Search Results (219)

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

The genetic diversity of cattle plays a crucial role in adapting to environmental challenges and enhancing production traits. While research has predominantly focused on single nucleotide polymorphisms (SNPs), small indel and structural variants (SVs) also significantly contribute to genetic variation. This study investigates the distribution and functional impact of insertions and deletions in five Hubei indigenous cattle breeds. A total of 3,208,816 deletions and 2,082,604 insertions were identified, with the majority found in intergenic and intronic regions. Hotspot regions enriched in immune-related genes were identified, underscoring the role of these variants in disease resistance and environmental adaptation. Our analysis revealed a strong influence of transposable elements (TEs), particularly LINEs and SINEs, on genomic rearrangements. The variants were also found to overlap with economically important traits, such as meat quality, reproduction, and immune response. Population structure analysis revealed genetic differentiation among the breeds, with Wuling cattle showing the highest differentiation. Notably, the NOTCH2 gene was identified as a candidate for regional adaptation due to its significant differentiation across populations. These findings provide valuable genomic resources for enhancing breeding programs, aiming at improving the productivity and resilience of indigenous cattle breeds in China. 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

Transposable elements (TEs) make up around half of the human genome. Their transcription is repressed in most somatic cells to maintain genome integrity and function. The repression is chiefly maintained by a combination of epigenetic modifications such as DNA methylation and histone modifications. However, recent research suggests that liver steatosis is associated with extensive changes to the hepatocyte epigenome. Furthermore, studies in mice have reported diet- and drug-induced changes to TE transcript levels in liver. The confirmation of these effects in human liver has not previously been undertaken. Here, we examined TE transcription in liver tissue from three patient cohorts with histologically confirmed liver steatosis caused by alcohol consumption or metabolic dysfunction. The quantitation of the number of transcripts with TE-homology in RNA-Seq data from a cohort of 90 bariatric surgery patients with metabolic dysfunction-associated steatotic liver disease (MASLD) revealed a trend for the reduction in TEs of all classes due to increasing steatosis, but no effect of fibrosis. This pattern was also present in a separate cohort of MASLD and HCC patients, as RT-qPCR also showed a reduction in Alu element transcripts in advanced steatosis, but again, no effect of fibrosis. Contrastingly, in a cohort of alcohol-related liver disease patients, the reduction in LINE-1 transcripts was associated with either increased steatosis or increased fibrosis. Moreover, the examination of LINE-1 DNA methylation levels in the MASLD and HCC cohort indicated that DNA methylation was also negatively associated with LINE-1 transcription in MASLD. This study suggests that TE transcript levels in human liver are slightly reduced by steatosis, that DNA methylation is an influential epigenetic regulator of LINE-1 retrotransposon transcription in steatosis, and that Alu transcript levels in background liver could be a new biomarker for HCC in cirrhotic and non-cirrhotic MASLD. Full article

Transposable elements (TEs) are major drivers of plant genome plasticity, but the immediate molecular consequences of new TE insertions remain poorly understood. In this study, we generated a wild-type Arabidopsis thaliana population with novel insertions of ONSEN retrotransposon to investigate early epigenomic and transcriptomic changes using whole-genome and cDNA nanopore sequencing. We found that novel ONSEN insertions were distributed non-randomly, with a strong preference for genic regions, particularly in chromatin enriched for H2A.Z, H3K27me3, and H3K4me2. Most full-length ONSEN insertions within genes were rapidly recognized and spliced out as new introns (intronization), thereby mitigating potential deleterious effects on transcript isoforms. In some cases, ONSEN insertions provided alternative transcription start or termination sites, generating novel transcript isoforms. Genome-wide methylation analysis revealed that new ONSEN copies were efficiently and precisely targeted by DNA methylation. Independently on the location of the original ONSEN element, the euchromatic and heterochromatic insertions display distinct methylation signatures, reflecting the action of different epigenetic pathways. In conclusion, our results demonstrate that DNA methylation and alternative splicing are effective control mechanisms safeguarding the plant genome and transcriptome integrity after retrotransposition burst. Full article

Background: Glioma is the most common type of malignant brain tumor. Temozolomide (TMZ) is a limited systematic treatment option for glioma, including low-grade glioma (LGG) and glioblastoma (GBM). However, not all patients benefit from TMZ and some develop resistance to it. MGMT methylation has been used to identify patients who may benefit from TMZ, but it is not effective in all cases. Objectives: There is an urgent need for new biomarkers to predict the survival of patients who receive TMZ. Methods: We utilized a recently developed method called REdiscoverTE to precisely measure the expression of transposable elements (TE). We performed Cox regression analysis to assess the predictive ability for prognosis and conducted a series of correlation studies to uncover potential mechanisms. Results: We identified three TEs, LTR81B, LTR27B, and MER39B, that were strongly predictive of longer survival in glioma patients receiving chemotherapy. We discovered that the expression of these TEs was positively associated with immune cells that enhance the immune system and negatively associated with immune cells suppressing the immune response, as well as molecules that control immune checkpoints. These three TEs were also found to predict better survival in patients receiving immunotherapy. Conclusions: In conclusion, we demonstrate that the expression of TEs can serve as a novel biomarker for the overall survival of glioma patients who receive TMZ chemotherapy or immunotherapy. Full article

