The SOC1‐SPL module integrates photoperiod and gibberellic acid signals to control flowering time in Arabidopsis

Abstract

SUMMARYmiR156 and its target SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes constitute an endogenous flowering pathway in Arabidopsis. The SPL genes are regulated post-transcriptionally by miR156, and incorporate endogenous aging signals into floral gene networks. Intriguingly, the SPL genes are also regulated transcriptionally by FLOWERING LOCUS T (FT)-mediated photoperiod signals. However, it is unknown how photoperiod regulates the SPL genes. Here, we show that SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and FT regulate the SPL3, SPL4 and SPL5 genes by directly binding to the gene promoters in response to photoperiod signals. Notably, the SOC1 regulation of the SPL genes, termed the SOC1-SPL module, also mediates gibberellic acid (GA) signals to promote flowering under non-inductive short days (SDs). Under SDs, the inductive effects of GA on the SPL genes disappeared in the soc1-2 mutant, and the flowering of SPL3-overexpressing transgenic plants (35S:SPL3) was less sensitive to GA. In addition, the 35S:SPL3 · soc1-2 plants flowered much earlier than the soc1-2 mutant, supporting SOC1 regulation of the SPL genes. Our observations indicate that the SOC1-SPL module serves as a molecular link that integrates photoperiod and GA signals to promote flowering in Arabidopsis.

Cross-Repressive Interactions between SOC1 and the GATAs GNC and GNL/CGA1 in the Control of Greening, Cold Tolerance, and Flowering Time in Arabidopsis

“…Third, it may be that other unrelated proteins repress flowering in addition to GNC and GNL in the absence of GA. In this regard, it is interesting that the protein SPL9 was recently identified as a DELLA-controlled flowering time regulator in Arabidopsis and that GA was recently described to promote the expression of the SPL genes SPL3, SPL4, and SPL5 in a SOC1-dependent manner (Wu et al, 2009;Jung et al, 2012;Yu et al, 2012). Thus, DELLA repression of SPL gene expression and SPL protein activity could potentially delay flowering in ga1 in parallel to GNC and GNL.…”

ThemicroRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3Module Regulates Ambient Temperature-Responsive Flowering viaFLOWERING LOCUS Tin Arabidopsis

“…Our conclusion is consistent with the finding that the loss of FT function completely masks the early flowering phenotype of plants misexpressing SPL3 in the phloem . FD protein has been recently reported to bind to the G-box motifs in the SPL genomic loci (Jung et al, 2012), suggesting that the FT-FD module regulates SPL genes in the shoot apex in the control of flowering time. This hypothesis is supported by our observation that SPL3 expression was increased in the shoot apex regions of FD::FT plants, but remained unchanged in the leaves of SUC2::FT plants (Supplemental Fig.…”

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

“…This relay of information from GA to SOC1 occurs through degradation of the DELLA proteins RGA and RGL2 with a partial contribution from RGL1 (Cheng et al, 2004). In addition, GA has been shown to regulate flowering by interacting with photoperiod, ambient temperature and vernalization pathways (Galvão et al, 2015;Jung et al, 2012;Li et al, 2015;Osnato et al, 2012). The effect of GA is also spatially regulated.…”