Search Results (405)

The endosymbiotic theory, which is the crucial starting point of eukaryogenesis, was first mentioned in the philosophy of the pre-Socratic Greek philosopher Empedocles. According to him, everything merges into units with differential survival. Similarly, during eukaryogenesis, the fusion of two distinct units resulted in the creation of a new cell type that possessed a newly formed organelle, the mitochondrion. Since then, the mitochondrion has been a key regulator of health and immunity. Furthermore, many of its characteristics and functions are due to its endosymbiotic bacterial origin. For example, it possesses damage-associated molecular patterns that can activate inflammatory signaling pathways, has circular DNA with CpG-rich motifs, as well as a double phospholipid membrane, and divides by fission. Mitochondrial function plays a critical role in maintaining cellular homeostasis, as they meet the cell’s energy needs and regulate many of its functions. However, after cellular damage due to infection, radiation, or toxins, mitochondrial stress and dysfunction can occur and mitochondrial DNA can be released into the cytosol. Cytosolic mitochondrial DNA can then activate proinflammatory signaling pathways, mediated by TLR9 and cGAS, as well as inflammasomes, triggering inflammation and autoimmunity. Full article

Eukaryotes use diverse nutrient acquisition strategies, including autotrophy, heterotrophy, mixotrophy, and symbiosis, which shape the evolution of cell regulatory networks. The Target of Rapamycin (TOR) kinase is a conserved growth regulator that in most species functions within two complexes, TORC1 and TORC2. TORC1 is broadly conserved and uniquely sensitive to rapamycin, whereas the evolutionary distribution of TORC2 is less well-defined. We built a sensitive hidden Markov model (HMM)-based pipeline to survey core TORC1 and TORC2 components across more than 800 sequenced eukaryotic genomes spanning multiple major supergroups. Both complexes are present in early-branching lineages, consistent with their presence in the last eukaryotic common ancestor, followed by multiple lineage-specific losses of TORC2 and, more rarely, TORC1. A striking pattern emerges in which TORC2 is uniformly absent from photosynthetic autotrophs derived from primary endosymbiosis and frequently lost in those derived from secondary or tertiary events. In contrast, TORC2 is consistently retained in mixotrophs, which obtain carbon from both photosynthesis and environmental uptake, and in free-living obligate heterotrophs. These findings suggest that TORC2 supports heterotrophic metabolism and is often dispensable under strict autotrophy. Our results provide a framework for the evolutionary divergence of TOR signaling and highlight metabolic and ecological pressures that shape TOR complex retention across eukaryotes. Full article

The discovery of Asgard archaea has reshaped our understanding of eukaryotic origins, supporting a two-domain tree of life in which eukaryotes emerged from Archaea. Building on this revised framework, we propose the Pre-prokaryotic Organismal Lifeforms Existing Today (POLET) hypothesis, which suggests that relic pre-prokaryotic life forms—termed POLETicians—may persist in deep, anoxic, energy-limited environments. These organisms could represent a living bridge to the RNA world and other origin-of-life models, utilizing racemic oligoribonucleotides and peptides, non-enzymatic catalysis, and mineral-assisted compartmentalization. POLETicians might instead rely on radical-based redox chemistry or radiolysis for energy and maintenance. These biomolecules may be racemic or noncanonical, eluding conventional detection. New detection methods are required to determine such life. We propose generalized nanopore sequencing of any linear polymer—including mirror RNAs, mirror DNAs, or any novel genetic material—as a potential strategy to overcome chirality bias in modern sequencing technologies. These approaches, combined with chiral mass spectrometry and stereoisomer-resolved analytics, may enable the detection of molecular signatures from non-phylogenetic primitive lineages. POLETicians challenge the assumption that all life must follow familiar biochemical constraints and offer a compelling extension to our search for both ancient and extant forms of life hidden within Earth’s most extreme environments. Full article

