Search Results (336)

Polemonium caeruleum L. (Polemoniaceae) is a perennial flowering plant native to Eurasia and North America, which is used as a fodder, medicinal, and ornamental plant. Many issues related to the taxonomy and origin of this valuable species still remain unclear. The intraspecific genetic variability of P. caeruleum and chromosomal organization of its genome are insufficiently studied. For the first time, we analyzed NGS genomic data of P. caeruleum using ReapeatExplorer2/TAREAN/DANTE Pipelines. In its repeatome, we identified 66.08% of Class I retrotransposons; 0.57% of Class II transposons; 0.42% of ribosomal DNA; and 0.87% of satellite DNA (six high-confident and three low-confident putative satellite DNAs). FISH chromosome mapping of seven tandem DNAs was carried out in two P. caeruleum varieties and two wild populations. Our results demonstrated the effectiveness of using satDNAs Pol_C 46 and Pol_C 33 in combination with 45S rDNA and 5S rDNA for precise chromosome identification. This approach allowed us to study intraspecific chromosomal variability and detect chromosomal rearrangements in the studied accessions of P. caeruleum, which could be related to the speciation process. These novel molecular markers are important for chromosome studies within Polemonium to clarify its taxonomy and phylogeny, and also, they expand the potential of different breeding programs. Full article

Fanconi anemia (FA) is a genetic disorder characterized by congenital anomalies, bone marrow failure, and cancer predisposition. Among other solid cancers, head and neck squamous cell carcinoma (FA HNSCC) is the most common cancer type in individuals with FA. The FA pathway is required for the complete repair of DNA interstrand crosslinks (ICLs), and unresolved ICLs result in cell cycle arrest, apoptosis, or complex chromosomal rearrangements due to chromosome breaks, ultimately leading to tumorigenesis. FA HNSCCs present earlier (median age of onset in the 30s) and exhibit a more aggressive course with frequent recurrence and second primaries, and entail a poorer survival rate compared to sporadic HNSCC. FA HNSCCs are mostly human papillomavirus (HPV)-negative and frequently carry somatic copy number variations (CNVs), which amplify oncogenes implicated in sporadic HNSCC, but single-nucleotide variants or small insertions and deletions are less frequent than in HPV-negative sporadic HNSCC. A subset of sporadic HNSCC carries pathogenic mutations or promoter methylation in FA genes, which also harbor characteristic somatic CNVs, suggesting shared molecular underpinnings with FA HNSCC. Heightened inflammation from genomic instability and transcriptional activation of retrotransposons contribute to tumorigenesis and increased invasiveness by the epithelial-to-mesenchymal transition. Due to heightened sensitivity to DNA crosslinking agents in patients with FA, platinum-based chemotherapy is generally avoided, which presents a significant hurdle for treatment and thereby leaves limited therapeutic options. Surgical management is the mainstay of therapy if possible, and targeted therapy has been increasingly studied in HNSCC in FA. Full article

Cyclophyllideans, which diverged from diphyllobothriideans, have evolved compact genomes to meet ecological and biological demands associated with rapid development, early maturation, and prolific asexual reproduction. This streamlining is accompanied by inactivation of transposable elements (TEs), including retrotransposons. In contrast, diphyllobothriideans retain large, retrotransposon-rich genomes, but information on their individual retrotransposons is lacking. Here, Saci2-like long terminal repeat (LTR) retrotransposons, formerly annotated as lennie in taeniid cestodes, were identified in the diphyllobothriideans Spirometra erinaceieuropaei and Sparganum proliferum, along with orthologs from Schistocephalus solidus and Ligula intestinalis. The Saci2 homologs in these genomes diversified into at least eight families, exhibiting substantial variation in LTR and primer binding site sequences, reflecting ongoing regulatory diversification. Phylogenetic and divergence analyses indicated that they maintain structural and functional integrity under purifying selection, while early signs of inactivation appeared in S. proliferum. These findings suggest that diphyllobothriideans have faced little pressure for genome compaction, permitting the retention of functional retrotransposons, whereas cyclophyllideans, particularly taeniids, underwent genome streamlining linked to shortened life cycles and high fecundity, resulting in retrotransposon degradation. This contrast underscores the reciprocal relationship between biological demands and genome remodeling with TE inactivation in metazoans. Full article

