The Cold Signaling Attenuator HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 Activates FLOWERING LOCUS C Transcription via Chromatin Remodeling under Short-Term Cold Stress in Arabidopsis    

Abstract

Exposure to short-term cold stress delays flowering by activating the floral repressor FLOWERING LOCUS C (FLC) in Arabidopsis thaliana. The cold signaling attenuator HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 (HOS1) negatively regulates cold responses. Notably, HOS1-deficient mutants exhibit early flowering, and FLC expression is suppressed in the mutants. However, it remains unknown how HOS1 regulates FLC expression. Here, we show that HOS1 induces FLC expression by antagonizing the actions of FVE and its interacting partner histone deacetylase 6 (HDA6) under short-term cold stress. HOS1 binds to FLC chromatin in an FVE-dependent manner, and FVE is essential for the HOS1-mediated activation of FLC transcription. HOS1 also interacts with HDA6 and inhibits the binding of HDA6 to FLC chromatin. Intermittent cold treatments induce FLC expression by activating HOS1, which attenuates the activity of HDA6 in silencing FLC chromatin, and the effects of intermittent cold are diminished in hos1 and fve mutants. These observations indicate that HOS1 acts as a chromatin remodeling factor for FLC regulation under short-term cold stress.

Red Light-Mediated Degradation of CONSTANS by the E3 Ubiquitin Ligase HOS1 Regulates Photoperiodic Flowering in Arabidopsis

“…On the other hand, the double mutant hos1-3 co-10 and the triple mutant hos1-3 co-10 phyB-9 showed that hos1 mutation is still able to accelerate co late flowering phenotype in all combinations tested ( Figures 1D and 1E), indicating that HOS1 has an additional role in flowering time control besides regulating CO. This is consistent with previous data demonstrating that HOS1 is required to maintain high expression levels of the floral repressor FLC (Lee et al, 2001;Lazaro et al, 2012;Jung et al, 2013). We analyzed FLC transcript levels in the single, double, and triple mutant plants and observed that the hos1 mutation consistently reduces FLC expression in every combination analyzed compared with the wild type (Supplemental Figure 1).…”

“…FLC also plays a role in flowering time control under short-term cold stress, conditions in which flowering is delayed (Seo et al, 2009). The effects of intermittent cold treatments on FLC expression and flowering time are strongly diminished in hos1 mutants (Seo et al, 2009;Jung et al, 2013), indicating that the activation of the FLC gene by cold stress is mediated by HOS1 (Jung et al, 2014). Recently, it has been shown that HOS1 binds to FLC chromatin and that this binding is significantly induced by cold stress (Jung et al, 2013).…”

“…We and other groups have shown that HOS1 is required for full activation of the floral repressor gene FLC and that the early flowering phenotype of hos1 mutants partially depends on FLC (Ishitani et al, 1998;Lee et al, 2001Lee et al, , 2012Lazaro et al, 2012;Jung et al, 2013) (Supplemental Figure 1). FLC also plays a role in flowering time control under short-term cold stress, conditions in which flowering is delayed (Seo et al, 2009).…”

A comparative transcriptomic approach to understanding the formation of cork

“…FLC (FLOWERING LOCUS C) is a floral repressor that integrates vernalization responses (Sheldon et al 2000) and in perennial trees an FLC-like gene has also been highlighted as a candidate for bud dormancy regulation (Porto et al 2015). FLC regulation is basically performed by chromatin remodelling since FLC expression is epigenetically regulated (Shindo et al 2006;Jung et al 2013;Crevillén et al 2014). Taking into account that FLC has a role in xylem differentiation (Sibout et al 2008), it can be surmised that FLC also has a function in phellem development.…”

Chloroplast retrograde signal regulates flowering

“…In addition, FVE is also implicated in the photoperiod flowering pathway and is postulated to bind chromatin as a large protein complex of ∼1.0 MDa (54,55). Thus, it is likely that these versatile functions of FVE in environment-controlled flowering are achieved through specific interactions with distinct partners like HOS1 and CUL4-DDB1 (54,56). Collectively, our findings suggest that PTM functions not only as a messenger between chloroplast and nucleus, but also as a multifaceted adaptor to recruit specific partners to trigger diverse transcriptional reprogramming events.…”