Sequential action of FRUITFULL as a modulator of the activity of the floral regulators SVP and SOC1

Vicente Balanzà,Irene Martínez-Fernández,Cristina Ferrándiz

doi:10.1093/jxb/ert482

Abstract

The role in flowering time of the MADS-box transcription factor fruitfulL (FUL) has been proposed in many works. FUL has been connected to several flowering pathways as a target of the photoperiod, ambient temperature, and age pathways and it is has been shown to promote flowering in a partially redundant manner with suppressor of overexpression of constans 1 (SOC1). However, the position of FUL in these genetic networks, as well as the functional output of FUL activity during floral transition, remains unclear. In this work, a genetic approach has been undertaken to understand better the functional hierarchies involving FUL and other MADS-box factors with well established roles as floral integrators such as SOC1, short vegetative phase (svp) or flowering locus C (FLC). Our results suggest a prominent role of FUL in promoting reproductive transition when photoinductive signalling is suppressed by short-day conditions or by high levels of FLC expression, as in non-vernalized winter ecotypes. A model is proposed where the sequential formation of FUL-SVP and FUL-SOC1 heterodimers may mediate the vegetative and meristem identity transitions, counteracting the repressive effect of FLC and SVP on flowering.

Highlights

Arabidopsis thaliana adult life cycle comprises three major phase transitions that are mainly characterized by the identity of the lateral structures produced by the shoot apical meristem (SAM)
The results presented in this study show that FUL participates in both reproductive and meristem identity transitions modulating the activity of MADS-box factors with major regulatory roles in these phase changes
FUL and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) share common upstream regulators, as they are both activated by the FT–FD complex and repressed by SHORT VEGETATIVE PHASE (SVP) (Lee et al, 2007; Li et al, 2008; Torti and Fornara, 2012)

Summary

Introduction

Arabidopsis thaliana adult life cycle comprises three major phase transitions that are mainly characterized by the identity of the lateral structures produced by the shoot apical meristem (SAM). The vegetative phase transition marks the change from the production of juvenile leaves to the production of adult leaves Both types of leaves form a rosette through the period of vegetative growth of the plant and, triggered by both environmental and endogenous cues, the SAM undergoes two subsequent phase transitions leading to reproductive development: the reproductive transition that causes bolting of the primary inflorescence and the production of cauline leaves subtending secondary inflorescences, and the meristem identity transition, after which the SAM will produce floral meristems directly (Araki, 2001; Yamaguchi et al, 2009; Huijser and Schmid, 2011). All these pathways converge at the level of a few genes, named floral transition integrators

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Conclusion