Search Results (116)

Background/Objectives: Nucleotide-binding leucine-rich repeat (NLR) proteins are major intracellular immune receptors involved in effector-triggered immunity. However, the evolutionary diversity and genomic organization of NLR repertoires remain incompletely characterized in Solanaceae crops and their wild relatives. This study aimed to investigate the pan-NLRome landscape and evolutionary patterns of tomato and related species. Methods: A comparative pan-NLRome analysis was performed across five angiosperms, including cultivated tomato (Solanum lycopersicum) and four related species (Solanum chilense, Solanum lycopersicoides, Solanum pimpinellifolium, and Arabidopsis thaliana). NLR genes were identified using an integrated HMMER- and BLASTp-based pipeline, followed by chromosome anchoring, orthogroup (OG) classification, phylogenetic analysis, spatial organization analysis, and evaluation of associations with long terminal repeat (LTR) retrotransposons. Results: A total of 1566 chromosome-anchored NLR genes were assigned to 150 OGs. Core OGs represented 25.3% of total OG diversity but contained a large proportion of NLR genes. Rarefaction analysis indicated continuous accumulation of novel OGs with increasing species sampling, supporting an open pan-NLRome structure. Phylogenetic analysis identified 18 NLR subfamilies, with SF_03 and SF_01 together accounting for approximately 79% of NLR genes. Dispersed homologs represented the predominant spatial arrangement pattern, accounting for 85.1% of NLR gene pairs across Solanaceae species. Conclusions: This study provides a comparative genomic framework for understanding NLR diversity and evolution in tomato and related Solanum species, highlighting the dynamic expansion and spatial organization of plant immune receptor repertoires and providing valuable resources for resistance gene discovery. Full article

Quercus oxyphylla (E. H. Wilson) Hand.-Mazz. is a threatened evergreen subalpine tree species with fragmented habitats native to China. Here, we present a de novo chromosome-level genome assembly of this oak species by integrating PacBio long-read high-fidelity (HiFi) sequencing and Hi-C mapping technologies. The assembled genome size of Q. oxyphylla in this study is 824.15 megabases (Mb) in length with 12 putative chromosomes. Genome annotation of this oak species identified 514.09 Mb of repeat sequences, 53,730 protein-coding genes and 1048 non-coding RNA sequences. Genomic analyses of whole-genome duplication (WGD) and long terminal repeat retrotransposon (LTR-RT) insertion events in Q. oxyphylla revealed no species-specific WGD and recent accumulation of LTR-RTs in the genome within the last seven million years. A phylogenomic analysis with eight oak representatives confirmed the framework phylogeny of genus Quercus and indicated that Q. oxyphylla possibly split with the ancestor of Cerris oaks about 20.4 million years ago. We identified 2074 expanded and 903 contracted gene families across the genome assembly of Q. oxyphylla, while the significantly expanded gene families had notable disease resistance-related genes that were mainly enriched in plant–pathogen interaction pathways. The high-quality genome assembly of Q. oxyphylla generated in this study provides a valuable genome resource for the genetic conservation and management of Q. oxyphylla, and may facilitate our understanding of genome evolution and species adaptation of the oak lineage. Full article

Vicia villosa Roth var. glabrescens (smooth vetch) is an economically important legume cover crop valued for its nitrogen-fixing capacity, high biomass yield, and adaptability across diverse agroecosystems. Here, we present a chromosome-scale, high-quality genome assembly of V. villosa var. glabrescens, constructed using PacBio HiFi sequencing combined with Hi-C scaffolding. The assembly spans 3.70 Gb with a scaffold N50 of 4.69 Mb and exhibits lower heterozygosity (0.9%) compared to V. villosa Roth (3.1%). Genome analysis revealed significant expansion of long terminal repeat retrotransposons (LTR-RTs), as well as lineage-specific proliferation of miniature inverted-repeat transposable elements (MITEs) in V. villosa var. glabrescens. Comparative genomics with V. villosa Roth highlighted gene family expansions associated with trichome development, providing insights into the genetic basis of morphological and adaptive differences within the Vicia species. This reference genome provides a foundational resource for accelerating the breeding of V. villosa varieties with enhanced agronomic traits and contributes to a broader understanding of legume genomics and plant genome evolution. Full article

