Evidence map›Paper›PMID 41942859›Full record

ArticleBMC molecular and cell biology2026

Telomere-to-telomere characterization of rDNA chromosome in the myxomycete Didymium iridis.

Arif Khan, Tor Erik Jørgensen, Lars Martin Jakt, Bård Ove Karlsen, Annica Hedberg, Steinar Daae Johansen

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Article in BMC molecular and cell biology, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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1 · What the graph read from it

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2 · The registry

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3 · Its place in the literature

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4 · The record

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5 · Who and what money

Authors and funding

6 authors.

Arif KhanGenomics Division, Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway.
Tor Erik JørgensenGenomics Division, Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway.
Lars Martin JaktGenomics Division, Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway.
Bård Ove KarlsenDepartment of Laboratory Medicine, Nordland Hospital Trust, Bodø, Norway.
Annica HedbergDepartment of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, Tromsø, Norway.
Steinar Daae JohansenGenomics Division, Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway. steinar.d.johansen@nord.no.

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundThe ribosomal DNA (rDNA) of the myxomycete Didymium iridis is located on a linear, multi-copy, non-Mendelian chromosome. Efforts to determine the complete sequence by short-read sequencing technologies have been prevented by the presence of highly repetitive regions. Here we use high coverage (~10,000 x) long-read Oxford Nanopore Technology to determine the rDNA chromosome sequence in haploid amoebae from telomere-to-telomere.

resultsThe 20 kb rDNA chromosome, which is present at ~ 132 copies per haploid genome, is capped by regular TTAGGG telomeric repeats at both ends and carries an 11.3 kb pre-rRNA transcription unit coding for the small and large subunit rRNAs. The rRNA genes are further interrupted by autocatalytic group I introns, one of which encodes a homing endonuclease and two catalytic RNA domains with different functions in RNA processing. RNA mapping analyses from amoeba, microcyst, flagellate, and plasmodium stages, based on Illumina short-read sequencing, support the presence of a mature intron homing endonuclease mRNA both in haploid and diploid life stages in D. iridis. The non-transcribed sequence region upstream of the transcription unit contains several direct repeat arrays, including a highly complex upstream promoter region likely to be involved in pre-rRNA transcription regulation. Adjacent to the upstream telomere, a 4.2 kb palindromic region with potential for cruciform structure formation is found. Here, two putative replication origin candidates are located.

conclusionsHigh coverage Oxford Nanopore Technology sequencing results in excellent resolution of complex sequence repeat feature in the D. iridis rDNA chromosome. The rRNA genes are interrupted by complex group I introns and RNA sequencing supports intron autocatalytic processing in haploid and diploid life stages. This study provides new insights into structural arrangements of nuclear rDNA in eukaryotic microorganisms.

Indexed as

ChromosomesDNA, RibosomalMyxomycetesTelomereBase SequenceIntronsDNA, RibosomalCatalytic RNADirect repeatGroup I intronHoming endonuclease mRNAMyxomycetePalindromic repeatSpliceosomal intron

Identifiers

PMID41942859
PMCPMC13182076

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.