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Yu Y, Portolés S, Ren Y, Sun G, Wang XF, Zhang H, Guo S. The key clock component ZEITLUPE (ZTL) negatively regulates ABA signaling by degradation of CHLH in Arabidopsis. FRONTIERS IN PLANT SCIENCE 2022; 13:995907. [PMID: 36176682 PMCID: PMC9513469 DOI: 10.3389/fpls.2022.995907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Accepted: 08/18/2022] [Indexed: 06/16/2023]
Abstract
Ubiquitination-mediated protein degradation plays important roles in ABA signal transduction and delivering responses to chloroplast stress signals in plants, but additional E3 ligases of protein ubiquitination remain to be identified to understand the complex signaling network. Here we reported that ZEITLUPE (ZTL), an F-box protein, negatively regulates abscisic acid (ABA) signaling during ABA-inhibited early seedling growth and ABA-induced stomatal closure in Arabidopsis thaliana. Using molecular biology and biochemistry approaches, we demonstrated that ZTL interacts with and ubiquitinates its substrate, CHLH/ABAR (Mg-chelatase H subunit/putative ABA receptor), to modulate CHLH stability via the 26S proteasome pathway. CHLH acts genetically downstream of ZTL in ABA and drought stress signaling. Interestingly, ABA conversely induces ZTL phosphorylation, and high levels of ABA also induce CHLH proteasomal degradation, implying that phosphorylated ZTL protein may enhance the affinity to CHLH, leading to the increased degradation of CHLH after ABA treatment. Taken together, our results revealed a possible mechanism of reciprocal regulation between ABA signaling and the circadian clock, which is thought to be essential for plant fitness and survival.
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Affiliation(s)
- Yongtao Yu
- National Watermelon and Melon Improvement Center, Beijing Academy of Agriculture and Forestry Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, China
| | - Sergi Portolés
- MOE Key Lab of Bioinformatics, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yi Ren
- National Watermelon and Melon Improvement Center, Beijing Academy of Agriculture and Forestry Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, China
| | - Guangyu Sun
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Sciences, Northeast Forestry University, Harbin, Heilongjiang, China
| | - Xiao-Fang Wang
- MOE Key Lab of Bioinformatics, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Huihui Zhang
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Sciences, Northeast Forestry University, Harbin, Heilongjiang, China
| | - Shaogui Guo
- National Watermelon and Melon Improvement Center, Beijing Academy of Agriculture and Forestry Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, China
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2
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Jaganathan GK, Han Y, Li W, Song D, Song X, Shen M, Zhou Q, Zhang C, Liu B. Physiological Mechanisms Only Tell Half Story: Multiple Biological Processes are involved in Regulating Freezing Tolerance of Imbibed Lactuca sativa Seeds. Sci Rep 2017; 7:44166. [PMID: 28287125 PMCID: PMC5347015 DOI: 10.1038/srep44166] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 01/26/2017] [Indexed: 11/09/2022] Open
Abstract
The physiological mechanisms by which imbibed seeds survive freezing temperatures in their natural environment have been categorized as freezing avoidance by supercooling and freezing tolerance by extracellular freeze-desiccation, but the biochemical and molecular mechanisms conferring seed freezing tolerance is unexplored. In this study, using imbibed Lactuca sativa seeds we show that fast cooled seeds (60 °C h-1) suffered significantly higher membrane damage at temperature between -20 °C and -10 °C than slow cooled (3 °Ch-1) seeds (P < 0.05), presumably explaining viability loss during fast cooling when temperature approaches -20 °C. Total soluble sugars increase in low temperature environment, but did not differ significantly between two cooling rates (P > 0.05). However, both SOD activity and accumulation of free proline were induced significantly after slow cooling to -20 °C compared with fast cooling. RNA-seq demonstrated that multiple pathways were differentially regulated between slow and fast cooling. Real-time verification of some differentially expressed genes (DEGs) revealed that fast cooling caused mRNA level changes of plant hormone and ubiquitionation pathways at higher sub-zero temperature, whilst slow cooling caused mRNA level change of those pathways at lower sub-zero ttemperatures. Thus, we conclude that imbibed seed tolerate low temperature not only by physiological mechanisms but also by biochemical and molecular changes.