Piwi-interacting RNAs (piRNAs) play a crucial role in silencing transposable elements (TEs) in the germ cells of Metazoa by acting as sequence-specific guides. Originating from distinct genomic loci, called piRNA clusters, piRNA can trigger an epigenetic conversion of TE insertions into piRNA clusters by means of a paramutation-like process. However, the variability in piRNA clusters’ capacity to induce such conversions remains poorly understood. Here, we investigated two Drosophila virilis strains with differing capacities to produce piRNAs from the subtelomeric RhoGEF3 and Adar gene loci. We found that active piRNA generation correlates with high levels of the heterochromatic mark histone 3 lysine 9 trimethylation (H3K9me3) over genomic regions that give rise to piRNAs. Importantly, the maternal transmission of piRNAs drives their production in the progeny, even from homologous loci previously inactive in piRNA biogenesis. The RhoGEF3 locus, once epigenetically converted, maintained enhanced piRNA production in subsequent generations lacking the original allele carrying the active piRNA cluster. In contrast, piRNA expression from the converted Adar locus was lost in offspring lacking the inducer allele. The present findings suggest that the paramutation-like behavior of piRNA clusters may be influenced not only by piRNAs but also by structural features and the chromatin environment in the proximity to telomeres, providing new insights into the epigenetic regulation of the Drosophila genome. Full article

The possible regulatory effects of C2H2 zinc finger proteins, which are important transcription factors, on intertidal seaweed responses to abiotic stress are unclear. This study was conducted to comprehensively analyze the C2H2 gene family of a representative intertidal seaweed species (Pyropia haitanensis) and clarify its genomic characteristics and biological functions. A total of 107 PhC2H2 zinc finger protein-encoding genes distributed on five P. haitanensis chromosomes were identified and divided into three subgroups. The expression levels of 85, 61, 58, 45, and 41 PhC2H2 genes responded in the maturation of filaments, high-temperature, salt, low-irradiance, and dehydration stress, respectively. The PhC2H2 gene family was conserved during Porphyra evolution, with no indications of large-scale genome-wide replication events. On average, PhC2H2 genes had more transposable element (TE) insertions than Pyropia yezoensis and Porphyra umbilicalisC2H2 genes, suggesting that TE insertions may have been the main driver of PhC2H2 gene family expansion. A key gene (PhC2H2.94) screened following a quantitative trait locus analysis was significantly responsive to high-temperature stress and was associated with photosynthesis, peroxisomes, the ubiquitin proteasome pathway, and the endoplasmic reticulum-related protein processing pathway, which contribute to the stress tolerance of P. haitanensis. Additionally, PhC2H2.94 transgenic Chlamydomonas reinhardtii exhibited increased tolerance to heat stress. This study provides new insights and genetic resources for characterizing the molecular mechanism underlying intertidal seaweed responses to abiotic stresses and breeding stress-resistant macroalgae. Full article

Background: The African hedgehog (Atelerix albiventris) exhibits specialized skin differentiation leading to spine formation, yet its regulatory mechanisms remain unclear. Transposable elements (TEs), particularly LINEs (long interspersed nuclear elements) and SINEs (short interspersed nuclear elements), are known to influence genome organization and gene regulation. Objectives: Given the high proportion of SINEs in the hedgehog genome, this study aims to characterize the distribution, evolutionary dynamics, and potential regulatory roles of LINEs and SINEs, focusing on their associations with chromatin architecture, DNA methylation, and gene expression. Methods: We analyzed LINE and SINE distribution using HiFi sequencing and classified TE families through phylogenetic reconstruction. Hi-C data were used to explore TE interactions with chromatin architecture, while whole-genome 5mCpG methylation was inferred from PacBio HiFi reads of muscle tissue using a deep-learning-based approach. RNA-seq data from skin tissues were analyzed to assess TE expression and potential associations with genes linked to spine development. Results: SINEs form distinct genomic blocks in GC-rich and highly methylated regions, whereas LINEs are enriched in AT-rich, hypomethylated regions. LINEs and SINEs are associated differently with A/B compartments, with SINEs in euchromatin and LINEs in heterochromatin. Methylation analysis suggests that younger TEs tend to have higher methylation levels, and expression analysis indicates that some differentially expressed TEs may be linked to genes involved in epidermal and skeletal development. Conclusions: This study provides a genome-wide perspective on LINE and SINE distribution, methylation patterns, and potential regulatory roles in A. albiventris. While not establishing a direct causal link, the findings suggest that TEs may influence gene expression associated with spine development, offering a basis for future functional studies. Full article

