Photoperiodic Control of Carbon Distribution during the Floral Transition inArabidopsis

M Isabel Ortiz-Marchena,Federico Valverde,Beatriz Cano,Fatima E Said,José M Romero,Eva Lucas-Reina,Tomás Albi,Francisco J Romero-Campero,M Teresa Ruiz

doi:10.1105/tpc.114.122721

M Isabel Ortiz-Marchena, Federico Valverde + Show 7 more

Open Access

https://doi.org/10.1105/tpc.114.122721

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Abstract

Flowering is a crucial process that demands substantial resources. Carbon metabolism must be coordinated with development through a control mechanism that optimizes fitness for any physiological need and growth stage of the plant. However, how sugar allocation is controlled during the floral transition is unknown. Recently, the role of a CONSTANS (CO) ortholog (Cr-CO) in the control of the photoperiod response in the green alga Chlamydomonas reinhardtii and its influence on starch metabolism was demonstrated. In this work, we show that transitory starch accumulation and glycan composition during the floral transition in Arabidopsis thaliana are regulated by photoperiod. Employing a multidisciplinary approach, we demonstrate a role for CO in regulating the level and timing of expression of the GRANULE BOUND STARCH SYNTHASE (GBSS) gene. Furthermore, we provide a detailed characterization of a GBSS mutant involved in transitory starch synthesis and analyze its flowering time phenotype in relation to its altered capacity to synthesize amylose and to modify the plant free sugar content. Photoperiod modification of starch homeostasis by CO may be crucial for increasing the sugar mobilization demanded by the floral transition. This finding contributes to our understanding of the flowering process.

Highlights

The plant life cycle is strongly influenced by environmental conditions, which affect the plant’s capacity to obtain energy for growth and development (Nicotra et al, 2010)
We describe that the dynamic response of starch polymer to daylength is regulated by CO through the modification of GRANULE BOUND STARCH SYNTHASE (GBSS) expression during the floral transition
As we were interested in establishing if the starch accumulation pattern (Lu et al, 2005; Gibon et al, 2009) was influenced by the floral stage of the plant, we measured the amount of plant starch in Arabidopsis leaves every 4 h for 24 h in light/8-h-dark cycle (LD) and SD, 2 d before and 2 d after the appearance of the floral bud (Figure 1A)

Summary

Introduction

The plant life cycle is strongly influenced by environmental conditions, which affect the plant’s capacity to obtain energy for growth and development (Nicotra et al, 2010). The floral transition is a crucial developmental decision for a plant because failing to produce a reproductive signal at the correct time of the year seriously limits its capacity to yield descendants, and, for this reason, this process is strictly regulated (Casal et al, 2004). Based on an analysis of flowering time mutants in Arabidopsis thaliana, a network of genes involved in the regulation of the floral transition was identified (Koornneef et al, 1991). These genes respond to different external stimuli and generate inductive or inhibitory signal cascades whose equilibrium decides the reproductive fate of the plant (Fornara et al, 2010).

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