Biology subjects

Delaunay, A.

Publications and source records attributed to Delaunay, A..

5 recordsLinked to original sources

bioRxiv2026

Megaherbivore mortality risk from temperature extremes is buffered by vegetation productivity but amplified by rainfall

Demographic risks from climate change remain poorly understood for megaherbivore species which face unique challenges because their large food requirements impose strong bottom-up limitation while their small surface-area-to-volume ratio limits heat dissipation. Here, we test how megaherbivore mortality is shaped by the concurrent effects of temperature and rainfall along with vegetation productivity, a potentially critical modifier of climate effects. By analysing four decades of monthly mortality records from 4,457 semi-captive Asian elephants across Myanmar, we identify multiple environmental pathways regulating megaherbivore mortality. Elephant mortality increased at extreme hot and cold temperatures in regions with low annual vegetation productivity, whereas high vegetation productivity buffered against such U-shaped effects of temperature. Furthermore, high rainfall amplified the negative impacts of extreme heat, underlining risks arising from the joint effects of heat and humidity. Seasonal declines in vegetation productivity did not explain the elevated mortality at temperature extremes. Together, our findings show that megaherbivores face elevated risks from global warming, but such risks strongly depend on vegetation productivity and humidity, highlighting multiple pathways through which climate change can shape the dynamics of megaherbivore populations.

ecology↗

bioRxiv2024

Epigenetic memory of temperature during somatic embryo maturation in 2-year-old maritime pine trees

Embryogenesis is a brief but potentially critical phase in the tree life cycle for adaptive phenotypic plasticity. Using somatic embryogenesis in maritime pine, we found that temperature during the maturation phase affects embryo development and post-embryonic tree growth for up to three years. We examined whether this somatic stress memory could stem from temperature- and/or development-induced changes in DNA methylation. To do this, we developed a 200 Mb custom sequence capture bisulfite analysis of genes and promoters to identify differentially methylated cytosines (DMCs) between temperature treatments (18, 23, and 28{degrees}C) and developmental stages (immature and cotyledonary embryos, shoot apical meristem of 2-year-old plants) and investigate if these differences can be mitotically transmitted from embryonic to post-embryonic development (epigenetic memory). We revealed a high prevalence of temperature-induced DMCs in genes (8-14%) compared to promoters (less than 1%) in all 3 cytosine contexts. Developmental DMCs showed a comparable pattern but only in the CG context, and with a high trend towards hypo-methylation, particularly in the promoters. A high percentage of DMCs induced by developmental transitions were found memorized in genes (up to 45-50%) and promoters (up to 90%). In contrast, temperature-induced memory was lower and confined to genes after both embryonic (up to 14%) and post-embryonic development (up to 8%). Using stringent criteria, we identified ten genes involved in defense responses and adaptation, embryo development and chromatin regulation that are candidates for the establishment of a persistent epigenetic memory of temperature sensed during embryo maturation in maritime pine. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=131 HEIGHT=200 SRC="FIGDIR/small/600784v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@17a70f1org.highwire.dtl.DTLVardef@18d186borg.highwire.dtl.DTLVardef@3e27f5org.highwire.dtl.DTLVardef@b15348_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2023

From maternal glucocorticoid and thyroid hormones to epigenetic regulation of gene expression: an experimental study in a wild bird species

