Telomeres, essential for maintaining genomic stability, are typically preserved through the action of telomerase, a ribonucleoprotein complex that synthesizes telomeric DNA. One of its two core components, telomerase RNA (TR), serves as the template for this synthesis, and its evolution across different species is both complex and diverse. This review discusses recent advancements in understanding TR evolution, with a focus on plants (Viridiplantae). Utilizing novel bioinformatic tools and accumulating genomic and transcriptomic data, combined with corresponding experimental validation, researchers have begun to unravel the intricate pathways of TR evolution and telomere maintenance mechanisms. Contrary to previous beliefs, a monophyletic origin of TR has been demonstrated first in land plants and subsequently across the broader phylogenetic megagroup Diaphoretickes. Conversely, the discovery of plant-type TRs in insects challenges assumptions about the monophyletic origin of TRs in animals, suggesting evolutionary innovations coinciding with arthropod divergence. The review also highlights key challenges in TR identification and provides examples of how these have been addressed. Overall, this work underscores the importance of expanding beyond model organisms to comprehend the full complexity of telomerase evolution, with potential applications in agriculture and biotechnology.

• Klíčová slova
• TR evolution, TR identification, non-coding RNA, telomerase RNA, telomere,
• MeSH
• fylogeneze MeSH
• molekulární evoluce * MeSH
• RNA rostlin * genetika   MeSH
• RNA * genetika   metabolismus   MeSH
• rostliny * genetika   MeSH
• telomerasa * genetika   metabolismus   MeSH
• telomery * genetika   metabolismus   MeSH
• Viridiplantae * genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• RNA rostlin * MeSH
• RNA * MeSH
• telomerasa * MeSH
• telomerase RNA MeSH Prohlížeč

Discoveries over the recent decade have demonstrated the unexpected diversity of telomere DNA motifs in nature. However, currently available resources, 'Telomerase database' and 'Plant rDNA database', contain just fragments of all relevant literature published over decades of telomere research as they have a different primary focus and limited updates. To fill this gap, we gathered data about telomere DNA sequences from a thorough literature screen as well as by analysing publicly available NGS data, and we created TeloBase (http://cfb.ceitec.muni.cz/telobase/) as a comprehensive database of information about telomere motif diversity. TeloBase is supplemented by internal taxonomy utilizing popular on-line taxonomic resources that enables in-house data filtration and graphical visualisation of telomere DNA evolutionary dynamics in the form of heat tree plots. TeloBase avoids overreliance on administrators for future data updates by having a simple form and community-curation system for application and approval, respectively, of new telomere sequences by users, which should ensure timeliness of the database and topicality. To demonstrate TeloBase utility, we examined telomere motif diversity in species from the fungal genus Aspergillus, and discovered (TTTATTAGGG)n sequence as a putative telomere motif in the plant family Chrysobalanaceae. This was bioinformatically confirmed by analysing template regions of identified telomerase RNAs.

• MeSH
• databáze genetické * MeSH
• nukleotidové motivy MeSH
• rostliny genetika   MeSH
• telomerasa * genetika   MeSH
• telomery genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• telomerasa * MeSH

BACKGROUND: Telomeres are the nucleoprotein complexes that physically cap the ends of eukaryotic chromosomes. Most plants possess Arabidopsis-type telomere sequences (TSs). In addition to terminal TSs, more diverse interstitial TSs exists in plants. Although telomeres have been sufficiently studied, the actual diversity of TSs in land plants is underestimated. RESULTS: We investigate genotypes from seven natural populations with contrasting environments of four Chenopodium species to reveal the variability in TSs by analyzing Oxford Nanopore reads. Fluorescent in situ hybridization was used to localize telomeric repeats on chromosomes. We identified a number of derivative monomers that arise in part of both terminal and interstitial telomeric arrays of a single genotype. The former presents a case of block-organized double-monomer telomers, where blocks of Arabidopsis-type TTTAGGG motifs were interspersed with blocks of derivative TTTAAAA motifs. The latter is an integral part of the satellitome with transformations specific to the inactive genome fraction. CONCLUSIONS: We suggested two alternative models for the possible formation of derivative monomers from telomeric heptamer motifs of Arabidopsis-type. It was assumed that derivatization of TSs is a ubiquitous process in the plant genome but occurrence and frequencies of derivatives may be genotype-specific. We also propose that the formation of non-canonical arrays of TSs, especially at chromosomal termini, may be a source for genomic variability in nature.

