Role Of Transposable Elements Research Articles

Comparative RNA-seq analysis reveals transposable element-mediated transcriptional reprogramming under phosphorus-starvation stress in rice (Oryza sativa L.)

Phosphorus (P) deficiency hinders crop productivity of 50 % of the rice grown in Asia, Africa, and South America. About 90 % of the phosphate in fertilizers applied to the crops gets fixed in the soil, reducing its availability to plants. This necessitates increased use of phosphatic fertilizers leading to higher cost of cultivation and environmental pollution. Although molecular mechanisms of P-deficiency tolerance in rice are being deciphered, the role of transposable elements (TEs) in transcriptional reprogramming under P-starvation/deficiency stress has not yet been reported. To investigate the role of Pup1 QTL in controlling TE-mediated reprogramming of gene expression, a pair of contrasting rice [Pusa-44 and its Near-Isogenic Line (NIL)-23] genotypes were grown hydroponically under control and stressed (0 ppm Pi) conditions. Comparative RNA-seq analysis of root and shoot tissues from 45-day-old plants of the rice genotypes revealed TE-mediated transcriptional reprogramming affecting biological processes and cellular components. Significantly up-regulated expression of several TEs under P-starvation stress, controlled by Pup1 QTL, particularly in shoots of NIL-23 indicates their crucial role in P homeostasis. Moreover, comparative physio-biochemical analyses confirmed the stress tolerance of NIL-23. Several biological processes including DNA replication/repair, metabolism, signaling, and phosphorylation were modulated through differential (mainly up-regulated) expression of TEs (controlled by Pup1 QTL) in shoots of NIL-23 under P-starvation. To the best of our knowledge, this is a pioneer study on the role of TEs in reprogramming biological processes/molecular functions/cellular components involved in P-use efficiency in rice under stress. The findings advance our understanding of the functions of Pup1 to improve the P-use efficiency/productivity of rice in P-deficient soils.

The role of transposable elements in long-term memory formation

The role of transposable elements in long-term memory formation

Pathogen infection alters the gene expression landscape of transposable elements in Drosophila melanogaster.

Transposable elements make up substantial proportions of eukaryotic genomes and many are thought to be remnants of ancient viral infections. Current research has begun to highlight the role transposable elements can play in the immune system response to infections. However, most of our knowledge about transposable element expression during infection is limited by the specific host and pathogen factors from each study, making it difficult to compare studies and develop broader patterns regarding the role of transposable elements during infection. Here, we use the tools and resources available in the model, Drosophila melanogaster, to analyze multiple gene expression datasets of flies subject to bacterial, fungal, and viral infections. We analyzed differences in pathogen species, host genotype, host tissue, and sex to understand how these factors impact transposable element expression during infection. Our results highlight both shared and unique transposable element expression patterns between pathogens and suggest a larger effect of pathogen factors over host factors for influencing transposable element expression.

The evolutionary consequences of interactions between the epigenome, the genome and the environment.

The epigenome is the suite of interacting chemical marks and molecules that helps to shape patterns of development, phenotypic plasticity and gene regulation, in part due to its responsiveness to environmental stimuli. There is increasing interest in understanding the functional and evolutionary importance of this sensitivity under ecologically realistic conditions. Observations that epigenetic variation abounds in natural populations have prompted speculation that it may facilitate evolutionary responses to rapid environmental perturbations, such as those occurring under climate change. A frequent point of contention is whether epigenetic variants reflect genetic variation or are independent of it. The genome and epigenome often appear tightly linked and interdependent. While many epigenetic changes are genetically determined, the converse is also true, with DNA sequence changes influenced by the presence of epigenetic marks. Understanding how the epigenome, genome and environment interact with one another is therefore an essential step in explaining the broader evolutionary consequences of epigenomic variation. Drawing on results from experimental and comparative studies carried out in diverse plant and animal species, we synthesize our current understanding of how these factors interact to shape phenotypic variation in natural populations, with a focus on identifying similarities and differences between taxonomic groups. We describe the main components of the epigenome and how they vary within and between taxa. We review how variation in the epigenome interacts with genetic features and environmental determinants, with a focus on the role of transposable elements (TEs) in integrating the epigenome, genome and environment. And we look at recent studies investigating the functional and evolutionary consequences of these interactions. Although epigenetic differentiation in nature is likely often a result of drift or selection on stochastic epimutations, there is growing evidence that a significant fraction of it can be stably inherited and could therefore contribute to evolution independently of genetic change.