This study investigated interspecific and intraspecific polymorphism in Rheum (Polygonaceae) from Kazakhstan using the inter-primer binding site (iPBS) retrotransposon marker system. The results revealed considerable variation in the level and nature of genetic polymorphism both within and among Rheum species and ecopopulations across different regions of Kazakhstan. Rh. compactum and the ecopopulation Rh. tataricum from the Zhambyl Region (ZH) exhibited the lowest levels of polymorphism, supporting their designation as conservation priorities. Genetic differentiation analysis among species and ecopopulations identified clear distinctions, resulting in the formation of well-defined clusters with high bootstrap support. Minimal genetic distances were observed between the two ecopopulations of Rh. tataricum, along with a high degree of intraspecific genetic homogeneity in Rh. compactum and Rh. nanum. A distinct genetic divergence between Rh. compactum and the other taxa was detected, reinforcing its status as a separate species rather than a synonym of Rh. altaicum. The iPBS markers proved effective for investigating genetic variation in Rheum, offering valuable insights for future studies aimed at understanding the evolutionary history of the genus. Full article

The Long Interspersed Element-1 (L1) retrotransposon is an ancient genetic parasite that comprises a significant part of the human genome. ORF2p is a multifunctional enzyme with endonuclease (EN) and reverse transcriptase (RT) activities that mediate target-primed reverse transcription of RNA into DNA. Structural studies of LINE-1 ORF2p consistently show a single Mg²⁺ cation in the reverse transcriptase active site, conflicting with the common DNA polymerase mechanism which involves two divalent cations. We explored a reaction pathway of the DNA elongation based on the recent high-resolution ternary complex structure of the ORF2p. The combined quantum and molecular mechanics approach at the QM (PBE0-D3/6-31G**)/MM (CHARMM) level is employed for biased umbrella sampling molecular dynamics simulations followed by umbrella integration utilized to obtain the free energy profile. The nucleotidyl transfer reaction proceeds in a single step with a free energy barrier of 15.1 ± 0.8 kcal/mol, and 7.8 ± 1.2 kcal/mol product stabilization relative to reagents. Concerted nucleophilic attack by DNA O3′ and proton transfer to Asp703 occur without a second catalytic metal ion. Estimated rate constant ∼60 s⁻¹ aligns with RT kinetics, while analysis of the Laplacian of the electron density along the cleaving P-O bond identifies a dissociative mechanism. Full article

In Drosophila gonads, transposable elements (TEs) are repressed by the Piwi-interacting RNA (piRNA) pathway operating both co-transcriptionally and post-transcriptionally. In the non-gonadal tissues, TEs are mainly repressed by the short interfering RNA (siRNA) pathway with Argonaute 2 (Ago2) functioning as an effector protein. It is generally assumed that this pathway acts at the post-transcriptional level. However, recent data point to its possible involvement in co-transcriptional silencing as well. Here, using DamID, we found a drastic decrease in HP1a on TEs (especially on the LTR-containing retrotransposons) and other heterochromatin regions in Ago2-mutant Drosophila brain. HP1a reduction is accompanied by the increased chromatin accessibility of TEs, indicating their derepression. Accordingly, several LTR-containing retrotransposons were up-regulated in the larval brain of Ago2 mutants. Moreover, upon the knock-down of lamin Dm0 in neurons, HP1a was increased predominantly on the same set of TEs that had reduced HP1a binding in Ago2 mutants. We hypothesize that, since Ago2 was localized to the common complex with lamin Dm0, the depletion of the latter may release Ago2 in the nucleoplasm, thus enhancing the recruitment of HP1a on TEs. Our findings support the hypothesis that TEs in the Drosophila brain are silenced, in part, through Ago2-mediated recruitment of HP1a. Full article

