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Authors: Ronald J. Myers, María Ángeles Peláez-Vico and Yosef Fichman.
Plant, Cell & Environment (2024)
One-sentence summary: Reactive oxygen species waves can be triggered by varying types of stress stimuli in local tissues and spread from cell to cell to induce systemic acclimation.
Abstract: "Reactive oxygen species (ROS) play a critical role in plant development and stress responses, acting as key components in rapid signalling pathways. The ‘ROS wave’ triggers essential acclimation processes, ultimately ensuring plant survival under diverse challenges. This review explores recent advances in understanding the composition and functionality of the ROS wave within plant cells. During their initiation and propagation, ROS waves interact with other rapid signalling pathways, hormones and various molecular compounds. Recent research sheds light on the intriguing lack of a rigid hierarchy governing these interactions, highlighting a complex interplay between diverse signals. Notably, ROS waves culminate in systemic acclimation, a crucial outcome for enhanced stress tolerance. This review emphasizes the versatility of ROS, which act as flexible players within a network of short- and long-term factors contributing to plant stress resilience. Unveiling the intricacies of these interactions between ROS and various signalling molecules holds immense potential for developing strategies to augment plant stress tolerance, contributing to improved agricultural practices and overall ecosystem well-being."
Authors: Ryo Tachibana, Susumu Abe, Momo Marugami, Ayumi Yamagami, Rino Akema, Takao Ohashi, Kaisei Nishida, Shohei Nosaki, Takuya Miyakawa, Masaru Tanokura, Jong-Myong Kim, Motoaki Seki, Takehito Inaba, Minami Matsui, Kentaro Ifuku, Tetsuo Kushiro, Tadao Asami & Takeshi Nakano
Nature Communications (2023)
Editor's view: The authors identify BPG4, a novel regulator of chloroplast development. BPG4 directly suppresses transcriptional activity of GLK to fine-tune photosynthesis associated nuclear gene expression, and regulates chloroplast development and homeostasis.
Abstract: "Chloroplast development adapts to the environment for performing suitable photosynthesis. Brassinosteroids (BRs), plant steroid hormones, have crucial effects on not only plant growth but also chloroplast development. However, the detailed molecular mechanisms of BR signaling in chloroplast development remain unclear. Here, we identify a regulator of chloroplast development, BPG4, involved in light and BR signaling. BPG4 interacts with GOLDEN2-LIKE (GLK) transcription factors that promote the expression of photosynthesis-associated nuclear genes (PhANGs), and suppresses their activities, thereby causing a decrease in the amounts of chlorophylls and the size of light-harvesting complexes. BPG4 expression is induced by BR deficiency and light, and is regulated by the circadian rhythm. BPG4 deficiency causes increased reactive oxygen species (ROS) generation and damage to photosynthetic activity under excessive high-light conditions. Our findings suggest that BPG4 acts as a chloroplast homeostasis factor by fine-tuning the expression of PhANGs, optimizing chloroplast development, and avoiding ROS generation."
Authors: Ying Liu and Guohua Xu.
Molecular Plant (2023)
Excerpts: "Song et al. (2023) discovered that N-induced tillering relies on a balance between N and Fe status in rice. More importantly, a central transcriptional regulator of rice N signaling, NIN-LIKE PROTEIN 4 (OsNLP4) (Wu et al., 2021), plays a vital role in this process. The authors found that OsNLP4 directly regulates the expression of a large set of genes involved in N and Fe uptake, utilization, and signaling pathways, thus coordinating N–Fe balance in rice. Further investigation revealed that OsNLP4 can bind to the promoter of the strigolactone (SL) signaling gene OsD3, repressing its expression to shut down SL signaling, stimulate tillering, and improve yield (Song et al., 2023). These results highlight OsNLP4 as a vital integrator that coordinates rice tillering and productivity with external N and Fe availability (Figure 1)."
"Under balanced N–Fe conditions, the nuclear retention of OsNLP4 is promoted in a nitrate-dependent manner, which allows OsNLP4 to activate the expression of a large set of genes involved in N and Fe uptake and utilization and suppress D3 expression and SL signaling, thus stimulating tillering and improving grain yield in rice (Song et al., 2023). An appropriate N–Fe balance also enables OsNLP4 to up-regulate the expression of several ROS-scavenging genes and reduce ROS (H2O2) levels in rice."
