Direct interaction of AGL24 and SOC1 integrates flowering signals in Arabidopsis

Abstract

During the transition from vegetative to reproductive growth, the shoot meristem of flowering plants acquires the inflorescence identity to generate flowers rather than vegetative tissues. An important regulator that promotes the inflorescence identity in Arabidopsis is AGAMOUS-LIKE 24 (AGL24), a MADS-box transcription factor. Using a functional estradiol-inducible system in combination with microarray analysis, we identified AGL24-induced genes, including SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1), a floral pathway integrator. Chromatin immunoprecipitation (ChIP) analysis of a functional AGL24-6HA-tagged line revealed in vivo binding of AGL24-6HA to the regulatory region of SOC1. Mutagenesis of the AGL24 binding site in the SOC1 promoter decreased Pro SOC1 :GUS expression and compromised SOC1 function in promoting flowering. Our results show that SOC1 is one of the direct targets of AGL24, and that SOC1 expression is upregulated by AGL24 at the shoot apex at the floral transitional stage. ChIP assay using a functional SOC1-9myc-tagged line and promoter mutagenesis analysis also revealed in vivo binding of SOC1-9myc to the regulatory regions of AGL24 and upregulation of AGL24 at the shoot apex by SOC1. Furthermore, we found that as in other flowering genetic pathways, the effect of gibberellins on flowering under short-day conditions was mediated by the interaction between AGL24 and SOC1. These observations suggest that during floral transition, a positive-feedback loop conferred by direct transcriptional regulation between AGL24 and SOC1 at the shoot apex integrates flowering signals.

CHD3 chromatin-remodeling factor PICKLE regulates floral transition partially via modulating LEAFY expression at the chromatin level in Arabidopsis

“…In this respect, it is pertinent to make a conclusion that LFY may partly mediate the PKL regulation of flowering time control via chromatin modification. Interestingly, AGL24 and SOC1 regulate each other and act together to activate LFY transcription (Liu et al, 2008;Lee et al, 2008) while both AGL8/FUL and LFY are independent downstream targets of SPL3 in flowering time and meristem identity control (Yamaguchi et al, 2009). Both SOC1 and LFY are direct targets of AGL8/FUL that binds to a region 2.2 kb upstream to the ATG codon of the LFY gene (Balanza et al, 2014), overlapping with a previously identified region that is also bound by SOC1 (Lee et al, 2008).…”

Nuclear factor Y-mediated H3K27me3 demethylation of the SOC1 locus orchestrates flowering responses of Arabidopsis

“…NF-Y binding mediates the regulation of SOC1 by CO and GA. To test in vivo whether CO and GA signalling regulate SOC1 through NF-Y binding to the NFYBE in the SOC1 promoter, we used an established pSOC1:b-glucuronidase (GUS) construct in which the GUS reporter gene was driven by a 2-kb SOC1 promoter upstream of the translational start site 5 . Based on this construct, we further created a mutated reporter gene cassette containing the Mut1 version of the NFYBE, 5 0 -TTCAgtAAgACgATT-3 0 (Fig.…”

“…In Arabidopsis, the timing of this transition is controlled by a complex network of flowering genetic pathways in response to developmental cues and environmental signals 1 . The interactions among these flowering pathways regulate the expression of two floral pathway integrators, FLOWERING LOCUS T (FT) and SUPPRESOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), which in turn activate the genes involved in the formation of floral meristems [2][3][4][5] . The major flowering pathways include photoperiod and gibberellin (GA) pathways that promote flowering in response to seasonal changes in day length and the endogenous phytohormone GA, respectively.…”

RiceLHS1/OsMADS1Controls Floret Meristem Specification by Coordinated Regulation of Transcription Factors and Hormone Signaling Pathways

“…ChIP was carried out as described (Liu et al, 2008) with some modifications. Briefly, about 250 mg of 1% formaldehyde-fixed young wild-type rice panicles (0.2-2 cm) was ground in liquid nitrogen and then sonicated to yield chromatin with DNA of less than 500 bp.…”