Centromere and telomere sequence alterations reflect the rapid genome evolution within the carnivorous plant genusGenlisea

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Linear chromosomes of eukaryotic organisms invariably possess centromeres and telomeres to ensure proper chromosome segregation during nuclear divisions and to protect the chromosome ends from deterioration and fusion, respectively. While centromeric sequences may differ between species, with arrays of tandemly repeated sequences and retrotransposons being the most abundant sequence types in plant centromeres, telomeric sequences are usually highly conserved among plants and other organisms. The genome size of the carnivorous genusGenlisea(Lentibulariaceae) is highly variable. Here we study evolutionary sequence plasticity of these chromosomal domains at an intrageneric level. We show thatGenlisea nigrocaulis(1C = 86 Mbp; 2n = 40) andG. hispidula(1C = 1550 Mbp; 2n = 40) differ as to their DNA composition at centromeres and telomeres.G. nigrocaulisand its close relativeG. pygmaearevealed mainly 161 bp tandem repeats, whileG. hispidulaand its close relativeG. subglabradisplayed a combination of four retroelements at centromeric positions.G. nigrocaulisandG. pygmaeachromosome ends are characterized by the Arabidopsis-type telomeric repeats (TTTAGGG);G. hispidulaandG. subglabrainstead revealed two intermingled sequence variants (TTCAGG and TTTCAGG). These differences in centromeric and, surprisingly, also in telomeric DNA sequences, uncovered between groups with on average a > 9-fold genome size difference, emphasize the fast genome evolution within this genus. Such intrageneric evolutionary alteration of telomeric repeats with cytosine in the guanine-rich strand, not yet known for plants, might impact the epigenetic telomere chromatin modification.

Significance Statement

The genus Genlisea is characterized by one of the largest genome size ranges reported so far. Here we show that species with very small or large genomes differ in their centromeric and surprisingly also telomeric sequence composition and represent the first alteration in telomere repeats within a genus.

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