PT  - JOURNAL ARTICLE
AU  - Run Jin
AU  - Samantha Klasfeld
AU  - Meilin Fernandez Garcia
AU  - Jun Xiao
AU  - Soon-Ki Han
AU  - Adam Konkol
AU  - Yang Zhu
AU  - Doris Wagner
TI  - LEAFY is a pioneer transcription factor and licenses cell reprogramming to floral fate
AID  - 10.1101/2020.03.16.994418
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.03.16.994418
4099  - http://biorxiv.org/content/early/2020/03/18/2020.03.16.994418.short
4100  - http://biorxiv.org/content/early/2020/03/18/2020.03.16.994418.full
AB  - Master transcription factors reprogram cell fate in multicellular eukaryotes. Pioneer transcription factors have prominent roles in this process because of their ability to contact their cognate binding motifs in closed chromatin. Reprogramming is pervasive in plants, whose development is plastic and tuned by the environment, yet no bonafide pioneer transcription factor has - been identified in this kingdom. Here we show that the master transcription factor LEAFY (LFY), which promotes floral fate through upregulation of the floral commitment factor APETALA1 (AP1), is a pioneer transcription factor. In vitro, LFY binds in a sequence-specific manner and with high affinity to the endogenous AP1 target locus DNA assembled into a nucleosome. In vivo, LFY associates with nucleosome occupied binding sites at the majority of its target loci, including AP1, where it co-occupies DNA with histones. Moreover, the LFY DNA contact helix shares defining properties with those of strong nucleosome binding pioneer factors. At the AP1 locus, LFY unlocks chromatin locally by displacing the H1 linker histone and by recruiting SWI/SNF chromatin remodelers, but broad changes in chromatin accessibility occur later and require activity of additional, non-pioneer transcription, factors. Our study provides a mechanistic framework for patterning of inflorescence architecture and uncovers striking similarities between plant and animal pioneer transcription factors. Further analyses aimed at elucidating the defining characteristics of pioneer transcription factors will allow harnessing these for enhanced cell fate reprogramming.