Repression of FLOWERING LOCUS C and FLOWERING LOCUS T by the Arabidopsis Polycomb Repressive Complex 2 Components

Danhua Jiang,Yuqi Wang,Yuehui He,Yizhong Wang,Brian P Dilkes

doi:10.1371/journal.pone.0003404

Danhua Jiang, Yuqi Wang + Show 3 more

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https://doi.org/10.1371/journal.pone.0003404

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Abstract

Polycomb group (PcG) proteins are evolutionarily conserved in animals and plants, and play critical roles in the regulation of developmental gene expression. Here we show that the Arabidopsis Polycomb repressive complex 2 (PRC2) subunits CURLY LEAF (CLF), EMBRYONIC FLOWER 2 (EMF2) and FERTILIZATION INDEPENDENT ENDOSPERM (FIE) repress the expression of FLOWERING LOCUS C (FLC), a central repressor of the floral transition in Arabidopsis and FLC relatives. In addition, CLF directly interacts with and mediates the deposition of repressive histone H3 lysine 27 trimethylation (H3K27me3) into FLC and FLC relatives, which suppresses active histone H3 lysine 4 trimethylation (H3K4me3) in these loci. Furthermore, we show that during vegetative development CLF and FIE strongly repress the expression of FLOWERING LOCUS T (FT), a key flowering-time integrator, and that CLF also directly interacts with and mediates the deposition of H3K27me3 into FT chromatin. Our results suggest that PRC2-like complexes containing CLF, EMF2 and FIE, directly interact with and deposit into FT, FLC and FLC relatives repressive trimethyl H3K27 leading to the suppression of active H3K4me3 in these loci, and thus repress the expression of these flowering genes. Given the central roles of FLC and FT in flowering-time regulation in Arabidopsis, these findings suggest that the CLF-containing PRC2-like complexes play a significant role in control of flowering in Arabidopsis.

Highlights

The transition from a vegetative to a reproductive phase is a major developmental switch in the plant life cycle that must be properly timed to ensure maximal reproductive success
We found that FLOWERING LOCUS C (FLC), MADS AFFECTING FLOWERING 4 (MAF4) and MADS AFFECTING FLOWERING 5 (MAF5) were de-repressed in clf, whereas transcripts of FLOWERING LOCUS M (FLM), MADS AFFECTING FLOWERING 2 (MAF2) and MADS AFFECTING FLOWERING 3 (MAF3) in clf remained at levels similar to wild-type Col (Figure 1A); CURLY LEAF (CLF) plays an essential role in repressing the expression of FLC, MAF4 and MAF5 during vegetative development
Our studies reveal that the Arabidopsis Polycomb repressive complex 2 (PRC2)-like complex subunits CLF, EMBRYONIC FLOWER 2 (EMF2) and FERTILIZATION INDEPENDENT ENDOSPERM (FIE) repress the expression of FLC and FLC relatives including MAF4 and MAF5, and that CLF directly binds to and mediates the deposition of repressive H3K27me3 in these three loci

Summary

Introduction

The transition from a vegetative to a reproductive phase (i.e., flowering) is a major developmental switch in the plant life cycle that must be properly timed to ensure maximal reproductive success. In Arabidopsis thaliana, this transition is genetically controlled by several pathways, including the autonomous pathway, the photoperiod pathway and the vernalization pathway, which form a regulatory network [1,2]. This network integrates the endogenous developmental state of the plant with environmental cues (e.g., day length and temperature) to precisely control the timing of the floral transition [1,2]. The vernalization pathway represses FLC expression in response to a prolonged cold exposure (a typical winter) to accelerate flowering in Arabidopsis [10,11]. Besides FLC, in the Arabidopsis genome there are five close FLC relatives including FLOWERING LOCUS M (FLM), MADS AFFECTING FLOWERING 2 (MAF2), MADS AFFECTING FLOWERING 3

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