When cleaning facilitates cluttering-genome in ciliates

Article Multidisciplinary Sciences

MITE infestation accommodated by genome editing in the germline genome of the ciliate Blepharisma

Brandon K. B. Seah et al.

Summary: During sexual conjugation, ciliates eliminate internal sequences from the germline genome to produce the functional somatic genome. We assembled 40,000 Internal Eliminated Sequences (IESs) of Blepharisma stoltei to gain insight into IESs and ciliate genome editing. Contrary to expectations, the germline genome of Blepharisma contains few transposases but instead has a high abundance of a Miniature Inverted-repeat Transposable Element (MITE) derived from a Pogo-family transposon.

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA (2023)

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Review Genetics & Heredity

Throwing away DNA: programmed downsizing in somatic nuclei

Katherine H. Drotos et al.

Summary: During development, programmed elimination of DNA leads to different DNA sequences and content in somatic cell nuclei compared to germline nuclei, which has a significant impact on genome architecture and stability. Whole-genome sequencing has expanded the understanding of taxa exhibiting this trait and identified the genes and transposable elements involved in certain taxa. This study compares the mechanisms used by various organisms, such as ciliates, nematodes, copepods, and lamprey, to reduce their genome size during development, and proposes tests to understand the evolution and maintenance of this trait. The study also explores the potential functional roles of programmed DNA elimination (PDE) in genomic defense, development regulation, sex determination, co-option, and modulation of nucleotypic effects, emphasizing the importance of studying genome evolution.

TRENDS IN GENETICS (2022)

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Article Biochemistry & Molecular Biology

Massive colonization of protein-coding exons by selfish genetic elements in Paramecium germline genomes

Diamantis Sellis et al.

Summary: Ciliates are unicellular eukaryotes with a complex genomic architecture including internal eliminated sequences (IESs) that have undergone multiple waves of gains, some of which are under strong purifying selection. The evolution of IESs in Paramecium highlights the important role of selfish genetic elements in shaping genome complexity and gene expression, similar to the evolution of introns in eukaryotes.

PLOS BIOLOGY (2021)

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Article Multidisciplinary Sciences