Biology subjects

Piron-Prunier, F.

Publications and source records attributed to Piron-Prunier, F..

5 recordsLinked to original sources

bioRxiv2024

Novel crosstalk between DNA methylation and H3K27me3 revealed at Arabidopsis transposable elements

Transposable elements (TEs) are usually silenced by DNA methylation and H3K9me2, but in the absence of DNA methylation they can instead acquire the Polycomb-associated mark H3K27me3. Here, we initially set out to test whether DNA methylation and H3K27me3 compete during TE silencing establishment in Arabidopsis. Although we observe this competition at one newly inserted transgenic TE, we remarkably find that H3K27me3 deposition at another neo-inserted TE requires the de novo methyltransferase DRM2, revealing that DNA methylation can also promote Polycomb recruitment. Accordingly, genome-wide H3K27me3 profiling in different DNA methylation mutants shows that DNA methylation either antagonizes or promotes H3K27me3 in a locus-specific manner. Targeted DNA methylation experiments as well as the use of a drm2 catalytic mutant further demonstrate that DNA methylation directly influences Polycomb recruitment. Overall, our work reveals a previously unappreciated interplay between DNA methylation and Polycomb pathways that maintains genome and epigenome integrity in eukaryotes.

molecular biology↗

bioRxiv2024

Alternative silencing states of Transposable Elements in Arabidopsis

The DNA methylation/H3K9me2 and Polycomb-group proteins (PcG)-H3K27me3 pathways have long been considered mutually exclusive and specific to TEs and genes, respectively. However, H3K27me3 can be recruited to many TEs in the absence of DNA methylation machinery and sometimes also co-occur with DNA methylation. In this study, we show that TEs can also be solely targeted by H3K27me3 in wild-type Arabidopsis plants. These H3K27me3-marked TEs not only comprise degenerate relics but also seemingly intact copies that display the epigenetic features of responsive PcG target genes as well as an active H3K27me3 regulation. We also show that H3K27me3 can be deposited on newly inserted transgenic TE sequences in a TE-specific manner indicating that silencing is determined in cis. Finally, comparison of Arabidopsis natural accessions reveals the existence of a category of TEs - which we refer to as "bifrons" - that are marked by DNA methylation or H3K27me3 depending on the ecotype. This variation can be linked to intrinsic TE features and to trans- acting factors, and reveals a change in epigenetic status across TE lifespan. Our study sheds light on an alternative mode of TE silencing associated with H3K27me3 instead of DNA methylation in flowering plants. It also suggests dynamic switching between the two epigenetic marks at the species level, a new paradigm that might extend to other multicellular eukaryotes.

molecular biology↗

bioRxiv2021

Supergene formation is associated with a major shift in genome-wide patterns of diversity in a butterfly

Selection shapes genetic diversity around target mutations, yet little is known about how selection on specific loci affects the genetic trajectories of populations, including their genome-wide patterns of diversity and demographic responses. Here we study the patterns of genetic variation and geographic structure in a neotropical butterfly, Heliconius numata, and its closely related allies in the so-called melpomene-silvaniform clade. H. numata is known to have evolved an inversion supergene which controls variation in wing patterns involved in mimicry associations with distinct groups of co-mimics whereas it is associated to disassortative mate preferences and heterozygote advantage at this locus. We contrasted patterns of genetic diversity and structure 1) among extant polymorphic and monomorphic populations of H. numata, 2) between H. numata and its close relatives, and 3) between ancestral lineages. We show that H. numata populations which carry the inversions as a balanced polymorphism show markedly distinct patterns of diversity compared to all other taxa. They show the highest genetic diversity and effective population size estimates in the entire clade, as well as a low level of geographic structure and isolation by distance across the entire Amazon basin. By contrast, monomorphic populations of H. numata as well as its sister species and their ancestral lineages all show lower effective population sizes and genetic diversity, and higher levels of geographical structure across the continent. One hypothesis is that the large effective population size of polymorphic populations could be caused by the shift to a regime of balancing selection due to the genetic load and disassortative preferences associated with inversions. Testing this hypothesis with forward simulations supported the observation of increased diversity in populations with the supergene. Our results are consistent with the hypothesis that the formation of the supergene triggered a change in gene flow, causing a general increase in genetic diversity and the homogenisation of genomes at the continental scale.

evolutionary biology↗

bioRxiv2020

Convergence in light transmission properties of transparent wing areas in clearwing mimetic butterflies

Mullerian mimicry is a positive interspecific interaction, whereby co-occurring defended prey species share a common aposematic signal. In Lepidoptera, aposematic species typically harbour conspicuous opaque wing colour patterns with convergent optical properties among co-mimetic species. Surprisingly, some aposematic mimetic species have partially transparent wings, raising the questions of whether optical properties of transparent patches are also convergent, and of how transparency is achieved. Here we conducted a comparative study of wing optics, micro and nanostructures in neotropical mimetic clearwing Lepidoptera, using spectrophotometry and microscopy imaging. We show that transparency, as perceived by predators, is convergent among co-mimics. Underlying micro- and nanostructures are also convergent despite a large structural diversity. We reveal that while transparency is primarily produced by microstructure modifications, nanostructures largely influence light transmission, maybe enabling additional fine-tuning in transmission properties. This study shows that transparency might not only enable camouflage but can also be part of aposematic signals.

evolutionary biology↗

bioRxiv2017

Renewed diversification following Miocene landscape turnover in a Neotropical butterfly radiation

\"This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100032)\"\n\nThe Neotropical region has experienced a dynamic landscape evolution throughout the Miocene, with the large wetland Pebas occupying western Amazonia until 11-8 my ago and continuous uplift of the Andes mountains along the western edge of South America. Although the complex dynamics between the Andes and Amazonia may have strongly affected the trajectory of Neotropical biodiversity, there is little evidence for such an influence from time-calibrated phylogenies of groups that diversified during this period. Here, we generate one of the most comprehensive time-calibrated molecular phylogenies of a group of Neotropical insects: the butterfly tribe Ithomiini. Our tree includes 340 species (87% of extant species), spanning 26 million years of diversification in the Neotropics. We investigate temporal and spatial patterns of diversification, focusing on the influence of Miocene landscape tranformations on the dynamics of speciation, extinction and biotic interchanges at the Amazonia/Andes interface. We find that Ithomiini likely began diversifying at the interface between the Andes and the Amazonia around 26.4 my ago. Five subtribes with a very low extant diversity started diversifying early in western Amazonia, but a rapid decrease in diversification rate due to increased extinction rate between 20 and 10 my ago suggests a negative impact of the Pebas wetland system on these early lineages. By contrast, the clade containing the five most species-rich subtribes (85% of extant species) was characterized by a high, positive net diversification rate. This clade diversified exclusively in the Central Andes from 20 to 10 my ago. After the demise of the Pebas system (11-8 my ago), we found a sudden increase of interchanges with the Northern Andes and Amazonia, followed by local diversification, which led to a substantial renewal of diversification. In general, ecological turnovers throughout the Miocene strongly determined the dynamics of speciation, and extinction and interchanges, and appear as a key driving force shaping the regions current extraordinary biodiversity.

evolutionary biology↗