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Affiliation(s)
- Ganesh K. Jaganathan
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Yingying Han
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Weijie Li
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Danping Song
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Xiaoyan Song
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Mengqi Shen
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Qiang Zhou
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Chenxue Zhang
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
| | - Baolin Liu
- Institute of Biothermal Science and Technology, University of Shanghai for Science and technology, 516 Jungong Road, Shanghai 200093, China
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3
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Zhang XF, Jiang T, Wu Z, Du SY, Yu YT, Jiang SC, Lu K, Feng XJ, Wang XF, Zhang DP. Cochaperonin CPN20 negatively regulates abscisic acid signaling in Arabidopsis. PLANT MOLECULAR BIOLOGY 2013; 83:205-18. [PMID: 23783410 PMCID: PMC3777161 DOI: 10.1007/s11103-013-0082-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 05/26/2013] [Indexed: 05/08/2023]
Abstract
Previous study showed that the magnesium-protoporphyrin IX chelatase H subunit (CHLH/ABAR) positively regulates abscisic acid (ABA) signaling. Here, we investigated the functions of a CHLH/ABAR interaction protein, the chloroplast co-chaperonin 20 (CPN20) in ABA signaling in Arabidopsis thaliana. We showed that down-expression of the CPN20 gene increases, but overexpression of the CPN20 gene reduces, ABA sensitivity in the major ABA responses including ABA-induced seed germination inhibition, postgermination growth arrest, promotion of stomatal closure and inhibition of stomatal opening. Genetic evidence supports that CPN20 functions downstream or at the same node of CHLH/ABAR, but upstream of the WRKY40 transcription factor. The other CPN20 interaction partners CPN10 and CPN60 are not involved in ABA signaling. Our findings show that CPN20 functions negatively in the ABAR-WRKY40 coupled ABA signaling independently of its co-chaperonin role, and provide a new insight into the role of co-chaperones in the regulation of plant responses to environmental cues.
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Affiliation(s)
- Xiao-Feng Zhang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Tao Jiang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Zhen Wu
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Shu-Yuan Du
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yong-Tao Yu
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Shang-Chuan Jiang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Kai Lu
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Xiu-Jing Feng
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Xiao-Fang Wang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Da-Peng Zhang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
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4
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Du SY, Zhang XF, Lu Z, Xin Q, Wu Z, Jiang T, Lu Y, Wang XF, Zhang DP. Roles of the different components of magnesium chelatase in abscisic acid signal transduction. PLANT MOLECULAR BIOLOGY 2012; 80:519-37. [PMID: 23011401 PMCID: PMC3472068 DOI: 10.1007/s11103-012-9965-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 08/26/2012] [Indexed: 05/12/2023]
Abstract
The H subunit of Mg-chelatase (CHLH) was shown to regulate abscisic acid (ABA) signaling and the I subunit (CHLI) was also reported to modulate ABA signaling in guard cells. However, it remains essentially unknown whether and how the Mg-chelatase-catalyzed Mg-protoporphyrin IX-production differs from ABA signaling. Using a newly-developed surface plasmon resonance system, we showed that ABA binds to CHLH, but not to the other Mg-chelatase components/subunits CHLI, CHLD (D subunit) and GUN4. A new rtl1 mutant allele of the CHLH gene in Arabidopsis thaliana showed ABA-insensitive phenotypes in both stomatal movement and seed germination. Upregulation of CHLI1 resulted in ABA hypersensitivity in seed germination, while downregulation of CHLI conferred ABA insensitivity in stomatal response in Arabidopsis. We showed that CHLH and CHLI, but not CHLD, regulate stomatal sensitivity to ABA in tobacco (Nicotiana benthamiana). The overexpression lines of the CHLD gene showed wild-type ABA sensitivity in Arabidopsis. Both the GUN4-RNA interference and overexpression lines of Arabidopsis showed wild-type phenotypes in the major ABA responses. These findings provide clear evidence that the Mg-chelatase-catalyzed Mg-ProtoIX production is distinct from ABA signaling, giving information to understand the mechanism by which the two cellular processes differs at the molecular level.
