CHARACTERIZATION AND DEVELOPMENTAL PATTERNS OF TELOMERASE EXPRESSION IN PLANTS

Telomerase activity is developmentally regulated in mammals. Here we e xamine telomerase activity in plants, whose development differs in fun damental ways from that of animals. Using a modified version of the te lomere repeat amplification protocol (TRAP) assay, we detected an acti vity in extracts from carrots, cauliflower, soybean, Arabidopsis, and rice with all the characteristics expected for a telomerase synthesizi ng the plant telomere repeat sequence TTTAGGG. The activity was depend ent on RNA and protein components, required dGTP, dATP, and dTTP, but not dCTP, and generated products with a seven nucleotide periodicity. Telomerase activity was abundant in cauliflower meristematic tissue an d undifferentiated cells from Arabidopsis, soybean, and carrot suspens ion cultures, but was low or not detectable in a sampling of different iated tissues from mature plants. Telomerase from cauliflower meristem atic tissues exhibited relaxed DNA sequence requirements, which might reflect the capacity to form telomeres on broken chromosomes in Fire, The dramatic differences in telomerase expression and their correlatio n with cellular proliferation capacity mirror changes in human telomer ase levels during differentiation and immortalization, Hence, telomera se activation appears to be a conserved mechanism involved in conferri ng long-term proliferation capacity.