Retrotransposons exhibit increased activity in cancer cells. One possible approach to anticancer therapy is to use this activity to influence the energy balance in cells. Abnormal distribution of retrotransposons in the genome requires additional energy consumption, which can lead to a significant decrease in the total amount of free ATP molecules in the cell. A decrease in ATP levels below a certain threshold can in turn trigger a cell death program. To investigate the possibility of such a scenario, we developed a mathematical model of the cellular energy balance that describes the dynamics of energy consumption by the main cellular processes, including costs of retrotransposon activity. The model considers changes in the concentrations of ATP, active retrotransposons (LINE-1 and SINE) in the human genome, as well as mRNAs and proteins that are expression products of retrotransposon and constitutive genes. We estimated the parameter values in the model based on literature data and numerical optimization. We found a single stable stationary solution, characterized by low retrotransposon activity, and used it as the reference steady state for further analysis. Parametric sensitivity analysis revealed the parameters whose changes had the greatest impact on cellular ATP levels. The LINE-1 deactivation rate constant and the maximum LINE-1 transcription rate were the most sensitive among the transposon-related parameters. Perturbation of these parameters led to a decrease in the number of free ATP to 30% of the reference value and below. Transcription of retrotransposons under perturbed parameters became comparable to the translation of constitutive genes in terms of energy costs. The presented results indicate that cancer cell death can be initiated by increasing the load on the energy balance due to the activation of transposons. Full article

The blood orange arose from the insertion of a retrotransposon adjacent to the Ruby gene, an MYB-type transcriptional activator of anthocyanin production, as reported previously. However, the intricate process of anthocyanin regulation among different varieties of blood orange remains incompletely understood. In this study, mRNA levels of the transcription factors Ruby and TT8 were found to be upregulated in the juice vesicle tissues of a variety with higher concentrations of anthocyanins in the pulp compared with another variety with a lower anthocyanin content. In contrast, comparative analysis of the two varieties using two-dimensional electrophoresis and mass spectrometry did not identify differentially expressed proteins related to anthocyanin biosynthesis in the juice vesicle tissues. Furthermore, higher anthocyanin contents were observed in various tissues of transgenic Arabidopsis thaliana overexpressing the Ruby gene from blood orange compared with the wildtype plant. Moreover, the long terminal repeat (LTR) region of a retrotransposon inserted upstream of the Ruby locus exhibited the ability to drive reporter expression through histochemical assay in a transgenic seedling. Thus, a PCR-based molecular marker was developed, targeting the upstream sequence of the Ruby locus to identify Citrus hybrids with the unique trait of red-fleshed fruit. Intriguingly, bisulfite sequencing revealed differentially methylated regions within a Gag-Pol polyprotein-encoding sequence of a retrotransposon adjacent to Ruby locus when comparing two varieties with different anthocyanin contents. A higher average level of methylation status was observed in the fruit with a lower anthocyanin content. In conclusion, methylation modifications at specific upstream positions on the Ruby locus may influence anthocyanin production in blood oranges. Full article

The Qinghai–Tibet Plateau (QTP) harbors extreme environmental conditions (e.g., low temperature, intense UV radiation, and hypoxia), presenting unique challenges for biological adaptation. However, the genetic mechanisms underlying the adaptation of macrofungi to high-altitude environments on the QTP remain poorly understood. In this study, we de novo sequenced and assembled the genomes of three Laccaria species collected from the QTP, aiming to unravel the genomic basis of their adaptation to high altitudes. The genomic data indicates that the genome of high-altitude species is slightly larger than that of their low-altitude relatives, particularly due to LTR retrotransposons, which also show a negative correlation with altitude. The expanded and positively selected gene families in high-altitude species were enriched in pathways related to DNA damage repair, maintenance of cell membrane stability, signal transduction, enzyme activity, stress response, and reproduction. In contrast, contracted gene families in high-altitude species were primarily associated with disease and immune responses, likely due to the reduced pathogen pressure in extreme high-altitude environments. Additionally, species-specific genes of high-altitude Laccaria were enriched in functions related to enzyme activity, membrane stability, and signal transduction, further supporting their adaptive roles. Analysis of carbohydrate-active enzymes (CAZymes) showed distinct gene family distributions between high- and low-altitude species, with several families absent in the low-altitude species, suggesting their potential involvement in environmental adaptation. Overall, our findings indicate that genome size expansion driven by LTR retrotransposons, coordinated evolution of gene families, positive selection, and divergence in CAZymes collectively may contribute to the adaptation of Laccaria to extreme high-altitude environments. This study provides basic data into the genetic mechanisms of fungal adaptation to harsh plateau environments and lays a foundation for further research on extremophilic fungi. Full article