Authors: Ruizhen Yang, Ziyi Yang, Meng Xing, Yexing Jing, Yunwei Zhang, Kewei Zhang, Yun Zhou, Huixian Zhao, Weihua Qiao and Jiaqiang Sun.
Journal of Genetics and Genomics (2023)
Abstract: "Brassinosteroids (BRs) are vital plant steroid hormones involved in numerous aspects of plant life including growth, development, and responses to various stresses. However, the underlying mechanisms of how BR regulates abiotic stress responses in wheat (Triticum aestivum L.) remain to be elucidated. Here, we find that BR signal core transcription factor BRASSINAZOLE-RESISTANT1 (TaBZR1) is significantly up-regulated by salt treatment. Overexpression of Tabzr1-1D (a gain-of-function TaBZR1 mutant protein) improves wheat salt tolerance. Furthermore, we show that TaBZR1 binds directly to the G-box motif in the promoter of ABA biosynthesis gene TaNCED3 to activate its expression and promotes ABA accumulation. Moreover, TaBZR1 associates with the promoters of ROS-scavenging genes TaGPX2 and TaGPX3 to activate their expression. Taken together, our results elucidate that TaBZR1 improve salt-stress tolerance by activating some genes involved in the biosynthesis of ABA and ROS scavenging in wheat, which give us a new strategy to improve the salt tolerance of wheat."
Author: Qianqian Qin.
Journal of Plant Physiology (2023)
Abstract: "Reactive oxygen species (ROS) are initially considered to be toxic byproducts of aerobic metabolic reactions. However, increasing evidence has shown that they have emerged as signaling molecules involved in several basic biological processes. Recent studies highlight the pivotal role of ROS in the maintenance of shoot and root stem cell niche. In this review, we discuss the impact of ROS distribution and their gradients on the stability of the stem cell niches (SCN) in shoot apical meristem (SAM) and root apical meristem (RAM) by determining the balance between stemness and differentiation. We also summarize several important transcription factors that are involved in the regulation of ROS balance in SAM and RAM, regulating key enzymes in ROS metabolism, especially SOD and peroxidase. ROS are also tightly interconnected with phytohormones in the control of the stem cell fate. Besides, ROS are also important regulators of the cell cycle in controlling the size of the stem cells. Understanding the regulation mechanisms of ROS production, polarization gradient distribution, homeostasis, and downstream signal transduction in cells will open exciting new perspectives for plant developmental biology."
Authors: Muhammad Saad Shoaib Khan, Sulaiman Ahmed, Aziz ul Ikram, Fakhir Hannan, Muhammad Umair Yasin, Jin Wang, Biying Zhao, Faisal Islam and Jian Chen.
Physiologia Plantarum (2023)
Highlights: • Melatonin acts as a redox network regulator in plants via regulating secondary messengers signaling. • Melatonin regulates the activity of redox-sensitive proteins and transcription factors. • Melatonin influences gene expression and physiological processes in response to stresses. • Melatonin synergically work with other hormones to confer plant resistance and stress adaptability.
Abstract: "Plants being sessile in nature, are exposed to unwarranted threats as a result of constantly changing environmental conditions. These adverse factors can have negative impacts on their growth, development, and yield. Hormones are key signaling molecules enabling cells to respond rapidly to different external and internal stimuli. In plants, melatonin (MT) plays a critical role in the integration of various environmental signals and activation of stress-response networks to develop defense mechanisms and plant resilience. Additionally, melatonin can tackle the stress-induced alteration of cellular redox equilibrium by regulating the expression of redox homeostasis-related genes and proteins. The purpose of this article is to compile and summarize the scientific research pertaining to MT's effects on plants' resilience to biotic and abiotic stresses. Here, we have summarized that MT exerts a synergistic effect with other phytohormones, for instance, ethylene, jasmonic acid, and salicylic acid, and activates plant defense-related genes against phytopathogens. Furthermore, MT interacts with secondary messengers like Ca2+, nitric oxide, and reactive oxygen species to regulate the redox network. This interaction triggers different transcription factors to alleviate stress-related responses in plants. Hence, the critical synergic role of MT with diverse plant hormones and secondary messengers demonstrates phytomelatonin's importance in influencing multiple mechanisms to contribute to plant resilience against harsh environmental factors."
Authors: Teng Wang, Zheng Sun, Siqi Wang, Shan Feng, Ruiming Wang, Chunlin Zhu, Linlin Zhong, Yunjiang Cheng, Manzhu Bao and Fan Zhang.
