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Kinmonth-Schultz H, Walker SM, Bingol K, Hoyt DW, Kim YM, Markillie LM, Mitchell HD, Nicora CD, Taylor R, Ward JK. Oligosaccharide production and signaling correlate with delayed flowering in an Arabidopsis genotype grown and selected in high [CO2]. PLoS One 2023; 18:e0287943. [PMID: 38153952 PMCID: PMC10754469 DOI: 10.1371/journal.pone.0287943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 12/05/2023] [Indexed: 12/30/2023] Open
Abstract
Since industrialization began, atmospheric CO2 ([CO2]) has increased from 270 to 415 ppm and is projected to reach 800-1000 ppm this century. Some Arabidopsis thaliana (Arabidopsis) genotypes delayed flowering in elevated [CO2] relative to current [CO2], while others showed no change or accelerations. To predict genotype-specific flowering behaviors, we must understand the mechanisms driving flowering response to rising [CO2]. [CO2] changes alter photosynthesis and carbohydrates in plants. Plants sense carbohydrate levels, and exogenous carbohydrate application influences flowering time and flowering transcript levels. We asked how organismal changes in carbohydrates and transcription correlate with changes in flowering time under elevated [CO2]. We used a genotype (SG) of Arabidopsis that was selected for high fitness at elevated [CO2] (700 ppm). SG delays flowering under elevated [CO2] (700 ppm) relative to current [CO2] (400 ppm). We compared SG to a closely related control genotype (CG) that shows no [CO2]-induced flowering change. We compared metabolomic and transcriptomic profiles in these genotypes at current and elevated [CO2] to assess correlations with flowering in these conditions. While both genotypes altered carbohydrates in response to elevated [CO2], SG had higher levels of sucrose than CG and showed a stronger increase in glucose and fructose in elevated [CO2]. Both genotypes demonstrated transcriptional changes, with CG increasing genes related to fructose 1,6-bisphosphate breakdown, amino acid synthesis, and secondary metabolites; and SG decreasing genes related to starch and sugar metabolism, but increasing genes involved in oligosaccharide production and sugar modifications. Genes associated with flowering regulation within the photoperiod, vernalization, and meristem identity pathways were altered in these genotypes. Elevated [CO2] may alter carbohydrates to influence transcription in both genotypes and delayed flowering in SG. Changes in the oligosaccharide pool may contribute to delayed flowering in SG. This work extends the literature exploring genotypic-specific flowering responses to elevated [CO2].
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Affiliation(s)
- Hannah Kinmonth-Schultz
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States of America
- Departiment of Biology, Tennessee Technological University, Cookeville, TN, United States of America
| | - Stephen Michael Walker
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States of America
| | - Kerem Bingol
- Department of Energy, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - David W. Hoyt
- Department of Energy, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Young-Mo Kim
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Lye Meng Markillie
- Department of Energy, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Hugh D. Mitchell
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Carrie D. Nicora
- Department of Energy, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Ronald Taylor
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Joy K. Ward
- Department of Biology, College of Arts and Sciences, Case Western Reserve University, Cleveland, OH, United States of America
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Wang Y, Su C, Yu Y, He Y, Wei H, Li N, Li H, Duan J, Li B, Li J, Davis SJ, Wang L. TIME FOR COFFEE regulates phytochrome A-mediated hypocotyl growth through dawn-phased signaling. THE PLANT CELL 2022; 34:2907-2924. [PMID: 35543486 PMCID: PMC9338810 DOI: 10.1093/plcell/koac138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/24/2022] [Indexed: 05/14/2023]
Abstract
To enhance plant fitness under natural conditions, the circadian clock is synchronized and entrained by light via photoreceptors. In turn, the circadian clock exquisitely regulates the abundance and activity of photoreceptors via largely uncharacterized mechanisms. Here we show that the clock regulator TIME FOR COFFEE (TIC) controls the activity of the far-red light photoreceptor phytochrome A (phyA) at multiple levels in Arabidopsis thaliana. Null mutants of TIC displayed dramatically increased sensitivity to light irradiation with respect to hypocotyl growth, especially to far-red light. RNA-sequencing demonstrated that TIC and phyA play largely opposing roles in controlling light-regulated gene expression at dawn. Additionally, TIC physically interacts with the transcriptional repressor TOPLESS (TPL), which was associated with the significantly increased PHYA transcript levels in the tic-2 and tpl-1 mutants. Moreover, TIC interacts with phyA in the nucleus, thereby affecting phyA protein turnover and the formation of phyA nuclear speckles following light irradiation. Genetically, phyA was found to act downstream of TIC in regulating far red light-inhibited growth. Taken together, these findings indicate that TIC acts as a major negative regulator of phyA by integrating transcriptional and post-translational mechanisms at multiple levels.