The Role of Transposable Elements in Long-Term Memory Formation

The Role of Transposable Elements in Long-Term Memory Formation

An Analysis of a Transposable Element Expression Atlas during 27 Developmental Stages in Porcine Skeletal Muscle: Unveiling Molecular Insights into Pork Production Traits.

The development and growth of porcine skeletal muscle determine pork quality and yield. While genetic regulation of porcine skeletal muscle development has been extensively studied using various omics data, the role of transposable elements (TEs) in this context has been less explored. To bridge this gap, we constructed a comprehensive atlas of TE expression throughout the developmental stages of porcine skeletal muscle. This was achieved by integrating porcine TE genomic coordinates with whole-transcriptome RNA-Seq data from 27 developmental stages. We discovered that in pig skeletal muscle, active Tes are closely associated with active epigenomic marks, including low levels of DNA methylation, high levels of chromatin accessibility, and active histone modifications. Moreover, these TEs include 6074 self-expressed TEs that are significantly enriched in terms of muscle cell development and myofibril assembly. Using the TE expression data, we conducted a weighted gene co-expression network analysis (WGCNA) and identified a module that is significantly associated with muscle tissue development as well as genome-wide association studies (GWAS) of the signals of pig meat and carcass traits. Within this module, we constructed a TE-mediated gene regulatory network by adopting a unique multi-omics integration approach. This network highlighted several established candidate genes associated with muscle-relevant traits, including HES6, CHRNG, ACTC1, CHRND, MAMSTR, and PER2, as well as novel genes like ENSSSCG00000005518, ENSSSCG00000033601, and PIEZO2. These novel genes hold promise for regulating muscle-related traits in pigs. In summary, our research not only enhances the TE-centered dissection of the genetic basis underlying pork production traits, but also offers a general approach for constructing TE-mediated regulatory networks to study complex traits or diseases.

The role of transposable elements in aging and cancer.

Transposable elements (TEs) constitute a large portion of the human genome. Various mechanisms at the transcription and post-transcription levels developed to suppress TE activity in healthy conditions. However, a growing body of evidence suggests that TE dysregulation is involved in various human diseases, including age-related diseases and cancer. In this review, we explained how sensing TEs by the immune system could induce innate immune responses, chronic inflammation, and following age-related diseases. We also noted that inflammageing and exogenous carcinogens could trigger the upregulation of TEs in precancerous cells. Increased inflammation could enhance epigenetic plasticity and upregulation of early developmental TEs, which rewires the transcriptional networks and gift the survival advantage to the precancerous cells. In addition, upregulated TEs could induce genome instability, activation of oncogenes, or inhibition of tumor suppressors and consequent cancer initiation and progression. So, we suggest that TEs could be considered therapeutic targets in aging and cancer.

Role of Transposable Elements in Genome Stability: Implications for Health and Disease.

Most living organisms have in their genome a sizable proportion of DNA sequences capable of mobilization; these sequences are commonly referred to as transposons, transposable elements (TEs), or jumping genes. Although long thought to have no biological significance, advances in DNA sequencing and analytical technologies have enabled precise characterization of TEs and confirmed their ubiquitous presence across all forms of life. These findings have ignited intense debates over their biological significance. The available evidence now supports the notion that TEs exert major influence over many biological aspects of organismal life. Transposable elements contribute significantly to the evolution of the genome by giving rise to genetic variations in both active and passive modes. Due to their intrinsic nature of mobility within the genome, TEs primarily cause gene disruption and large-scale genomic alterations including inversions, deletions, and duplications. Besides genomic instability, growing evidence also points to many physiologically important functions of TEs, such as gene regulation through cis-acting control elements and modulation of the transcriptome through epigenetic control. In this review, we discuss the latest evidence demonstrating the impact of TEs on genome stability and the underling mechanisms, including those developed to mitigate the deleterious impact of TEs on genomic stability and human health. We have also highlighted the potential therapeutic application of TEs.

The Role of Transposable Elements in Sexual Development.

Up to 50% of most mammalian genomes are made up of transposable elements (TEs) that have the potential to mobilize around the genome. Despite this prevalence, research on TEs is only beginning to gain traction within the field of neuroscience. While TEs have long been regarded as “junk” or parasitic DNA, it has become evident that they are adaptive DNA and RNA regulatory elements. In addition to their vital role in normal development, TEs can also interact with steroid receptors, which are key elements to sexual development. In this review, we provide an overview of the involvement of TEs in processes related to sexual development- from TE activity in the germline to TE accumulation in sex chromosomes. Moreover, we highlight sex differences in TE activity and their regulation of genes related to sexual development. Finally, we speculate on the epigenetic mechanisms that may govern TEs’ role in sexual development. In this context, we emphasize the need to further the understanding of sexual development through the lens of TEs including in a variety of organs at different developmental stages, their molecular networks, and evolution.

