Geminiviruses and Plant Gene Expression

视网膜母细胞瘤蛋白和E2F转录因子是动物细胞分裂和分化的关键调控因子。相关蛋白质已经在植物中被发现，但对它们的功能知之甚少。在动物中，我们对pRb和E2F的大部分知识来自于对DNA肿瘤病毒及其肿瘤抗原蛋白的研究。这些病毒蛋白与低磷酸化的pRb(与细胞周期停滞和分化相关的形式)相互作用，破坏pRb/E2F复合体，导致宿主基因表达和细胞周期重入。最近的实验表明，双生病毒使用类似的机制来改变植物的细胞周期控制。本研究的总体目标是分析寄主基因在双生病毒侵染过程中的表达，并利用这些重要的植物病毒作为工具来研究pRband E2F如何调控植物基因的表达。第一个目标是建立一个用于研究双生病毒介导的寄主诱导和pRb相互作用的拟南芥系统。该系统将结合巨型病毒和拟南芥的遗传和数据库工具来研究植物中的pRb和E2F功能。第二个目的是利用基因图谱技术描述与双生病毒感染相关的拟南芥基因表达的全球变化。第三个目标是培育表达野生型和突变型病毒蛋白的转基因植物，这些蛋白只在pRb结合能力上有所不同。比较这些品系的表达谱将有助于深入了解受pRb和E2F控制的植物基因的特性。总之，这些实验很可能识别其产物与植物的细胞分裂周期、内复制、分化和疾病相关的基因。这些研究为研究高等真核生物完整成熟组织的去分化过程和细胞分裂周期提供了一个独特的机会。它们有可能揭示这两个重要过程的植物特有成分，并可能通过洞察改变植物生长的战略对农业产生深远影响。

The retinoblastoma protein (pRb) and the E2F transcription factors are key regulators of celldivision and differentiation in animals. Related proteins have been identified in plants, but little isknown about their functions. In animals, much of our knowledge of pRb and E2F is from studiesof DNA tumor viruses and their tumor antigen proteins. These viral proteins interact withunder-phosphorylated pRb (the form associated with cell cycle arrest and differentiation) anddisrupt pRb/E2F complexes, leading to altered host gene expression and cell cycle reentry.Recent experiments suggested that geminiviruses use a similar mechanism to alter cell cyclecontrols in plants. The overall goals of this research are to analyze host gene expressionduring geminivirus infection and to use these important plant viruses as tools to study how pRband E2F regulate plant gene expression. The first aim is to develop an Arabidopsis system forstudying geminivirus-mediated host induction and pRb interactions. This system will combinegeminiviruses with Arabidopsis genetic and database tools to study pRb and E2F function inplants. The second aim is characterize the global changes in Arabidopsis gene expressionassociated with geminivirus infection using gene profiling technology. The third aim is togenerate transgenic plants that express wild type and mutant viral proteins that differ only in theirpRb binding capacities. Comparison of the expression profiles of these lines will provide insightinto the identities of plant genes controlled by pRb and E2F. Together, these experiments arelikely to identify genes whose products are associated with the cell division cycle,endoreduplication, differentiation, and disease in plants. The studies represent a unique opportunity to study the dedifferentiation process and the return to the cell division cycle in intact mature tissues of a higher eukaryote. They have the potential to uncover plant-specific components of these two important processes and may have a profound impact on agriculture by providing insight into strategies for altering plant growth.