• Klíčová slova
• Evolution, Oxford nanopore sequencing, Plant, Population, Species, Telomere,
• MeSH
• Arabidopsis * genetika   MeSH
• Eukaryota MeSH
• genotyp MeSH
• hybridizace in situ fluorescenční MeSH
• lidé MeSH
• telomery genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH

Telomeres are essential structures formed from satellite DNA repeats at the ends of chromosomes in most eukaryotes. Satellite DNA repeat sequences are useful markers for karyotyping, but have a more enigmatic role in the eukaryotic cell. Much work has been done to investigate the structure and arrangement of repetitive DNA elements in classical models with implications for species evolution. Still more is needed until there is a complete picture of the biological function of DNA satellite sequences, particularly when considering non-model organisms. Celebrating Gregor Mendel's anniversary by going to the roots, this review is designed to inspire and aid new research into telomeres and satellites with a particular focus on non-model organisms and accessible experimental and in silico methods that do not require specialized equipment or expensive materials. We describe how to identify telomere (and satellite) repeats giving many examples of published (and some unpublished) data from these techniques to illustrate the principles behind the experiments. We also present advice on how to perform and analyse such experiments, including details of common pitfalls. Our examples are a selection of recent developments and underexplored areas of research from the past. As a nod to Mendel's early work, we use many examples from plants and insects, especially as much recent work has expanded beyond the human and yeast models traditional in telomere research. We give a general introduction to the accepted knowledge of telomere and satellite systems and include references to specialized reviews for the interested reader.

• Klíčová slova
• FISH, NGS, TRAP, eukaryotic tree of life, interstitial telomere sequences, retroelements, satellite, subtelomere structure, telomerase RNA, telomere evolution,
• MeSH
• DNA MeSH
• lidé MeSH
• repetitivní sekvence nukleových kyselin MeSH
• satelitní DNA * MeSH
• sekvence nukleotidů MeSH
• telomery * genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• DNA MeSH
• satelitní DNA * MeSH

Long-read technologies hold the promise to obtain more complete genome assemblies and to make them easier. Coupled with long-range technologies, they can reveal the architecture of complex regions, like centromeres or rDNA clusters. These technologies also make it possible to know the complete organization of chromosomes, which remained complicated before even when using genetic maps. However, generating a gapless and telomere-to-telomere assembly is still not trivial, and requires a combination of several technologies and the choice of suitable software. Here, we report a chromosome-scale assembly of a banana genome (Musa acuminata) generated using Oxford Nanopore long-reads. We generated a genome coverage of 177X from a single PromethION flowcell with near 17X with reads longer than 75 kbp. From the 11 chromosomes, 5 were entirely reconstructed in a single contig from telomere to telomere, revealing for the first time the content of complex regions like centromeres or clusters of paralogous genes.

