AUTHOR=Steinbach Yvonne 

TITLE=The Arabidopsis thalianaCONSTANS-LIKE 4 (COL4) – A Modulator of Flowering Time

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00651

DOI=10.3389/fpls.2019.00651

ISSN=1664-462X

ABSTRACT=<p>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 <italic>FLOWERING LOCUS T</italic> (<italic>FT</italic>) 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 <italic>CONSTANS</italic>-<italic>LIKE 4</italic> (<italic>COL4)</italic>, 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 <italic>FT</italic> and <italic>FT</italic>-like genes as well as on <italic>SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1</italic> (<italic>SOC1</italic>). Reduction of <italic>COL4</italic> expression level leads to an increase of <italic>FT</italic> and <italic>APETALA 1</italic> (<italic>AP1</italic>) expression and to accelerated flowering, while the increase of <italic>COL4</italic> 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.</p>