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。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发育PCD的理想模式系统。 花边植物原产于马达加斯加，在水族箱条件下很难生长。我已经成功地开发了一个无菌培养的花边植物系统，以研究发育中的PCD。我们仍然不知道在叶片发育的适当阶段是什么线索触发PCD，信号通路和分子机制。因此，本论文的总体目标是利用生物化学和显微技术，从以下四个方面研究花边植物细胞穿孔的诱导因素和调控机制：1）研究花边植物PCD过程中肌动蛋白骨架的变化; 2）比较同一种植物的诱导和发育PCD; 3）建立花边植物的稳定和瞬时转化方案; 4）检测钙抑制剂对植物细胞死亡的影响。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. 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. Lace plant is native to Madagascar and difficult to grow in aquarium conditions. I have successfully developed an axenically cultured lace plant system to work on developmental PCD. We still do not know what cues trigger PCD at the appropriate stage of leaf development, the signaling pathways, and the molecular mechanisms. Therefore, my overall aim is to identify factors inducing perforations and the mechanisms that regulate the PCD in lace plant using biochemical and microscopical techniques with four approaches: 1) To investigate changes in the actin cytoskeleton during lace plant PCD; 2) To compare induced and developmental PCD in the same plant species; 3) To develop both a stable and transient transformation protocol for lace plant; 4) To test the effect of calcium inhibitors on cell death in plants. These results will help us to determine whether there are common mechanisms between animal and plant PCD or whether they evolved independently.