Biology subjects

Blevins, T.

Publications and source records attributed to Blevins, T..

8 recordsLinked to original sources

bioRxiv2026

BIRD-Seq: B2 Protein Integrated End-to-End Pipeline for dsRNA Detection and Nanopore Sequencing for Virus Monitoring

Double-stranded RNA (dsRNA) is a near-universal hallmark of active viral infection. Despite its role as a pan-viral replication intermediate, dsRNA-centred technologies for virus monitoring remain scarce and largely rely on monoclonal antibody-based approaches that, while highly sensitive, are costly and difficult to engineer, scale, or integrate with downstream assays. Here, we present a modular and antibody-free pipeline for quantitative and qualitative dsRNA analysis built around an engineered B2 protein from Flock House virus with nanomolar-range binding affinity. The pipeline is compatible with absorbance- or luminescence-based measurement formats. In a sandwich assay configuration (Sand-BIRD), sub-ng mL-1 quantification of dsRNA is achieved, comparable to the gold standard J2 monoclonal antibody, directly from crude biological samples without RNA extraction. Sand-BIRD reliably detects viral infection in both plant samples (Tomato bushy stunt virus and Grapevine fanleaf virus) and mosquitoes (West Nile virus and Dengue virus) with commercial-grade reliability. dsRNA eluted from positive samples were further processed directly by Oxford Nanopore direct sequencing, enabling identification of virus species without prior sequence knowledge or total RNA extraction. Together, this work establishes an end-to-end, sequence-agnostic workflow for direct RNA-duplex quantification and sequencing (BIRD-Seq), which has compelling potential for emerging infectious disease surveillance and next-generation point-of-care (PoC) diagnostics. Technology ReadinessBIRD-Seq is an integrated pipeline for agnostic dsRNA detection and sequencing designed for broad-spectrum virus monitoring. A Technology Readiness Level (TRL) 5 under NASAs classification framework has been reached as BIRD-Seq has been validated in laboratory-relevant environments using real-world samples, including virus-infected plants and mosquitoes. The ELISA-based sensing platform employs engineered variants of the B2 protein (from Flock House virus) in a sandwich assay format for dsRNA capture and detection, achieving sensitivity comparable to the gold-standard J2 monoclonal antibody. Unlike traditional antibody-based methods, the B2 protein offers key practical advantages: straightforward production in bacterial expression systems, high versatility, and reduced manufacturing costs, as well as direct compatibility with crude extract monitoring, eliminating the need for RNA extraction. Captured B2/RNA duplexes can then be directly eluted from the ELISA microplates and subjected to downstream nanopore direct RNA sequencing, providing both quantitative and qualitative information on the underlying virus infection, a capacity enabled by the near-universal nature of dsRNA as a pathogen-associated molecular pattern. That said, further validation on large-scale field-collected and clinical samples will be essential before widespread deployment can be envisioned. While the B2 sandwich assay offers favorable cost-efficiency over antibody-based alternatives, the relatively high cost of Oxford Nanopore direct RNA sequencing remains an important economic constraint. Nevertheless, the growing importance of dsRNA detection across virus sensing, mRNA vaccine development, innate immunity research, and human disease diagnostics, combined with the increasing role of portable long-read sequencing in emerging infectious disease (EIDs) surveillance, positions BIRD-Seq as an innovative and competitive diagnostic platform. Highlights- Double-stranded RNA (dsRNA) is one of the critical pathogen-associated molecular patterns for viral invasion in the host. A protein-based sandwich assay for dsRNA detection in crude biological samples with a sub-ng mL-1 order detection limit was developed, achieving similar sensing efficiency in comparison to expensive and proprietary monoclonal antibody-based ELISA methods. - The quantitative detection of RNA duplex is coupled with an Oxford nanopore direct dsRNA sequencing method for virus species identification and qualitative analysis. - This is one of the very first dsRNA-centered end-to-end workflows for virus monitoring and sequencing, validated for both infected plant and animal samples.

