Different modes of de novo telomere formation by plant telomerases

• Published in: The Plant journal : for cell and molecular biology Vol. 26; no. 1; pp. 77 - 87
• Main Authors: Fitzgerald, Matthew S., Shakirov, Eugene V., Hood, Elizabeth E., McKnight, Thomas D., Shippen, Dorothy E.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.04.2001; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; Arabidopsis; Arabidopsis - enzymology; Arabidopsis thaliana; Biological and medical sciences; chromosome healing; Chromosomes - genetics; DNA, Plant - biosynthesis; DNA, Plant - metabolism; Economic plant physiology; Enzymes; fidelity; Fundamental and applied biological sciences. Psychology; Glycine max; Glycine max - enzymology; maize; Metabolism; Nutrition. Photosynthesis. Respiration. Metabolism; Plant physiology and development; Plants - enzymology; Plants - genetics; Poaceae - enzymology; Sequence Analysis, DNA; Species Specificity; Substrate Specificity; telomerase; Telomerase - classification; Telomerase - metabolism; Telomere - metabolism; TRAP assay; Zea mays; Monocotyledones; RNA-directed DNA polymerase; Telomere; Cereal crop; Arabidopsis thaliana; Sorghum bicolor; Cruciferae; Gramineae; Dicotyledones; Telomerization; Angiospermae; Substrate attachment; Repair; Zea mays; Weed; Enzyme; Transferases; Interspecific comparison; Chromosome; Glycine max; Caryophyllaceae; Grain legume; Nucleotidyltransferases; Leguminosae; Spermatophyta; Experimental plant
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313x.2001.01010.x

Summary The telomerase reverse transcriptase can recognize broken chromosome ends and add new telomeres de novo in a reaction termed ‘chromosome healing’. Here we investigate new telomere formation in vitro by telomerases from a variety of flowering plant species. Comparing the electrophoretic mobilities and nucleotide sequences of the products, we uncovered three different modes of new telomere formation. The soybean telomerase, designated a Class I enzyme, only elongated DNA primers ending in telomeric nucleotides. Arabidopsis and maize telomerases, designated Class II enzymes, efficiently extended completely non‐telomeric sequences by positioning the 3′ terminus at a preferred site on the RNA template. Silene latifolia and sorghum telomerases constituted class III enzymes that elongated non‐telomeric DNA primers by annealing them at alternative sites on the RNA template. For all enzymes, errors were prevalent during synthesis of the first two repeats, likely reflecting lateral instability of the primer 3′ terminus on the template during the initial rounds of elongation. Class III telomerases, however, were five‐ to 13‐fold more error prone than class II, generating more mistakes in distal repeats added to the primers. This remarkable variability in enzyme–DNA interactions among plant telomerases does not reflect phylogenetic relationships, and therefore implies that the telomerase active site can evolve rapidly.