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Affiliation(s)
| | | | | | - Yuqing He
- Key Laboratory of Plant Molecular Physiology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hua Wei
- Key Laboratory of Plant Molecular Physiology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Na Li
- Key Laboratory of Plant Molecular Physiology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jie Duan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Bin Li
- Key Laboratory of Plant Molecular Physiology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People’s Republic of China
| | - Jigang Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Seth J Davis
- Department of Biology, University of York, Heslington, York YO10 5DD, UK
- State Key Laboratory of Crop Stress Biology, School of Life Sciences, Henan University, Kaifeng 475004, China
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Talloji P, Nehlin L, Hüttel B, Winter N, Černý M, Dufková H, Hamali B, Hanczaryk K, Novák J, Hermanns M, Drexler N, Eifler K, Schlaich N, Brzobohatý B, Bachmair A. Transcriptome, metabolome and suppressor analysis reveal an essential role for the ubiquitin-proteasome system in seedling chloroplast development. BMC PLANT BIOLOGY 2022; 22:183. [PMID: 35395773 PMCID: PMC8991883 DOI: 10.1186/s12870-022-03536-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 03/15/2022] [Indexed: 05/25/2023]
Abstract
BACKGROUND Many regulatory circuits in plants contain steps of targeted proteolysis, with the ubiquitin proteasome system (UPS) as the mediator of these proteolytic events. In order to decrease ubiquitin-dependent proteolysis, we inducibly expressed a ubiquitin variant with Arg at position 48 instead of Lys (ubK48R). This variant acts as an inhibitor of proteolysis via the UPS, and allowed us to uncover processes that are particularly sensitive to UPS perturbation. RESULTS Expression of ubK48R during germination leads to seedling death. We analyzed the seedling transcriptome, proteome and metabolome 24 h post ubK48R induction and confirmed defects in chloroplast development. We found that mutations in single genes can suppress seedling lethality, indicating that a single process in seedlings is critically sensitive to decreased performance of the UPS. Suppressor mutations in phototropin 2 (PHOT2) suggest that a contribution of PHOT2 to chloroplast protection is compromised by proteolysis inhibition. CONCLUSIONS Overall, the results reveal protein turnover as an integral part of a signal transduction chain that protects chloroplasts during development.
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Affiliation(s)
- Prabhavathi Talloji
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria
| | - Lilian Nehlin
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria
| | - Bruno Hüttel
- Max Planck Genome Centre Cologne, Max Planck Institute for Plant Breeding Research, 50829, Cologne, Germany
| | - Nikola Winter
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria
| | - Martin Černý
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, CZ-613 00, Brno, Czech Republic
| | - Hana Dufková
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, CZ-613 00, Brno, Czech Republic
| | - Bulut Hamali
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria
- Present address: Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR, 97331, USA
| | - Katarzyna Hanczaryk
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria
| | - Jan Novák
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, CZ-613 00, Brno, Czech Republic
| | - Monika Hermanns
- Institute of Plant Physiology (Bio III), RWTH-Aachen, 52056, Aachen, Germany
| | - Nicole Drexler
- Vienna Biocenter Core Facilities, Electron Microscopy, A-1030, Vienna, Austria
| | - Karolin Eifler
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria
| | - Nikolaus Schlaich
- Institute of Plant Physiology (Bio III), RWTH-Aachen, 52056, Aachen, Germany
| | - Břetislav Brzobohatý
- Department of Molecular Biology and Radiobiology, Faculty of AgriSciences, Mendel University in Brno, CZ-613 00, Brno, Czech Republic
- CEITEC - Central European Institute of Technology, Mendel University in Brno, CZ-61300, Brno, Czech Republic
| | - Andreas Bachmair
- Department of Biochemistry and Cell Biology, Max Perutz Labs/Center for Molecular Biology, University of Vienna, A-1030, Vienna, Austria.
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Chen H, Lee J, Lee JM, Han M, Emonet A, Lee J, Jia X, Lee Y. MSD2, an apoplastic Mn-SOD, contributes to root skotomorphogenic growth by modulating ROS distribution in Arabidopsis. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2022; 317:111192. [PMID: 35193741 DOI: 10.1016/j.plantsci.2022.111192] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 01/07/2022] [Accepted: 01/17/2022] [Indexed: 05/22/2023]
Abstract
Reactive oxygen species (ROS) play essential roles as a second messenger in various physiological processes in plants. Due to their oxidative nature, ROS can also be harmful. Thus, the generation and homeostasis of ROS are tightly controlled by multiple enzymes. Membrane-localized NADPH oxidases are well known to generate ROS during developmental and stress responses, but the metabolic pathways of the superoxide (O2-) generated by them in the apoplast are poorly understood, and the identity of the apoplastic superoxide dismutase (SOD) is unknown in Arabidopsis. Here, we show that a putative manganese SOD, MSD2 is secreted and possesses a SOD activity that can be inhibited by nitration at tyrosine 68. The expression of MSD2 in roots is light condition-dependent, suggesting that MSD2 may act on ROS metabolism in roots during the light-to-dark transition. Root architecture is governed by ROS distribution that exhibits opposite gradient of H2O2 and O2-, which is indeed altered in etiolated msd2 mutants and accompanied by changes in the onset of differentiation. These results provide a missing link in our understanding of ROS metabolism and suggest that MSD2 plays a role in root skotomorphogenesis by regulating ROS distribution, thereby playing a pivotal role in plant growth and development.
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Affiliation(s)
- Huize Chen
- Higher Education Key Laboratory of Plant Molecular and Environmental Stress Response in Shanxi Province, Shanxi Normal University, Taiyuan, 030000, Shanxi, PR China; Research Institute of Basic Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jinsu Lee
- Research Institute of Basic Sciences, Seoul National University, Seoul, 08826, Republic of Korea; Research Center for Plant Plasticity, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jung-Min Lee
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Minsoo Han
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Aurélia Emonet
- Department of Plant Molecular Biology, University of Lausanne, Biophore Building, UNIL-Sorge, 1015, Lausanne, Switzerland
| | - Jiyoun Lee
- Department of New Biology, DGIST, Daegu, 42988, Republic of Korea
| | - Xingtian Jia
- Higher Education Key Laboratory of Plant Molecular and Environmental Stress Response in Shanxi Province, Shanxi Normal University, Taiyuan, 030000, Shanxi, PR China
| | - Yuree Lee
- Research Center for Plant Plasticity, Seoul National University, Seoul, 08826, Republic of Korea; School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea; Plant Genomics and Breeding Institute, Seoul National University, Seoul, 08826, Republic of Korea.
