Regulation and Identity of Florigen: FLOWERING LOCUS T Moves Center Stage

Abstract

The transition from vegetative to reproductive growth is controlled by day length in many plant species. Day length is perceived in leaves and induces a systemic signal, called florigen, that moves through the phloem to the shoot apex. At the shoot apical meristem (SAM), florigen causes changes in gene expression that reprogram the SAM to form flowers instead of leaves. Analysis of flowering of Arabidopsis thaliana placed the CONSTANS/FLOWERING LOCUS T (CO/FT ) module at the core of a pathway that promotes flowering in response to changes in day length. We describe progress in defining the molecular mechanisms that activate this module in response to changing day length and the increasing evidence that FT protein is a major component of florigen. Finally, we discuss conservation of FT function in other species and how variation in its regulation could generate different flowering behaviors.

A reverse genetics approach identifies novel mutants in light responses and anthocyanin metabolism in petunia

“…Using the obtained sequence information in a reverse genetics approach, we have identified a novel petunia mutant carrying a mutation in CCT (CO, CO-like, TOC1) domain (Strayer et al 2000;Valverde 2011). In Arabidopsis, the CONSTANS family of zinc finger proteins acts between the circadian clock and genes controlling meristem identity in the photoperiodic flowering pathway (Turck et al 2008). Arabidopsis is a facultative longday plant that flowers earlier under long days (LDs) than under short days (SDs), whereas in rice, flowering is induced by SDs (Thomas and Vince-Prue 1996).…”

“…Arabidopsis is a facultative longday plant that flowers earlier under long days (LDs) than under short days (SDs), whereas in rice, flowering is induced by SDs (Thomas and Vince-Prue 1996). Photoperiodicflowering induction in model plants occurs via internal and external coincidence model (Song et al 2010), where the coincidence between the levels of CO mRNA and the illuminated or dark period of the day activates the transcription of FLOWERING LOCUS T (FT ) or its orthologs, which, in turn, are involved in the control of meristem-identity genes, shifting from vegetative to reproductive development (Turck et al 2008;Song et al 2010). In day-neutral tomato, the FT ortholog, SINGLE FLOWER TRUSS (SFT ), has been demonstrated to trigger the systemic signal responsible for pleiotropic regulation of growth and flowering (Lifschitz et al 2006).…”

Higher plants use LOV to perceive blue light

“…This review will not cover our knowledge of circadian biology and of the regulation of flowering by the photoperiod (for recent reviews please consult [34][35][36]), but briefly describe the mode of action of this novel class of blue light photoreceptors.…”

“…FKF1 promotes the expression of CO a central element of day-length-regulated flowering [34,36,38]. The regulation of CO occurs both at the transcriptional and post-translational level involving multiple photoreceptors from distinct families [34,36,42,43].…”

“…The regulation of CO occurs both at the transcriptional and post-translational level involving multiple photoreceptors from distinct families [34,36,42,43]. CO transcription is regulated by day length while the protein is unstable in the dark and stabilized during the day [34,36]. FKF1 regulates the stability of Cycling Dof Factor 1 (CDF1), which directly represses CO expression [44].…”