bioengineering↗

bioRxiv2026

Transposable element-derived siRNAs control viral disease in Arabidopsis

Crop diseases caused by viruses can result in significant economic losses. However, the mechanisms that lead to disease are not well understood. Meanwhile, metagenomic surveys have revealed that most plants in nature are tolerant to viruses, thus maintain their fitness despite of recurrent infection. Using plants that transition from a diseased state to a tolerant state during virus infection, we demonstrate that tolerance depends on the virus-induced production of 21-nucleotide small interfering RNAs (siRNAs) from transposable elements (TEs). These findings indicate that siRNAs derived from TE sequences play a pivotal role in mitigating the detrimental effects of viral infection on plant health.

plant biology↗

bioRxiv2024

Structural insights into maturation and translationof a plant mitoribosome

Ribosomes are key molecular machines that translate mRNA into proteins. Mitoribosomes are specific ribosomes found in mitochondria, which have been shown to be remarkably diverse across eukaryotic lineages. In plants, they possess unique features, including additional rRNA domains stabilized by numerous pentatricopeptide repeat proteins. However, the molecular mechanisms of translation by plant mitoribosomes remain largely unknown. Here, we use cryo-electron microscopy to provide a high-resolution structural characterization of the flowering plant mitoribosome, in translating and maturation states. The structure reveals the mitoribosome bound to tRNA in the peptidyl site, along with a segment of mRNA and a nascent polypeptide. Moreover, we identify an extensive set of ribosomal RNA modifications that we confirmed by nanopore sequencing. Additionally, we observe a late assembly intermediate of the small ribosomal subunit, in complex with the RsgA assembly factor. This reveals how a plant-specific extension of RsgA blocks the mRNA channel to prevent premature mRNA association before complete small subunit maturation. Our findings elucidate key aspects of translation in flowering plant mitochondria, revealing its distinct features compared to other eukaryotic lineages.

molecular biology↗

bioRxiv2023

CLSY docking to Pol IV requires a conserved domain critical for small RNA biogenesis and transposon silencing.

Eukaryotes must balance the need for gene transcription by RNA polymerase II (Pol II) against the danger of mutations caused by transposable element (TE) proliferation. In plants, these gene expression and TE silencing activities are divided between different RNA polymerases. Specifically, RNA polymerase IV (Pol IV), which evolved from Pol II, transcribes TEs to generate small interfering RNAs (siRNAs) that guide DNA methylation and block TE transcription by Pol II. While the Pol IV complex is recruited to TEs via SNF2-like CLASSY (CLSY) proteins, how Pol IV partners with the CLSYs remains unknown. Here we identified a conserved CYC-YPMF motif that is specific to Pol IV and is positioned on the complex exterior. Furthermore, we found that this motif is essential for the co-purification of all four CLSYs with Pol IV, but that only one CLSY is present in any given Pol IV complex. These findings support a "one CLSY per Pol IV" model where the CYC-YPMF motif acts as a CLSY-docking site. Indeed, mutations in and around this motif phenocopy pol iv null mutants. Together, these findings provide structural and functional insights into a critical protein feature that distinguishes Pol IV from other RNA polymerases, allowing it to promote genome stability by targeting TEs for silencing.

molecular biology↗

bioRxiv2023

Transposition of HOPPLA in siRNA-deficient plants suggests a limited effect of the environment on retrotransposon mobility in Brachypodium distachyon