Background/Objectives: Variation in repeatome composition is a major determinant of genome architecture and an important substrate for evolutionary change in plants. Despite the availability of genomic sequence data, repeatome-wide assessments have not been performed for Epidendrum, the largest Neotropical genus of Orchidaceae. Here, we assessed repeatome profiles across 34 Epidendrum species using publicly available genomic datasets. Methods:Epidendrum repeatomes were characterized with the RepeatExplorer2 pipeline, and patterns of repeat composition were evaluated for phylogenetic structure using a species phylogeny. Results: Repeat composition showed no clear phylogenetic structure, with closely related species often displaying divergent satDNA and TE profiles. satDNA content varied widely among species (15.5–69% of the repeatome fraction). A total of 208 satDNA families were detected, which were used to build a custom database for comparative analyses. We detected 73 satDNA clusters shared among species, whereas only three were species-specific. Regarding TEs, Class I elements were the most abundant repeats, dominated by Ty3-Gypsy LTR retrotransposons. Only two Class II TIR superfamilies were detected (EnSpm/CACTA and hAT). Conclusions: This study provides the first comprehensive characterization of the Epidendrum repeatome and establishes a resource for future work on cytogenomic diversity within this megagenus. The heterogeneous distribution of repeats among closely related species is consistent with lineage-specific amplification and loss, highlighting rapid repeatome turnover in Epidendrum. Potential drivers, as hybridization and ecological differentiation, should be tested explicitly in future analyses integrating broader genome size sampling and trait data. Full article

Non-long terminal repeat (Non-LTR) retrotransposons are mobile genetic elements that replicate through a “copy-and-paste” mechanism, enabling their expansion within the genome. Aberrant activation of these elements can induce genomic instability, elicit cellular stress responses, and activate inflammasome signaling, leading to tissue injury and disease. The central process of sterile inflammation involves the release and recognition of damage-associated molecular patterns (DAMPs), endogenous molecules that initiate inflammatory responses and form a common basis for many sterile inflammatory disorders. Recent studies have identified non-LTR retrotransposons as key endogenous triggers of DAMP-like signaling that drive sterile inflammation in both neuronal and non-neuronal tissues, contributing to the development of neurodegenerative and other chronic inflammatory diseases. In this review, we summarize recent advances in understanding how non-LTR retrotransposons, particularly LINE and SINE elements, influence sterile inflammation and disease pathogenesis. We highlight how their mobilization reshapes genomic architecture and gene regulation, and how the resulting signaling cascades promote chronic inflammation, immune dysregulation, and tissue injury. We also discuss emerging therapeutic strategies aimed at suppressing retrotransposon activity or interrupting downstream inflammatory signaling for treating sterile inflammation-related diseases. Full article

Transposable elements (TEs) are ubiquitous components of plant genomes that profoundly influence plant diversity, adaptation, and genome structure. Transposition of TEs is primarily suppressed by distinct DNA methylation systems. However, the distribution of DNA methylation at the level of individual TEs in plants remains poorly understood. Here, we address this question by generating per-base cytosine methylation maps of individual long terminal repeat retrotransposons (LTR-RTEs) for the large sunflower (Helianthus annuus L.) and the small Arabidopsis thaliana genomes. A. thaliana was selected as the model species, for which genome-wide DNA methylation profiles have been extensively characterized in prior studies. Our analysis revealed significant heterogeneity in methylation patterns both between and within individual LTR-RTE lineages. We also found that the sunflower genes harboring intact or fragmented LTR-RTE insertions exhibit altered DNA methylation and expression profiles, with intact LTR-RTE insertions enriched in stress-response and regulatory pathways. Our interspecies comparison of DNA methylation patterns indicates that methylation patterns are intrinsic features of LTR-RTE lineages, conserved across diverse plant species but influenced by factors such as insertion age, element length, and proximity to genes. Furthermore, we identified epigenetically distinct clusters of Tork and Athila sunflower elements corresponding to separate phylogenetic clades, suggesting a link between epigenetic regulation and the genetic diversity of plant LTR-RTEs. Full article

Long Terminal Repeat (LTR) retrotransposons (LTR-RTEs) comprise up to 90% of some plant genomes and drive genome diversification through their amplification. Novel insertions arise during the final stages of the LTR-RTE life cycle, which depends on both LTR-RTE-encoded proteins and host cellular factors. The LTR-RTE elements require host transcriptional machinery for RNA production, followed by nuclear processing/export, translation, virus-like particle assembly, reverse transcription, and genomic integration. This review addresses the following question: What host proteins promote LTR-RTE transposition in plants? Our analysis of recent literature on host factors and cellular compartments implicated in the retrotransposition cycle reveals the extensive integration of LTR-RTEs into host processes. Nonetheless, the precise mechanisms remain poorly resolved, especially in plants with their rich repertoire of LTR-RTEs. We propose integrating plant mobilomics with transposition reporters, genome editing, synthetic biology, and interactomics to elucidate plant-specific mechanisms. Full article

