Characterisation of an unusual telomere motif (TTTTTTAGGG)_n in the plant Cestrum elegans (Solanaceae), a species with a large genome

Abstract

SUMMARYThe 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.

Satellite DNA in Plants: More than Just Rubbish

“…Furthermore, Allium lack any known telomeric sequence [Sýkorová et al, 2006]. Within Solanaceae, the genera Cestrum , Vestia and Sessea lack the plant or the human telomeric motifs at the tips of the chromosomes [Sýkorová et al, 2003b], but recently, the motif TTTTTTAGGG has been found at the telomeres in Cestrum [Peška et al, 2015]. In fact, a broad phylogenetic survey unveiled that the human-type repeat is the most common one and possibly ancestral in eukaryotes, but alternative motifs replaced it along the phylogeny of diverse eukaryotic lineages, some of them several times independently [Fulnečková et al, 2013].…”

A Bioinformatics Approach to Identify Telomere Sequences

“…Superscripts: 1 [26]; 2 [19]; 3 [25]; 4 this paper; 5 Putative telomere repeats identified by SERF requiring further cytological validations. NGS: Next-generation sequencing; SERF: Sequence repeat finder. …”

“…The recent detection of novel telomere motifs, especially in the order Asparagales [26], illustrates the challenge and warrants the need to switch from the conventional approach to one that utilizes modern sequencing technology and analysis platforms for an effective utilization of available resources. Such a shift is occurring and is seen in the discovery of the telomere motifs of C. elegans [19] and A. cepa [26,34]. …”

“…The Arabidopsis -type telomere is lost in Cestrum elegans from the family Solanaceae [18] and is replaced by an unusual 10 base pair (bp) telomere motif (TTTTTTAGGG) n maintained by telomerase [19]. Yet, many model plant species for telomere studies from this family, such as Nicotiana tabacum , Solanum lycopersicum and Solanum tuberosum , carry the ancestral-type telomere motif (TTTAGGG) n at their chromosome termini [2022].…”

Plant artificial chromosome technology and its potential application in genetic engineering

“…Telomeres are the natural ends of chromosomes, which protect the chromosome from deterioration or fusion with other chromosomes. Most higher plants have the Arabidopsis-type of telomeres with long arrays of telomere repeat (TTTAGGG) n except some plant species in the order of Asparagales and the Solanaceae family where the telomere repeat sequences are replaced with (TTAGGG) n and (TTTTTTAGGG) n , respectively (Peska et al, 2015). The minisatellite telomere repeats are lost in Allium and are probably replaced with an unknown mechanism (Peska et al, 2015;Sykorova et al, 2006).…”