The characterization of unusual telomere sequence sheds light on patterns of telomere evolution, maintenance and function. Plant species from the closely related genera Cestrum, Vestia and Sessea (family Solanaceae) lack known plant telomeric sequences. Here we characterize the telomere of Cestrum elegans, work that was a challenge because of its large genome size and few chromosomes (1C 9.76 pg; n = 8). We developed an approach that combines BAL31 digestion, which digests DNA from the ends and chromosome breaks, with next-generation sequencing (NGS), to generate data analysed in RepeatExplorer, designed for de novo repeats identification and quantification. We identify an unique repeat motif (TTTTTTAGGG)n in C. elegans, occurring in ca. 30 400 copies per haploid genome, averaging ca. 1900 copies per telomere, and synthesized by telomerase. We demonstrate that the motif is synthesized by telomerase. The occurrence of an unusual eukaryote (TTTTTTAGGG)n telomeric motif in C. elegans represents a switch in motif from the 'typical' angiosperm telomere (TTTAGGG)n . That switch may have happened with the divergence of Cestrum, Sessea and Vestia. The shift in motif when it arose would have had profound effects on telomere activity. Thus our finding provides a unique handle to study how telomerase and telomeres responded to genetic change, studies that will shed more light on telomere function.

Faculty of Science and CEITEC Central European Institute of Technology Masaryk University Kamenice 5 CZ 62500 Brno Czech Republic

Institute of Biophysics Academy of Sciences of the Czech Republic v v i Královopolská 135 CZ 61265 Brno Czech Republic

School of Biological and Chemical Sciences Queen Mary University of London London E1 4NS UK

References provided by Crossref.org

TeloBase: a community-curated database of telomere sequences across the tree of life

Mega-sized pericentromeric blocks of simple telomeric repeats and their variants reveal patterns of chromosome evolution in ancient Cycadales genomes

Telomeres and Their Neighbors

Telomeric DNA sequences in beetle taxa vary with species richness

Extraordinary diversity of telomeres, telomerase RNAs and their template regions in Saccharomycetaceae

Origin and Fates of TERT Gene Copies in Polyploid Plants

Composition and Function of Telomerase-A Polymerase Associated with the Origin of Eukaryotes

Origin, Diversity, and Evolution of Telomere Sequences in Plants

Telomerase RNAs in land plants

Comparative Dissection of Three Giant Genomes: Allium cepa, Allium sativum, and Allium ursinum

Telomeres in Plants and Humans: Not So Different, Not So Similar

Telomere- and Telomerase-Associated Proteins and Their Functions in the Plant Cell

Transitions between the Arabidopsis-type and the human-type telomere sequence in green algae (clade Caudivolvoxa, Chlamydomonadales)

Telomerase lost?