Expression and Regulation of Telomerase in Arabidopsis Thaliana

端粒是一种核蛋白结构，它在真核生物染色体的末端形成一个保护帽，保护它们免受端到端融合和降解。端粒是通过端粒酶的作用产生和维持的，端粒酶是一种具有逆转录酶活性的核糖核蛋白复合物。在哺乳动物中，端粒酶是决定细胞增殖能力的生物钟的一部分，因为它的表达与衰老和肿瘤发生密切相关。先前的研究表明，模式植物拟南芥对端粒功能障碍表现出异常高的耐受性。在本研究中，将采用分子、遗传学和细胞遗传学的方法来研究端粒酶如何向拟南芥基因组传递稳定性，并鉴定端粒酶全酶复合物的新成分。第一个目标是通过研究缺乏端粒酶的植物如何在端粒酶活性恢复时恢复，来检查植物基因组的可塑性和发育概况。目的二和三集中于鉴定和表征端粒酶全酶的组成部分。分子和生物化学方法将用于鉴定端粒酶的RNA亚基。当端粒酶RNA在手时，突变将被引入端粒模板结构域，以研究端粒核苷酸序列的改变如何影响基因组的稳定性。第三个目的是研究dyskerin在拟南芥中的功能。人类dyskerin蛋白与端粒酶RNA亚基结合。该基因的突变导致先天性角化异常，其特征是干细胞增殖缺陷。目的三将确定dyskerin是否在拟南芥端粒维持和端粒酶RNP生物发生中发挥作用。作为这项研究的一部分，拟南芥dyskerin基因的突变将被改造，试图模仿植物中的角化不良病。总之，这些研究不仅将提供关于端粒酶在植物中的作用的新信息，而且也有可能深入了解端粒酶RNP全酶的结构及其在向广泛的高等真核生物传递基因组稳定性方面的功能。

Telomeres are nucleoprotein structures that form a protective cap on the ends of eukaryotic chromosomes and protect them from end-to-end fusions and degradation. Telomeres are generated and sustained through the action of telomerase, a ribonucleoprotein complex with reverse transcriptase activity. In mammals, telomerase is part of a biological clock that determines the capacity for cellular proliferation, as its expression is strongly linked to aging and tumorigenesis. Previous studies have shown that the model plant, Arabidopsis, exhibits an exceptionally high tolerance to telomere dysfunction. In this research, molecular, genetic and cytogenetic approaches will be conducted to investigate how telomerase conveys stability to the Arabidopsis genome and to identify new components of the telomerase holoenzyme complex. The first objective is to examine the plasticity of the plant genome and developmental profile by studying how plants that lack telomerase can recover when the enzyme activity is restored. Objectives two and three focus on identifying and characterizing components of the telomerase holoenzyme. Molecular and biochemical approaches will be used to identify the RNA subunit of telomerase. When the telomerase RNA is in hand, mutations will be introduced into the telomere templating domain to investigate how changing the nucleotide sequence of the telomere affects genome stability. The third objective is to examine the function of dyskerin in Arabidopsis. The human dyskerin protein binds to the telomerase RNA subunit. Mutations in this gene lead to the genetic disorder, dyskeratosis congenita, which is characterized by defects in stem cell proliferation. Objective three will determine whether dyskerin plays a role in telomere maintenance and telomerase RNP biogenesis in Arabidopsis. As part of this study, a mutation will be engineered in the Arabidopsis dyskerin gene in an attempt to mimic the disease dyskeratosis in plants. Together, these studies will not only provide novel information about the role of telomerase in plants, but are also likely to yield insight into the structure of the telomerase RNP holoenzyme and its function in conveying genome stability to a broad range of higher eukaryotes.