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5
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Schenk T, Trimborn L, Chen S, Schenkel C, Hoecker U. Light-induced degradation of SPA2 via its N-terminal kinase domain is required for photomorphogenesis. PLANT PHYSIOLOGY 2021; 187:276-288. [PMID: 33822236 PMCID: PMC8418447 DOI: 10.1093/plphys/kiab156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 03/19/2021] [Indexed: 06/12/2023]
Abstract
Arabidopsis (Arabidopsis thaliana) CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) and members of the SUPPRESSOR OF PHYTOCHROMEA-105 (SPA) protein family form an E3 ubiquitin ligase that suppresses light signaling in darkness by polyubiquitinating positive regulators of the light response. COP1/SPA is inactivated by light to allow photomorphogenesis to proceed. Mechanisms of inactivation include light-induced degradation of SPA1 and, in particular, SPA2, corresponding to a particularly efficient inactivation of COP1/SPA2 by light. Here, we show that SPA3 and SPA4 proteins are stable in the light, indicating that light-induced destabilization is specific to SPA1 and SPA2, possibly related to the predominant function of SPA1 and SPA2 in dark-grown etiolating seedlings. SPA2 degradation involves cullin and the COP10-DEETIOLATED-DAMAGED-DNA BINDING PROTEIN (DDB1) CDD complex, besides COP1. Consistent with this finding, light-induced SPA2 degradation required the DDB1-interacting Trp-Asp (WD)-repeat domain of SPA2. Deletion of the N-terminus of SPA2 containing the kinase domain led to strong stabilization of SPA2 in darkness and fully abolished light-induced degradation of SPA2. This prevented seedling de-etiolation even in very strong far-red and blue light and reduced de-etiolation in red light, indicating destabilization of SPA2 through its N-terminal domain is essential for light response. SPA2 is exclusively destabilized by phytochrome A in far-red and blue light. However, deletion of the N-terminal domain of SPA2 did not abolish SPA2-phytochrome A interaction in yeast nor in vivo. Our domain mapping suggests there are two SPA2-phytochrome A interacting domains, the N-terminal domain and the WD-repeat domain. Conferring a light-induced SPA2-phyA interaction only via the WD-repeat domain may thus not lead to COP1/SPA2 inactivation.
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Affiliation(s)
- Tobias Schenk
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Str. 47b, Cologne 50674, Germany
| | - Laura Trimborn
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Str. 47b, Cologne 50674, Germany
| | - Song Chen
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Str. 47b, Cologne 50674, Germany
| | - Christian Schenkel
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Str. 47b, Cologne 50674, Germany
| | - Ute Hoecker
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Str. 47b, Cologne 50674, Germany
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6
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Ponnu J, Hoecker U. Illuminating the COP1/SPA Ubiquitin Ligase: Fresh Insights Into Its Structure and Functions During Plant Photomorphogenesis. FRONTIERS IN PLANT SCIENCE 2021; 12:662793. [PMID: 33841486 PMCID: PMC8024647 DOI: 10.3389/fpls.2021.662793] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/04/2021] [Indexed: 05/07/2023]
Abstract
CONSTITUTIVE PHOTOMORPHOGENIC 1 functions as an E3 ubiquitin ligase in plants and animals. Discovered originally in Arabidopsis thaliana, COP1 acts in a complex with SPA proteins as a central repressor of light-mediated responses in plants. By ubiquitinating and promoting the degradation of several substrates, COP1/SPA regulates many aspects of plant growth, development and metabolism. In contrast to plants, human COP1 acts as a crucial regulator of tumorigenesis. In this review, we discuss the recent important findings in COP1/SPA research including a brief comparison between COP1 activity in plants and humans.
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Qu GP, Li H, Lin XL, Kong X, Hu ZL, Jin YH, Liu Y, Song HL, Kim DH, Lin R, Li J, Jin JB. Reversible SUMOylation of FHY1 Regulates Phytochrome A Signaling in Arabidopsis. MOLECULAR PLANT 2020; 13:879-893. [PMID: 32298785 DOI: 10.1016/j.molp.2020.04.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 02/15/2020] [Accepted: 04/08/2020] [Indexed: 06/11/2023]
Abstract
In response to far-red light (FR), FAR-RED ELONGATED HYPOCOTYL 1 (FHY1) transports the photoactivated phytochrome A (phyA), the primary FR photoreceptor, into the nucleus, where it initiates FR signaling in plants. Light promotes the 26S proteasome-mediated degradation of FHY1, which desensitizes FR signaling, but the underlying regulatory mechanism remains largely unknown. Here, we show that reversible SUMOylation of FHY1 tightly regulates this process. Lysine K32 (K32) and K103 are major SUMOylation sites of FHY1. We found that FR exposure promotes the SUMOylation of FHY1, which accelerates its degradation. Furthermore, we discovered that ARABIDOPSIS SUMO PROTEASE 1 (ASP1) interacts with FHY1 in the nucleus under FR and facilitates its deSUMOylation. FHY1 was strongly SUMOylated and its protein level was decreased in the asp1-1 loss-of-function mutant compared with that in the wild type under FR. Consistently, asp1-1 seedlings exhibited a decreased sensitivity to FR, suggesting that ASP1 plays an important role in the maintenance of proper FHY1 levels under FR. Genetic analysis further revealed that ASP1 regulates FR signaling through an FHY1- and phyA-dependent pathway. Interestingly, We found that continuous FR inhibits ASP1 accumulation, perhaps contributing to the desensitization of FR signaling. Taken together, these results indicate that FR-induced SUMOylation and ASP1-dependent deSUMOylation of FHY1 represent a key regulatory mechanism that fine-tunes FR signaling.
