The GIGANTEA-ENHANCED EM LEVEL Complex Enhances Drought Tolerance via Regulation of Abscisic Acid Synthesis1[OPEN]

• Published in: Plant physiology (Bethesda) 2020-09, Vol.184 (1), p.443-458
• Main Authors: Baek, Dongwon, Kim, Woe-Yeon, Cha, Joon-Yung, Park, Hee Jin, Shin, Gilok, Park, Junghoon, Lim, Chae Jin, Chun, Hyun Jin, Li, Ning, Kim, Doh Hoon, Lee, Sang Yeol, Pardo, Jose M., Kim, Min Chul, Yun, Dae-Jin
• Format: Article
• Language: English
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.20.00779

The GIGANTEA-ENHANCED EM LEVEL complex enhances plant tolerance to drought by modulating the diurnal transcription of a gene encoding a rate-limiting enzyme in abscisic acid biosynthesis. Drought is one of the most critical environmental stresses limiting plant growth and crop productivity. The synthesis and signaling of abscisic acid (ABA), a key phytohormone in the drought stress response, is under photoperiodic control. GIGANTEA (GI), a key regulator of photoperiod-dependent flowering and the circadian rhythm, is also involved in the signaling pathways for various abiotic stresses. In this study, we isolated ENHANCED EM LEVEL (EEL)/basic Leu zipper 12, a transcription factor involved in ABA signal responses, as a GI interactor in Arabidopsis ( Arabidopsis thaliana ). The diurnal expression of 9-CIS-EPOXYCAROTENOID DIOXYGENASE 3 ( NCED3 ), a rate-limiting ABA biosynthetic enzyme, was reduced in the eel , gi-1 , and eel gi-1 mutants under normal growth conditions. Chromatin immunoprecipitation and electrophoretic mobility shift assays revealed that EEL and GI bind directly to the ABA-responsive element motif in the NCED3 promoter. Furthermore, the eel , gi-1 , and eel gi-1 mutants were hypersensitive to drought stress due to uncontrolled water loss. The transcript of NCED3 , endogenous ABA levels, and stomatal closure were all reduced in the eel , gi-1 , and eel gi-1 mutants under drought stress. Our results suggest that the EEL-GI complex positively regulates diurnal ABA synthesis by affecting the expression of NCED3 , and contributes to the drought tolerance of Arabidopsis.