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Affiliation(s)
- Shu-Yuan Du
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Xiao-Feng Zhang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Zekuan Lu
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101 China
| | - Qi Xin
- College of Biological Sciences, China Agricultural University, Beijing, 100094 China
| | - Zhen Wu
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Tao Jiang
- College of Biological Sciences, China Agricultural University, Beijing, 100094 China
| | - Yan Lu
- College of Biological Sciences, China Agricultural University, Beijing, 100094 China
| | - Xiao-Fang Wang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Da-Peng Zhang
- MOE Systems Biology and Bioinformatics Laboratory, School of Life Sciences, Tsinghua University, Beijing, 100084 China
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5
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Ye N, Jia L, Zhang J. ABA signal in rice under stress conditions. RICE (NEW YORK, N.Y.) 2012; 5:1. [PMID: 24764501 PMCID: PMC3834477 DOI: 10.1186/1939-8433-5-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 02/27/2012] [Indexed: 05/18/2023]
Abstract
Ever since its discovery, abscisic acid (ABA) has been intensively studied due to its versatile functions in plant developmental and physiological processes. Many signaling details of ABA have been well elucidated and reviewed. The identification of ABA receptors is a great breakthrough in the field of ABA study, whereas the discovery of ABA transporter has changed our concept that ABA is delivered solely by passive transport. The intensity of ABA signaling pathway is well known to be controlled by multi-regulators. Nonetheless, the interaction and coordination among ABA biosynthesis, catabolism, conjugation and transportation are seldom discussed. Here, we summarize the biological functions of ABA in response to different stresses, especially the roles of ABA in plant defense to pathogen attack, and discuss the possible relationships of these determinants in controlling the specificity and intensity of ABA signaling pathway in the rice.
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Affiliation(s)
- Nenghui Ye
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Liguo Jia
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Jianhua Zhang
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China
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Guo J, Yang X, Weston DJ, Chen JG. Abscisic acid receptors: past, present and future. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2011; 53:469-79. [PMID: 21554537 DOI: 10.1111/j.1744-7909.2011.01044.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Jin-Gui Chen (Corresponding author) Abscisic acid (ABA) is the key plant stress hormone. Consistent with the earlier studies in support of the presence of both membrane- and cytoplasm-localized ABA receptors, recent studies have identified multiple ABA receptors located in various subcellular locations. These include a chloroplast envelope-localized receptor (the H subunit of Chloroplast Mg(2+) -chelatase/ABA Receptor), two plasma membrane-localized receptors (G-protein Coupled Receptor 2 and GPCR-type G proteins), and one cytosol/nucleus-localized Pyrabactin Resistant (PYR)/PYR-Like (PYL)/Regulatory Component of ABA Receptor 1 (RCAR). Although the downstream molecular events for most of the identified ABA receptors are currently unknown, one of them, PYR/PYL/RCAR was found to directly bind and regulate the activity of a long-known central regulator of ABA signaling, the A-group protein phosphatase 2C (PP2C). Together with the Sucrose Non-fermentation Kinase Subfamily 2 (SnRK2s) protein kinases, a central signaling complex (ABA-PYR-PP2Cs-SnRK2s) that is responsible for ABA signal perception and transduction is supported by abundant genetic, physiological, biochemical and structural evidence. The identification of multiple ABA receptors has advanced our understanding of ABA signal perception and transduction while adding an extra layer of complexity.