Mucor lusitanicus has emerged as a model organism for studying RNAi in early-diverging fungi. This fungus exhibits intricate RNAi pathways that play crucial roles in regulating gene expression, destroying invasive exogenous genetic material, and controlling the movement of transposable elements (TEs) to ensure genome stability. One of the most fascinating RNAi pathways of this fungus is the non-canonical RNAi pathway (NCRIP), which is independent of Dicer and Argonaute proteins and uses the atypical RNase III R3B2 to degrade specific target messenger RNAs (mRNAs), playing an essential role in genome stability and virulence. Despite accumulating data suggesting that this pathway is a degradation mechanism, there has been no conclusive evidence. Here, we conducted a comparative transcriptomic analysis of mRNA and small RNAs regulated by r3b2, identifying 35 direct NCRIP targets. Most of these direct NCRIP targets correspond to TEs, highlighting the significant role of this RNAi pathway in TE control. Detailed functional analysis of the NCRIP targets confirmed the crucial role of r3b2 in regulating gene expression of protein-coding genes and controlling TEs other than centromeric GremLINE1 transposons, emphasizing the important role of r3b2 in genome stability. Interestingly, the RNAs of the NCRIP targets harbor a unique motif consisting of CAG repeats which are known to form hairpin structures which are targeted by RNA interference. Additionally, the generation of transformants expressing mRNAs containing the luciferase reporter gene along direct NCRIP targets reveals that this RNAi pathway is a true degradation mechanism for specific mRNAs. These results are expected to contribute to the understanding of the regulation of the NCRIP pathway through the analysis of its direct targets identified here. Full article

Transposable elements (TEs) are crucial for genome evolution and ecological adaptation, but their dynamics in non-model plants are poorly understood. Using genomic, transcriptomic, and population genomic approaches, we analyzed the TE landscape of Barthea barthei (Melastomataceae), a species distributed across tropical and subtropical southern China. We identified 64,866 TE copies (16.76% of a 235 Mb genome), dominated by Ty3/Gypsy retrotransposons (8.82%) and DNA/Mutator elements (2.7%). A genome-wide analysis revealed 13 TE islands enriched in genes related to photosynthesis, tryptophan metabolism, and stress response. We identified 3859 high-confidence TE insertion polymorphisms (TIPs), including 29 fixed insertions between red and white flower ecotypes, affecting genes involved in cell wall modification, stress response, and secondary metabolism. A transcriptome analysis of the flower buds identified 343 differentially expressed TEs between the ecotypes, 30 of which were near or within differentially expressed genes. The non-random distribution (primarily within 5 kb of genes) and association with adaptive traits suggest a significant role in B. barthei’s successful colonization of diverse habitats. Our findings provide insights into how TEs contribute to plant genome evolution and ecological adaptation in tropical forests, particularly through their influence on regulatory networks governing stress response and development. Full article

Using male sterile (MS) lines instead of normal inbred maternal lines in hybrid seed production can increase the yield and quality with lower production costs. Therefore, developing a new MS germplasm is essential for maize hybrid seed production in the future. Here, we reported a male sterility gene ms*-N125, cloned from a newly found MS mutant ms*-N125. This mutant has an underdeveloped tassel that showed impaired glumes and shriveled anthers without pollen grains. The MS locus of ms*-N125 was mapped precisely to a 112-kb-interval on the chromosome 5. This interval contains only three candidate genes, Zm958, Zm959, and Zm960. Sequencing results showed that only candidate Zm960 harbored a 548-bp transposable element (TE) in its 9th exon, and the two other candidate genes were found to have no genetic variations between the mutant and wild type (WT). Thus, Zm960 is the only candidate gene for male sterility of the mutant ms*-N125. In addition, we screened another recessive MS mutant, ms*-P884, which exhibited similar male sterility phenotypes to ms*-N125. Sequencing Zm960 in ms*-P884 showed a 600-bp TE located in its 2nd exon. Zm960 encodes an ATP-binding cassette in the G subfamily of ABC (ABCG) transporters, ZmABCG2a, with both mutants which harbored an Ac/Ds-like transposon in each. To verify the function of ZmABCG2a for male sterility further, we found an ethyl methanesulfonate (EMS) mutant, zmabcg2a*, which displayed male sterility and tassel phenotypes highly similar to ms*-N125 and ms*-P884, confirming that ZmABCG2a must be the gene for male sterility in maize. In addition, the results of lipid metabolome analysis of ms*-N125 young tassels showed that the total lipid content of the mutant was significantly lower than that of the WT, with 15 subclasses of lipids, including PE (phosphatidylethanolamine), PC (phosphatidylcholine), DG (digalactosyldiacylglycerols), and MGDG (monogalactosyldiacylglycerol) which were significantly down-regulated in the ms*-N125 mutant versus its wild type. In summary, we identified alternate mutations of the ZmABCG2a gene, which may be a potential germplasm for hybrid seed production in maize. Full article