Mobile elements, particularly long terminal repeat retrotransposons (LTR-RTEs), are abundant and dynamic components of plant genomes. Although viral infections are known to transcriptionally activate retrotransposons, it remains unclear whether such virus-induced activation leads to their mobilization. To address this question, we examined LTR-RTE activation in Arabidopsis thaliana, Brassica napus, and Nicotiana benthamiana following infection with the RNA viruses Tobacco rattle virus (TRV), Potato virus X (PVX), and Tobacco ringspot virus (TRSV). Nanopore cDNA sequencing revealed virus-specific transcriptional responses, with PVX uniquely triggering a strong transcriptional burst of diverse LTR-RTE families in N. benthamiana. To test the role of viral suppressors of RNA silencing (VSRs) in this process, we analyzed extrachromosomal circular DNA (eccDNA) from plants infected with TRV expressing the VSR P19. This analysis identified eccDNA derived from Ty3/Gypsy Galadriel elements, demonstrating that viral infection can promote not only retrotransposon transcription but also eccDNA production, which may indicate the ability of LTR-RTEs to transpose. These findings clearly illustrate that plant–virus interactions can induce not only changes in gene transcription, but also the activation of multiple retrotransposons, highlighting a potential evolutionary interface linking antiviral defense and transposon regulation. Full article

Blueberries (Vaccinium spp.) are valued for their nutritional benefits but face challenges in germplasm identification, phylogenetic analysis, and breeding due to their complex genetic background. Long Terminal Repeat Retrotransposons (LTR-RTs), major drivers of plant genetic diversity, offer a basis for the Inter-Retrotransposon Amplified Polymorphism (IRAP) system, which excels in germplasm identification, diversity assessment, and relatedness studies. Here, we developed a blueberry IRAP system using Ty1-copia reverse transcriptase sequences. From 25 core primers, we obtained 266 polymorphic loci (average PIC = 0.866). These IRAP markers fingerprinted 112 accessions and revealed relationships through Nei’s diversity index (H = 0.361), Shannon’s index (I = 0.533), AMOVA (9.33% among regions; 90.67% within populations; Nm = 1.50), UPGMA dendrograms (three clusters at 0.615 similarity), and PCoA, indicating weak geographic structure across Guiyang, Qiandongnan, and Bijie consistent with Nm = 1.50 (homogenizing gene flow). The dendrogram and PCoA indicate among-accession heterogeneity with weak geographic structuring across Guiyang, Qiandongnan, and Bijie, consistent with the AMOVA and gene-flow estimates. We also built a Molecular IDs database for differentiation. IRAP proved highly efficient for identification and analysis, matching SSR/SNP polymorphism levels while offering advantages like low-cost agarose gel resolution for detecting subtle clonal variants in polyploids—outperforming SSRs in field triage and complementing SNPs’ high throughput. This supports IP protection and breeding. Together with established SSR/SNP platforms, this IRAP approach can support IP protection and breeding as a complementary, cost-effective option. Full article

Transposable elements (TEs) are major components of plant genomes and play crucial roles in adaptive genome evolution and stress tolerance. Under abiotic stress, activated TEs can generate abundant genetic variation and regulate the expression of stress-responsive genes. As a pioneer species in desert and saline–alkali environments, Tamarix chinensis L. has been little studied with respect to the abundance and evolutionary relationships of its LTR retrotransposons, particularly their activation patterns under salt and alkali stresses. This study aimed to investigate the characteristics of the reverse transcriptase (RT) domain of LTR retrotransposons in T. chinensis and to determine their patterns of activation in response to salt and alkali stresses. A total of 629 Ty1-copia and 607 Ty3-gypsy RT nucleotide sequences, which displayed high AT/GC ratios and evidence of stop codon insertions, were identified in T. chinensis by amplicon sequencing. Among these, 211 Ty1-copia and 117 Ty3-gypsy RT sequences with potential transpositional activity each contained distinct domains, suggesting a high degree of conservation. Phylogenetic analysis revealed that the RT sequences of T. chinensis are closely related to those of mangrove, wild potato, and Ipomoea, and may have undergone horizontal transfer. Expression analysis showed that 634 and 181 RT sequences were activated under salt and alkali stresses, respectively, with the majority belonging to salt-induced Ty1-copia families. Compared with the control group, under salt and alkali stresses, the cTy1-copia elements (Ty1-copia with amplificated from cDNA of T. chinensis, the same below) with dominant abundance were mainly concentrated in the Angela subfamily, while the cTy3-gypsy elements induced by alkali stress were primarily distributed in the Tekay and Reina subfamilies. Furthermore, four cTy1-copia and five cTy3-gypsy were identified as candidate key LTR retrotransposons responsive to salt and alkali stresses. Overall, this study provides new insights into the epigenetic mechanisms underlying the adaptation of T. chinensis to saline and alkali stresses and offers a theoretical basis for its potential applications in saline–alkali land reclamation. 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

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

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

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