Biology subjects

jullien, p. E.

Publications and source records attributed to jullien, p. E..

3 recordsLinked to original sources

bioRxiv2021

DNA METHYLTRANSFERASE 3 (MET3) is regulated by Polycomb Group complex during Arabidopsis endosperm development

Complex epigenetic changes occur during plant reproduction. These regulations ensure the proper transmission of epigenetic information as well as allowing for zygotic totipotency. In Arabidopsis, the main DNA methyltransferase is called MET1 and is responsible for methylating cytosine in the CG context. The Arabidopsis genome encodes for three additional reproduction-specific homologs of MET1, namely MET2a, MET2b and MET3. In this paper, we show that the DNA methyltransferase MET3 is expressed in the seed endosperm and its expression is further restricted to the chalazal endosperm. MET3 is biallelically expressed in the endosperm but displays a paternal expression bias. We found that MET3 expression is regulated by the Polycomb complex proteins FIE and MSI1. Seed development is not impaired in met3 mutant, and we could not observe significant transcriptional changes in met3 mutant. Interestingly, we found that MET3 regulates gene expression in a Polycomb mutant background suggesting a further complexification of the interplay between H3K27me3 and DNA methylation in the seed endosperm. Key messageThe DNA METHYLTRANSFERASE MET3 is controlled by Polycomb group complex during endosperm development.

plant biology↗

bioRxiv2021

METHYLOME DYNAMIC UPON PROTEASOME INHIBITION BY THE PSEUDOMONAS VIRULENCE FACTOR SYRINGOLIN A

DNA methylation is an important epigenetic mark required for proper gene expression and silencing of transposable elements. DNA methylation patterns can be modified by environmental factors such as pathogen infection, where modification of DNA methylation can be associated with plant resistance. To counter the plant defense pathways, pathogens produce effectors molecule, several of which act as proteasome inhibitors. Here we investigated the effect of proteasome inhibition by the bacterial virulence factor Syringolin A on genome-wide DNA methylation. We show that Syringolin A treatment results in an increase of DNA methylation at centromeric and pericentromeric regions of Arabidopsis chromosomes. We identify several CHH DMRs that are enriched in the proximity of transcriptional start sites. Syringolin A treatment does not result in significant changes in small RNA composition. However, significant changes in genome transcriptional activity can be observed, including a strong upregulation of resistance genes that are located on chromosomal arms. We hypothesize that DNA methylation changes could be linked to the upregulation of some atypical members of the de novo DNA methylation pathway: AGO3, AGO9 and DRM1. Our data suggests that modification of genome-wide DNA methylation resulting from an inhibition of the proteasome by bacterial effectors could be part of a epi-genomic arms race against pathogens.

plant biology↗

bioRxiv2020

ASYMMETRIC EXPRESSION OF ARGONAUTES IN ARABIDOPSIS REPRODUCTIVE TISSUES

AO_SCPLOWBSTRACTC_SCPLOWDuring sexual reproduction, development of a totipotent zygote from the fusion of highly differentiated gametes is accompanied by dynamic regulation of gene expression. This notably involves RNA silencing operated by Argonautes (AGO) effector proteins. While AGOs roles during Arabidopsis somatic life have been extensively investigated, less is known about their expression during reproduction, which proceeds via double-fertilization of an egg and a central cell, leading respectively to the embryo and a supportive tissue known as endosperm. Using full-locus translational reporters for all ten Arabidopsis AGOs, we uncover cell-specific expression patterns and AGO-intrinsic subcellular localizations in reproductive tissues. However, while some Arabidopsis AGOs are enriched in both male and female gametes, i.e. sperm and egg cells, they are comparably low-expressed in accessory, i.e. vegetative and central cells. Likewise, following fertilization, several AGOs are expressed in the early embryo, yet below detection in the early endosperm. Thus, there is pre- and post-fertilization asymmetry between the embryo and endosperm lineages. Later during embryo development, AGO9, AGO5 and AGO7 are restricted to the apical embryonic meristem in contrast to AGO1, AGO4, AGO6 and AGO10. Beside shedding light onto potential roles for RNA silencing during Arabidopsis reproduction, the plant material generated here should constitute a valuable asset enabling functional AGOs studies in many tissues beyond those involved in reproduction. Summary statementArabidopsis genome encodes ten Argonautes proteins showing distinct expression pattern as well as intracellular localisation during sexual reproduction.

developmental biology↗