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

Citation:

Jin, J., Klasfeld, S., Zhu, Y., Fernandez Garcia, M., Xiao, J., Han, S.K., Konkol, A., Zhu, Y. & Wagner, D. (2021). LEAFY is a pioneer transcription factor and licenses cell reprogramming to floral fate. Nature Communications, 12(1), 626.


Abstract:

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 little is known about pioneer transcription factors 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 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. Upon binding, 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. Our study provides a mechanistic framework for patterning of inflorescence architecture and uncovers striking similarities between LFY and animal pioneer transcription factor.

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Press Release

Molecular regulation of plant developmental transitions and plant architecture via PEPB family proteins – an update on mechanism of action

Citation:

Zhu, Y., Klasfeld, S., & Wagner, D. (2021). Molecular regulation of plant developmental transitions and plant architecture via PEPB family proteins–an update on mechanism of action. Journal of Experimental Botany, eraa598


Abstract:

This year marks the 100 th anniversary of the experiments by Garner and Allard (Garner and Allard, 1920) that showed that plants measure the duration of the night and day (the photoperiod) to time flowering. This discovery led to the identification of Flowering Locus T (FT) in Arabidopsis and Heading Date 3a (Hd3a) in rice as a mobile signal that promotes flowering in tissues distal to the site of cue perception. FT/Hd3a belong to the family of phosphatidylethanolamine binding proteins (PEBPs). Collectively, these proteins control plant developmental transitions and plant architecture. Several excellent recent reviews have focused on the roles of PEBP proteins in diverse plant species; here we will primarily highlight recent advances that enhance our understanding of the mechanism of action of PEBP proteins and discuss critical open questions.

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TERMINAL FLOWER 1-FD complex target genes and competition with FLOWERING LOCUS T

Citation:

Zhu, Y., Klasfeld, S., Jeong, C.W., Jin, R., Goto, K., Yamaguchi, N., & Wagner, D.(2020). TERMINAL FLOWER 1-FD complex target genes and competition with FLOWERING LOCUS T. Nature Communications, 11(2), 5118.


Abstract:

Plants monitor seasonal cues to optimize reproductive success by tuning onset of reproduction and inflorescence architecture. TERMINAL FLOWER 1 (TFL1) and FLOWERING LOCUS T (FT) and their orthologs antagonistically regulate these life history traits, yet their mechanism of action, antagonism and targets remain poorly understood. Here, we show that TFL1 is recruited to thousands of loci by the bZIP transcription factor FD. We identify the master regulator of floral fate, LEAFY (LFY) as a target under dual opposite regulation by TFL1 and FT and uncover a pivotal role of FT in promoting flower fate via LFY upregulation. We provide evidence that the antagonism between FT and TFL1 relies on competition for chromatin-bound FD at shared target loci. Direct TFL1-FD regulated target genes identify this complex as a hub for repressing both master regulators of reproductive development and endogenous signalling pathways. Our data provide mechanistic insight into how TFL1-FD sculpt inflorescence architecture, a trait important for reproductive success, plant architecture and yield.

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Press Release

Dr. Doris Wagner becomes monitoring editor for SCIENCE ADVANCES

Communication in science is of utmost importance for scientific advancement. Science Advances is an online-only gold open access journal from American Association for the Advancement of Science (AAAS), the publisher of Science. Debuty Editor, Dr. Elizabeth Haswell, is heading up a brand new editorial pod dedicated to plant biology and she chose fantastic editors including Dr. Doris Wagner of the Wagner Lab. Others on the team include Dr. John McDowell, Dr. Mary Lou Guerinot, Dr. Thorsten Hamann, Dr. Keiko Sugimoto, Dr. Elizabeth Kellogg, and Dr. Sarah O’Connor.

START OF A NEW DECADE

The Wagner Lab escaped campus and celebrated the start of 2020 with a warm fire, delicious dinner, and a silly white elephant game. Cheers were made as we look forward to future graduations and publications.

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

Citation:

Zhu, Y., & Wagner, D. (2020). Plant inflorescence architecture: the formation, activity, and fate of axillary meristems. Cold Spring Harbor perspectives in biology12(1), a034652.


