Ciliated protists are among the oldest unicellular organisms with a heterotrophic lifestyle and share a common ancestor with Plantae. Unlike any other eukaryotes, there are two distinct nuclei in ciliates with separate germline and somatic cell functions. Here, we assembled a near-complete macronuclear genome of Fabrea salina, which belongs to one of the oldest clades of ciliates. Its extremely minimized genome (18.35 Mb) is the smallest among all free-living heterotrophic eukaryotes and exhibits typical streamlined genomic features, including high gene density, tiny introns, and shrinkage of gene paralogs. Gene families involved in hypersaline stress resistance, DNA replication proteins, and mitochondrial biogenesis are expanded, and the accumulation of phosphatidic acid may play an important role in resistance to high osmotic pressure. We further investigated the morphological and transcriptomic changes in the macronucleus during sexual reproduction and highlighted the potential contribution of macronuclear residuals to this process. We believe that the minimized genome generated in this study provides novel insights into the genome streamlining theory and will be an ideal model to study the evolution of eukaryotic heterotrophs.
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http://dx.doi.org/10.1093/molbev/msac062 | DOI Listing |
Nucleic Acids Res
December 2024
MOE Key Laboratory of Evolution & Marine Biodiversity and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.
The ciliate Tetrahymena thermophila is a well-established unicellular model eukaryote, contributing significantly to foundational biological discoveries. Despite its acknowledged importance, current studies on Tetrahymena biology face challenges due to gene annotation inaccuracy, particularly the notable absence of untranslated regions (UTRs). To comprehensively annotate the Tetrahymena macronuclear genome, we collected extensive transcriptomic data spanning various cell stages.
View Article and Find Full Text PDFFront Biosci (Landmark Ed)
November 2024
Department of Cancer Cell Biology, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia.
Background: In the twentieth century, the textbook idea of packaging genomic material in the cell nucleus and metaphase chromosomes was the presence of a hierarchy of structural levels of chromatin organization: nucleosomes - nucleosomal fibrils -30 nm fibrils - chromomeres - chromonemata - mitotic chromosomes. Chromomeres were observed in partially decondensed chromosomes and interphase chromatin as ~100 nm globular structures. They were thought to consist of loops of chromatin fibres attached at their bases to a central protein core.
View Article and Find Full Text PDFBMC Biol
October 2024
Laboratory of Marine Protozoan Biodiversity and Evolution, Marine College, Shandong University, Weihai, 264209, China.
Background: As a potential model organism for studies of environmental and cell biology, Paramecium duboscqui is a special euryhaline species of Paramecium that can be found in fresh, brackish, or marine water in natural salinity ranges between 0‰ and 33‰. However, the genome information as well as molecular mechanisms that account for its remarkable halotolerant traits remain extremely unknown. To characterize its genome feature, we combined PacBio and Illumina sequencing to assemble the first high-quality and near-complete macronuclear genome of P.
View Article and Find Full Text PDFISME J
January 2024
Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong 266003, China.
Phenotypic plasticity, which involves phenotypic transformation in the absence of genetic change, may serve as a strategy for organisms to survive in complex and highly fluctuating environments. However, its reaction norm, molecular basis, and evolution remain unclear in most organisms, especially microbial eukaryotes. In this study, we explored these questions by investigating the reaction norm, regulation, and evolution of phenotypic plasticity in the cosmopolitan marine free-living ciliates Glauconema spp.
View Article and Find Full Text PDFMicrob Genom
July 2024
Laboratório de Diversidade Genética, Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.
Several hundred ciliate species live in animals' guts as a part of their microbiome. Among them, (Trichostomatia, Pycnotrichidae), the largest described ciliate, is found exclusively associated with (capybara), the largest known rodent reaching up to 90 kg. Here, we present the sequence, structural and functional annotation of this giant microeukaryote macronuclear genome and discuss its phylogenetic placement.
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