The Plant Journal (2023)
Abstract: "Carnation (Dianthus caryophyllus L.) is one of the most famous and ethylene sensitive cut flowers worldwide, but how ethylene interacts with other plant hormones and factors to regulate petal senescence in carnation is largely unknown. Here we found that a WRKY family transcription factor, DcWRKY33, was significantly up-regulated by ethylene treatment. Silencing and overexpression of DcWRKY33 could delay and accelerate the senescence of carnation petal respectively. Meanwhile, ABA and H2O2 treatments could also accelerate the senescence of carnation petal by inducing the expression of DcWRKY33. Further, DcWRKY33 can directly bind to the promoters of ethylene biosynthesis genes (DcACS1 and DcACO1), ABA biosynthesis genes (DcNCED2 and DcNCED5) and ROS generating gene (DcRBOHB) to activate their expression. Lastly, relationships are existed between ethylene, ABA and ROS. This study elucidated that DcWRKY33 promotes petal senescence by activating genes involved in the biosynthesis of ethylene, ABA and accumulation of ROS in carnation, which give us new strategy to prolong the vase life of cut carnation."
Authors: Alok Ranjan, Ragini Sinha, Sneh L. Singla-Pareek, Ashwani Pareek and Anil Kumar Singh.
Physiologia Plantarum (2022)
Abstract: "Root system architecture plays an important role in plant adaptation to drought stress. The root system architecture (RSA) consists of several structural features, which includes number and length of main and lateral roots along with the density and length of root hairs. These features exhibit plasticity under water-limited environments and could be critical to developing crops with efficient root systems for adaptation under drought. Recent advances in the omics approaches have significantly improved our understanding of the regulatory mechanisms of RSA remodelling under drought and the identification of genes and other regulatory elements. Plant response to drought stress at physiological, morphological, biochemical and molecular levels in root cells is regulated by various phytohormones and their crosstalk. Stress-induced reactive oxygen species play a significant role in regulating root growth and development under drought stress. Several transcription factors responsible for the regulation of RSA under drought have proven to be beneficial for developing drought tolerant crops. Molecular breeding programs for developing drought-tolerant crops have been greatly benefitted by the availability of quantitative trait loci (QTLs) associated with the RSA regulation. In the present review, we have discussed the role of various QTLs, signalling components, transcription factors, microRNAs and crosstalk among various phytohormones in shaping RSA and present future research directions to better understand various factors involved in RSA remodelling for adaptation to drought stress. We believe that the information provided herein may be helpful in devising strategies to develop crops with better RSA for efficient uptake and utilization of water and nutrients under drought conditions."
Authors: Jorge Hernández-García, Rui Sun, Antonio Serrano-Mislata, Keisuke Inoue, Carlos Vargas-Chávez, David Esteve-Bruna, Vicent Arbona, Shohei Yamaoka, Ryuichi Nishihama, Takayuki Kohchi and Miguel A. Blázquez.
Current Biology (2021)
Editor's view: DELLA proteins coordinate growth and stress responses as part of gibberellin signaling in angiosperms. Hernández-García, Sun, et al. show that this role is also conserved in Marchantia polymorpha despite the lack of a bona fide gibberellin perception module in bryophytes.
Highlights: • MpDELLA accumulation impairs thallus growth and cell division • MpDELLA interacts with MpPIF to modulate developmental traits • MpDELLA expression increases under oxidative stress and promotes stress tolerance • Coordination between growth and stress responses by DELLA predates GA signaling
Abstract: "Plant survival depends on the optimal use of resources under variable environmental conditions. Among the mechanisms that mediate the balance between growth, differentiation, and stress responses, the regulation of transcriptional activity by DELLA proteins stands out. In angiosperms, DELLA accumulation promotes defense against biotic and abiotic stress and represses cell division and expansion, while the loss of DELLA function is associated with increased plant size and sensitivity toward stress.1 Given that DELLA protein stability is dependent on gibberellin (GA) levels2 and GA metabolism is influenced by the environment,3 this pathway is proposed to relay environmental information to the transcriptional programs that regulate growth and stress responses in angiosperms.4,5 However, DELLA genes are also found in bryophytes, whereas canonical GA receptors have been identified only in vascular plants.6, 7, 8, 9, 10 Thus, it is not clear whether these regulatory functions of DELLA predated or emerged with typical GA signaling. Here, we show that, as in vascular plants, the only DELLA in the liverwort Marchantia polymorpha also participates in the regulation of growth and key developmental processes and promotes oxidative stress tolerance. Moreover, part of these effects is likely caused by the conserved physical interaction with the MpPIF transcription factor. Therefore, we suggest that the role in the coordination of growth and stress responses was already encoded in the DELLA protein of the common ancestor of land plants, and the importance of this function is underscored by its conservation over the past 450 million years."