Bridging the Gap Between Environmental Adversity and Neuropsychiatric Disorders: The Role of Transposable Elements.

Long regarded as “junk DNA,” transposable elements (TEs) have recently garnered much attention for their role in promoting genetic diversity and plasticity. While many processes involved in mammalian development require TE activity, deleterious TE insertions are a hallmark of several psychiatric disorders. Moreover, stressful events including exposure to gestational infection and trauma, are major risk factors for developing psychiatric illnesses. Here, we will provide evidence demonstrating the intersection of stressful events, atypical TE expression, and their epigenetic regulation, which may explain how neuropsychiatric phenotypes manifest. In this way, TEs may be the “bridge” between environmental perturbations and psychopathology.

Roles of transposable elements on plant genome evolution, epigenetics and adaptation

<p indent="0mm">Transposable elements (TEs) are mobile DNA sequences within the genome, and their structure and transposition mechanism are highly diverse. TEs can be divided into retrotransposons (RTs; Class I) and DNA transposons (Class II), depending on whether their transposition intermediate is RNA or DNA. RTs transpose in a “copy-and-paste” manner and are therefore considered to be an essential contributor during genome expansion. RTs can be further divided into long terminal repeat retrotransposons (LTR-RTs) and non-long terminal repeat retrotransposons (non-LTR-RTs). <italic>Copia</italic> and <italic>Gypsy</italic> are two superfamilies of LTR-RTs commonly found in plant genomes, and their structural differences lie in the <italic>INT</italic> positions in the internal sequence of the <italic>pol</italic> open reading frame (ORF). Non-LTR-RTs include long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), which lack LTRs and usually have poly(A) or simple repeats at their 3′ end. DNA transposons directly cut the DNA sequence at the original site by transposase and insert a new site, similar to “cut-and-paste”. Insertion of DNA transposons into new sites results in target site duplications (TSDs), and DNA strand breaks due to transposition are repaired by DNA repair mechanisms. DNA transposons in plants can be further divided into “cut-and-paste” transposons and <italic>Helitrons</italic> with the “rolling circle” transposition pattern. TEs play an important role in genome evolution. In the process of their insertion, deletion, and amplification, the host may alter its genome size, gene expression, and gene function. Additionally, TEs may mediate chromosomal rearrangements through homologous recombination or alternative transposition. Overall, TEs are very powerful mutagens that can affect the stability of their host genomes. In order to defend against the transposition of TEs, the host has evolved various silencing mechanisms. In plants, the silencing of TEs is mainly established through RNA-directed DNA methylation (RdDM), which can stably repress the activity of TEs across generations. Methylation not only silences TEs but may also result in DNA methylation of nearby genes and affect expression and function of host genes. Interestingly, the phenotypic differences caused by the insertion of TEs play an important role in crop domestication. Methylation does not always keep TEs silent, such as burst events in some TE families. The evidence for the interaction between TEs and the host is growing, especially under environmental stress conditions, and TEs can be re-activated to help the host survive under stressful conditions. Furthermore, the insertion of TEs is preferred in many cases, and their insertion can be tolerated. Thus, TEs may not be completely inhibited, and they and their hosts may develop a cooperative relationship under environmental stress. This review summarizes some relevant research on TEs in plant genome evolution, introduces commonly occurring TEs found in plants, and examines how TEs are involved in plant genome evolution, epigenetic regulation, and the symbiotic relationship with the host under cooperative stress.

Roles of transposable elements in the regulation of mammalian transcription.

Transposable elements (TEs) comprise about half of the mammalian genome. TEs often contain sequences capable of recruiting the host transcription machinery, which they use to express their own products and promote transposition. However, the regulatory sequences carried by TEs may affect host transcription long after the TEs have lost the ability to transpose. Recent advances in genome analysis and engineering have facilitated systematic interrogation of the regulatory activities of TEs. In this Review, we discuss diverse mechanisms by which TEs contribute to transcription regulation. Notably, TEs can donate enhancer and promoter sequences that influence the expression of host genes, modify 3D chromatin architecture and give rise to novel regulatory genes, including non-coding RNAs and transcription factors. We discuss how TEs spur regulatory evolution and facilitate the emergence of genetic novelties in mammalian physiology and development. By virtue of their repetitive and interspersed nature, TEs offer unique opportunities to dissect the effects of mutation and genomic context on the function and evolution of cis-regulatory elements. We argue that TE-centric studies hold the key to unlocking general principles of transcription regulation and evolution.

