DAY NEUTRAL FLOWERING does not act through GIGANTEA and FKF1 to regulate CONSTANS expression and flowering time.

The regulation of CONSTANS (CO) gene expression and protein levels is the critical factor in determining a plant's response to photoperiod, flowering is induced when high levels of CO protein are present in the light. The regulation of CO transcription is mediated in part by GIGANTEA (GI), FKF1 and the CYCLING DOF FACTORS (CDFs) and factors affecting the levels of these proteins will also affect CO expression. The DAY NEUTRAL FLOWERING (DNF) protein is an E3 ligase involved in repressing CO expression in the early part of the day. In this article we present evidence to support the argument that DNF is not acting through the GI/FKF1/CDF regulatory mechanism to repress CO expression, but that it acts on another transcriptional activator of CO.