Long terminal repeat retrotransposons (LTR-RTs) are powerful mutagens regarded as a major source of genetic novelty and important drivers of evolution. Yet, the uncontrolled and potentially selfish proliferation of LTR-RTs can lead to deleterious mutations and genome instability, with large fitness costs for their host. While population genomics data suggest that an ongoing LTR-RT mobility is common in many species, the understanding of their dual role in evolution is limited. Here, we harness the genetic diversity of 320 sequenced natural accessions of the Mediterranean grass Brachypodium distachyon to characterize how genetic and environmental factors influence plant LTR-RT dynamics in the wild. When combining a coverage-based approach to estimate global LTR-RT copy number variations with mobilome-sequencing of nine accessions exposed to eight different stresses, we find little evidence for a major role of environmental factors in LTR-RT accumulations in B. distachyon natural accessions. Instead, we show that loss of RNA polymerase IV (Pol IV), which mediates RNA-directed DNA methylation in plants, results in high transcriptional and transpositional activities of RLC_BdisC024 (HOPPLA) LTR-RT family elements, and that these effects are not stress-specific. This work supports findings indicating an ongoing mobility in B. distachyon and reveals that host RNA-directed DNA methylation rather than environmental factors controls their mobility in this wild grass model. Author summaryLong terminal repeat retrotransposons (LTR-RTs) are major components of plant genomes. Their copy- and-paste replication mechanism allows them to rapidly increase in copy number, with potentially negative effects on host fitness. On the other hand, because they can rewire transcriptional networks and alter phenotypes, their mobility is an important driver of evolution. Ever since their discovery, LTR-RT activity has been linked to stress exposure, suggesting that LTR-RTs modulate the pace of evolution in response to the environment. In this study, we test this hypothesis by harnessing the genetic variation in a set of 320 natural accessions of the Mediterranean grass Brachypodium distachyon originating from diverse habitats. We find little evidence for the importance of stresses in activating B. distachyon LTR-RTs. Instead, we show that the loss of RNA polymerase IV, a component of plant retrotransposon silencing, leads to the activation and transposition of an LTR-RT family that we name HOPPLA. HOPPLA is the first LTR-RT family in B. distachyon shown to transpose in real-time. These findings open up new avenues for studying retrotransposon-mediated evolution in this close relative of staple crops, such as rice and wheat.

genomics↗

bioRxiv2023

Multimegabase-scale DNA hypermethylation and condensed chromatin correlate with chromosome-specific rRNA gene silencing in Arabidopsis

Arabidopsis thaliana has two nucleolus organizer regions (NORs), consisting of long tandem arrays of 45S rRNA genes on chromosomes 2 (NOR2) and 4 (NOR4). The rRNA gene subtypes mapping to NOR2 are mostly silenced during development, whereas most of those mapping to NOR4 are active. Cytosine methylation of promoters plays a significant role in rRNA gene silencing, but recent findings demonstrate that gene body methylation also play a key role in gene silencing. Previous studies have demonstrated that CG methylation plays a role in rRNA gene silencing. However, it remains to be determined whether Chromomethylase 2 (CMT2)-mediated, RdDM-independent CHH methylation plays any role in rRNA gene silencing. To find out the relative importance of cytosine methylation in each of the sequence contexts (CG, CHG, and CHH, where H=A, T, or C), we studied multiple DNA methylation-deficient Arabidopsis mutants. Primarily, we show that the mutants that displayed higher losses of CG or CHH methylation at rDNA loci, display higher degrees of NOR2 rRNA gene silencing disruption. Using whole genome bisulfite sequencing data, we show that the loss of RdDM-independent CMT2, not the loss of RdDM-dependent DRM2, erases most of the CHH methylation at rDNA loci, while retaining CG methylation levels comparable to those of wild-type Col-0, demonstrating the sufficiency of CHH methylation loss for releasing rRNA gene silencing. Analysis of Arabidopsis and tomato NOR sequences revealed that in 45S rRNA gene sequences, cytosines mostly occur in the CHH context, followed by CG and the lowest being in CHG contexts. The predominance of CHH sites is even more pronounced when the rRNA gene promoter and spacer promoter(s) are considered (0-7% CG, 14-25% CHG, and 79-80% CHH), suggesting a mechanism to explain the stronger disruption of NOR2 gene silencing in mutants that display higher losses of CHH methylation. Our data also reveal a role for gene body methylation in rRNA gene silencing. We show that NOR2 genes are relatively hypermethylated compared to NOR4, consistent with findings from recent studies. By contrast, human rRNA genes have more CG sites than CHH and CHG, correlating with the evolutionary loss of CMTs in mammals. CMTs are plant-specific, which primarily methylate CHG and CHH sites. Our data define a critical role for CMT2-mediated RdDM-independent CHH methylation, in combination with MET1-mediated CG methylation, in rRNA gene silencing, which is entirely mediated by CG methylation in mammals.

