Scholarlink

Background <p>Paramecia belong to the ciliate phylum of unicellular eukaryotes characterized by nuclear dimorphism. A diploid germline micronucleus (MIC) transmits genetic information across sexual generations. A polyploid transcriptionally active somatic macronucleus (MAC) develops at each sexual generation from a copy of the MIC through programmed DNA elimination (PDE) of &gt; 30% of germline DNA. PDE requires the domesticated PiggyMac (Pgm) transposase. Assembly of <i>Paramecium</i> germline genomes has presented an enormous challenge owing to the difficulty of MIC isolation.</p> Results <p>We report chromosome-scale short-read MIC assemblies for 7 species from the <i>P. aurelia</i> species complex. We discovered a novel clade of Helitrons, with 9–10-kb transposase ORFs under purifying selection, that have remained active in all <i>P. aurelia</i> lineages. A long-read assembly for <i>P. tetraurelia</i> together with a genetic linkage map provided a nearly telomere-to-telomere assembly.</p> Conclusions <p>The ~ 100-Mb genome consists of tiny (300&#xa0;kb–1.2&#xa0;Mb) and numerous (~ 160) germline chromosomes with the highest recombination rate ever reported for a eukaryote (420&#xa0;cM/Mb). The ends of the chromosomes consist of Helitrons inserted in telomeric C<sub>4</sub>A<sub>2</sub> repeats, forming a distinct genomic compartment that is eliminated very early during MAC development in a Pgm-independent manner.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

The tiny germline chromosomes of Paramecium aurelia have an exceptionally high recombination rate and are capped by a new class of Helitrons

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年4月16日

查看全文
  • Olivier Arnaiz,
  • Frédéric Guérin,
  • Arnaud Couloux,
  • Caridad Miró-Pina,
  • Guillaume Pellerin,
  • Irina Nekrasova,
  • Joëlle Amselem,
  • Jean-Marc Aury,
  • Simran Bhullar,
  • Andrea Frapporti,
  • Emmanuelle Lerat,
  • Isabelle Luyten,
  • Sophie Malinsky,
  • Nathalie Mathy,
  • Alexey Potekhin,
  • Vinciane Régnier,
  • Natalia Sawka-Gądek,
  • Amandine Touzeau,
  • Augustin de Vanssay,
  • Coralie Zangarelli,
  • Hadi Quesneville,
  • Mireille Bétermier,
  • Karine Labadie,
  • Laurent Duret,
  • Eric Meyer,
  • Sandra Duharcourt,
  • Linda Sperling

摘要

Background

Paramecia belong to the ciliate phylum of unicellular eukaryotes characterized by nuclear dimorphism. A diploid germline micronucleus (MIC) transmits genetic information across sexual generations. A polyploid transcriptionally active somatic macronucleus (MAC) develops at each sexual generation from a copy of the MIC through programmed DNA elimination (PDE) of > 30% of germline DNA. PDE requires the domesticated PiggyMac (Pgm) transposase. Assembly of Paramecium germline genomes has presented an enormous challenge owing to the difficulty of MIC isolation.

Results

We report chromosome-scale short-read MIC assemblies for 7 species from the P. aurelia species complex. We discovered a novel clade of Helitrons, with 9–10-kb transposase ORFs under purifying selection, that have remained active in all P. aurelia lineages. A long-read assembly for P. tetraurelia together with a genetic linkage map provided a nearly telomere-to-telomere assembly.

Conclusions

The ~ 100-Mb genome consists of tiny (300 kb–1.2 Mb) and numerous (~ 160) germline chromosomes with the highest recombination rate ever reported for a eukaryote (420 cM/Mb). The ends of the chromosomes consist of Helitrons inserted in telomeric C4A2 repeats, forming a distinct genomic compartment that is eliminated very early during MAC development in a Pgm-independent manner.