Exogenous abscisic acid represses rice flowering via SAPK8-ABF1-Ehd1/Ehd2 pathway

Liqun Tang; Guanghao Li; Huimei Wang; Juan Zhao; Zhiyong Li; Xixi Liu; Yazhou Shu; Wanning Liu; Shuang Wang; Jie Huang; Jiezheng Ying; Xiaohong Tong; Wenya Yuan; Xiangjin Wei; Shaoqing Tang; Yifeng Wang; Qingyun Bu; Jian Zhang

doi:10.1016/j.jare.2023.06.012

Exogenous abscisic acid represses rice flowering via SAPK8-ABF1-Ehd1/Ehd2 pathway

J Adv Res. 2023 Jul 1:S2090-1232(23)00175-3. doi: 10.1016/j.jare.2023.06.012. Online ahead of print.

Authors

Liqun Tang¹, Guanghao Li¹, Huimei Wang¹, Juan Zhao¹, Zhiyong Li¹, Xixi Liu¹, Yazhou Shu¹, Wanning Liu¹, Shuang Wang¹, Jie Huang¹, Jiezheng Ying¹, Xiaohong Tong¹, Wenya Yuan², Xiangjin Wei¹, Shaoqing Tang¹, Yifeng Wang³, Qingyun Bu⁴, Jian Zhang⁵

Affiliations

¹ State key laboratory of rice biology and breeding, China National Rice Research Institute, Hangzhou 311400, China.
² Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
³ State key laboratory of rice biology and breeding, China National Rice Research Institute, Hangzhou 311400, China. Electronic address: wangyifeng@caas.cn.
⁴ Northeast Institute of Geography and Agroecology, Key Laboratory of Soybean Molecular Design Breeding, the Chinese Academy of Sciences, Harbin 150081, China; The Innovative Academy of Seed Design, the Chinese Academy of Sciences, Beijing 100101, China. Electronic address: buqingyun@iga.ac.cn.
⁵ State key laboratory of rice biology and breeding, China National Rice Research Institute, Hangzhou 311400, China. Electronic address: zhangjian@caas.cn.

PMID: 37399924
DOI: 10.1016/j.jare.2023.06.012

Abstract

Introduction: Rice flowering is a major agronomic trait, determining yield and ecological adaptability in particular regions. ABA plays an essential role in rice flowering, but the underlying molecular mechanism remains largely elusive.

Objectives: In this study, we demonstrated a "SAPK8-ABF1-Ehd1/Ehd2" pathway, through which exogenous ABA represses rice flowering in a photoperiod-independent manner.

Methods: We generated abf1 and sapk8 mutants using the CRISPR-Cas9 method. Using yeast two-hybrid, Pull down, BiFC and kinase assays, SAPK8 interacted and phosphorylated ABF1. ABF1 directly bound to the promoters of Ehd1 and Ehd2 using ChIP-qPCR, EMSA, and LUC transient transcriptional activity assay, and suppressed the transcription of these genes.

Results: Under both long day and short day conditions, simultaneous knock-out of ABF1 and its homolog bZIP40 accelerated flowering, while SAPK8 and ABF1 over-expression lines exhibited delayed flowering and hypersensitivity to ABA-mediated flowering repression. After perceiving the ABA signal, SAPK8 physically binds to and phosphorylates ABF1 to enhance its binding to the promoters of master positive flowering regulators Ehd1 and Ehd2. Upon interacting with FIE2, ABF1 recruited PRC2 complex to deposit H3K27me3 suppressive histone modification on Ehd1 and Ehd2 to suppress these genes transcription, thereby leading to later flowering.

Conclusion: Our work highlighted the biological functions of SAPK8 and ABF1 in ABA signaling, flowering control and the involvement of a PRC2-mediated epigenetic repression mechanism in the transcription regulation governed by ABF1 on ABA-mediated rice flowering repression.

Keywords: Abscisic acid; Flowering; Polycomb Repressive Complex 2 (PRC2); Rice (Oryza sativa L.); SnRK2; bZIP.