The Arabidopsis thaliana CONSTANS-LIKE 4 (COL4) - A Modulator of Flowering Time.

Yvonne Steinbach

doi:10.3389/fpls.2019.00651

Abstract

Appropriate control of flowering time is crucial for crop yield and the reproductive success of plants. Flowering can be induced by a number of molecular pathways that respond to internal and external signals. In Arabidopsis, expression of the key florigenic signal FLOWERING LOCUS T (FT) is positively regulated by CONSTANS (CO) a BBX protein sharing high sequence similarity with 16 CO-like proteins. Within this study, we investigated the role of the Arabidopsis CONSTANS-LIKE 4 (COL4), whose role in flowering control was unknown. We demonstrate that, unlike CO, COL4 is a flowering repressor in long days (LD) and short days (SD) and acts on the expression of FT and FT-like genes as well as on SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). Reduction of COL4 expression level leads to an increase of FT and APETALA 1 (AP1) expression and to accelerated flowering, while the increase of COL4 expression causes a flowering delay. Further, the observed co-localization of COL4 protein and CO in nuclear speckles supports the idea that the two act as an antagonistic pair of transcription factors. This interaction may serve the fine-tuning of flowering time control and other light dependent plant developmental processes.

Highlights

Flowering is controlled by a network of well-established molecular pathways, which respond to internal and external signals, such as cold, light duration and quality, ambient temperature, as well as biotic and abiotic stresses
This effect was stronger in short days (SD) (Figure 1D), where both alleles flowered around 14 days earlier compared to wild-type (118 ± 3.4 days to bolting (DTB))
For plants the exact regulation of flowering time is critical for their reproductive success, whereby CO acts as a key activator of flowering in Arabidopsis and other plant species

Summary

Introduction

Flowering is controlled by a network of well-established molecular pathways, which respond to internal and external signals, such as cold, light duration and quality, ambient temperature, as well as biotic and abiotic stresses (reviewed in: Andres and Coupland, 2012; Matsoukas et al, 2012; Leijten et al, 2018). In Arabidopsis, flowering is promoted mainly by the expression of the flowering integrators FLOWERING LOCUS T (FT), SUPPRESSOR OF CONSTANS 1 (SOC1/ AGL20) and, redundantly to FT, it’s homolog TWIN SISTER OF FT (TSF) (Suarez-Lopez et al, 2001; An et al, 2004; Valverde et al, 2004; Yamaguchi et al, 2005). In the SAM, the formation of an FD-14-3-3 complex with FT or ATC and the other FT-homolog TERMINAL FLOWER 1 (TFL), induces or delays flowering, respectively, by changing the expression of the meristem identity genes APETALA1 (AP1) and CAULIFLOWER (CAL) as well as LEAFY (LFY) and AGAMOUS-LIKE 24 (AGL24) (Abe et al, 2005; Liu et al, 2008; Hanano and Goto, 2011; Taoka et al, 2011). Reduction in CO level leads to late flowering in LD while overexpression promotes flowering in LD and SD (Putterill et al, 1995; Onouchi et al, 2000; Robson et al, 2001; Takada and Goto, 2003; Jang et al, 2008)

Methods

Results

Conclusion