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Affiliation(s)
- Gao-Ping Qu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hong Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xiao-Li Lin
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Xiangxiong Kong
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Zi-Liang Hu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yin Hua Jin
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yu Liu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hang-Lin Song
- Yanbian Academy of Agriculture Sciences, Yanji 133001, China
| | - Dae Heon Kim
- Department of Biology, Sunchon National University, Sunchon 57922, South Korea
| | - Rongcheng Lin
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jigang Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jing Bo Jin
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
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8
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Han X, Huang X, Deng XW. The Photomorphogenic Central Repressor COP1: Conservation and Functional Diversification during Evolution. PLANT COMMUNICATIONS 2020; 1:100044. [PMID: 33367240 PMCID: PMC7748024 DOI: 10.1016/j.xplc.2020.100044] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 03/19/2020] [Accepted: 04/07/2020] [Indexed: 05/23/2023]
Abstract
Green plants on the earth have evolved intricate mechanisms to acclimatize to and utilize sunlight. In Arabidopsis, light signals are perceived by photoreceptors and transmitted through divergent but overlapping signaling networks to modulate plant photomorphogenic development. COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) was first cloned as a central repressor of photomorphogenesis in higher plants and has been extensively studied for over 30 years. It acts as a RING E3 ubiquitin ligase downstream of multiple photoreceptors to target key light-signaling regulators for degradation, primarily as part of large protein complexes. The mammalian counterpart of COP1 is a pluripotent regulator of tumorigenesis and metabolism. A great deal of information on COP1 has been derived from whole-genome sequencing and functional studies in lower green plants, which enables us to illustrate its evolutionary history. Here, we review the current understanding about COP1, with a focus on the conservation and functional diversification of COP1 and its signaling partners in different taxonomic clades.
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Affiliation(s)
- Xue Han
- State Key Laboratory of Protein and Plant Gene Research, School of Advanced Agricultural Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- Peking University-Southern University of Science and Technology Institute of Plant and Food Science, Department of Biology, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xi Huang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, China
| | - Xing Wang Deng
- State Key Laboratory of Protein and Plant Gene Research, School of Advanced Agricultural Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- Peking University-Southern University of Science and Technology Institute of Plant and Food Science, Department of Biology, Southern University of Science and Technology, Shenzhen 518055, China
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Yang Y, Liu H. Coordinated Shoot and Root Responses to Light Signaling in Arabidopsis. PLANT COMMUNICATIONS 2020; 1:100026. [PMID: 33367230 PMCID: PMC7748005 DOI: 10.1016/j.xplc.2020.100026] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 01/14/2020] [Accepted: 01/16/2020] [Indexed: 05/05/2023]
Abstract
Light is one of the most important environmental signals and regulates many biological processes in plants. Studies on light-regulated development have mainly focused on aspects of shoot growth, such as de-etiolation, cotyledon opening, inhibition of hypocotyl elongation, flowering, and anthocyanin accumulation. However, recent studies have demonstrated that light is also involved in regulating root growth and development in Arabidopsis. In this review, we summarize the progress in understanding how shoots and roots coordinate their responses to light through different light-signaling components and pathways, including the COP1 (CONSTITUTIVELY PHOTOMORPHOGENIC 1), HY5 (ELONGATED HYPOCOTYL 5), and MYB73/MYB77 (MYB DOMAIN PROTEIN 73/77) pathways.
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Affiliation(s)
- Yu Yang
- National Key Laboratory of Plant Molecular Genetics (NKLPMG), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology (SIPPE), Chinese Academy of Sciences, 200032 Shanghai, P. R. China
- University of Chinese Academy of Sciences, Shanghai 200032, P. R. China
| | - Hongtao Liu
- National Key Laboratory of Plant Molecular Genetics (NKLPMG), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology (SIPPE), Chinese Academy of Sciences, 200032 Shanghai, P. R. China
- Corresponding author
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10
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Molecular mechanisms underlying phytochrome-controlled morphogenesis in plants. Nat Commun 2019; 10:5219. [PMID: 31745087 PMCID: PMC6864062 DOI: 10.1038/s41467-019-13045-0] [Citation(s) in RCA: 183] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 10/17/2019] [Indexed: 11/08/2022] Open
Abstract
Phytochromes are bilin-binding photosensory receptors which control development over a broad range of environmental conditions and throughout the whole plant life cycle. Light-induced conformational changes enable phytochromes to interact with signaling partners, in particular transcription factors or proteins that regulate them, resulting in large-scale transcriptional reprograming. Phytochromes also regulate promoter usage, mRNA splicing and translation through less defined routes. In this review we summarize our current understanding of plant phytochrome signaling, emphasizing recent work performed in Arabidopsis. We compare and contrast phytochrome responses and signaling mechanisms among land plants and highlight open questions in phytochrome research.