Chromosome rearrangements during plant evolution can lead to alterations in genome structure and gene function, thereby influencing species adaptation and evolutionary processes. Gymnosperms, as an ancient group of plants, offer valuable insights into the morphological, physiological, and ecological characteristics of early terrestrial flora. The reconstruction of ancestral karyotypes in gymnosperms may provide critical clues for understanding their evolutionary history. In this study, we inferred the ancestral gymnosperm karyotype (AGK), which comprises 12 chromosomes, and conducted a collinearity analysis with existing gymnosperm genomes. Our findings indicate that chromosome numbers have remained remarkably stable throughout the evolution of gymnosperms. For species with multiplied chromosome numbers, such as gnetophytes, weak collinearities with the AGK were observed. Comparisons between the AGK and gnetophyte genomes revealed a biased pattern regarding retained duplication blocks. Furthermore, our analysis of transposable elements in Welwitschia mirabilis identified enriched regions containing LINE-1 retrotransposons within the syntenic blocks. Syntenic analysis between the AGK and angiosperms also demonstrated a biased distribution across chromosomes. These results provide a fundamental resource for further characterization of chromosomal evolution in gymnosperms. Full article

Capsicum (pepper) is an economically vital genus in the Solanaceae family, with most species possessing about 3 Gb genomes. However, the recently sequenced Capsicum rhomboideum (~1.7 Gb) represents the first reported case of an extremely compact genome in Capsicum, providing a unique and ideal model for studying genome size evolution. To elucidate the mechanisms driving this variation, we performed comparative genomic analyses between the compact Capsicum rhomboideum and the reference Capsicum annuum cv. CM334 (~2.9 Gb). Although their genome size differences initially suggested whole-genome duplication (WGD) as a potential driver, both species shared two ancient WGD events with identical timing, predating their divergence and thus ruling out WGD as a direct contributor to their size difference. Instead, transposable elements (TEs), particularly long terminal repeat retrotransposons (LTR-RTs), emerged as the dominant force shaping genome size variation. Genome size strongly correlated with LTR-RT abundance, and multiple LTR-RT burst events aligned with major phases of genome expansion. Notably, the integrity and transcriptional activity of LTR-RTs decline over evolutionary time; older insertions exhibit greater structural degradation and reduced activity, reflecting their dynamic nature. This study systematically delineated the evolutionary trajectory of LTR-RTs—from insertion and proliferation to decay–uncovering their pivotal role in driving Capsicum genome size evolution. Our findings advance the understanding of plant genome dynamics and provide a framework for studying genome size variation across diverse plant lineages. Full article

Introduction: Emerging research indicates that alterations in the methylation of retrotransposons may contribute to genomic instability and cellular aging in various autoimmune disorders and diabetes mellitus (DM). As relevant information for people with type 1 diabetes mellitus (PwT1D) is limited, we aimed to investigate long interspersed nuclear element-1 (LINE-1) methylation status in this population. Methods: DNA methylation levels and patterns of LINE-1 were examined in the peripheral blood of 35 PwT1D and 28 healthy controls (age- and sex-matched), by using the COmbined Bisulfite Restriction Analysis methodology (COBRA). Results: Total LINE-1 methylation rate (mC) was higher in PwT1D compared to controls [47.3% (46.6–47.8%) vs. 46.5% (44.7–47.3%), p < 0.05]. The partial LINE-1 methylation pattern (uCmC) was less frequently observed in patients vs. controls [28.4% (24.7–33.3%) vs. 33.1% (27.8–37.9%), p < 0.05]. Prevalence of other methylation patterns [partially methylated (mCuC), hypermethylated (mCmC) and hypomethylated (uCuC)] was similar in the two groups. Furthermore, levels of fasting glucose and glycated hemoglobin (HbA1c) were positively associated with total methylation (mC) [Spearman’s rho = 0.380, p = 0.002 and rho = 0.342, p = 0.006, respectively], but negatively associated with the partially methylated (uCmC) pattern [Spearman’s rho = −0.383, p = 0.002 and rho = −0.270, p = 0.033, respectively]. The LINE-1 (uCmC) methylation pattern was negatively associated with the age at diagnosis of T1D [Spearman’s rho = −0.341, p = 0.049], but positively associated with disease duration [Spearman’s rho = 0.388, p = 0.021]. Conclusions: PwT1D were found to have higher total LINE-1 methylation rate (mC) compared to healthy controls. The partial methylation pattern (uCmC) was less frequently observed in these patients and was negatively associated with the glycemic status and the age at diagnosis of T1D, while demonstrating a positive correlation with disease duration. Full article