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Affiliation(s)
- Jianjun Guo
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02114-2790, USA
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7
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Shang Y, Yan L, Liu ZQ, Cao Z, Mei C, Xin Q, Wu FQ, Wang XF, Du SY, Jiang T, Zhang XF, Zhao R, Sun HL, Liu R, Yu YT, Zhang DP. The Mg-chelatase H subunit of Arabidopsis antagonizes a group of WRKY transcription repressors to relieve ABA-responsive genes of inhibition. THE PLANT CELL 2010; 22:1909-35. [PMID: 20543028 PMCID: PMC2910980 DOI: 10.1105/tpc.110.073874] [Citation(s) in RCA: 375] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 04/10/2010] [Accepted: 05/25/2010] [Indexed: 05/17/2023]
Abstract
The phytohormone abscisic acid (ABA) plays a vital role in plant development and response to environmental challenges, but the complex networks of ABA signaling pathways are poorly understood. We previously reported that a chloroplast protein, the magnesium-protoporphyrin IX chelatase H subunit (CHLH/ABAR), functions as a receptor for ABA in Arabidopsis thaliana. Here, we report that ABAR spans the chloroplast envelope and that the cytosolic C terminus of ABAR interacts with a group of WRKY transcription factors (WRKY40, WRKY18, and WRKY60) that function as negative regulators of ABA signaling in seed germination and postgermination growth. WRKY40, a central negative regulator, inhibits expression of ABA-responsive genes, such as ABI5. In response to a high level of ABA signal that recruits WRKY40 from the nucleus to the cytosol and promotes ABAR-WRKY40 interaction, ABAR relieves the ABI5 gene of inhibition by repressing WRKY40 expression. These findings describe a unique ABA signaling pathway from the early signaling events to downstream gene expression.
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Affiliation(s)
- Yi Shang
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Lu Yan
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Zhi-Qiang Liu
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Zheng Cao
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Chao Mei
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Qi Xin
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Fu-Qing Wu
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Xiao-Fang Wang
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Shu-Yuan Du
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Tao Jiang
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Xiao-Feng Zhang
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Rui Zhao
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Hai-Li Sun
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Rui Liu
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
| | - Yong-Tao Yu
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Da-Peng Zhang
- Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
- Address correspondence to
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8
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Ma Y, Szostkiewicz I, Korte A, Moes D, Yang Y, Christmann A, Grill E. Regulators of PP2C phosphatase activity function as abscisic acid sensors. Science 2009; 324:1064-8. [PMID: 19407143 DOI: 10.1126/science.1172408] [Citation(s) in RCA: 1459] [Impact Index Per Article: 97.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The plant hormone abscisic acid (ABA) acts as a developmental signal and as an integrator of environmental cues such as drought and cold. Key players in ABA signal transduction include the type 2C protein phosphatases (PP2Cs) ABI1 and ABI2, which act by negatively regulating ABA responses. In this study, we identify interactors of ABI1 and ABI2 which we have named regulatory components of ABA receptor (RCARs). In Arabidopsis, RCARs belong to a family with 14 members that share structural similarity with class 10 pathogen-related proteins. RCAR1 was shown to bind ABA, to mediate ABA-dependent inactivation of ABI1 or ABI2 in vitro, and to antagonize PP2C action in planta. Other RCARs also mediated ABA-dependent regulation of ABI1 and ABI2, consistent with a combinatorial assembly of receptor complexes.