plant biology↗

bioRxiv2020

Epigenetic transgenerational effects on RNAi in Arabidopsis

Epigenetic states and even certain environmental responses in nematodes, mammals and seed plants can be inherited over successive generations. RNAi in plants is an epigenetic form of RNA degradation that is normally reset early in development. In contrast, competence, i.e., the susceptibility of a transgene for RNAi, is believed to be genetically determined and faithfully transmitted over many generations. Unexpectedly, we found that the same yellow fluorescent protein (YFP) transgene in a monogenic, homozygous line of Arabidopsis exhibited two epigenetic states of RNAi: type I, which is initiated in rosette leaves and is stable in later developmental stages, and, type II, which is initiated after floral induction and is unstable. The incidence of type I plants descended from type I parents decreased over three successive generations of self-fertilized plants. By the third generation, a substantial fraction of plants from type I parents exhibited either the type II phenotype or remained high-YFP expressing throughout sporophytic development, indicating that silencing had been completely lost. Similarly, plants descended from type II parents showed a progressive shift from the type II phenotype and a complete loss of silencing. These results show that the silencing types (or states) of parental plants have significant influence on both silencing determination and silencing types (or states) of their offspring, however, this influence fades through several generations of self; as regardless of the types of the parental lines, competence for RNA silencing tends to loss after generations. Thus, we propose that RNA silencing in plants can be the target of transgenerational effects. While the underlying mechanisms are still unknown, our findings in the Arabidopsis RNA silencing system complement the current understanding of heritable RNAi in C. elegans, that this phenomenon is likely a common mechanism in Eukaryote systems.

plant biology↗

bioRxiv2017

Hybrid incompatibility caused by an epiallele

Hybrid incompatibility resulting from deleterious gene combinations is thought to be an important step towards reproductive isolation and speciation. Here we demonstrate involvement of a silent epiallele in hybrid incompatibility. In Arabidopsis thaliana strain Col-0, one of the two copies of a duplicated histidine biosynthesis gene, HISN6B is not expressed, for reasons that have been unclear, making its paralog, HISN6A essential. By contrast, in strain Cvi-0, HISN6B is essential because HISN6A is mutated. As a result of these differences, Cvi-0 x Col-0 hybrid progeny that are homozygous for both Col-0 HISN6B and Cvi-0 HISN6A do not survive. We show that HISN6B is not a defective pseudogene in the Col-0 strain, but a stably silenced epiallele. Mutating HISTONE DEACETYLASE 6 (HDA6) or the cytosine methyltransferase genes, MET1 or CMT3 erases HISN6Bs silent locus identity in Col-0, reanimating the gene such that hisn6a lethality and hybrid incompatibility are circumvented. These results show that HISN6-dependent hybrid lethality is a revertible epigenetic phenomenon and provide additional evidence that epigenetic variation has the potential to limit gene flow between diverging populations of a species.\n\nSignificance statementDeleterious mutations in different copies of a duplicated gene pair have the potential to cause hybrid incompatibility between diverging subpopulations, contributing to reproductive isolation and speciation. This study demonstrates a case of epigenetic gene silencing, rather than pseudogene creation by mutation, contributing to a lethal gene combination upon hybridization of two strains of Arabidopsis thaliana. The findings provide direct evidence that naturally occurring epigenetic variation can contribute to incompatible hybrid genotypes, reducing gene flow between strains of the same species.

genetics↗