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11
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Orthogonal regulation of phytochrome B abundance by stress-specific plastidial retrograde signaling metabolite. Nat Commun 2019; 10:2904. [PMID: 31266952 PMCID: PMC6606753 DOI: 10.1038/s41467-019-10867-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 06/04/2019] [Indexed: 11/30/2022] Open
Abstract
Plant survival necessitates constant monitoring of fluctuating light and balancing growth demands with adaptive responses, tasks mediated via interconnected sensing and signaling networks. Photoreceptor phytochrome B (phyB) and plastidial retrograde signaling metabolite methylerythritol cyclodiphosphate (MEcPP) are evolutionarily conserved sensing and signaling components eliciting responses through unknown connection(s). Here, via a suppressor screen, we identify two phyB mutant alleles that revert the dwarf and high salicylic acid phenotypes of the high MEcPP containing mutant ceh1. Biochemical analyses show high phyB protein levels in MEcPP-accumulating plants resulting from reduced expression of phyB antagonists and decreased auxin levels. We show that auxin treatment negatively regulates phyB abundance. Additional studies identify CAMTA3, a MEcPP-activated calcium-dependent transcriptional regulator, as critical for maintaining phyB abundance. These studies provide insights into biological organization fundamentals whereby a signal from a single plastidial metabolite is transduced into an ensemble of regulatory networks controlling the abundance of phyB, positioning plastids at the information apex directing adaptive responses. MEcPP is an evolutionarily conserved metabolite that acts as a plastid-to-nucleus retrograde signal to regulate adaptive responses to fluctuating light. Here the authors show that MEcPP regulates seedling development by stabilizing the phyB photoreceptor in an auxin and Ca2+ dependent manner.
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Podolec R, Ulm R. Photoreceptor-mediated regulation of the COP1/SPA E3 ubiquitin ligase. CURRENT OPINION IN PLANT BIOLOGY 2018; 45:18-25. [PMID: 29775763 DOI: 10.1016/j.pbi.2018.04.018] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/25/2018] [Accepted: 04/29/2018] [Indexed: 05/19/2023]
Abstract
Plants have evolved specific photoreceptors that capture informational cues from sunlight. The phytochrome, cryptochrome, and UVR8 photoreceptors perceive red/far-red, blue/UV-A, and UV-B light, respectively, and control overlapping photomorphogenic responses important for plant growth and development. A major repressor of such photomorphogenic responses is the E3 ubiquitin ligase formed by CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) and SUPPRESSOR OF PHYA-105 (SPA) proteins, which acts by regulating the stability of photomorphogenesis-promoting transcription factors. The direct interaction of light-activated photoreceptors with the COP1/SPA complex represses its activity via nuclear exclusion of COP1, disruption of the COP1-SPA interaction, and/or SPA protein degradation. This process enables plants to integrate different light signals at the level of the COP1/SPA complex to enact appropriate photomorphogenic responses according to the light environment.
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Affiliation(s)
- Roman Podolec
- Department of Botany and Plant Biology, Section of Biology, Faculty of Sciences, University of Geneva, CH-1211 Geneva 4, Switzerland; Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland
| | - Roman Ulm
- Department of Botany and Plant Biology, Section of Biology, Faculty of Sciences, University of Geneva, CH-1211 Geneva 4, Switzerland; Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland.
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13
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Agliassa C, Narayana R, Christie JM, Maffei ME. Geomagnetic field impacts on cryptochrome and phytochrome signaling. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2018; 185:32-40. [DOI: 10.1016/j.jphotobiol.2018.05.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/21/2018] [Accepted: 05/25/2018] [Indexed: 11/15/2022]
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14
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Zhang Y, Sun J, Xia H, Zhao C, Hou L, Wang B, Li A, Chen M, Zhao S, Wang X. Characterization of peanut phytochromes and their possible regulating roles in early peanut pod development. PLoS One 2018; 13:e0198041. [PMID: 29799880 PMCID: PMC5969742 DOI: 10.1371/journal.pone.0198041] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/11/2018] [Indexed: 12/20/2022] Open
Abstract
Arachis hypogaea L. geocarpy is a unique feature different from other legume plants. Flowering and fertilization occur above ground, while the following processes of pod formation and development proceed in the soil. The zygote divides only few times to develop into pre-embryo and then further embryo developmental process stops when the gynoecium is exposed to light condition or normal day/night period. In this study, eight phytochrome genes were identified in two wild peanuts (four in Arachis duranensis and four in Arachis ipaensis). Using RACE and homologous cloning, the full CDS of AhphyA, AhphyA-like, AhphyB and AhphyE were acquired in cultivated peanut. Protein structure analysis showed that the conservative coding domains of phytochromes from a number of other plant species were found in these proteins. The C-terminal of AhphyA, AhphyA-like and AhphyB could interact with phytochrome-interacting factor 3 in vitro. The expression patterns of these genes in various tissues were analyzed by qRT-PCR, and significant differences were observed. Interestingly, the expression levels of AhphyA-like changed significantly during gynophore growth and early pod development. Furthermore, protein accumulation patterns of AhphyA and AhphyB in gynophore were different during early pod development stages in that AhphyA and AhphyB proteins were not detected in S1 and S2 gynophores, while significant accumulation of AhphyA and AhphyB were detected in S3 gynophore. These results provided evidence that phytochromes mediated light signal transduction may play key roles in peanut geocarpy development.