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Affiliation(s)
- Yue Ma
- Lehrstuhl für Botanik, Technische Universität München, Am Hochanger 4, D-85354 Freising, Germany
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Sirichandra C, Wasilewska A, Vlad F, Valon C, Leung J. The guard cell as a single-cell model towards understanding drought tolerance and abscisic acid action. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:1439-63. [PMID: 19181866 DOI: 10.1093/jxb/ern340] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Stomatal guard cells are functionally specialized epidermal cells usually arranged in pairs surrounding a pore. Changes in ion fluxes, and more specifically osmolytes, within the guard cells drive opening/closing of the pore, allowing gas exchange while limiting water loss through evapo-transpiration. Adjustments of the pore aperture to optimize these conflicting needs are thus centrally important for land plants to survive, especially with the rise in CO(2) associated with global warming and increasing water scarcity this century. The basic biophysical events in modulating membrane transport have been gradually delineated over two decades. Genetics and molecular approaches in recent years have complemented and extended these earlier studies to identify major regulatory nodes. In Arabidopsis, the reference for guard cell genetics, stomatal opening driven by K(+) entry is mainly through KAT1 and KAT2, two voltage-gated K(+) inward-rectifying channels that are activated on hyperpolarization of the plasma membrane principally by the OST2 H(+)-ATPase (proton pump coupled to ATP hydrolysis). By contrast, stomatal closing is caused by K(+) efflux mainly through GORK, the outward-rectifying channel activated by membrane depolarization. The depolarization is most likely initiated by SLAC1, an anion channel distantly related to the dicarboxylate/malic acid transport protein found in fungi and bacteria. Beyond this established framework, there is also burgeoning evidence for the involvement of additional transporters, such as homologues to the multi-drug resistance proteins (or ABC transporters) as intimated by several pharmacological and reverse genetics studies. General inhibitors of protein kinases and protein phosphatases have been shown to profoundly affect guard cell membrane transport properties. Indeed, the first regulatory enzymes underpinning these transport processes revealed genetically were several protein phosphatases of the 2C class and the OST1 kinase, a member of the SnRK2 family. Taken together, these results are providing the first glimpses of an emerging signalling complex critical for modulating the stomatal aperture in response to environmental stimuli.
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Affiliation(s)
- Caroline Sirichandra
- Institut des Sciences du Végetal, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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Jang YH, Lee JH, Kim JK. Abscisic acid does not disrupt either the Arabidopsis FCA-FY interaction or its rice counterpart in vitro. PLANT & CELL PHYSIOLOGY 2008; 49:1898-1901. [PMID: 18854333 DOI: 10.1093/pcp/pcn151] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We examined the effect of (+)-ABA on the in vitro interaction of rice FCA and FY homologs, OsFCA and OsFY. From this analysis, we found no disruption of the OsFCA-OsFY complexes by ABA treatment. This result prompted us to examine the effect of ABA on the FCA-FY interaction. In these experiments, we could not reproduce the inhibitory effect of (+)-ABA on the interaction between FCA and FY. Based on these combined results, we believe that the inhibitory effect of (+)-ABA on the FCA-FY interaction should be cautiously reconsidered.
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Affiliation(s)
- Yun Hee Jang
- Plant Signaling Network Research Center, School of Life Sciences and Biotechnology, Korea University, Seoul, 136-701, Korea
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11
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Johnston CA, Willard MD, Kimple AJ, Siderovski DP, Willard FS. A sweet cycle for Arabidopsis G-proteins: Recent discoveries and controversies in plant G-protein signal transduction. PLANT SIGNALING & BEHAVIOR 2008; 3:1067-76. [PMID: 19513240 PMCID: PMC2634461 DOI: 10.4161/psb.3.12.7184] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 10/14/2008] [Indexed: 05/20/2023]
Abstract
Heterotrimeric G-proteins are a class of signal transduction proteins highly conserved throughout evolution that serve as dynamic molecular switches regulating the intracellular communication initiated by extracellular signals including sensory information. This property is achieved by a guanine nucleotide cycle wherein the inactive, signaling-incompetent Galpha subunit is normally bound to GDP; activation to signaling-competent Galpha occurs through the exchange of GDP for GTP (typically catalyzed via seven-transmembrane domain G-protein coupled receptors [GPCRs]), which dissociates the Gbetagamma dimer from Galpha-GTP and initiates signal transduction. The hydrolysis of GTP, greatly accelerated by "Regulator of G-protein Signaling" (RGS) proteins, returns Galpha to its inactive GDP-bound form and terminates signaling. Through extensive characterization of mammalian Galpha isoforms, the rate-limiting step in this cycle is currently considered to be the GDP/GTP exchange rate, which can be orders of magnitude slower than the GTP hydrolysis rate. However, we have recently demonstrated that, in Arabidopsis, the guanine nucleotide cycle appears to be limited by the rate of GTP hydrolysis rather than nucleotide exchange. This finding has important implications for the mechanism of sugar sensing in Arabidopsis. We also discuss these data on Arabidopsis G-protein nucleotide cycling in relation to recent reports of putative plant GPCRs and heterotrimeric G-protein effectors in Arabidopsis.