Plant viruses have been traditionally considered pathogens restricted to plant hosts. However, recent studies have shown that some plant viruses can infect and replicate in filamentous fungi and oomycetes, suggesting that their host range is broader than previously thought, and that their ecological interactions are more complex. In this study, we investigated the ability of the well-characterized positive-sense RNA plant virus Tobacco mosaic virus (TMV) to replicate in four major phytopathogenic fungi from different taxonomic groups: Botrytis cinerea, Fusarium oxysporum f. sp. lycopersici, Verticillium dahliae, and Monilinia fructicola. Using a recombinant TMV-based vector expressing a green fluorescent protein (TMV-GFP-1056) as reporter, we demonstrated that TMV can enter, replicate, and persist within the mycelia of B. cinerea and V. dahliae—at least through the first subculture. However, it cannot replicate in F. oxysporum f. sp. lycopersici and M. fructicola. RNA interference (RNAi) is a conserved eukaryotic epigenetic mechanism that provides an efficient defence against viruses. We explored the role of RNAi in the interaction between TMV and the mycelia of V. dahliae and B. cinerea. Our results revealed a strong induction of the Dicer-like 1 and Argonaute 1 genes, which are key compounds of the RNA silencing pathway. This RNAi-based response impaired TMV-GFP replication in both fungi. Notably, despite viral replication and RNAi activation, the virulence of V. dahliae and B. cinerea on their respective host plants remained unaffected. These findings reinforce the emerging recognition of cross-kingdom virus transmission and interactions, which likely play a crucial role in pathogen ecology and viral evolution. Understanding these virus–fungus interactions not only sheds light on RNAi interference silencing mechanisms but also suggests that plant viruses like TMV could serve as simple and effective tools for functional genomic studies in fungi, such as in V. dahliae and B. cinerea. Full article

Telomeres are terminal regions of chromosomes that protect and stabilize chromosome structures. Telomeres are usually composed of specific DNA repeats (motifs) that are maintained by telomerase and a complex of specific proteins. Telomeric DNA sequences are generally highly conserved throughout the evolution of different groups of eukaryotes. The most common motif in insects is TTAGG, but it is not universal, including in the large order Hemiptera. In particular, several derived telomeric motifs were identified in this order by analyzing chromosome-level genome assemblies or by FISH screening the chromosomes of target species. Here, we analyzed chromosome-level genome assemblies of 16 species from three hemipteran suborders, including Sternorrhyncha (Coccoidea: Planococcus citri, Acanthococcus lagerstroemiae, and Trionymus diminutus; Aphidoidea: Tuberolachnus salignus, Metopolophium dirhodum, Rhopalosiphum padi, and Schizaphis graminum), Auhenorrhyncha (Cicadomorpha: Allygus modestus, Arthaldeus pascuellus, Aphrophora alni, Cicadella viridis, Empoasca decipiens, and Ribautiana ulmi), and Heteroptera (Gerromorpha: Gerris lacustris; Pentatomomorpha: Aradus depressus and A. truncatus). In addition, scaffold-level genome assemblies of three more species of Heteroptera (Gerromorpha: Gerris buenoi, Microvelia longipes, and Hermatobates lingyangjiaoensis) were examined. The presumably ancestral insect motif TTAGG was found at the ends of chromosomes of all species studied using chromosome-level genome assembly analysis, with four exceptions. In Aphrophora alni, we detected sequences of 4 bp repeats of TGAC, which were tentatively identified as a telomeric motif. In Gerris lacustris, from the basal true bug infraorder Gerromorpha, we found a 10 bp motif TTAGAGGTGG, previously unknown not only in Heteroptera or Hemiptera but also in Arthropoda in general. Blast screening of the scaffold-level assemblies showed that TTAGAGGTGG is also likely to be a telomeric motif in G. buenoi and Microvelia. longipes, while the results obtained for H. lingyangjiaoensis were inconclusive. In A. depressus and A. truncatus from the basal for Pentatomomorpha family Aradidae, we found a 10 bp motif TTAGGGATGG. While the available data allowed us to present two alternative hypotheses about the evolution of telomeric motifs in Heteroptera, further data are needed to verify them, especially for the yet unstudied basal infraorders Enicocephalomorpha, Dipsocoromorpha, and Leptopodomorpha. Full article

This review explores the interaction of annexins with membranes across a variety of eukaryotic domains of life, highlighting this protein family’s role in cellular processes due to its lipid and calcium-binding properties. By comparing annexins’ functions in diverse organisms, we aim to uncover novel insights into their mechanisms of action, particularly in membrane repair, protein trafficking, and potential channel formation. Despite extensive research on mammalian and plant annexins, there is limited information on annexins in invertebrates, fungi, and protists. This review seeks to bridge this knowledge gap, providing a comprehensive understanding of annexin–membrane interactions and their potential implications for cellular function and disease mechanisms across eukaryotic lineages. Full article

