Expression and Regulation of Telomerase in Arabidopsis Thaliana

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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.