• MeSH
• banánovník genetika   MeSH
• chromozomy rostlin genetika   MeSH
• genom rostlinný * MeSH
• nanopórové sekvenování MeSH
• nanopóry MeSH
• telomery * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Telomeres are protective structures at the ends of eukaryotic chromosomes, and disruption of their nucleoprotein composition usually results in genome instability and cell death. Telomeric DNA sequences have generally been found to be exceptionally conserved in evolution, and the most common pattern of telomeric sequences across eukaryotes is (TxAyGz)n maintained by telomerase. However, telomerase-added DNA repeats in some insect taxa frequently vary, show unusual features, and can even be absent. It has been speculated about factors that might allow frequent changes in telomere composition in Insecta. Coleoptera (beetles) is the largest of all insect orders and based on previously available data, it seemed that the telomeric sequence of beetles varies to a great extent. We performed an extensive mapping of the (TTAGG)n sequence, the ancestral telomeric sequence in Insects, across the main branches of Coleoptera. Our study indicates that the (TTAGG)n sequence has been repeatedly or completely lost in more than half of the tested beetle superfamilies. Although the exact telomeric motif in most of the (TTAGG)n-negative beetles is unknown, we found that the (TTAGG)n sequence has been replaced by two alternative telomeric motifs, the (TCAGG)n and (TTAGGG)n, in at least three superfamilies of Coleoptera. The diversity of the telomeric motifs was positively related to the species richness of taxa, regardless of the age of the taxa. The presence/absence of the (TTAGG)n sequence highly varied within the Curculionoidea, Chrysomeloidea, and Staphylinoidea, which are the three most diverse superfamilies within Metazoa. Our data supports the hypothesis that telomere dysfunctions can initiate rapid genomic changes that lead to reproductive isolation and speciation.

• MeSH
• brouci genetika   MeSH
• DNA genetika   MeSH
• eukaryotické buňky fyziologie   MeSH
• fylogeneze MeSH
• genetické techniky MeSH
• tandemové repetitivní sekvence genetika   MeSH
• telomerasa genetika   MeSH
• telomery genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA MeSH
• telomerasa MeSH

Telomerase RNA (TR) carries the template for synthesis of telomere DNA and provides a scaffold for telomerase assembly. Fungal TRs are long and have been compared to higher eukaryotes, where they show considerable diversity within phylogenetically close groups. TRs of several Saccharomycetaceae were recently identified, however, many of these remained uncharacterised in the template region. Here we show that this is mainly due to high variability in telomere sequence. We predicted the telomere sequences using Tandem Repeats Finder and then we identified corresponding putative template regions in TR candidates. Remarkably long telomere units and the corresponding putative TRs were found in Tetrapisispora species. Notably, variable lengths of the annealing sequence of the template region (1-10 nt) were found. Consequently, species with the same telomere sequence may not harbour identical TR templates. Thus, TR sequence alone can be used to predict a template region and telomere sequence, but not to determine these exactly. A conserved feature of telomere sequences, tracts of adjacent Gs, led us to test the propensity of individual telomere sequences to form G4. The results show highly diverse values of G4-propensity, indicating the lack of ubiquitous conservation of this feature across Saccharomycetaceae.

• MeSH
• benzothiazoly metabolismus   MeSH
• fluorescence MeSH
• G-kvadruplexy MeSH
• genetická variace * MeSH
• genetické matrice * MeSH
• reprodukovatelnost výsledků MeSH
• RNA genetika   MeSH
• Saccharomycetales genetika   MeSH
• sekvence nukleotidů MeSH
• telomerasa genetika   MeSH
• telomery genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• benzothiazoly MeSH
• RNA MeSH
• telomerasa MeSH
• telomerase RNA MeSH Prohlížeč
• thioflavin T MeSH Prohlížeč

The canonical DNA polymerases involved in the replication of the genome are unable to fully replicate the physical ends of linear chromosomes, called telomeres. Chromosomal termini thus become shortened in each cell cycle. The maintenance of telomeres requires telomerase-a specific RNA-dependent DNA polymerase enzyme complex that carries its own RNA template and adds telomeric repeats to the ends of chromosomes using a reverse transcription mechanism. Both core subunits of telomerase-its catalytic telomerase reverse transcriptase (TERT) subunit and telomerase RNA (TR) component-were identified in quick succession in Tetrahymena more than 30 years ago. Since then, both telomerase subunits have been described in various organisms including yeasts, mammals, birds, reptiles and fish. Despite the fact that telomerase activity in plants was described 25 years ago and the TERT subunit four years later, a genuine plant TR has only recently been identified by our group. In this review, we focus on the structure, composition and function of telomerases. In addition, we discuss the origin and phylogenetic divergence of this unique RNA-dependent DNA polymerase as a witness of early eukaryotic evolution. Specifically, we discuss the latest information regarding the recently discovered TR component in plants, its conservation and its structural features.