Steroids are found in bacteria and eukaryotes, and genes potentially encoding steroid metabolic enzymes have also been identified in giant viruses. For decades, hydroxylated steroids have been utilized in medicine to treat various human diseases. The hydroxylation of steroids can be achieved using microbial enzymes, especially cytochrome P450 monooxygenases (CYPs/P450s) and is well documented. Understanding the structural determinants that govern the regio- and stereoselectivity of steroid hydroxylation by P450s is essential in order to fully exploit their potential. Herein, we present a comprehensive analysis of the steroid-hydroxylating CYP109 family across the domains of life and delineate the structural determinants that govern steroid hydroxylation. Data mining, annotation, and phylogenetic analysis revealed that CYP109 family members are highly populated in bacteria, and indeed, these members passed from bacteria to archaea by horizontal gene transfer, leading to the evolution of P450s in archaea. Analysis of twelve CYP109 crystal structures revealed large, flexible, and dynamic active site cavities that can accommodate multiple ligands. The correct positioning and orientation of the steroid in the active site cavity and the nature of the C17 substituent on the steroid molecule influence catalysis. In an analogous fashion to the CYP107 family, the amino acid residues within the CYP109 binding pocket involve hydrophilic and hydrophobic interactions, influencing substrate orientations and anchoring and determining the site of hydroxylation and catalytic activity. A handful of amino acids, such as Val84, Val292, and Ser387 in CYP109B4, have been found to play a role in determining the catalytic regiospecificity, and a single amino acid, such as Arg74 in CYP109A2, has been found to be essential for the enzymatic activity. This work serves as a reference for the precise understanding of CYP109 structure–function relationships and for P450 enzymes in general. The findings will guide the genetic engineering of CYP109 enzymes to produce valuable steroid molecules of medicinal and biotechnological importance. Full article

The origin and evolution of genes are central themes in evolutionary biology and genomics, shedding light on how molecular innovations shape biological complexity and adaptation. This review explores the principal mechanisms underlying gene emergence in eukaryotes, including gene duplication, de novo gene birth, horizontal gene transfer, viral gene domestication, and exon shuffling. We examine the population dynamics that govern the fixation of new genes, their functional integration, and the selective forces acting upon them—from purifying selection to adaptive innovation. Examples such as NOTCH2NL and SRGAP2C, which originated through recent segmental duplications followed by neofunctionalization, illustrate how duplicate-derived de novo genes can play a key role in human brain development. In addition, we highlight the emerging relevance of nuclear architecture in determining the evolutionary fate of new genes, offering a spatial dimension to gene innovation. We also discuss methodological approaches for detecting new genes and inferring selection, and finally, we highlight the emerging role of the human pangenome in revealing hidden gene diversity and its implications for evolutionary and biomedical research. Understanding gene innovation not only enhances our grasp of evolutionary processes but also informs clinical studies on disease susceptibility and human uniqueness. Full article

Photosynthetic eukaryotes have shaped the Earth’s biosphere by producing oxygen and organic compounds using light energy in specialized organelles called plastids. Plastids evolved from free-living cyanobacteria ingested by heterotrophic unicellular eukaryotes. Two such independent engulfment processes, called cyanobacterial endosymbioses, have been reported. The first gave rise to primary plastids and three Archaeplastida lineages: glaucophytes, red algae, and green algae with land plants, whereas the second resulted in chromatophores in the rhizarian amoeba Paulinella. Importantly, Archaeplastidans donated their plastids to many protist groups, further spreading photosynthesis across the tree of life. To reveal complex plastid evolution, we performed comprehensive phylogenetic and molecular clock analyses using new fossil calibrations and the largest number yet of plastid-encoded proteins from 108 taxa, representing diverse photosynthetic organisms. Our results indicate that primary plastids evolved prior to 2.1–1.8 Ga, i.e., before glaucophytes diverged from other Archaeplastidans, and Paulinella chromatophores were likely before 292–266 Ma. Red and green algae were engulfed by cryptophyte and chlorarachniophyte ancestors between 1.7–1.4 Ga and 1.1–1.0 Ga, respectively; the former subsequently triggered plastid transfers to other eukaryotes. We also examined the impact of molecular clocks and calibration sets on age estimates, showing that clocks are the main source of variation. Full article

