Transcription Factor Interplay between LEAFY and APETALA1/CAULIFLOWER during Floral Initiation

Abstract

The transcription factors LEAFY (LFY) and APETALA1 (AP1), together with the AP1 paralog CAULIFLOWER (CAL), control the onset of flower development in a partially redundant manner. This redundancy is thought to be mediated, at least in part, through the regulation of a shared set of target genes. However, whether these genes are independently or cooperatively regulated by LFY and AP1/CAL is currently unknown. To better understand the regulatory relationship between LFY and AP1/CAL and to obtain deeper insights into the control of floral initiation, we monitored the activity of LFY in the absence of AP1/CAL function. We found that the regulation of several known LFY target genes is unaffected by AP1/CAL perturbation, while others appear to require AP1/CAL activity. Furthermore, we obtained evidence that LFY and AP1/CAL control the expression of some genes in an antagonistic manner. Notably, these include key regulators of floral initiation such as (), which had been previously reported to be directly repressed by both LFY and AP1. We show here that expression is suppressed by AP1 but promoted by LFY. We further demonstrate that LFY has an inhibitory effect on flower formation in the absence of AP1/CAL activity. We propose that LFY and AP1/CAL act as part of an incoherent feed-forward loop, a network motif where two interconnected pathways or transcription factors act in opposite directions on a target gene, to control the establishment of a stable developmental program for the formation of flowers.

LEAFY is a pioneer transcription factor and licenses cell reprogramming to floral fate

“…Although LFY alone is sufficient to activate AP1 78, 79 , accumulation of this floral commitment factor is delayed relative LFY activity. Under floral inductive conditions in inflorescences AP1 upregulation occurs two to three days after that of LFY 52, 80, 81 . The delay in AP1 upregulation is of biological significance as it enables formation of branches prior to the irreversible switch to flower fate 52 .…”

Plant Inflorescence Architecture: The Formation, Activity, and Fate of Axillary Meristems

“…Other related MADS box proteins, such as CAULIFLOWER (CAL) and FRUITFULL (FUL) also promote determinacy (Ferrandiz et al 2000). In addition, consistent with its role in floral commitment, AP1 directly silences TFL1 with assistance from the SEPALLATA family transcription factor SEP4 (Ferrandiz et al 2000;Kaufmann et al 2010;Liu et al 2013;Serrano-Mislata et al 2016;Goslin et al 2017). Because of its role in the switch to reproductive development (inflores-cence formation), the role of FT in promoting floral fate is difficult to assess (Yamaguchi et al 2014).…”

Crosstalk in the darkness: bulb vernalization activates meristem transition via circadian rhythm and photoperiodic pathway

“…The onset of flower development in Arabidopsis is controlled by the interplay between LEAFY (LFY), APETALA1 (AP1) and its paralog CAULIFLOWER (CAL) [24]. We have already shown that garlic homolog of LFY (gaLFY) acts as a key-gene in the floral transition, as well as in inflorescence and flower differentiation [77].…”