Biology subjects

Bonnet, D. M.

Publications and source records attributed to Bonnet, D. M..

3 recordsLinked to original sources

bioRxiv2022

Non-cell autonomous small RNA silencing in female gametes and early embryo of Arabidopsis

In recent years, small RNA movement has been both hypothesized and shown to be an integral part of the epigenetic DNA methylation reprogramming occurring during plant reproduction. It was suggested that the release of epigenetic silencing in accessory cell types or tissues is necessary to reinforce epigenetic silencing in the gametes (egg cell and sperm cells) which would in turn ensure the genomic stability of the next generation plant. Small RNA movement was indeed shown to occur during male gametogenesis. However, the situation within the female gametophyte and in early seed development is mostly unknown. Here, we show that small RNA can induce non-cell autonomous silencing from the central cell towards the egg cell but also from the synergids to the egg cell and central cell. In addition, we also observe a non-cell-autonomous silencing from the central cell or endosperm towards the early embryo. Our data shows, that in addition to the movement of sRNAs during pollen development, sRNA movement also occurs in the female gametes.

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↗