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Authors: Muhammad Ahsan Altaf, Biswaranjan Behera, Vikas Mangal, Rajesh Kumar Singhal, Ravinder Kumar, Sanket More, Safina Naz, Sayanti Mandal, Abhijit Dey, Muhammad Saqib, Gopi Kishan, Awadhesh Kumar, Brajesh Singh, Rahul Kumar Tiwari and Milan Kumar Lal.
Functional Plant Biology (2024)
Abstract: "Solanaceous crops act as a source of food, nutrition and medicine for humans. Soil salinity is a damaging environmental stress, causing significant reductions in cultivated land area, crop productivity and quality, especially under climate change. Solanaceous crops are extremely vulnerable to salinity stress due to high water requirements during the reproductive stage and the succulent nature of fruits and tubers. Salinity stress impedes morphological and anatomical development, which ultimately affect the production and productivity of the economic part of these crops. The morpho-physiological parameters such as root-to-shoot ratio, leaf area, biomass production, photosynthesis, hormonal balance, leaf water content are disturbed under salinity stress in Solanaceous crops. Moreover, the synthesis and signalling of reactive oxygen species, reactive nitrogen species, accumulation of compatible solutes, and osmoprotectant are significant under salinity stress which might be responsible for providing tolerance in these crops. The regulation at the molecular level is mediated by different genes, transcription factors, and proteins, which are vital in the tolerance mechanism. The present review aims to redraw the attention of the researchers to explore the mechanistic understanding and potential mitigation strategies against salinity stress in Solanaceous crops, which is an often-neglected commodity."
Authors: Jingqiu Xia, Jiawen Liang, Mengmeng Yu, Rui Wang, Chen Sun, Huishan Song, Qinghua Xu, Jing Cang, Yuying Wang and Da Zhang.
Environmental and Experimental Botany (2024)
Highlights • TaMED25 is involved in JA signal pathway. • TaMED25 expression responded to low temperature stress in wheat. • Overexpression of TaMED25 gene enhances freeze resistance in Arabidopsis plants. • TaMED25 is localized in the nucleus. • TaMED25 interacts with TaJAZ7, TaMYC2 and TaICE41 proteins.
Abstract: "The MEDIATOR (MED) complex is a molecular bridge that regulates transcription by connecting transcription factors (TFs) and specific gene promoters. The MED subunit 25 (MED25) can interact with specific TFs in the phytohormone signaling pathways to regulate the transcription of downstream genes and affect various physiological processes in plants. Although MED25 plays an important role in adaptation to abiotic stresses, it is still unclear whether MED25 is involved in freezing tolerance in wheat. In this study, we found that the expression of TaMED25 was significantly increased under extremely low temperatures (–25 °C) in Dongnongdongmai1 (Dn1) plants, a variety of winter wheat with excellent cold-stress resistance,and hypothesized that TaMED25 may be a novel regulator of freezing tolerance in this wheat variety. To further characterize the function of TaMED25 in freezing tolerance, we cloned TaMED25 from Dn1 plants and overexpressed it in Arabidopsis thaliana. The results showed that the overexpression of TaMED25 improved freezing tolerance in Arabidopsis plants, with decreased relative conductivity, enhanced ability to effectively scavenge reactive oxygen species (ROS), and increased expression of cold-responsive genes. Furthermore, we proposed that TaMED25 mediates jasmonate-induced cold resistance in plants, possibly by interacting with TaJAZ7 and TaMYC2 of the jasmonate signaling pathway and TaICE41 of the ICE–CBF–COR pathway. Our findings reveal the functions of MED25 in plants and provide a scientific basis for an in-depth analysis of the transcriptional regulation mechanism of freezing tolerance in winter wheat."
Authors: Gyanendra Kumar Rai, Sonal Mishra, Rekha Chouhan, Muntazir Mushtaq, Aksar Ali Chowdhary, Pradeep K. Rai, Ranjeet Ranjan Kumar, Pradeep Kumar, Francisco Perez-Alfocea, Giuseppe Colla, Mariateresa Cardarelli, Vikas Srivastava and Sumit G. Gandhi.
