BLISTER Regulates Polycomb-Target Genes, Represses Stress-Regulated Genes and Promotes Stress Responses in Arabidopsis thaliana.

Julia A. Kleinmanns,David Heckmann,Daniel Schubert,Nicole Schatlowski

doi:10.3389/fpls.2017.01530

Julia A. Kleinmanns, David Heckmann + Show 2 more

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https://doi.org/10.3389/fpls.2017.01530

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Abstract

HIGHLIGHTS The PRC2 interacting protein BLISTER likely acts downstream of PRC2 to silence Polycomb target genes and is a key regulator of specific stress responses in Arabidopsis.Polycomb group (PcG) proteins are key epigenetic regulators of development. The highly conserved Polycomb repressive complex 2 (PRC2) represses thousands of target genes by trimethylating H3K27 (H3K27me3). Plant specific PcG components and functions are largely unknown, however, we previously identified the plant-specific protein BLISTER (BLI) as a PRC2 interactor. BLI regulates PcG target genes and promotes cold stress resistance. To further understand the function of BLI, we analyzed the transcriptional profile of bli-1 mutants. Approximately 40% of the up-regulated genes in bli are PcG target genes, however, bli-1 mutants did not show changes in H3K27me3 levels at all tested genes, indicating that BLI regulates PcG target genes downstream of or in parallel to PRC2. Interestingly, a significant number of BLI regulated H3K27me3 target genes is regulated by the stress hormone absciscic acid (ABA). We further reveal an overrepresentation of genes responding to abiotic stresses such as drought, high salinity, or heat stress among the up-regulated genes in bli mutants. Consistently, bli mutants showed reduced desiccation stress tolerance. We conclude that the PRC2 associated protein BLI is a key regulator of stress-responsive genes in Arabidopsis: it represses ABA-responsive PcG target genes, likely downstream of PRC2, and promotes resistance to several stresses such as cold and drought.

Highlights

Epigenetic gene regulation has important roles in genome defense and in the regulation of development and the response of organisms to environmental cues and can be mediated by posttranslational modifications of histones or DNA methylation
We previously showed that BLI regulates expression of several Polycomb group (PcG) target genes but likely has PcG-independent functions (Schatlowski et al, 2010), but it remained unclear whether BLI is general regulator of PcG target genes and whether the function of BLI in the cold stress response is linked to PcG function
Because CURLY LEAF (CLF) function is masked by partial redundancy with SWN, we compared the overlap of genes differentially expressed in bli-1 and the strong clf-28 swn-7 double mutant (Farrona et al, 2011), which is completely deficient in post-embryonic Polycomb Repressive Complex 2 (PRC2) function (Chanvivattana et al, 2004; Lafos et al, 2011)

Summary

Introduction

Epigenetic gene regulation has important roles in genome defense and in the regulation of development and the response of organisms to environmental cues and can be mediated by posttranslational modifications of histones or DNA methylation. Polycomb group proteins are key epigenetic regulators of development, assemble in large complexes and maintain gene repression. BLISTER Represses Stress Responses and silences target genes by tri-methylation of histone 3 lysine 27 (H3K27me). Trithorax group (TrxG) proteins, such as ARABIDOPSIS TRITHORAX1 (ATX1) (Alvarez-Venegas et al, 2003), ULTRAPETALA1 (ULT1) (Carles and Fletcher, 2009), and BRAHMA (BRM) (Farrona et al, 2004), act antagonistically to PRC2. TrxG proteins activate gene expression through setting H3K4me and by ATP-dependent chromatin remodeling

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