Transposable element variants and their potential adaptive impact in urban populations of the malaria vector Anopheles coluzzii.

Anopheles coluzzii is one of the primary vectors of human malaria in sub-Saharan Africa. Recently, it has spread into the main cities of Central Africa threatening vector control programs. The adaptation of An. coluzzii to urban environments partly results from an increased tolerance to organic pollution and insecticides. Some of the molecular mechanisms for ecological adaptation are known, but the role of transposable elements (TEs) in the adaptive processes of this species has not been studied yet. As a first step toward assessing the role of TEs in rapid urban adaptation, we sequenced using long reads six An. coluzzii genomes from natural breeding sites in two major Central Africa cities. We de novo annotated TEs in these genomes and in an additional high-quality An. coluzzii genome, and we identified 64 new TE families. TEs were nonrandomly distributed throughout the genome with significant differences in the number of insertions of several superfamilies across the studied genomes. We identified seven putatively active families with insertions near genes with functions related to vectorial capacity, and several TEs that may provide promoter and transcription factor binding sites to insecticide resistance and immune-related genes. Overall, the analysis of multiple high-quality genomes allowed us to generate the most comprehensive TE annotation in this species to date and identify several TE insertions that could potentially impact both genome architecture and the regulation of functionally relevant genes. These results provide a basis for future studies of the impact of TEs on the biology of An. coluzzii.

Regulatory regions in natural transposable element insertions drive interindividual differences in response to immune challenges in Drosophila

BackgroundVariation in gene expression underlies interindividual variability in relevant traits including immune response. However, the genetic variation responsible for these gene expression changes remains largely unknown. Among the non-coding variants that could be relevant, transposable element insertions are promising candidates as they have been shown to be a rich and diverse source of cis-regulatory elements.ResultsIn this work, we use a population genetics approach to identify transposable element insertions likely to increase the tolerance of Drosophila melanogaster to bacterial infection by affecting the expression of immune-related genes. We identify 12 insertions associated with allele-specific expression changes in immune-related genes. We experimentally validate three of these insertions including one likely to be acting as a silencer, one as an enhancer, and one with a dual role as enhancer and promoter. The direction in the change of gene expression associated with the presence of several of these insertions is consistent with an increased survival to infection. Indeed, for one of the insertions, we show that this is the case by analyzing both natural populations and CRISPR/Cas9 mutants in which the insertion is deleted from its native genomic context.ConclusionsWe show that transposable elements contribute to gene expression variation in response to infection in D. melanogaster and that this variation is likely to affect their survival capacity. Because the role of transposable elements as regulatory elements is not restricted to Drosophila, transposable elements are likely to play a role in immune response in other organisms as well.

On the Role of Transposable Elements in the Regulation of Gene Expression and Subgenomic Interactions in Crop Genomes

Transposable elements (TEs) represent a major and variable portion of plant genomes, and recent progress in genetics and genomics has highlighted the importance of different TE species as a useful genetic tool in crop breeding. TEs can cause changes in the pattern of gene expression, and regulate gene function by various means such as cis- up- or down-regulation of nearby genes through insertion at promoter, intron, exon and down-stream regions, and trans-production of short interfering RNAs (siRNAs) via two RNA-directed DNA methylation (RdDM) pathways. siRNAs generated through different RdDM pathways differ in length and have variable effects on TEs. For instance, noncoding siRNAs of 20–60 nt produced by RNA polymerase IV (dicer-independent) and 21/22 nt by Pol II (dicer-dependent) have only minor effects on TEs compared with 24 nt siRNAs produced by Pol IV (dicer-dependent pathways). Following whole-genome duplication (WGD) events after polyploidization in allopolyploids, TEs from either parent are able to induce siRNAs to regulate the complex polyploid genome. Those designated as ‘controllers’ usually reside in the dominant parent and affect the TEs of the recessive parent. Subgenome cross-talk thus appears to contribute to epigenetic regulation as well as reshuffling or restructuring of subgenomes and creation of novel patterns of genes expression/and variation in local or global copy number. In this review, we focus on recent progress in unraveling the role of TEs in gene expression regulation via TE-derived siRNAs in the context of polyploid plant evolution and environmental stress, and explore how ancient WGD and recent polyploidy affected the evolution of TE-induced epigenetic mechanisms.

Role of Transposable Elements in Gene Regulation in the Human Genome.

