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Plant Cell. 2019 Jul;31(7):1488-1505. doi: 10.1105/tpc.18.00450. Epub 2019 May 8.

Integration of Transcriptional Repression and Polycomb-Mediated Silencing of WUSCHEL in Floral Meristems.

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State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210023, China.
Biological Science, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara, 630-0192, Japan.
Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi-shi, Saitama, 332-0012, Japan.
Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6084.
Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore.
Biological Science, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara, 630-0192, Japan


Arabidopsis (Arabidopsis thaliana) floral meristems terminate after the carpel primordia arise. This is achieved through the temporal 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. 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, which is a known activator of WUS and can oppose polycomb repression. KNU also physically interacts with FERTILIZATION-INDEPENDENT ENDOSPERM, a key polycomb repressive complex2 component, and mediates the subsequent deposition of the repressive histone H3 lysine 27 trimethylation 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.

[Available on 2020-07-01]

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