Abstract
The transcription factor CONSTANS (CO) is a central component that promotes Arabidopsis flowering under long-day conditions (LDs). Here, we show that the microRNA319-regulated TEOSINTE BRANCHED/CYCLOIDEA/PCF (TCP) transcription factors promote photoperiodic flowering through binding to the CO promoter and activating its transcription. Meanwhile, these TCPs directly interact with the flowering activators FLOWERING BHLH (FBHs), but not the flowering repressors CYCLING DOF FACTORs (CDFs), to additively activate CO expression. Furthermore, both the TCPs and FBHs physically interact with the flowering time regulator PHYTOCHROME AND FLOWERING TIME 1 (PFT1) to facilitate CO transcription. Our findings provide evidence that a set of transcriptional activators act directly and additively at the CO promoter to promote CO transcription, and establish a molecular mechanism underlying the regulation of photoperiodic flowering time in Arabidopsis.
Highlights
Flowering is a transition from the vegetative to the reproductive phase in the plant life cycle, which is crucial for successful reproduction
We demonstrate that the microRNA319-regulated TEOSINTE BRANCHED/CYCLOIDEA/ PCF (TCP) transcription factors directly bind to the CO promoter
These TEOSINTE BRANCHED/CYCLOIDEA/PCF (TCP) physically interact with the flowering activators FLOWERING BHLH (FBHs) and the flowering regulator PHYTOCHROME AND FLOWERING TIME 1 (PFT1) to form a complex to activate CO transcription and promote photoperiodic flowering under long-day conditions (LDs)
Summary
Flowering is a transition from the vegetative to the reproductive phase in the plant life cycle, which is crucial for successful reproduction. Genetic approaches in the model plant Arabidopsis, in which flowering is often promoted under long-day (LD) but is delayed during short-day (SD) conditions, reveal that CONSTANS (CO) plays crucial roles in photoperiod monitoring and flowering time determination [1,2,3]. Under LDs, CO displays a biphasic diurnal expression pattern that its transcript levels first rise at the late afternoon to form a small peak in the light period, and a second peak appears during the midnight [5]. The induction of CO mRNA levels at dusk under LDs but not the peak expression at night is essential for the CO protein accumulation and subsequent photoperiodic flowering promotion
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