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Affiliation(s)
- Christopher A Johnston
- Department of Pharmacology; University of North Carolina School of Medicine; Chapel Hill, North Carolina USA
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12
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Kwak JM, Mäser P, Schroeder JI. The Clickable Guard Cell, Version II: Interactive Model of Guard Cell Signal Transduction Mechanisms and Pathways. THE ARABIDOPSIS BOOK 2008; 6:e0114. [PMID: 22303239 PMCID: PMC3243356 DOI: 10.1199/tab.0114] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Guard cells are located in the leaf epidermis and pairs of guard cells surround and form stomatal pores, which regulate CO(2) influx from the atmosphere into leaves for photosynthetic carbon fixation. Stomatal guard cells also regulate water loss of plants via transpiration to the atmosphere. Signal transduction mechanisms in guard cells integrate a multitude of different stimuli to modulate stomatal apertures. Stomata open in response to light. Stomata close in response to drought stress, elevated CO(2), ozone and low humidity. In response to drought, plants synthesize the hormone abscisic acid (ABA) that triggers closing of stomatal pores. Guard cells have become a highly developed model system for dissecting signal transduction mechanisms in plants and for elucidating how individual signaling mechanisms can interact within a network in a single cell. Many new findings have been made in the last few years. This chapter is an update of an electronic interactive chapter in the previous edition of The Arabidopsis Book (Mäser et al. 2003). Here we focus on mechanisms for which genes and mutations have been characterized, including signaling components for which there is substantial signaling, biochemical and genetic evidence. Ion channels have been shown to represent targets of early signal transduction mechanisms and provide functional signaling and quantitative analysis points to determine where and how mutations affect branches within the guard cell signaling network. Although a substantial number of genes and proteins that function in guard cell signaling have been identified in recent years, there are many more left to be identified and the protein-protein interactions within this network will be an important subject of future research. A fully interactive clickable electronic version of this publication can be accessed at the following web site: http://www-biology.ucsd.edu/labs/schroeder/clickablegc2/. The interactive clickable version includes the following features: Figure 1. Model for the roles of ion channels in ABA signaling.Figure 2. Blue light signaling pathways in guard cells.Figure 3. ABA signaling pathways in guard cells.Figure 1 is linked to explanations that appear upon mouse-over. Figure 2 and Figure 3 are clickable and linked to info boxes, which in turn are linked to TAIR, to relevant abstracts in PubMed, and to updated background explanations from Schroeder et al (2001), used with permission of Annual Reviews of Plant Biology.
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Affiliation(s)
- June M. Kwak
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742
| | - Pascal Mäser
- Institute of Cell Biology, University of Berne, CH-3012 Bern, Switzerland
| | - Julian I. Schroeder
- Division of Biological Sciences, Cell and Developmental Biology Section and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116
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Rich RL, Myszka DG. Survey of the year 2007 commercial optical biosensor literature. J Mol Recognit 2008; 21:355-400. [DOI: 10.1002/jmr.928] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Guo J, Zeng Q, Emami M, Ellis BE, Chen JG. The GCR2 gene family is not required for ABA control of seed germination and early seedling development in Arabidopsis. PLoS One 2008; 3:e2982. [PMID: 18714360 PMCID: PMC2500181 DOI: 10.1371/journal.pone.0002982] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 07/27/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The plant hormone abscisic acid (ABA) regulates diverse processes of plant growth and development. It has recently been proposed that GCR2 functions as a G-protein-coupled receptor (GPCR) for ABA. However, the structural relationships and functionality of GCR2 have been challenged by several independent studies. A central question in this controversy is whether gcr2 mutants are insensitive to ABA, because gcr2 mutants were shown to display reduced sensitivity to ABA under one experimental condition (e.g. 22 degrees C, continuous white light with 150 micromol m(-2) s(-1)) but were shown to display wild-type sensitivity under another slightly different condition (e.g. 23 degrees C, 14/10 hr photoperiod with 120 micromol m(-2) s(-1)). It has been hypothesized that gcr2 appears only weakly insensitive to ABA because two other GCR2-like genes in Arabidopsis, GCL1 and GCL2, compensate for the loss of function of GCR2. PRINCIPAL FINDINGS In order to test this hypothesis, we isolated a putative loss-of-function allele of GCL2, and then generated all possible combinations of mutations in each member of the GCR2 gene family. We found that all double mutants, including gcr2 gcl1, gcr2 gcl2, gcl1 gcl2, as well as the gcr2 gcl1 gcl2 triple mutant displayed wild-type sensitivity to ABA in seed germination and early seedling development assays, demonstrating that the GCR2 gene family is not required for ABA responses in these processes. CONCLUSION These results provide compelling genetic evidence that GCR2 is unlikely to act as a receptor for ABA in the context of either seed germination or early seedling development.
