PSC Frontier Seminar series
Title: Timed Termination of Floral Stem Cell in Arabidopsis
Speaker: Prof. Bo Sun, College of Life Sciences, Nanjing University
Time: 4:00 pm
Day/Date: December 18th, 2019 (Wednesday)
Host: Prof. Yuehui HE
Venue: PSC Auditorium
In Arabidopsis, the floral meristem is essential for the production of floral organs. The floral meristem is initially maintained to contribute cells for floral organ formation. However, this stem cell activity needs be completely terminated at a certain floral developmental stage to ensure the proper development of floral reproductive organs. This is achieved through the temporal repression of WUSCHEL (WUS), which is responsible 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. We show that KNU integrates initial transcriptional repression with polycomb-mediated stable silencing of WUS. KNU 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 FERTILIZATIONINDEPENDENT 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.