Identification and Characterization of Cell Survival Genes from Plants

植物生物学中一个新出现的问题是，植物在发育和病原体攻击过程中是否表现出与哺乳动物程序性细胞死亡(细胞凋亡)类似的元素。在植物-病原菌相互作用方面，细胞死亡发生在感病和抗性寄主反应中。例如，在抗性反应中，植物中的特定识别反应触发了“超敏反应”(HR)的形成和寄主防御机制的激活。HR触发细胞死亡途径，从而限制病原体的生长和疾病的发展。从历史上看，HR一直被认为是坏死的产物，但一些研究表明，HR过程中的细胞死亡涉及到植物编码的细胞自杀程序的激活，这可能类似于细胞凋亡。敏感的相互作用也会导致宿主细胞死亡，尽管目前还不清楚宿主在多大程度上(如果有的话)参与了这种反应。最近在我的实验室获得的数据有力地表明，在病原菌感染的烟草植株的疾病发展过程中，细胞凋亡正在发生。已观察到细胞凋亡的显著特征，包括离散的DNA片段化(例如，DNA梯形图)和核固缩。这些凋亡反应在转基因抗病烟草中不会发生。根据这些数据以及来自其他实验室的报告，似乎动物细胞自杀的成分在植物中是功能保守的。这项研究的中心假设是，植物与动物具有某些共同的细胞凋亡特征。该项目的目标是：(I)鉴定与动物细胞凋亡途径中发现的基因功能相似的植物基因，并评估这些基因的分辨率，即植物中的细胞死亡过程。了解植物如何调控细胞自杀将提供有关植物对环境胁迫的反应的信息，并有可能产生有效的抗病植物。

An emerging question in plant biology is whether plants display analogous elements of mammalian-programmed cell death (apoptosis) during development and pathogen attack. With respect to plant-pathogen interactions, cell death occurs in both susceptible disease and resistant host responses. For example, in resistant reactions, specific recognition responses in plants trigger formation of the "hypersensitive response" (HR) and activation of host defense mechanisms. HR triggers a cell death pathway resulting in restriction of pathogen growth and disease development. Historically HR has been considered a product of necrosis, but several studies have suggested that cell death during HR involves activation of a plant-encoded program for cell suicide that may resemble apoptosis. Susceptible interactions also result in host cell death although it is unclear to what degree (if any) the host participates in this response. Recent data obtained in my laboratory strongly suggest that during disease development in pathogen infected susceptible tobacco plants, apoptosis is occurring. Hallmark characteristics of apoptosis, including discrete DNA fragmentation (e.g., DNA ladders) and nuclear condensation have been observed. These apoptotic responses do not occur in the transgenic, disease resistant tobacco. Based on these data, as well as reports from other laboratories, it appears that elements of animal cell suicide are functionally conserved in plants. The central hypothesis of this research is that plants share certain features of apoptosis with animals. The goal of this project are: (I) to identify and characterize plant genes which functionally resemble those found in animal apoptosis pathways and evaluate these genes in resolution, the cell death process in plants. An understanding of how plants regulate cellular suicide will provide information regarding plant response to environmental stress and have the potential to generate effective disease resistant plants.