Tandem repeats in eukaryotic genomes exhibit intrinsic instability that drives rapid evolutionary diversification. However, their evolutionary dynamics in allopolyploid species such as the water hyacinth (Pontederia crassipes or Eichhornia crassipes) remain largely unexplored. Our study used integrated genomic and cytogenetic analyses of this allotetraploid species to characterize five representative tandem repeats, revealing distinct genomic distribution patterns and copy number polymorphisms. The highly abundant centromeric tandem repeat, putative CentEc, was co-localized with the centromeric retrotransposon CREc, indicating conserved centromeric architecture. Remarkably, putative CentEc sequences showed high sequence conservation (91–100%) despite subgenome divergence, indicative of active concerted evolution. Fluorescence in situ hybridization (FISH) analysis showed ubiquitous telomeric repeats across all chromosomes, while an interstitial chromosome region tandem repeat (ICREc) displayed chromosome-specific localization, both exhibiting copy number variation. Furthermore, differential rDNA organization was observed. 5S rDNA was detected on a single chromosome pair, whereas 35S rDNA exhibited multichromosomal distribution with varying intensities. A comparative analysis of subgenome-specific rDNA sequences revealed substantial heterogeneity in both 5S and 35S rDNA units, suggesting subgenome-biased evolutionary trajectories. Collectively, these findings elucidate the structural and evolutionary significance of tandem repeats in shaping the water hyacinth genome, highlighting mechanisms of concerted evolution and subgenome-biased adaptation in invasive polyploids. Full article

Mammalian renal intercalated cells are known for their role in acid secretion and maintaining acid–base balance. Herein, we discuss the theoretical reasons behind their development based on published data, focusing on the unique characteristics of renal intercalated cell biology that distinguish them from other mammalian cell types, while simultaneously attempting to explain the persistence of cells similar to intercalated cells throughout evolution. In addition, we traced these characteristics phylogenetically back to the simplest organisms. Intercalated cells have several functions and attributes. First, they contribute to kidney defense mechanisms in response to both infectious and non-infectious kidney damage. Second, intercalated cells are energized by V-ATPases in a manner similar to that of protozoa. Third, they possess T-antigens, which are commonly found in embryonic and cancer cells and which confer invasive abilities to these cells. Fourth, their plasticity enables the regeneration of other epithelial cells. These observations indicate that the origins of renal intercalated cells may be traceable back to amoeboid cells that originated from an evolutionary lineage including protists, or even to the last eukaryote common ancestor. The theoretical framework presented herein supports two predictions: first, that sponge amoebocytes possess membrane V-ATPase and are sensitive to bafilomycin, but not to ouabain; and second, that sponge amoebocytes—along with cells from diploblasts (such as Xenacoelomorpha), cnidarians, worms, fish and mollusk ionocytes, and the entire cell lineage containing V-ATPase, carbonic anhydrase, and anion exchangers (HCO₃⁻/Cl⁻)—have innate immunity, cellular dedifferentiation, and regeneration capabilities. Full article

In eukaryotes, the mitogen-activated protein kinase (MAPK) cascade pathway is a highly conserved cell signaling mechanism that is essential for stress response, growth, and development. MAPK cascade genes have currently been identified and characterized in a wide range of fungi, although they have not been fully understood in early divergent fungal lineages like the Mucoromycota, which contains Mucoromycotina, Glomeromycotina, and Mortierellomycotina. In this study, a genome-wide investigation of Blakeslea trispora (Mucorales, Choanephoraceae) revealed a total of 19 MAPK cascade genes, including 9 BtMAPKKKs, 4 BtMAPKKs, and 6 BtMAPKs genes. Using phylogenetic analysis, it was found that the kinase domain sequences and motif composition of the three MAPK, MAPKK, and MAPKKK lineages are substantially conserved in fungi. Whole genome duplication analysis indicated that B. trispora has four and nine duplication pairs in the MAPK and MAPKKK genes, respectively, which are expanded by segmental replication events. BtHog2, the orthologous protein of Hog1, exhibits a substantial rise in transcription levels under blue light irradiation, indicating its function in light signal response and transduction. Several sets of interacting protein pairs were found using molecular docking analysis and yeast two-hybrid assay, providing a comprehensive MAPK cascade signaling network in B. trispore. Furthermore, MAPK cascade proteins show varying transcription levels in response to blue light and sex hormone stimulation, as well as variable treatment duration. BtMAPKKK9 and BtBck1 are strongly induced during sexual interaction, indicating their involvement in the response to trisporic acid and the subsequent alterations in hyphal cell wall structure. These findings shed light on the evolution of MAPK cascade genes and the functional mechanisms underlying MAPK cascade genes in response to light and sex hormone signaling pathways in B. trispore. Full article