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Affiliation(s)
- Ye Zhang
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
| | - Jinbo Sun
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
- College of Life Science, Shandong Normal University, Jinan, PR China
| | - Han Xia
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
- College of Life Science, Shandong Normal University, Jinan, PR China
| | - Chuanzhi Zhao
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
- College of Life Science, Shandong Normal University, Jinan, PR China
| | - Lei Hou
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
| | - Baoshan Wang
- College of Life Science, Shandong Normal University, Jinan, PR China
| | - Aiqin Li
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
| | - Min Chen
- College of Life Science, Shandong Normal University, Jinan, PR China
| | - Shuzhen Zhao
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
- College of Life Science, Shandong Normal University, Jinan, PR China
- * E-mail: (XW); (SZ)
| | - Xingjun Wang
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences; Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Jinan, PR China
- College of Life Science, Shandong Normal University, Jinan, PR China
- * E-mail: (XW); (SZ)
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15
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Krahmer J, Ganpudi A, Abbas A, Romanowski A, Halliday KJ. Phytochrome, Carbon Sensing, Metabolism, and Plant Growth Plasticity. PLANT PHYSIOLOGY 2018; 176:1039-1048. [PMID: 29254984 PMCID: PMC5813586 DOI: 10.1104/pp.17.01437] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 12/11/2017] [Indexed: 05/05/2023]
Abstract
Phytochrome signaling controls biomass accumulation, growth plasticity, and metabolism.
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Affiliation(s)
- Johanna Krahmer
- Institute for Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
| | - Ashwin Ganpudi
- Institute for Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
| | - Ammad Abbas
- Institute for Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
| | - Andrés Romanowski
- Institute for Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
| | - Karen J Halliday
- Institute for Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
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16
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Kim JY, Song JT, Seo HS. COP1 regulates plant growth and development in response to light at the post-translational level. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:4737-4748. [PMID: 28992300 DOI: 10.1093/jxb/erx312] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Photoreceptors perceive different wavelengths of light and transduce light signals downstream via a range of proteins. COP1, an E3 ubiquitin ligase, regulates light signaling by mediating the ubiquitination and subsequent proteasomal degradation of photoreceptors such as phytochromes and cryptochromes, as well as various development-related proteins including other light-responsive proteins. COP1 is itself regulated by direct interactions with several signaling molecules that modulate its activity. The control of photomorphogenesis by COP1 is also regulated by its localization to the cytoplasm in response to light. COP1 thus acts as a tightly regulated switch that determines whether development is skotomorphogenic or photomorphogenic. In this review, we discuss the effects of COP1 on the abundance and activity of various development-related proteins, including photoreceptors, and summarize the regulatory mechanisms that influence COP1 activity and stability in plants.
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Affiliation(s)
- Joo Yong Kim
- Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea
| | - Jong Tae Song
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - Hak Soo Seo
- Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea
- Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-921, Korea
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17
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Phosphorylation and negative regulation of CONSTITUTIVELY PHOTOMORPHOGENIC 1 by PINOID in Arabidopsis. Proc Natl Acad Sci U S A 2017; 114:6617-6622. [PMID: 28584104 DOI: 10.1073/pnas.1702984114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) plays crucial roles in various cellular processes via its E3 ubiquitin ligase activity in organisms, ranging from fungi to humans. As a key component in regulating various biological events, COP1 itself is precisely controlled at multiple layers. Here, we report a negative regulator of COP1, PINOID (PID), which positively mediates photomorphogenic development. Specifically, PID genetically and physically interacts with COP1 and directly phosphorylates COP1 at Ser20. As a result, this posttranslational modification serves to repress COP1 activity and promote photomorphogenesis. Our findings signify a key regulatory mechanism for precisely maintaining COP1 activity, thereby ensuring appropriate development in plants.
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18
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Hoecker U. The activities of the E3 ubiquitin ligase COP1/SPA, a key repressor in light signaling. CURRENT OPINION IN PLANT BIOLOGY 2017; 37:63-69. [PMID: 28433946 DOI: 10.1016/j.pbi.2017.03.015] [Citation(s) in RCA: 138] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 03/17/2017] [Accepted: 03/28/2017] [Indexed: 05/21/2023]
Abstract
Light is a critical signal to integrate plant growth and development with the environment. Downstream of photoreceptors, the E3 ubiquitin ligase COP1/SPA is a key repressor of photomorphogenesis which targets many positive regulators of light signaling, mainly transcription factors, for degradation in darkness. In light-grown plants COP1/SPA activity is repressed, allowing light responses to occur. This review provides an overview on our current knowledge on COP1/SPA repressor function, focusing in particular on the roles of the respective protein domains and the mechanisms of light-induced inactivation of COP1/SPA. Moreover, we summarize how COP1 activity is regulated by other interacting proteins, such as a SUMO E3 ligase and Phytochrome-Interacting Factors (PIFs), as well as by hormones. At last, several novel functions of COP1 that were recently revealed are included.
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Affiliation(s)
- Ute Hoecker
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Str. 47b, D-50674 Cologne, Germany.
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19
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Menon C, Sheerin DJ, Hiltbrunner A. SPA proteins: SPAnning the gap between visible light and gene expression. PLANTA 2016; 244:297-312. [PMID: 27100111 DOI: 10.1007/s00425-016-2509-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Accepted: 03/26/2016] [Indexed: 05/23/2023]
Abstract
In this review we focus on the role of SPA proteins in light signalling and discuss different aspects, including molecular mechanisms, specificity, and evolution. The ability of plants to perceive and respond to their environment is key to their survival under ever-changing conditions. The abiotic factor light is of particular importance for plants. Light provides plants energy for carbon fixation through photosynthesis, but also is a source of information for the adaptation of growth and development to the environment. Cryptochromes and phytochromes are major photoreceptors involved in control of developmental decisions in response to light cues, including seed germination, seedling de-etiolation, and induction of flowering. The SPA protein family acts in complex with the E3 ubiquitin ligase COP1 to target positive regulators of light responses for degradation by the 26S proteasome to suppress photomorphogenic development in darkness. Light-activated cryptochromes and phytochromes both repress the function of COP1, allowing accumulation of positive photomorphogenic factors in light. In this review, we highlight the role of the SPA proteins in this process and discuss recent advances in understanding how SPAs link light-activation of photoreceptors and downstream signaling.