Offspring phenotype at birth is determined by its genotype and the prenatal environment including exposure to maternal hormones. Variation in both maternal glucocorticoids and thyroid hormones can affect offspring phenotype. However, the underlying molecular mechanisms shaping the offspring phenotype, especially those contributing to long-lasting effects, remain unclear. Epigenetic changes (such as DNA methylation) have been postulated as mediators of long-lasting effects of early-life environment. In this study, we determined the effects of elevated prenatal glucocorticoid and thyroid hormones on handling stress response (breath rate), DNA methylation and gene expression of glucocorticoid receptor (GCR) and thyroid hormone receptor (THR) in great tit (Parus major). Eggs were injected before incubation onset with corticosterone (main avian glucocorticoid) and/or thyroid hormones (thyroxine and triiodothyronine) to simulate variation in maternal hormone deposition. Breath rate during handling and gene expression of GCR and THR were evaluated 14 days after hatching. Methylation status of GCR and THR genes were analyzed from the longitudinal blood samples taken 7 and 14 days after hatching, as well as in the following autumn. Elevated prenatal corticosterone level significantly increased the breath rate during handling, indicating enhanced stress response and/or metabolism. Prenatal corticosterone manipulation had CpG-site-specific effects on DNA methylation at the GCR putative promoter region, while it did not significantly affect GCR gene expression. GCR expression was negatively associated with earlier hatching date and chick size. THR methylation or expression did not exhibit any significant relationship with the hormonal treatments or the examined covariates, suggesting that TH signaling may be more robust due to its crucial role in development. This study supports the view that maternal corticosterone may influence offspring metabolism and stress response via epigenetic alterations, yet their possible adaptive role in optimizing offspring phenotype to the prevailing conditions, context-dependency, and the underlying molecular interplay needs further research.

evolutionary biology↗

bioRxiv2022

DNA methylome combined with chromosome cluster-oriented analysis provides an early signature for cutaneous melanoma aggressiveness

Aberrant DNA methylation is a well-known feature of tumours and has been associated with metastatic melanoma. However, since melanoma cells are highly heterogeneous, it has been challenging to use affected genes to predict tumour aggressiveness, metastatic evolution, and patients outcomes. We hypothesized that common aggressive hypermethylation signatures should emerge early in tumorigenesis and should be shared in aggressive cells, independent of the physiological context under which this trait arises. We compared paired melanoma cell lines with the following properties: (i) each pair comprises one aggressive counterpart and its parental cell line, and (ii) the aggressive cell lines were each obtained from different host and their environment (human, rat, and mouse), though starting from the same parent cell line. Next, we developed a multi-step genomic pipeline that combines the DNA methylome profile with a chromosome cluster-oriented analysis. A total of 229 differentially hypermethylated genes were commonly found in the aggressive cell lines. Genome localization analysis revealed hypermethylation peaks and clusters, identifying eight hypermethylated gene promoters for validation in tissues from melanoma patients. Five CpG identified in primary melanoma tissues were transformed into a DNA methylation score that can predict survival (Log-rank test, p=0.0008). This strategy is potentially universally applicable to other diseases involving DNA methylation alterations.

cancer biology↗

bioRxiv2020

Hypomethylated poplars show higher tolerance to water deficit and highlight a dual role for DNA methylation in shoot meristem: regulation of stress response and genome integrity

As fixed and long living organisms subjected to repeated environmental stresses, trees have developed mechanisms such as phenotypic plasticity that help them to cope with fluctuating environmental conditions. Here, we tested the role DNA methylation as a hub of integration, linking plasticity and physiological response to water deficit in the shoot apical meristem of the model tree poplar (Populus). Using a reverse genetic approach, we compared hypomethylated RNAi-ddm1 lines to wild-type trees for drought tolerance. An integrative analysis was realized with phytohormone balance, methylomes, transcriptomes and mobilomes. Hypomethylated lines were more tolerant when subjected to moderate water deficit and were intrinsically more tolerant to drought-induced cavitation. The alteration of the DDM1 machinery induced variation in DNA methylation in a cytosine context dependent manner, both in genes and transposable elements. Hypomethylated lines subjected to water deficit showed altered expression of genes involved in phytohormone pathways, such as salicylic acid and modified hormonal balance. Several transposable elements showed stress- and/or line-specific patterns of reactivation, and we could detect copy number variations for two of them in stressed ddm1 lines. Overall, our data highlight two major roles for DNA methylation in the shoot apical meristem: control of stress response and plasticity through transduction of hormone signaling and maintenance of genome integrity through the control of transposable elements.

plant biology↗