Background/Objectives: SINEs (short interspersed elements) are eukaryotic non-autonomous retrotransposons. They are transcribed by RNA polymerase III (pol III) and generate non-coding RNAs. The 3′ end of many mammalian SINEs contains a polyadenylation signal (AATAAA), a pol III transcription terminator, and an A-rich tail. Studies have shown that, in human HeLa cells that have been transiently transfected with such SINEs, short pol III-generated SINE transcripts undergo polyadenylation, resulting in the addition of a long poly(A)-tail. Notably, this AAUAAA-dependent polyadenylation is not characteristic of any other transcripts synthesized by pol III. B2 SINEs, found in the genomes of mouse-like rodents, exemplify all these features. Methods: In this study, we implemented a novel approach to sequencing pol III-generated B2 transcripts from mouse cell cultures (L929 and 4T1) and organs (brain and testis). Results: Transcription occurred in 16,000–20,000 B2 copies in each cell type, 51–62% of which were transcribed in all four cell types. Effective transcription terminators (e.g., TCT_>3 and T_≥4) were found in approximately 40% of the transcribed B2 copies. The transcripts of these B2 copies contained a truncated terminator sequence, as pol III transcriptional arrest is known to occur within the terminator, with a poly(A)-tail immediately downstream. Such a tail could only have formed through RNA polyadenylation. Conclusions: These results demonstrate that B2 transcripts synthesized by pol III are capable of polyadenylation in mouse cells. We discuss the transcription of B2 copies with and without moderately efficient pol III terminators (TCTTT) and provide examples of the polyadenylation of such transcripts. Full article

The ability of a nucleic acid molecule to self-replicate is the driving force behind the evolution of cellular life and the transition from RNA to DNA as the genetic material. Thus, the physicochemical properties of genome replication, such as the requirement for a terminal hydroxyl group for de novo DNA synthesis, are conserved in all three domains of life: eukaryotes, bacteria, and archaea. Canonical DNA replication is initiated from specific chromosomal sequences termed origins. Early bacterial models of DNA replication proposed origins as regulatory points for spatiotemporal control, with replication factors acting on a single origin on the chromosome. In eukaryotes and archaea, however, replication initiation usually involves multiple origins, with complex spatiotemporal regulation in the former. An alternative replication initiation mechanism, recombination-dependent replication, is observed in every cellular domain (and viruses); DNA synthesis is initiated instead from the 3′ end of a recombination intermediate. In the domain archaea, species including Haloferax volcanii are not only capable of initiating DNA replication without origins but grow faster without them. This raises questions about the necessity and nature of origins. Why have archaea retained such an alternative DNA replication initiation mechanism? Might recombination-dependent replication be the ancestral mode of DNA synthesis that was used during evolution from the primordial RNA world? This review provides a historical overview of major advancements in the study of DNA replication, followed by a comparative analysis of replication initiation systems in the three domains of life. Our current knowledge of origin-dependent and recombination-dependent DNA replication in archaea is summarised. Full article

Transposon is the main component of the eukaryotic genome, and more and more plant genome data show that transposons are diverse in regulating genome structure, variation, function and evolution, with different transposition mechanisms in the genome. Hybridization and polyploidy play an important role in promoting plant speciation and evolution, and recent studies have shown that polyploidy is usually accompanied by the expansion of transposons, which affect the genome size and structure of polyploid plants. Transposons can insert into genes and intergenic regions, resulting in great differences in the overall genome structure of closely related plant species, and it can also capture gene segments in the genome to increase the copy number of genes. In addition, transposons influence the epigenetic modification state of the genome and regulate the expression of the gene, while plant phenotype, biological and abiotic stress response are also regulated by transposons. Overall, transposons play an important role in the plant genome, especially polyploid plant genome, adaptation and evolution. Full article