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Affiliation(s)
- Chiara Menon
- Faculty of Biology, Institute of Biology II, University of Freiburg, Schänzlestrasse 1, 79104, Freiburg, Germany
- Center for Plant Molecular Biology, University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - David J Sheerin
- Faculty of Biology, Institute of Biology II, University of Freiburg, Schänzlestrasse 1, 79104, Freiburg, Germany
| | - Andreas Hiltbrunner
- Faculty of Biology, Institute of Biology II, University of Freiburg, Schänzlestrasse 1, 79104, Freiburg, Germany.
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18, 79104, Freiburg, Germany.
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20
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Photoreceptor effects on plant biomass, resource allocation, and metabolic state. Proc Natl Acad Sci U S A 2016; 113:7667-72. [PMID: 27330114 DOI: 10.1073/pnas.1601309113] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Plants sense the light environment through an ensemble of photoreceptors. Members of the phytochrome class of light receptors are known to play a critical role in seedling establishment, and are among the best-characterized plant signaling components. Phytochromes also regulate adult plant growth; however, our knowledge of this process is rather fragmented. This study demonstrates that phytochrome controls carbon allocation and biomass production in the developing plant. Phytochrome mutants have a reduced CO2 uptake, yet overaccumulate daytime sucrose and starch. This finding suggests that even though carbon fixation is impeded, the available carbon resources are not fully used for growth during the day. Supporting this notion, phytochrome depletion alters the proportion of day:night growth. In addition, phytochrome loss leads to sizeable reductions in overall growth, dry weight, total protein levels, and the expression of CELLULOSE SYNTHASE-LIKE genes. Because cellulose and protein are major constituents of plant biomass, our data point to an important role for phytochrome in regulating these fundamental components of plant productivity. We show that phytochrome loss impacts core metabolism, leading to elevated levels of tricarboxylic acid cycle intermediates, amino acids, sugar derivatives, and notably the stress metabolites proline and raffinose. Furthermore, the already growth-retarded phytochrome mutants are less responsive to growth-inhibiting abiotic stresses and have elevated expression of stress marker genes. This coordinated response appears to divert resources from energetically costly biomass production to improve resilience. In nature, this strategy may be activated in phytochrome-disabling, vegetation-dense habitats to enhance survival in potentially resource-limiting conditions.
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21
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Chen S, Lory N, Stauber J, Hoecker U. Photoreceptor Specificity in the Light-Induced and COP1-Mediated Rapid Degradation of the Repressor of Photomorphogenesis SPA2 in Arabidopsis. PLoS Genet 2015; 11:e1005516. [PMID: 26368289 PMCID: PMC4569408 DOI: 10.1371/journal.pgen.1005516] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 08/19/2015] [Indexed: 11/18/2022] Open
Abstract
The Arabidopsis COP1/SPA E3 ubiquitin ligase is a key negative regulator that represses light signaling in darkness by targeting transcription factors involved in the light response for degradation. The COP1/SPA complex consists of COP1 and members of the four-member SPA protein family (SPA1-SPA4). Genetic analysis indicated that COP1/SPA2 function is particularly strongly repressed by light when compared to complexes carrying the other three SPAs, thereby promoting a light response after exposure of plants to extremely low light. Here, we show that the SPA2 protein is degraded within 5–15 min after exposure of dark-grown seedlings to a pulse of light. Phytochrome photoreceptors are required for the rapid degradation of SPA2 in red, far-red and also in blue light, whereas cryptochromes are not involved in the rapid, blue light-induced reduction in SPA2 protein levels. These results uncover a photoreceptor-specific mechanism of light-induced inhibition of COP1/SPA2 function. Phytochrome A (phyA) is required for the severe blue light responsiveness of spa triple mutants expressing only SPA2, thus confirming the important role of phyA in downregulating SPA2 function in blue light. In blue light, SPA2 forms a complex with cryptochrome 1 (cry1), but not with cryptochrome 2 (cry2) in vivo, indicating that the lack of a rapid blue light response of the SPA2 protein is only in part caused by a failure to interact with cryptochromes. Since SPA1 interacts with both cry1 and cry2, these results provide first molecular evidence that the light-regulation of different SPA proteins diverged during evolution. SPA2 degradation in the light requires COP1 and the COP1-interacting coiled-coil domain of SPA2, supporting that SPA2 is ubiquitinated by COP1. We propose that light perceived by phytochromes causes a switch in the ubiquitination activity of COP1/SPA2 from ubiquitinating downstream substrates to ubiquitinating SPA2, which subsequently causes a repression of COP1/SPA2 function. Plants have evolved photoreceptors that initiate a signaling cascade to adjust growth and development to the ambient light environment. The CUL4-dependent COP1/SPA E3 ubiquitin ligase is a key negative regulator of light signaling whose function is repressed by light. Recent research has identified mechanisms that are common to both phytochrome and cryptochrome photoreceptors. Here, we have identified a mechanism of light-induced COP1/SPA repression that is specific to phytochrome photoreceptors. We show that the SPA2 protein is very rapidly degraded in red, far-red and blue light in a phytochrome-dependent fashion. We further show that SPA2 degradation in the light depends on COP1 and on the interaction of SPA2 with COP1. Hence, our results suggest a light-induced degradation of SPA2, but not of COP1, by the COP1/SPA2 ubiquitin ligase. The human ortholog of COP1, which functions without the plant-specific SPA proteins, is known to be regulated by autodegradation following DNA damage. Hence, autodegradation of components of this E3 ligase is a regulatory mechanism used in both humans and plants.