Frontiers in Plant Science (2023)
Abstract: "Salinity or salt stress has deleterious effects on plant growth and development. It imposes osmotic, ionic, and secondary stresses, including oxidative stress on the plants and is responsible for the reduction of overall crop productivity and therefore challenges global food security. Plants respond to salinity, by triggering homoeostatic mechanisms that counter salt-triggered disturbances in the physiology and biochemistry of plants. This involves the activation of many signaling components such as SOS pathway, ABA pathway, and ROS and osmotic stress signaling. These biochemical responses are accompanied by transcriptional modulation of stress-responsive genes, which is mostly mediated by salt-induced transcription factor (TF) activity. Among the TFs, the multifaceted significance of WRKY proteins has been realized in many diverse avenues of plants’ life including regulation of plant stress response. Therefore, in this review, we aimed to highlight the significance of salinity in a global perspective, the mechanism of salt sensing in plants, and the contribution of WRKYs in the modulation of plants’ response to salinity stress. This review will be a substantial tool to investigate this problem in different perspectives, targeting WRKY and offering directions to better manage salinity stress in the field to ensure food security."
Authors: Shuhuan Zhang, Weihao Miao, Ye Liu, Jiafu Jiang, Sumei Chen, Fadi Chen and Zhiyong Guan.
BMC Genomics (2023)
Abstract: "Background - Black spot disease caused by the necrotrophic fungus Alternaria spp. is one of the most devastating diseases affecting Chrysanthemum morifolium. There is currently no effective way to prevent chrysanthemum black spot. Results - We revealed that pre-treatment of chrysanthemum leaves with the methyl jasmonate (MeJA) significantly reduces their susceptibility to Alternaria alternata. To understand how MeJA treatment induces resistance, we monitored the dynamics of metabolites and the transcriptome in leaves after MeJA treatment following A. alternata infection. JA signaling affected the resistance of plants to pathogens through cell wall modification, Ca2+ regulation, reactive oxygen species (ROS) regulation, mitogen‐activated protein kinase cascade and hormonal signaling processes, and the accumulation of anti-fungal and anti-oxidant metabolites. Furthermore, the expression of genes associated with these functions was verified by reverse transcription quantitative PCR and transgenic assays. Conclusion - Our findings indicate that MeJA pre-treatment could be a potential orchestrator of a broad-spectrum defense response that may help establish an ecologically friendly pest control strategy and offer a promising way of priming plants to induce defense responses against A. alternata."
Authors: Lijun Cao, Heejin Yoo, Tianyuan Chen, Musoki Mwimba, Xing Zhang and Xinnian Dong.
bioRxiv (2023)
Abstract: "In plants, a local infection can lead to systemic acquired resistance (SAR) through increased production of salicylic acid (SA). For 30 years, the identity of the mobile signal and its direct transduction mechanism for systemic SA synthesis in initiating SAR have been hotly debated. We found that, upon pathogen challenge, the cysteine residue of transcription factor CHE undergoes sulfenylation in systemic tissues, enhancing its binding to the promoter of SA-synthesis gene, ICS1, and increasing SA production. This occurs independently of previously reported pipecolic acid (Pip) signal. Instead, H2O2 produced by NADPH oxidase, RBOHD, is the mobile signal that sulfenylates CHE in a concentration-dependent manner. This modification serves as a molecular switch that activates CHE-mediated SA-increase and subsequent Pip-accumulation in systemic tissues to synergistically induce SAR."
Authors: Lei Xu, Hongyu Zhao, Junbin Wang, Xuming Wang, Xianqing Jia, Long Wang, Zhuang Xu, Ruili Li, Kun Jiang, Zhixiang Chen, Jie Luo, Xiaodong Xie and Keke Yi.