Crinum thaianum, commonly known as water onion, is an endangered species which is primarily threatened by flood-control-related habitat destruction and illegal harvesting for export, resulting in a sharp population decline; its genetic data still remains poorly studied. Retrotransposon-based markers have received significant attention due to their higher potential informativeness compared to conventional marker methods in genetic diversity studies. This study focused on the screening of Ty1-copia retrotransposons, which have been widely studied and are commonly used as molecular markers in various plant species. Ty1-copia reverse transcriptase (rt) fragments were amplified using degenerate primers targeting conserved regions, followed by cloning and sequencing. Sequences were screened for rt gene homology and translated into amino acid sequences. Lineages were assigned by alignment, and phylogenetic analysis was performed for each isolated sequence with a set of well-classified rt genes. The p-distance values were calculated between the isolated sequences and their closest homologous sequences. A total of 123 isolated sequences were analyzed, representing conserved domains in the rt gene of Ty1-copia elements from C. thaianum and four other Crinum species. The results revealed sequence homology to the Ale, TAR, or Angela lineages, which showed the closest resemblance to 9, 4, and 110 isolated rt sequences, respectively. The conserved rt domain SIYGLKQA was mostly found in Angela (87.27%), while SLY/HGLKQS/L and SLYG/ELKQF/S were mostly found in Ale (66.67%) and TAR (75.00%), respectively. The p-distance values obtained from comparisons with Ty1-copia elements in other plants suggest that the Angela and TAR lineages are more evolutionarily conserved than the Ale lineage. Whilst our study sheds light on the variety of Ty1-copia retrotransposons in C. thaianum and other Crinum species, further research on additional Crinum species and other plants is required to enhance our understanding and facilitate future retrotransposon-based marker development. Full article

LTR retrotransposons are widespread genomic elements that significantly impact genome structure and function. In Arabidopsis thaliana, the EVD LTR retrotransposon encodes a GAG protein essential for retrotransposon particle assembly. Here, we present a comprehensive analysis of the structural features, intracellular localization, and transcriptomic effects of the EVD GAG (evdGAG) protein. Using AlphaFold3, we identified canonical capsid (CA-NTD and CA-CTD) and nucleocapsid (NC) domains, with predicted disordered regions likely facilitating oligomerization. Transient expression of GFP-tagged evdGAG in protoplasts of A. thaliana and distant plant species (Nicotiana benthamiana and Helianthus annuus) revealed the formation of multiple large cytoplasmic aggregates resembling retrosomes, often localized near the nucleus. Stable overexpression of evdGAG in wild-type and ddm1 mutant backgrounds induced significant transcriptomic changes, including up-regulation of stress response and defense-related genes and downregulation of photosynthesis and chloroplast-associated pathways. Importantly, genes linked to stress granule formation were also up-regulated, suggesting a role for evdGAG in modulating cellular stress responses. Our findings provide novel insights into the cellular and molecular properties of plant retrotransposon GAG proteins and their influence on host gene expression. Full article

Backround/Objectives: Mobile genetic elements (MGEs), in general, and transposable elements (TEs), in particular, constitute a major part of almost every eukaryotic genome, and several types of such elements have been classified based on size, genetic structure and transposition intermediate. Methods: The fast-growing availability of whole genome sequences of species across the living world provides almost unlimited possibilities for in-depth molecular analyses of all kinds, including the search for TEs. The aim of the present study was to perform the first molecular description and characterization of selected MGEs in leeches, namely, short interspersed nuclear element (SINE), long interspersed nuclear element (LINE) and long terminal repeat (LTR) retrotransposons. Results: Several representatives of all three groups of TEs could be identified, and some of the newly described elements display unique structural features compared to the archetype elements of the respective groups. Conclusions: Non-model organisms like leeches are an excellent source for new information on long-term studied objects like TEs and may provide new insights into the diversity and the putative biological impact of these MGEs. Full article