Transposable elements (TEs), also known as mobile elements (MEs), are interspersed repeats that constitute a major fraction of the genomes of higher organisms. As one of their important functional impacts on gene function and genome evolution, TEs participate in regulating the expression of genes nearby and even far away at transcriptional and post-transcriptional levels. There are two known principal ways by which TEs regulate the expression of genes. First, TEs provide cis-regulatory sequences in the genome with their intrinsic regulatory properties for their own expression, making them potential factors for regulating the expression of the host genes. TE-derived cis-regulatory sites are found in promoter and enhancer elements, providing binding sites for a wide range of trans-acting factors. Second, TEs encode for regulatory RNAs with their sequences showed to be present in a substantial fraction of miRNAs and long non-coding RNAs (lncRNAs), indicating the TE origin of these RNAs. Furthermore, TEs sequences were found to be critical for regulatory functions of these RNAs, including binding to the target mRNA. TEs thus provide crucial regulatory roles by being part of cis-regulatory and regulatory RNA sequences. Moreover, both TE-derived cis-regulatory sequences and TE-derived regulatory RNAs have been implicated in providing evolutionary novelty to gene regulation. These TE-derived regulatory mechanisms also tend to function in a tissue-specific fashion. In this review, we aim to comprehensively cover the studies regarding these two aspects of TE-mediated gene regulation, mainly focusing on the mechanisms, contribution of different types of TEs, differential roles among tissue types, and lineage-specificity, based on data mostly in humans.

Mapping Regulatory Determinants in Plants.

The domestication and improvement of many plant species have frequently involved modulation of transcriptional outputs and continue to offer much promise for targeted trait engineering. The cis-regulatory elements (CREs) controlling these trait-associated transcriptional variants however reside within non-coding regions that are currently poorly annotated in most plant species. This is particularly true in large crop genomes where regulatory regions constitute only a small fraction of the total genomic space. Furthermore, relatively little is known about how CREs function to modulate transcription in plants. Therefore understanding where regulatory regions are located within a genome, what genes they control, and how they are structured are important factors that could be used to guide both traditional and synthetic plant breeding efforts. Here, we describe classic examples of regulatory instances as well as recent advances in plant regulatory genomics. We highlight valuable molecular tools that are enabling large-scale identification of CREs and offering unprecedented insight into how genes are regulated in diverse plant species. We focus on chromatin environment, transcription factor (TF) binding, the role of transposable elements, and the association between regulatory regions and target genes.

The Role of Transposable Elements in Congenital Malformations with Notes on Their Potential Implications for Morphological Evolution in Mammals

The Role of Transposable Elements in Congenital Malformations with Notes on Their Potential Implications for Morphological Evolution in Mammals

Roles of Transposable Elements in the Different Layers of Gene Expression Regulation.

The biology of transposable elements (TEs) is a fascinating and complex field of investigation. TEs represent a substantial fraction of many eukaryotic genomes and can influence many aspects of DNA function that range from the evolution of genetic information to duplication, stability, and gene expression. Their ability to move inside the genome has been largely recognized as a double-edged sword, as both useful and deleterious effects can result. A fundamental role has been played by the evolution of the molecular processes needed to properly control the expression of TEs. Today, we are far removed from the original reductive vision of TEs as “junk DNA”, and are more convinced that TEs represent an essential element in the regulation of gene expression. In this review, we summarize some of the more recent findings, mainly in the animal kingdom, concerning the active roles that TEs play at every level of gene expression regulation, including chromatin modification, splicing, and protein translation.

The Role of Transposable Elements in Pongamia Unigenes and Protein Diversity.

Pongamia pinnata (also called Millettia pinnata), a non-edible oil yielding tree, is well known for its multipurpose benefits and acts as a potential source for medicine and biodiesel preparation. Due to increase in demand for cultivation, understanding of genetic diversity is an important parameter for further breeding and cultivation programme. Transposable elements (TEs) are a major component of plant genome but still, their evolutionary significance in Pongamia remains unexplored. In view to understand the role of TEs in genome diversity, Pongamia unigenes were screened for the presence of TE cassettes. Our analysis showed the presence of all categories of TE cassettes in unigenes with major contribution of long terminal repeat-retrotransposons towards unigene diversity. Interestingly, the insertion of some TEs was also observed in both organellar genomes. The study of insertion of TEs in coding sequence is of great interest as they may be responsible for protein diversity thereby influencing the phenotype. The present investigation confirms the exaptation phenomenon in pyruvate decarboxylase (PDC) gene where the entire exon sequence was derived from Ty3-gypsy like retrotransposon. The study of PDC protein revealed the translation of gypsy element into protein. Furthermore, the phylogenetic study confirmed the diversity in PDC gene due to insertion of the gypsy element, where the PDC genes with and without gypsy insertion were clustered separately.