Telomerase Activator 1: a Zinc-finger Protein That Acts Synergistically with Auxin to Control Telomerase Expression in Arabidopsis Thaliana

Telomerase Activator 1: A Zinc-Finger Protein That Acts Synergistically with Auxin to Control Telomerase Expression in Arabidopsis thaliana. (August 2003) Shuxin Ren, B.S., Beijing Agricultural University, Beijing, P.R. China Co-Chairs of Advisory Committee: Dr. Thomas D. McKnight Dr. Dorothy E. Shippen Telomerase is the key enzyme synthesizing telomeric DNA in most eukaryotic organisms. In mammals, telomerase expression is abundant in the germline cells but is undetectable in most other differentiated organs. Intensive studies of telomerase have focused on human cancerous cells, where over 90% of all cancerous tissues examined have telomerase activity. In wild-type Arabidopsis, telomerase expression is abundant in reproductive organs and dedifferentiated tissues such as flowers, siliques and calli but barely detectable in vegetative tissues (both rosette and cauline leaves). In this study, a biochemical screen strategy was developed for isolation of telomerase activating mutants in Arabidopsis thaliana. Through screening of Arabidopsis activation-tagged lines by a PCR-based TRAP assay, two tac (for telomerase activator) mutants were isolated. RTPCR analysis of AtTERT expression revealed that different mechanisms are involved in alternating telomerase activity in tac1 and tac2. We cloned and characterized the TAC1 gene. TAC1 encodes a single zinc finger protein and acts synergistically with auxin to induce telomerase expression without altering cell cycles. Telomere length was unperturbed in the mutant, but other phenotypes, such as altered root development and the ability of cells to grow in culture