Polycomb mutant partially suppresses DNA hypomethylation-associated phenotypes in Arabidopsis.

In plants and mammals, DNA methylation and histone H3 lysine 27 trimethylation (H3K27me3), which is deposited by the polycomb repressive complex 2, are considered as two specialized systems for the epigenetic silencing of transposable element (TE) and genes, respectively. Nevertheless, many TE sequences acquire H3K27me3 when DNA methylation is lost. Here, we show in that the gain of H3K27me3 observed at hundreds of TEs in the mutant defective in the maintenance of DNA methylation, essentially depends on CURLY LEAF (CLF), one of two partially redundant H3K27 methyltransferases active in vegetative tissues.

Transcriptional control and exploitation of an immune-responsive family of plant retrotransposons.

Mobilization of transposable elements (TEs) in plants has been recognized as a driving force of evolution and adaptation, in particular by providing genes with regulatory modules that impact their transcription. In this study, we employed an long-terminal repeat (LTR) promoter- fusion to show that this retrotransposon behaves like an immune-responsive gene during pathogen defense in We also showed that the endogenous copy "", which is activated in the presence of bacterial stress, is negatively regulated by both DNA methylation and polycomb-mediated silencing, a mode of repression typically found at protein-coding and microRNA genes. Interestingly, an -derived soloLTR is located upstream of the disease resistance gene and is devoid of DNA methylation and H3K27m3 marks.

RNA silencing is resistant to low-temperature in grapevine.

RNA silencing is a natural defence mechanism against viruses in plants, and transgenes expressing viral RNA-derived sequences were previously shown to confer silencing-based enhanced resistance against the cognate virus in several species. However, RNA silencing was shown to dysfunction at low temperatures in several species, questioning the relevance of this strategy in perennial plants such as grapevines, which are often exposed to low temperatures during the winter season. Here, we show that inverted-repeat (IR) constructs trigger a highly efficient silencing reaction in all somatic tissues in grapevines.

APC/C-mediated degradation of dsRNA-binding protein 4 (DRB4) involved in RNA silencing.

Background: Selective protein degradation via the ubiquitin-26S proteasome is a major mechanism underlying DNA replication and cell division in all Eukaryotes. In particular, the APC/C (Anaphase Promoting Complex or Cyclosome) is a master ubiquitin protein ligase (E3) that targets regulatory proteins for degradation allowing sister chromatid separation and exit from mitosis. Interestingly, recent work also indicates that the APC/C remains active in differentiated animal and plant cells.