Abstract:

The above-ground plant body in different plant species can have very distinct forms or architectures that arise by recurrent redeployment of a finite set of building blocks—leaves with axillary meristems, stems or branches, and flowers. The unique architectures of plant inflorescences in different plant families and species, on which this review focuses, determine the reproductive success and yield of wild and cultivated plants. Major contributors to the inflorescence architecture are the activity and developmental trajectories adopted by axillary meristems, which determine the degree of branching and the number of flowers formed. Recent advances in genetic and molecular analyses in diverse flowering plants have uncovered both common regulatory principles and unique players and/or regulatory interactions that underlie inflorescence architecture. Modulating activity of these regulators has already led to yield increases in the field. Additional insight into the underlying regulatory interactions and principles will not only uncover how their rewiring resulted in altered plant form, but will also enhance efforts at optimizing plant architecture in desirable ways in crop species.

Full Text

Integration of transcriptional repression and Polycomb-mediated silencing of WUSCHEL in floral meristems.

Citation:

Sun, B., Zhou, Y., Cai, J., Shang, E., Yamaguchi, N., Xiao, J., Looi, L.S., Wee, W.Y., Gao, X., Wagner, D. & Ito, T. (2019). Integration of transcriptional repression and Polycomb-mediated silencing of WUSCHEL in floral meristems. The Plant Cell, tpc-00450.

Abstract:

Arabidopsis floral meristems terminate after the carpel primordia arise. This is achieved through the timed repression of WUSCHEL (WUS), which is essential for stem cell maintenance. At floral stage 6, WUS is repressed by KNUCKLES (KNU), a repressor directly activated by AGAMOUS (AG). KNU was suggested to repress WUS through histone deacetylation. However, how the changes in the chromatin state of WUS are initiated and maintained to terminate the floral meristem remains elusive. Here, we show that KNU integrates initial transcriptional repression with polycomb-mediated stable silencing of WUS. After KNU is induced, it binds to the WUS promoter and causes eviction of SPLAYED (SYD), which is a known activator of WUS and can act in opposition to polycomb repression. KNU also physically interacts with FERTILIZATION-INDEPENDENT ENDOSPERM (FIE), a key PRC2 component, and mediates the subsequent deposition of the repressive histone H3 lysine 27 tri-methylation (H3K27me3) for stable silencing of WUS. This multi-step silencing of WUS leads to the termination of floral stem cells, ensuring proper carpel development. Thus, our work describes a detailed mechanism for heritable floral stem cell termination in a precise spatiotemporal manner.

Notes:

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Auxin Response Factors promote organogenesis by chromatin-mediated repression of the pluripotency gene SHOOTMERISTEMLESS

Citation:

Chung, Y., Zhu, Y., Wu, M., Simoni, S., Kuhn, A., Armenta-Medine, A., Jin, R., Østergaard, L., Gillmor, C.S., Wagner, D. (2019). Auxin Response Factors promote organogenesis by chromatin-mediated repression of the pluripotency gene SHOOTMERISTEMLESS. Nature Communications, 10(1), 886.

Abstract:

Specification of new organs from transit amplifying cells is critical for higher eukaryote development. In plants, a central stem cell pool maintained by the pluripotency factor SHOOTMERISTEMLESS (STM), is surrounded by transit amplifying cells competent to respond to auxin hormone maxima by giving rise to new organs. Auxin triggers flower initiation through Auxin Response Factor (ARF) MONOPTEROS (MP) and recruitment of chromatin remodelers to activate genes promoting floral fate. The contribution of gene repression to reproductive primordium initiation is poorly understood. Here we show that downregulation of the STM pluripotency gene promotes initiation of flowers and uncover the mechanism for STM silencing. The ARFs ETTIN (ETT) and ARF4 promote organogenesis at the reproductive shoot apex in parallel with MP via histone-deacetylation mediated transcriptional silencing of STM. ETT and ARF4 directly repress STM, while MP acts indirectly, through its target FILAMENTOUS FLOWER (FIL). Our data suggest that – as in animals- downregulation of the pluripotency program is important for organogenesis in plants.

Notes:

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