境诱导的。发育PCD的一个独特实例是花边植物叶中的穿孔（孔）形成。这些孔位于纵脉和横脉之间等距离，使叶子呈格子状。在穿孔形成期间，离散的细胞亚群经历PCD，而相邻细胞保持完整。花边植物原产于马达加斯加，在水族箱条件下很难生长。本人成功地建立了一套适合于花边植物PCD研究的组织培养体系。我们仍然不知道是什么线索触发PCD在叶发育的特定阶段，就信号通路和分子机制而言。本研究对花边植物穿孔形成过程中的细胞死亡过程进行了表征，表明花边植物是研究体内发育PCD的理想模式系统。因此，我的研究的长期目标是实现一个基本的理解，在发育PCD使用花边植物叶片形态建成作为模型系统的机制。这将通过以下目标实现：1）使用活细胞成像技术表征PCD事件的顺序并生成3D模型; 2）研究花边植物PCD过程中肌动蛋白细胞骨架的变化; 3）研究钙和线粒体内膜空间蛋白在PCD初始阶段的作用; 4）评估乙烯作为诱导信号在花边植物PCD中的作用; 5）用简并引物鉴定乙烯受体基因。这些结果将有助于我们确定动物和植物PCD之间是否存在共同的机制，或者它们是否独立进化。

Programmed cell death (PCD) is a genetically-enabled process in which select cells organize their own destruction. PCD is ubiquitous in all eukaryotic kingdoms and is employed by both unicellular and multicellular organisms as part of normal development or in response to external stimuli. In plants, PCD is necessary for growth and survival and can either be developmentally regulated or environmentally induced. A unique example of developmental PCD is perforation (holes) formation in lace plant leaves. These holes are situated equidistantly between longitudinal and transverse veins, giving leaves a lattice-like pattern. During perforation formation, discrete subpopulations of cells undergo PCD while adjacent cells remain intact. Lace plant is native to Madagascar and difficult to grow in aquarium conditions. I have successfully developed a tissue culture system to work on developmental PCD in lace plant. We still do not know what cues trigger PCD at a specific stage of leaf development, as far as the signaling pathways and the molecular mechanisms are concerned. I have characterized the cell death process during perforation formation in lace plant and showed that this aquatic plant is an ideal model system to study developmental PCD in vivo. Therefore, the long term objective of my research is to achieve a fundamental understanding of the mechanisms involved in developmental PCD using lace plant leaf morphogenesis as a model system. This will be achieved through the following objectives: 1) Characterize the order of PCD events using live cell imaging techniques and generate 3-D models; 2) Investigate changes in the actin cytoskeleton during lace plant PCD; 3) Investigate the roles of calcium and mitochondrial inner membrane space proteins in the initial stages of PCD; 4) Evaluate the role of ethylene as an induction signal in lace plant PCD; 5) Identify ethylene receptor genes using degenerate primers. These results will help us to determine whether there are common mechanisms between animal and plant PCD or whether they evolved independently.