Background/Objectives: The highly polymorphic Major Histocompatibility Complex (MHC) genomic region, located on the short arm of chromosome 6, is implicated genetically in Parkinson’s disease (PD), a progressive neurodegenerative disorder with motor and non-motor symptoms. Previously, we reported significant associations between SINE-VNTR-Alu (SVA) expression quantitative trait loci (eQTLs) and Human Leucocyte Antigen (HLA) class I genotypes in PD. In this study, we aimed to evaluate SVA associations and their regulatory effects on transposable element (TE) transcription in the MHC class I region. Methods: Transcriptome data from the peripheral blood cells of 1530 individuals in the Parkinson’s Progression Markers Initiative (PPMI) cohort were reanalyzed for TE and gene expression using publicly available bioinformatics tools, including Salmon and Matrix-eQTL. Results: Four structurally polymorphic SVAs regulated the transcription of 18 distinct clusters of 235 TE loci, comprising LINEs (33%), SINEs (19%), LTRs (35%), and ancient transposon DNA elements (12%) located near HLA genes. The transcribed TEs were predominantly short, with an average length of 445 nucleotides. The regulatory effects of these SVAs varied significantly in terms of TE types, numbers, and transcriptional activation or repression. The SVA-regulated TE RNAs in blood cells appear to function as enhancer-like elements, differentially influencing the expression of HLA class I genes, non-HLA genes, and noncoding RNAs. Conclusions: These findings highlight the roles of SVAs and their associated TEs in the complex regulatory networks governing coding and noncoding gene expression in the MHC class I region, with potential implications for immune function and disease susceptibility. Full article

Plant genomes possess numerous transposable element (TE) insertions that have occurred during evolution. Most TEs are silenced or diverged; therefore, they lose their ability to encode proteins and are transposed in the genome. Knowledge of active plant TEs and TE-encoded proteins essential for transposition and evasion of plant cell transposon silencing mechanisms remains limited. This study investigated active long terminal repeat (LTR) retrotransposons (RTEs) in sunflowers (Helianthus annuus), revealing heterogeneous and phylogenetically distinct RTEs triggered by epigenetic changes and heat stress. Many of these RTEs belong to three distinct groups within the Tekay clade, showing significant variations in chromosomal insertion distribution. Through protein analysis of these active RTEs, it was found that Athila RTEs and Tekay group 2 elements possess additional open reading frames (aORFs). The aORF-encoded proteins feature a transposase domain, a transmembrane domain, and nuclear localization signals. The aORF proteins of the Tekay subgroup exhibited remarkable conservation among over 500 Tekay members, suggesting their functional importance in RTE mobility. The predicted 3D structure of the sunflower Tekay aORF protein showed significant homology with Tekay proteins in rice, maize, and sorghum. Additionally, the structural features of aORF proteins resemble those of plant DRBM-containing proteins, suggesting their potential role in RNA-silencing modulation. These findings offer insights into the diversity and activity of sunflower RTEs, emphasizing the conservation and structural characteristics of aORF-encoded proteins. Full article

Zygotic genome activation (ZGA) is critical for early embryo development and is meticulously regulated by epigenetic modifications. H3K4me3 is a transcription-permissive histone mark preferentially found at promoters, but its distribution across genome features remains incompletely understood. In this study, we investigated the genome-wide enrichment of H3K4me3 during early embryo development and embryonic stem cells (ESCs) in both sheep and mice. We discovered that broad H3K4me3 domains were present in MII stage oocytes and were progressively diminished, while promoter H3K4me3 enrichment was increased and correlated with gene upregulation during ZGA in sheep. Additionally, we reported the dynamic distribution of H3K4me3 at the transposable elements (TEs) during early embryo development in both sheep and mice. Specifically, the H3K4me3 distribution of LINE1 and ERVL, two subsets of TEs, was associated with their expression during early embryo development in sheep. Furthermore, H3K4me3 enrichment in TEs was greatly increased during ZGA following Kdm5b knockdown, and the distribution of RNA polymerase II (Pol2) in TEs was also markedly increased in Kdm5b knockout ESCs in mice. These findings suggest that H3K4me3 plays important roles in regulating TE expression through interaction with RNA Pol2, providing valuable insights into the regulation of ZGA initiation and cell fate determination by H3K4me3. Full article