APETALA2 (AP2) is best known for its function in the outer two floral whorls, where it specifies the identities of sepals and petals by restricting the expression of AGAMOUS (AG) to the inner two whorls in Arabidopsis thaliana. Here, we describe a role of AP2 in promoting the maintenance of floral stem cell fate, not by repressing AG transcription, but by antagonizing AG activity in the center of the flower. We performed a genetic screen with ag-10 plants, which exhibit a weak floral determinacy defect, and isolated a mutant with a strong floral determinacy defect. This mutant was found to harbor another mutation in AG and was named ag-11. We performed a genetic screen in the ag-11 background to isolate mutations that suppress the floral determinacy defect. Two suppressor mutants were found to harbor mutations in AP2. While AG is known to shut down the expression of the stem cell maintenance gene WUSCHEL (WUS) to terminate floral stem cell fate, AP2 promotes the expression of WUS. AP2 does not repress the transcription of AG in the inner two whorls, but instead counteracts AG activity.
[1]Hunan Agr Univ, Hunan Prov Key Lab Phytohormones & Growth Dev, Hunan Prov Key Lab Crop Germplasm Innovat & Utili, Changsha 410128, Hunan, Peoples R China.
[2]Univ Calif Riverside, Dept Bot & Plant Sci, Inst Integrat Genome Biol, Riverside, CA 92521 USA.
[3]Nanjing Agr Univ, Coll Hort, 1 Weigang, Nanjing 210095, Jiangsu, Peoples R China.
[4]Fudan Univ, State Key Lab Genet Engn, Collaborat Innovat Ctr Genet & Dev, Inst Plant Biol,Sch Life Sci, Shanghai 200438, Peoples R China.
[5]Chinese Acad Sci, Inst Genet & Dev Biol, Ctr Agr Resources Res, State Key Lab Plant Cell & Chromosome Engn, Shijiazhuang 050021, Peoples R China.
[6]Shenzhen Univ, Coll Life Sci & Oceanog, Guangdong Prov Key Lab Plant Epigenet, Shenzhen 518060, Peoples R China.
[7]Univ Calif Riverside, Howard Hughes Med Inst, Riverside, CA 92521 USA.
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