Multiple genetic pathways act in response to developmental cues and environmental signals to promote the floral transition, by regulating several floral pathway integrators. These include FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). We show that the flowering repressor SHORT VEGETATIVE PHASE (SVP) is controlled by the autonomous, thermosensory, and gibberellin pathways, and directly represses SOC1 transcription in the shoot apex and leaf. Moreover, FT expression in the leaf is also modulated by SVP. SVP protein associates with the promoter regions of SOC1 and FT, where another potent repressor FLOWERING LOCUS C (FLC) binds. SVP consistently interacts with FLC in vivo during vegetative growth and their function is mutually dependent. Our findings suggest that SVP is another central regulator of the flowering regulatory network, and that the interaction between SVP and FLC mediated by various flowering genetic pathways governs the integration of flowering signals.
SummaryThe Arabidopsis Flowering Locus C (FLC) protein is a repressor of flowering regulated by genes in the autonomous and vernalization pathways. Previous genetic and transgenic data have suggested that FLC acts by repressing expression of the floral integrator genes SOC1 and FT. We have taken an in vivo approach to determine whether the FLC protein interacts directly with potential DNA targets. Using chromatin immunoprecipitation, we have shown that FLC binds to a region of the first intron of FT that contains a putative CArG box, and have confirmed that FLC binds to a CArG box in the promoter of the SOC1 gene. MADS box proteins are thought to bind their DNA targets as dimers or higher-order multimers. We have shown that FLC is a component of a multimeric protein complex in vivo and that more than one FLC polypeptides can be present in the complex.
(12)(13)(14)(15). The core PRC2 complex is Ϸ600 kDa, and it can be associated with additional proteins including Polycomb-like (PCL) and the histone deacetylase RPD3 (16) in a complex of 1,000 kDa. The E(Z) protein has histone 3 lysine 27 (H3K27) methyltransferase activity; addition of this mark of inactive chromatin is thought to be the basis of the repression of gene expression by PRC2 (17). Arabidopsis has homologues of PRC2 proteins that are required for the regulation of various devel- VIN3 is a member of a plant-specific protein family with plant homeodomain (PHD) and fibronectin 3 (FNIII) domains (7). VIN3 protein binds to regions of the promoter and first intron of FLC. Unlike the constitutively expressed VRN2 mRNA, the VIN3 mRNA is present at very low abundance during growth at warm temperatures, with expression increasing progressively during a vernalization treatment and returning to prevernalized levels when the plant is returned to normal temperatures (7). This cold-driven accumulation of VIN3 mRNA may be part of a mechanism to time the duration of vernalization and ensure that short cold periods do not promote flowering.The repression of FLC expression after vernalization is accompanied by modifications to histones associated with the FLC locus. In nonvernalized plants, FLC chromatin has high histone H3 acetylation (H3Ac) and H3K4 trimethylation (me3), marks of active chromatin but low levels of the inactive marks H3K9me2 and H3K27me2. After vernalization, H3Ac and H3K4me3 are reduced and H3K9me2 and H3K27me2 are increased (7,21,22). These changes suggest that the formation of a repressed chromatin state at FLC after vernalization is the basis of the epigenetic regulation of FLC. Loss of VIN3 function prevents loss of H3Ac and methylation of H3K9 and H3K27 in vernalized plants. In vrn2 mutants, vernalization gives a transient loss of H3Ac but there is no methylation of H3K9 or H3K27 after vernalization (7). These data suggest that VIN3 may recruit a histone deacetylase to FLC and that VRN2 acts as part of a PRC2-like complex to methylate histone H3 to epigenetically repress FLC expression in vernalized plants.In this paper, we use epitope-tagged proteins to show that VRN2 is associated with the polycomb group protein homologues FIE, SWINGER (SWN; also known as EZA1; ref. 23), and CURLY LEAF (CLF) in a PRC2-like complex and that these proteins are required for the repression of FLC by vernalization. We also show that VRN2 and VIN3 can be part of the same protein complex, suggesting a physical link between these two components of the vernalization response mechanism.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.