Regulation of Telomerase and Telomeres in Plants

Texas A&M Research Foundation, College Station TX

Investigators

Abstract

Telomeres are specialized nucleoprotein complexes at the ends of eukaryotic chromosomes that are essential for proper chromosome behavior and stability of the genome. Telomerase, a complex ribonucleoprotein with reverse transcriptase activity, is responsible for synthesizing and maintaining telomeric DNA in most organisms. Telomere biology has received a lot of attention in the last 10 years, largely for its potential roles in aging and cancer in mammals, but the critical functions of telomeres and telomerase are conserved in nearly all eukaryotes. The model plant Arabidopsis thaliana is a multicellular organism with a vast array of genetic tools make it an ideal system for investigating the regulation of telomerase. Although plants and animals became multicellular through independent evolutionary pathways, the fundamentals of telomere biology are broadly similar in these diverse lineages. At least some of results obtained in Arabidopsis should be applicable to a wide range of eukaryotes, including mammals. The overall goal of this project is to identify and characterize genes that regulate telomerase activity by screening activation-tagged lines of Arabidopsis for mutants that ectopically express telomerase in their leaves. The identification of one such gene has validated the utility of this approach. This gene, TELOMERASE ACTIVATOR 1 (TAC1), encodes a previously uncharacterized protein with a single zinc finger that appears to regulate telomerase activity by altering auxin metabolism. One aim of this project is to further define the mechanism by which TAC1 activates telomerase. Three additional telomerase-activation mutants, tac2, tac3, and tac4, have been isolated. A second aim of the work is to identify and characterize the gene in the tac2 mutant that activates telomerase. Characterization of tac3, tac4, and any newly identified mutants will proceed as resources allow. This research will elucidate fundamental mechanisms for maintaining stability of the plant genome, and at least in part, should be broadly applicable to other eukaryotes. Even the discovery of plant-specific mechanisms will provide illuminating examples for comparative telomere biology.