The m 6 A pathway protects the transcriptome integrity by restricting RNA chimera formation in plants

International audienceGlobal, segmental, and gene duplication-related processes are driving genome size and complexity in plants. Despite their evolutionary potentials, those processes can also have adverse effects on genome regulation, thus implying the existence of specialized corrective mechanisms. Here, we report that an N6-methyladenosine (m 6 A)-assisted polyadenylation (m-ASP) pathway ensures tran-scriptome integrity in Arabidopsis thaliana. Efficient m-ASP pathway activity requires the m 6 A methyltransferase-associated factor FIP37 and CPSF30L, an m 6 A reader corresponding to an YT512-B Homology Domain-containing protein (YTHDC)-type domain containing isoform of the 30-kD subunit of cleavage and polyadenylation specificity factor. Targets of the m-ASP pathway are enriched in recently rearranged gene pairs, displayed an atypical chromatin signature, and showed transcriptional readthrough and mRNA chimera formation in FIP37-and CPSF30L-deficient plants. Furthermore, we showed that the m-ASP pathway can also restrict the formation of chimeric gene/transposable-element transcript, suggesting a possible implication of this pathway in the control of transposable elements at specific locus. Taken together, our results point to selective recognition of 39-UTR m 6 A as a safeguard mechanism ensuring transcriptome integrity at rearranged genomic loci in plants

Comparative Genomic Paleontology across Plant Kingdom Reveals the Dynamics of TE-Driven Genome Evolution

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Horizontal Gene Transfers in Plants

In plants, as in all eukaryotes, the vertical transmission of genetic information through reproduction ensures the maintenance of the integrity of species. However, many reports over the past few years have clearly shown that horizontal gene transfers, referred to as HGTs (the interspecific transmission of genetic information across reproductive barriers) are very common in nature and concern all living organisms including plants. The advent of next-generation sequencing technologies (NGS) has opened new perspectives for the study of HGTs through comparative genomic approaches. In this review, we provide an up-to-date view of our current knowledge of HGTs in plants

Accessing epigenetic variation in the plant methylome

Cytosine DNA methylation is the addition of a methyl group to the 5' position of a cytosine, which plays a crucial role in plant development and gene silencing. Genome-wide profiling of DNA methylation is now possible using various techniques and strategies. Using these technologies, we are beginning to elucidate the extent and impact of variation in DNA methylation between individuals and/or tissues. Here, we review the different techniques used to analyze the methylomes at the whole-genome level and their applications to better understand epigenetic variations in plants

Characterization Of Interspecific Gene Flows at The Genome-wide Level in a Natural Ecosystem The Massane Forest Reveals New Insights Into Horizontal Transfer In plants

Abstract Horizontal transfer (HT) refers to the exchange of genetic material between divergent species by mechanisms other than reproduction. In recent years, several studies have demonstrated HTs in eukaryotes, particularly in the context of parasitic relationships and in model species. However, very little is known about HT in natural ecosystems, especially those involving non-parasitic wild species, and the nature of the ecological relationships that promote these HTs. In this work, we conducted a pilot study investigating HTs by sequencing the genomes of 17 wild non-model species from a natural ecosystem, the Massane forest, located in southern France. To this end, we developed a new computational pipeline called INTERCHANGE that is able to characterize HTs at the whole genome level without prior annotation and directly in the raw sequencing reads. Using this pipeline, we identified 12 HT events, half of which occurred between lianas and trees. We found that only LTRs-retrotransposons and predominantly those from the Copia superfamily were transferred between these wild species. This study revealed a possible new route for HTs between non-parasitic plants and provides new insights into the genomic characteristics of horizontally transferred DNA in plant genomes

A new approach for annotation of transposable elements using small RNA mapping

Publisher's PDFTransposable elements (TEs) are mobile genomic DNA sequences found in most organisms. They so densely populate the genomes of many eukaryotic species that they are often the major constituents. With the rapid generation of many plant genome sequencing projects over the past few decades, there is an urgent need for improved TE annotation as a prerequisite for genome-wide studies. Analogous to the use of RNA-seq for gene annotation, we propose a new method for de novo TE annotation that uses as a guide 24 nt-siRNAs that are a part of TE silencing pathways. We use this new approach, called TASR (for Transposon Annotation using Small RNAs), for de novo annotation of TEs in Arabidopsis, rice and soybean and demonstrate that this strategy can be successfully applied for de novo TE annotation in plants.Delaware Biotechnology Institute.University of Delaware. Department of Plant and Soil Sciences

Reconciling the evolutionary origin of bread wheat (Triticum aestivum)

In PressThe origin of bread wheat (Triticum aestivum; AABBDD) has been a subject of controversy and of intense debate in the scientific community over the last few decades. In 2015, three articles published in New Phytologist discussed the origin of hexaploid bread wheat (AABBDD) from the diploid progenitors Triticum urartu (AA), a relative of Aegilops speltoides (BB) and Triticum tauschii (DD). Access to new genomic resources since 2013 has offered the opportunity to gain novel insights into the paleohistory of modern bread wheat, allowing characterization of its origin from its diploid progenitors at unprecedented resolution. We propose a reconciled evolutionary scenario for the modern bread wheat genome based on the complementary investigation of transposable element and mutation dynamics between diploid, tetraploid and hexaploid wheat. In this scenario, the structural asymmetry observed between the A, B and D subgenomes in hexaploid bread wheat derives from the cumulative effect of diploid progenitor divergence, the hybrid origin of the D subgenome, and subgenome partitioning following the polyploidization events

RiTE database: a resource database for genus-wide rice genomics and evolutionary biology

BACKGROUND: Comparative evolutionary analysis of whole genomes requires not only accurate annotation of gene space, but also proper annotation of the repetitive fraction which is often the largest component of most if not all genomes larger than 50 kb in size. RESULTS: Here we present the Rice TE database (RiTE-db)--a genus-wide collection of transposable elements and repeated sequences across 11 diploid species of the genus Oryza and the closely-related out-group Leersia perrieri. The database consists of more than 170,000 entries divided into three main types: (i) a classified and curated set of publicly-available repeated sequences, (ii) a set of consensus assemblies of highly-repetitive sequences obtained from genome sequencing surveys of 12 species; and (iii) a set of full-length TEs, identified and extracted from 12 whole genome assemblies. CONCLUSIONS: This is the first report of a repeat dataset that spans the majority of repeat variability within an entire genus, and one that includes complete elements as well as unassembled repeats. The database allows sequence browsing, downloading, and similarity searches. Because of the strategy adopted, the RiTE-db opens a new path to unprecedented direct comparative studies that span the entire nuclear repeat content of 15 million years of Oryza diversity