Telomeres are specialized chromatin structures located at the ends of linear eukaryotic chromosomes, where they play a crucial role in maintaining genome stability and cellular longevity. Telomeres distinguish natural chromosomal termini from double-strand DNA breaks, thereby preventing inappropriate repair processes ("end-protection problem”). Telomeres also address the incomplete replication of DNA lagging strands, which would otherwise cause progressive chromosome shortening during cell division ("end-replication problem").
At the DNA level, telomeres consist of short repeats, TTAGGG in vertebrates and TTTAGGG in most plants. Despite the relatively high level of conservation of telomeric repeat motifs, telomere length is an extremely variable parameter; in plants, it ranges from roughly 0.5 kb in algae to hundreds of kilobases in species of the genus Nicotiana. Even within a single cell, telomeres on different chromosome arms can maintain distinct yet stable lengths. Telomere length is generally determined by the interplay between positive and negative regulatory factors. Positive regulators facilitate the assembly of the telomerase, a ribonucleotide enzyme complex able to elongate telomeres, and its recruitment to chromosome ends. Negative regulators include telomere-associated proteins that shape telomeric chromatin and restrict telomerase access to telomeres. While this balance can explain the species-specific telomere length determination, it does not account for characteristic length settings of telomeres on individual chromosome arms. Despite considerable efforts, the mechanisms governing chromosome arm-specific telomere length regulation remain unknown.
(i) Telomeres in Arabidopsis thaliana plants with restructured chromosomes
Using a CRISPR-Cas9-based approach, Arabidopsis thaliana plants with markedly restructured chromosomes were generated (Beying et al. 2020, Rönspies et al. 2025). In these plants, chromosome ends were relocated to new chromatin environments, providing an opportunity to dissect the contribution of cis- and trans-acting mechanisms to telomere length maintenance. Our comprehensive analyses demonstrated the remarkable robustness of A. thaliana to large-scale genome rearrangements (Helia et al. 2025, Rönspies et al. 2025).
(ii) Dynamics of telomeres in plant calli and regenerated plants
In our previous research, we observed disruption of telomere length homeostasis during long-term propagation of calli derived from A. thaliana seedlings. Through comparative analyses of telomere length dynamics and gene expression in calli originating from different organs of both model and crop species (A. thaliana, carrot, cabbage), as well as in plants regenerated from these cultures, we aim to identify factors that contribute to the telomere length setting.
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PhD candidates:
Ondřej Helia
Anna Kromerová
Grad. students:
Anna Vávra
Tereza Horáková
Alumni:
Klára Přikrylová
Martin Lyčka
Pavla Sováková
Kateřina Adamusová
Sylva Brabencová
Karin Jaške
Anna Ogrocká
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Martin Lyčka
National Taiwan University, Taipei, Taiwan
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Kateřina Adamcová
University of Copenhagen, Dánsko