New Phytologist (2023)
Abstract: "● The basal levels of salicylic acid (SA) vary dramatically among plant species. In the shoot, for example, rice contains almost 100 times higher SA levels than Arabidopsis. Despite its high basal levels, neither the biosynthetic pathway nor the biological functions of SA are well understood in rice. ● Combining with metabolites analysis, physiological, and genetic approaches, we found that the synthesis of basal SA in rice shoot is dependent on OsAIM1, which encodes a beta-oxidation enzyme in the phenylalanine ammonia-lyase (PAL) pathway. ● Compromised SA accumulation in the Osaim1 mutant led to a lower shoot temperature than wild-type plants. However, this shoot temperature defect resulted from increased transpiration due to elevated steady-state stomatal aperture in the mutant. Furthermore, the high basal SA level is required for sustained expression of OsWRKY45 to modulate the steady-state stomatal aperture and shoot temperature in rice. ● Taken together, these results provide the direct genetic evidence for the critical role of the PAL pathway in the biosynthesis of high basal level SA in rice, which plays an important role in the regulation of steady-state stomatal aperture to promote fitness under stress conditions."
Authors: Shupei Rao, Yuru Tian, Chong Zhang, Yingzhi Qin, Meiqin Liu, Shihui Niu, Yue Li and Jinhuan Chen.
Journal of Experimental Botany (2023)
Abstract: "Drought, which directly affected the yield of crops and trees, is a natural disaster with a profound impact on the economy. Improved water-use efficiency (WUE) and drought tolerance are currently known to be the relatively effective strategies to alleviate drought stress. OPEN STOMATA1 (OST1), the core of ABA signal, can further provide WUE by regulating the stomata closure and photosynthesis. Methyl jasmonate (MeJA) and abscisic acid (ABA) crosstalk is supposed to be involved in response to drought stress. However, detailed molecular mechanism is seriously insufficient. Here, Populus euphratica, which is naturally growing in arid and semiarid regions, was selected as the material to perform yeast mating using PeOST1 as a bait. We report that a nucleus-localized factor PeJAZ2 participated in MeJA signaling interacts with PeOST1. Overexpression of PeJAZ2 in poplar remarkably increased water deficit tolerance and WUE both in severe- and mild- drought stresses by regulating ABA signaling rather than ABA synthesis. Furthermore, PeJAZ2 overexpressing lines were shown to promote the ABA-induced stomatal closure and the hydrogen peroxide (H2O2) production. Collectively, these convincing evidences establish a mechanism that PeJAZ2 act as a positive regulator in response to drought stress via ABA-induced stomatal closure caused by H2O2 production, and provide a new sight for interpreting the cross-talk of ABA and JA signaling in regulating WUE and drought stress, to provide a basis for the drought tolerance mechanism of P. euphratica."
Authors: Yin Zhang, Yingzi Zhang, Quan Sun, Suwen Lu, Lijun Chai, Junli Ye and Xiuxin Deng.
The Plant Journal (2021)
Abstract: "Senescence is a gradual physiological process involving the integration of numerous internal and environmental signals. Abscisic acid (ABA) is a well-known inducer of senescence. However, the regulatory mechanisms underlying ABA-mediated senescence remain largely unknown. Here, we report that the citrus homeodomain leucine zipper I (HD-ZIP I) transcription factor CsHB5 functions as a regulator of ABA-triggered senescence. CsHB5 acts as a nucleus-localized transcriptional activator, the expression of which appeared to be closely associated with citrus senescence. Overexpression of CsHB5 in citrus calli upregulated the expression of ABA- and reactive oxygen species (ROS)-related genes, and significantly increased the content of ABA and hydrogen peroxide (H2O2), whereas silencing CsHB5 in citrus calli downregulated the expression of ABA-related genes. Additionally, heterogenous overexpression of CsHB5 in Solanum lycopersicum (tomato) and Arabidopsis thaliana (Arabidopsis) leads to early leaf yellowing under dark-induced senescence conditions. Meanwhile, the levels of ABA and H2O2 in transgenic tomatoes increased significantly and the lycopene content decreased. Transcriptome analysis of CsHB5-overexpressing citrus calli and tomato showed that CsHB5 was involved in multiple senescence-associated processes, including chlorophyll degradation, nutrient compound biosynthesis and transport, as well as ABA and ROS signal transduction. The results of yeast one-hybrid assays, electrophoretic mobility shift assays and dual luciferase assays indicated that CsHB5 directly binds to the promoters of ABA biosynthetic genes, including β-carotene hydroxylase 1 (BCH1) and 9-cis-epoxycarotenoid dioxygenase 2 (NCED2), thereby activating their transcription. Our findings revealed that CsHB5 participates in senescence, at least partly, by directly controlling ABA accumulation. Our work provides insight into the regulatory mechanisms underlying ABA-mediated senescence."
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