PWR/HDA9/ABI4 Complex Epigenetically Regulates ABA Dependent Drought Stress Tolerance in Arabidopsis.

Irfan Ullah Khan,Haris Ali Khan,Masood Jan,Shah Zareen,Chae Jin Lim,Dae-Jin Yun,Akhtar Ali,Woe Yeon Kim,Sang Yeol Lee,Jose M Pardo,Dongwon Baek,Junghoon Park

doi:10.3389/fpls.2020.00623

Abstract

Drought stress adversely affects plant growth and development and significantly reduces crop productivity and yields. The phytohormone abscisic acid (ABA) rapidly accumulates in response to drought stress and mediates the expression of stress-responsive genes that help the plant to survive dehydration. The protein Powerdress (PWR), which interacts with Histone Deacetylase 9 (HDA9), has been identified as a critical component regulating plant growth and development, flowering time, floral determinacy, and leaf senescence. However, the role and function of PWR and HDA9 in abiotic stress response had remained elusive. Here we report that a complex of PWR and HDA9 interacts with ABI4 and epigenetically regulates drought signaling in plants. T-DNA insertion mutants of PWR and HDA9 are insensitive to ABA and hypersensitive to dehydration. Furthermore, the expression of ABA-responsive genes (RD29A, RD29B, and COR15A) is also downregulated in pwr and hda9 mutants. Yeast two-hybrid assays showed that PWR and HDA9 interact with ABI4. Transcript levels of genes that are normally repressed by ABI4, such as CYP707A1, AOX1a and ACS4, are increased in pwr. More importantly, during dehydration stress, PWR and HDA9 regulate the acetylation status of the CYP707A1, which encodes a major enzyme of ABA catabolism. Taken together, our results indicate that PWR, in association with HDA9 and ABI4, regulates the chromatin modification of genes responsible for regulation of both the ABA-signaling and ABA-catabolism pathways in response to ABA and drought stress.

Highlights

During their life cycles, plants are continuously exposed to environmental challenges including light, heat, cold, flooding, high salinity, and drought stress
We detected no difference in acetyl histone H3 (AcH3) levels in the CYP707A2 promoter during dehydration stress in the pwr mutant compared with the wild type (WT) (Supplementary Figure S4C). These results indicated that during drought stress, PWR and Histone Deacetylase 9 (HDA9) repress the expression of CYP707A1 through histone deacetylation to allow abscisic acid (ABA) accumulation, and that the P1 region is important for the activation or repression of CYP707A1 during drought stress
SANTb-domain proteins such as PWR preferentially bind to acetylated histone Histone 3 (H3) but not H4

Summary

Introduction

Plants are continuously exposed to environmental challenges including light, heat, cold, flooding, high salinity, and drought stress. Drought stress results in considerable damage to plant growth, and more than 40% of crop production is lost to drought (Guy et al, 1985; May et al, 1998; Hasegawa et al, 2000). Upon exposure to drought stress, plants initiate the expression of resistance genes and subsequent activation of signaling pathways. Plants have developed complex molecular and signaling mechanisms to adapt to water deficit condition. They respond to drought stress either through osmotic adjustment and regulation of ion homeostasis or by controlling the damage repair system and the detoxification and removal of reactive oxygen species (ROS) (Shinozaki and Yamaguchi-Shinozaki, 2000; Zhu, 2002). The molecular and biochemical mechanism of these signaling pathways are not yet fully understood

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Conclusion