School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, Republic of Korea
School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, Republic of Korea
Yupeng Yang
Shanghai Center for Plant Stress Biology & National Key Laboratory for Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
Xiao Luo
Peking University Institute of Advanced Agricultural Sciences, Weifang, China
School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, Republic of Korea
School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, Republic of Korea
Youbong Hyun
School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, Republic of Korea
Yuehui He
Shanghai Center for Plant Stress Biology & National Key Laboratory for Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China; Peking University Institute of Advanced Agricultural Sciences, Weifang, China
School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, Republic of Korea
To synchronize flowering time with spring, many plants undergo vernalization, a floral-promotion process triggered by exposure to long-term winter cold. In Arabidopsis thaliana, this is achieved through cold-mediated epigenetic silencing of the floral repressor, FLOWERING LOCUS C (FLC). COOLAIR, a cold-induced antisense RNA transcribed from the FLC locus, has been proposed to facilitate FLC silencing. Here, we show that C-repeat (CRT)/dehydration-responsive elements (DREs) at the 3′-end of FLC and CRT/DRE-binding factors (CBFs) are required for cold-mediated expression of COOLAIR. CBFs bind to CRT/DREs at the 3′-end of FLC, both in vitro and in vivo, and CBF levels increase gradually during vernalization. Cold-induced COOLAIR expression is severely impaired in cbfs mutants in which all CBF genes are knocked-out. Conversely, CBF-overexpressing plants show increased COOLAIR levels even at warm temperatures. We show that COOLAIR is induced by CBFs during early stages of vernalization but COOLAIR levels decrease in later phases as FLC chromatin transitions to an inactive state to which CBFs can no longer bind. We also demonstrate that cbfs and FLCΔCOOLAIR mutants exhibit a normal vernalization response despite their inability to activate COOLAIR expression during cold, revealing that COOLAIR is not required for the vernalization process.
