The Arabidopsis E3 ubiquitin ligase PUB4 regulates BIK1 and is targeted by a bacterial type-III effector.

Plant immunity is tightly controlled by a complex and dynamic regulatory network, which ensures optimal activation upon detection of potential pathogens. Accordingly, each component of this network is a potential target for manipulation by pathogens. Here, we report that RipAC, a type III-secreted effector from the bacterial pathogen Ralstonia solanacearum, targets the plant E3 ubiquitin ligase PUB4 to inhibit pattern-triggered immunity (PTI).

H2A deubiquitinases UBP12/13 are part of the Arabidopsis polycomb group protein system.

Polycomb group (PcG) proteins form an epigenetic memory system in plants and animals, but interacting proteins are poorly known in plants. Here, we have identified Arabidopsis UBIQUITIN SPECIFIC PROTEASES (USP; UBP in plant and yeasts) 12 and 13 as partners of the plant-specific PcG protein LIKE HETEROCHROMATIN PROTEIN 1 (LHP1). UBP12 binds to chromatin of PcG target genes and is required for histone H3 lysine 27 trimethylation and repression of a subset of PcG target genes.

The WD40 Domain Protein MSI1 Functions in a Histone Deacetylase Complex to Fine-Tune Abscisic Acid Signaling.

MSI1 belongs to a family of histone binding WD40-repeat proteins. Arabidopsis thaliana contains five genes encoding MSI1-like proteins, but their functions in diverse chromatin-associated complexes are poorly understood. Here, we show that MSI1 is part of a histone deacetylase complex.

Variations on a theme: Polycomb group proteins in plants.

Polycomb group (PcG) proteins evolved early in evolution, probably in the common ancestor of animals and plants. In some unicellular organisms, such as Chlamydomonas and Tetrahymena, PcG proteins silence genes in heterochromatin, suggesting an ancestral function in genome defence. In angiosperms, the PcG system controls many developmental transitions.

Arabidopsis MSI1 connects LHP1 to PRC2 complexes.

Polycomb group (PcG) proteins form essential epigenetic memory systems for controlling gene expression during development in plants and animals. However, the mechanism of plant PcG protein functions remains poorly understood. Here, we probed the composition and function of plant Polycomb repressive complex 2 (PRC2).

Diversity of Polycomb group complexes in plants: same rules, different players?

Polycomb Group (PcG) proteins form an epigenetic memory system that is conserved in plants and animals and controls gene expression during development. Loss of plant PcG proteins leads to loss of organ identity and to cell overproliferation. Our understanding of plant PcG protein function has recently been advanced by the identification of additional proteins required for transcriptional repression by PcG and by the purification of an Arabidopsis PcG protein complex.