• Klíčová slova
• evolution, plant TERT, plant TR., telomerase, telomerase RNA (TR), telomerase reverse transcriptase (TERT),
• MeSH
• biologická evoluce * MeSH
• dějiny 20. století MeSH
• dějiny 21. století MeSH
• Eukaryota klasifikace   genetika   metabolismus   MeSH
• fylogeneze MeSH
• lidé MeSH
• RNA fyziologie   MeSH
• telomerasa chemie   fyziologie   MeSH
• telomery metabolismus   MeSH
• zvířata MeSH
• Check Tag
• dějiny 20. století MeSH
• dějiny 21. století MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• historické články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• RNA MeSH
• telomerasa MeSH
• telomerase RNA MeSH Prohlížeč

Telomeres are basic structures of eukaryote genomes. They distinguish natural chromosome ends from double-stranded breaks in DNA and protect chromosome ends from degradation or end-to-end fusion with other chromosomes. Telomere sequences are usually tandemly arranged minisatellites, typically following the formula (TxAyGz)n. Although they are well conserved across large groups of organisms, recent findings in plants imply that their diversity has been underestimated. Changes in telomeres are of enormous evolutionary importance as they can affect whole-genome stability. Even a small change in the telomere motif of each repeat unit represents an important interference in the system of sequence-specific telomere binding proteins. Here, we provide an overview of telomere sequences, considering the latest phylogenomic evolutionary framework of plants in the broad sense (Archaeplastida), in which new telomeric sequences have recently been found in diverse and economically important families such as Solanaceae and Amaryllidaceae. In the family Lentibulariaceae and in many groups of green algae, deviations from the typical plant telomeric sequence have also been detected recently. Ancestry and possible homoplasy in telomeric motifs, as well as extant gaps in knowledge are discussed. With the increasing availability of genomic approaches, it is likely that more telomeric diversity will be uncovered in the future. We also discuss basic methods used for telomere identification and we explain the implications of the recent discovery of plant telomerase RNA on further research about the role of telomerase in eukaryogenesis or on the molecular causes and consequences of telomere variability.

• Klíčová slova
• Allium, Cestrum, Genlisea, circular chromosomes, green algae, linear chromosomes, telomerase, telomeres,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

To elucidate the molecular nature of evolutionary changes of telomeres in the plant order Asparagales, we aimed to characterize telomerase RNA subunits (TRs) in these plants. The unusually long telomere repeat unit in Allium plants (12 nt) allowed us to identify TRs in transcriptomic data of representative species of the Allium genus. Orthologous TRs were then identified in Asparagales plants harbouring telomere DNA composed of TTAGGG (human type) or TTTAGGG (Arabidopsis-type) repeats. Further, we identified TRs across the land plant phylogeny, including common model plants, crop plants, and plants with unusual telomeres. Several lines of functional testing demonstrate the templating telomerase function of the identified TRs and disprove a functionality of the only previously reported plant telomerase RNA in Arabidopsis thaliana. Importantly, our results change the existing paradigm in plant telomere biology which has been based on the existence of a relatively conserved telomerase reverse transcriptase subunit (TERT) associating with highly divergent TRs even between closely related plant taxa. The finding of a monophyletic origin of genuine TRs across land plants opens the possibility to identify TRs directly in transcriptomic or genomic data and/or predict telomere sequences synthesized according to the respective TR template region.

• MeSH
• Allium genetika   MeSH
• Arabidopsis genetika   MeSH
• chřestotvaré genetika   MeSH
• fylogeneze * MeSH
• genom rostlinný genetika   MeSH
• lidé MeSH
• molekulární evoluce * MeSH
• RNA genetika   MeSH
• telomerasa genetika   MeSH
• telomery genetika   MeSH
• vyšší rostliny genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• RNA MeSH
• telomerasa MeSH
• telomerase RNA MeSH Prohlížeč