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Affiliation(s)
- Jianjun Guo
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Qingning Zeng
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mohammad Emami
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Brian E. Ellis
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jin-Gui Chen
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
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Chen JG, Ellis BE. GCR2 is a new member of the eukaryotic lanthionine synthetase component C-like protein family. PLANT SIGNALING & BEHAVIOR 2008; 3:307-10. [PMID: 19841654 PMCID: PMC2634266 DOI: 10.4161/psb.3.5.5292] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Accepted: 11/13/2007] [Indexed: 05/08/2023]
Abstract
GCR2 was recently proposed to represent a G-protein-coupled receptor (GPCR) for the plant hormone, abscisic acid (ABA). We and others provided evidence that GCR2 is unlikely to be a bona fide GPCR because it is not clearly predicted to contain seven transmembrane domains, a structural hallmark for classical GPCRs. Instead, GCR2 shows significant sequence similarity to homologs of bacterial lanthionine synthetase component C (LanC). Here, we provide additional analysis of GCR2 and LanC-like (LANCL) proteins in plants, and propose that GCR2 is a new member of the eukaryotic LANCL protein family.
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Affiliation(s)
- Jin-Gui Chen
- Department of Botany; University of British Columbia; Vancouver, Canada
| | - Brian E Ellis
- Michael Smith Laboratories; University of British Columbia; Vancouver, Canada
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Holdsworth MJ, Bentsink L, Soppe WJJ. Molecular networks regulating Arabidopsis seed maturation, after-ripening, dormancy and germination. THE NEW PHYTOLOGIST 2008; 179:33-54. [PMID: 18422904 DOI: 10.1111/j.1469-8137.2008.02437.x] [Citation(s) in RCA: 530] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The transition between dormancy and germination represents a critical stage in the life cycle of higher plants and is an important ecological and commercial trait. In this review we present current knowledge of the molecular control of this trait in Arabidopsis thaliana, focussing on important components functioning during the developmental phases of seed maturation, after-ripening and imbibition. Establishment of dormancy during seed maturation is regulated by networks of transcription factors with overlapping and discrete functions. Following desiccation, after-ripening determines germination potential and, surprisingly, recent observations suggest that transcriptional and post-transcriptional processes occur in the dry seed. The single-cell endosperm layer that surrounds the embryo plays a crucial role in the maintenance of dormancy, and transcriptomics approaches are beginning to uncover endosperm-specific genes and processes. Molecular genetic approaches have provided many new components of hormone signalling pathways, but also indicate the importance of hormone-independent pathways and of natural variation in key regulatory loci. The influence of environmental signals (particularly light) following after-ripening, and the effect of moist chilling (stratification) are increasingly being understood at the molecular level. Combined postgenomics, physiology and molecular genetics approaches are beginning to provide an unparalleled understanding of the molecular processes underlying dormancy and germination.
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Affiliation(s)
- Michael J Holdsworth
- Department of Agricultural and Environmental Sciences, School of BioSciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Leónie Bentsink
- Department of Molecular Plant Physiology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Wim J J Soppe
- Department of Plant Breeding and Genetics, Max Planck Institute for Plant Breeding Research, 50829, Cologne, Germany
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