A PHD finger protein involved in both the vernalization and photoperiod pathways in Arabidopsis

Abstract

The proper timing of flowering is critical for successful reproduction. The perception of the seasonal cues of daylength changes and exposure to cold influences flowering time in many plant species through the photoperiod and vernalization pathways, respectively. Here we show that a plant homeodomain (PHD) finger-containing protein, VIN3-LIKE 1 (VIL1), participates in both the photoperiod and vernalization pathways in Arabidopsis thaliana by regulating expression of the related floral repressors FLOWERING LOCUS C (FLC) and FLOWERING LO-CUS M (FLM). In the vernalization pathway, VIL1, along with VERNALIZATION INSENSITIVE 3 (VIN3), is necessary for the modifications to FLC and FLM chromatin that are associated with an epigenetically silenced state and with acquisition of competence to flower. In addition, VIL1 regulates FLM independently of VIN3 in a photoperiod-dependent manner.Supplemental material is available at http://www.genesdev.org.Received September 13, 2006; revised version accepted October 13, 2006. The transition to flowering is a critical developmental event in the plant life cycle. In many plants, the perception of seasonal changes affects the timing of this transition. Two environmental cues that many plant species monitor for flowering time control are the prolonged cold of winter and changing day length; these cues promote flowering through the vernalization and photoperiod pathways, respectively. Most accessions of Arabidopsis thaliana exhibit a facultative response to these signals: In the absence of either environmental cue, flowering is delayed but nevertheless eventually occurs.In Arabidopsis, vernalization results in the mitotically stable repression of the potent floral repressor, FLOW-ERING LOCUS C (FLC) (Michaels and Amasino 1999;Sheldon et al. 1999). Vernalization-mediated repression of FLC is associated with histone modifications such as methylation of histone H3 Lys 9 (H3K9) and Lys 27 (H3K27) as well as H3 deacetylation (Bastow et al. 2004;Sung and Amasino 2004). A plant homeodomain (PHD) finger-containing protein, VERNALIZATION , is required for FLC repression by vernalization and the associated modifications to FLC chromatin (Sung and Amasino 2004). Here we show that a related PHD finger-containing protein, VIN3-LIKE 1 (VIL1), identified in a screen for proteins that interact with VIN3, cooperates with VIN3 in the vernalizationmediated repression of FLC. Furthermore, independently of VIN3 activity, VIL1 mediates the photoperiod-specific repression of another member of the FLC clade. Thus, VIL1 is involved in the regulation of flowering by two environmental-sensing pathways. Results and DiscussionBecause VIN3 is essential for the vernalization response (Sung and Amasino 2004) and PHD finger-containing proteins are often members of multisubunit chromatin remodeling complexes (Bienz 2006), we searched for potential components of a VIN3 complex using the yeast two-hybrid system. This screen revealed two independent VIN3-interacting clones encoding C-terminal regions of At3g24440. In...

NO FLOWERING IN SHORT DAY (NFL) is a bHLH transcription factor that promotes flowering specifically under short-day in Arabidopsis

“…For example, phyB, dnf, spa1 and cop1 flower early, whereas vil1, vil2 and a gain-of-function mutation in IAA7/AXR2 (axr2-1) flower late specifically under SD conditions (Ishikawa et al, 2006;Kim and Sung, 2010;Laubinger et al, 2006;Mai et al, 2011;McNellis et al, 1994;Morris et al, 2010;Reed et al, 1993;Sung et al, 2006). However, vil1, vil2 and axr2-1 mutants display quantitative differences in flowering time compared with the wt and still flower under SD conditions (Kim and Sung, 2010;Mai et al, 2011;Sung et al, 2006). Although the ga1 mutant also failed to flower under SD, ga1 flowers significantly later under LD as well (Michaels and Amasino, 1999b;Wilson et al, 1992).…”

“…For example, plant homeodomain finger-containing proteins such as VIN3-LIKE 1 and 2 [VIL1 (also known as VRN5) and VIL2] have been shown to promote flowering through epigenetic repression of MAF1 and MAF5 genes, respectively, under SD conditions (Kim and Sung, 2010;Sung et al, 2006). vil1 and vil2 mutants flower later only under SD conditions, but do eventually flower.…”

Rice leaf inclination2, a VIN3-like protein, regulates leaf angle through modulating cell division of the collar

“…Previous studies of VIN3-like proteins focused on their roles in vernalization of Arabidopsis and wheat [28,29]. Arabidopsis VIN3 is a component of the polycomblike protein complex and is responsible for vernalizationmediated repression of the FLC gene, and vin3 mutant shows the late-flowering phenotype only after vernalization [42].…”

“…Arabidopsis VIN3 is a component of the polycomblike protein complex and is responsible for vernalizationmediated repression of the FLC gene, and vin3 mutant shows the late-flowering phenotype only after vernalization [42]. VIN3-LIKE 1 (VIL1) participates in both the photoperiod and vernalization pathways [28], suggesting the critical role of VIN3-like proteins in regulation of flowering [28,42,43]). In this study, we showed that spontaneous mutants of LC2, a rice homolog of Arabidopsis VIN3, present the late-flowering phenotype, suggesting that even in rice, a nonvernalized plant, the VIN3-like protein also participates in flowering time control.…”

“…Analysis through Basic Local Alignment Search Tool indicated that the LC2 protein shares the highest identity (74% over the entire protein) with Tm-VIL2, a predicted member of the VIN3-like protein in wheat, and 37% identity with AtVIL2 and AtVIN3 [27][28][29]. Previous structural analysis has shown that VIN3-like proteins contain several highly conserved elements including a plant homeodomain finger motif (PHD, characterized by a conserved Cys4-His-Cys3 pattern and known to be associated with chromatin-mediated transcriptional regulation [27,30,31]), a fibronectin type III domain (FNIII, one of the repeated structural motifs discovered in fibronectin and involved in protein-protein interactions [32,33]), and a VIN3-interacting domain (VID, conserved among all members of this family [29]).…”