Identification and characterization of tac5, a telomerase activation mutant, characterization of DNA damage responses and assessment of interactions between telomere-related proteins in Arabidopsis thaliana



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statistics, 2) unadjusted inferential statistics, 3) stratified analysis, and 4) multivariable models. My investigation produced results in accord with generally accepted notions in addition to significant findings that interestingly counter current preconceptions. Intraspecies contact was more common than inter-species, with indirect contact occurring more frequently than direct. Direct contact between species occurred extremely rarely. The most important factors that influenced the rate of contact for both species were water, winter, and cultivated fields. Information regarding probability of infectious agent survival and transfer will be used in the future to advance current epidemiological models, including geographicautomata (Ward et al. 2007: In Press) and cellular automata models (Doran and Laffan 2005) to better understand and manage integrated domestic cattle and free-ranging wildlife populations. Such modeling provides essential and necessary knowledge for developing prevention, detection, response, and recovery strategies ? employed in advance, during, and after a disease outbreak, respectively. responsible for telomere activation. In addition tac5 showed sensitivity to hydrogen peroxide treatment, suggesting a novel role of telomerase in the mitochondrial environment. Chapter III reports the role of PARP proteins in plant telomere biology. Both AtPARP1 and AtPARP2 are transcriptionally upregulated in response to DNA damage treatment or telomere dysfunction. However, in contrast to mammalian PARPs, the Arabidopsis proteins do not appear to have a function in telomere length maintenance as indicated by TRF analysis or in promoting genome stability maintenance as indicated by cytogenetic studies. Further analysis of PARP interactions at dysfunctional telomeres in the genetically tractable Arabidopsis model may provide insight into the cellular response to dysfunctional telomeres. As explained in chapter IV, the yeast two-hybrid screen was utilized to confirm the interactions of ATR with AtPOT2 and Ku80 and to identify novel interacting partners of Arabidopsis telomere proteins. At2g04410 (Unknown protein) was identified as a direct interacting partner of AtPOT1. This interaction was confirmed in vitro by coimmunoprecipitation assay. Further analysis of the unknown protein may shed light on AtPOT1?s function in telomere maintenance.