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Affiliation(s)
- Song Chen
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Cologne, Germany
| | - Niels Lory
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Cologne, Germany
| | - Johannes Stauber
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Cologne, Germany
| | - Ute Hoecker
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Cologne, Germany
- * E-mail:
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22
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Rattanapisit K, Cho MH, Bhoo SH. Lysine 206 in Arabidopsis phytochrome A is the major site for ubiquitin-dependent protein degradation. J Biochem 2015; 159:161-9. [PMID: 26314334 DOI: 10.1093/jb/mvv085] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 07/22/2015] [Indexed: 11/14/2022] Open
Abstract
Phytochrome A (phyA) is a light labile phytochrome that mediates plant development under red/far-red light condition. Degradation of phyA is initiated by red light-induced phyA-ubiquitin conjugation through the 26S proteasome pathway. The N-terminal of phyA is known to be important in phyA degradation. To determine the specific lysine residues in the N-terminal domain of phyA involved in light-induced ubiquitination and protein degradation, we aligned the amino acid sequence of the N-terminal domain of Arabidopsis phyA with those of phyA from other plant species. Based on the alignment results, phytochrome over-expressing Arabidopsis plants were generated. In particular, wild-type and mutant (substitutions of conserved lysines by arginines) phytochromes fused with GFP were expressed in phyA(-)211 Arabidopsis plants. Degradation kinetics of over-expressed phyA proteins revealed that degradation of the K206R phyA mutant protein was delayed. Delayed phyA degradation of the K206R phyA mutant protein resulted in reduction of red-light-induced phyA-ubiquitin conjugation. Furthermore, seedlings expressing the K206R phyA mutant protein showed an enhanced phyA response under far-red light, resulting in inhibition of hypocotyl elongation as well as cotyledon opening. Together, these results suggest that lysine 206 is the main lysine for rapid ubiquitination and protein degradation of Arabidopsis phytochrome A.
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Affiliation(s)
- Kaewta Rattanapisit
- Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 17104, Korea
| | - Man-Ho Cho
- Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 17104, Korea
| | - Seong Hee Bhoo
- Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 17104, Korea
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23
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Klose C, Viczián A, Kircher S, Schäfer E, Nagy F. Molecular mechanisms for mediating light-dependent nucleo/cytoplasmic partitioning of phytochrome photoreceptors. THE NEW PHYTOLOGIST 2015; 206:965-71. [PMID: 26042244 PMCID: PMC4406131 DOI: 10.1111/nph.13207] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 11/05/2014] [Indexed: 05/19/2023]
Abstract
The photoreceptors phytochromes monitor the red/far-red part of the spectrum, exist in the biologically active Pfr (far-red absorbing) or inactive Pr (red absorbing) forms, and function as red/far-red light-regulated molecular switches to modulate plant development and growth. Phytochromes are synthesized in the cytoplasm, and light induces translocation of the Pfr conformer into the nucleus. Nuclear import of phytochromes is a highly regulated process and is fine-tuned by the quality and quantity of light. It appears that phytochrome A (phyA) and phytochrome B (phyB) do not possess active endogenous nuclear import signals (NLSs), thus light-induced translocation of these photoreceptors into the nucleus requires direct protein–protein interactions with their NLS-containing signaling partners. Sub-cellular partitioning of the various phytochrome species is mediated by different molecular machineries. Translocation of phyA into the nucleus is promoted by FAR-RED ELONGATED HYPOCOTYL 1 (FHY1) and FHY1-LIKE (FHL), but the identity of nuclear transport facilitators mediating the import of phyB-E into the nucleus remains elusive. Phytochromes localized in the nucleus are associated with specific protein complexes, termed photobodies. The size and distribution of these structures are regulated by the intensity and duration of irradiation, and circumstantial evidence indicates that they are involved in fine-tuning phytochrome signaling.
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Affiliation(s)
- Cornelia Klose
- Institute of Botany, University of FreiburgSchänzlestrasse 1, D-79104, Freiburg, Germany
| | - András Viczián
- Institute of Plant Biology, Biological Research CentreTemesvári krt. 62, H-6726, Szeged, Hungary
| | - Stefan Kircher
- Institute of Botany, University of FreiburgSchänzlestrasse 1, D-79104, Freiburg, Germany
| | - Eberhard Schäfer
- Institute of Botany, University of FreiburgSchänzlestrasse 1, D-79104, Freiburg, Germany
| | - Ferenc Nagy
- Institute of Plant Biology, Biological Research CentreTemesvári krt. 62, H-6726, Szeged, Hungary
- School of Biological Sciences, Institute of Molecular Plant Science, University of EdinburghEdinburgh, EH9 3JH, UK
- Author for correspondence: Ferenc Nagy Tel: +36 62599718
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24
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Sheerin DJ, Menon C, zur Oven-Krockhaus S, Enderle B, Zhu L, Johnen P, Schleifenbaum F, Stierhof YD, Huq E, Hiltbrunner A. Light-activated phytochrome A and B interact with members of the SPA family to promote photomorphogenesis in Arabidopsis by reorganizing the COP1/SPA complex. THE PLANT CELL 2015; 27:189-201. [PMID: 25627066 PMCID: PMC4330587 DOI: 10.1105/tpc.114.134775] [Citation(s) in RCA: 226] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 11/28/2014] [Accepted: 01/08/2015] [Indexed: 05/18/2023]
Abstract
Phytochromes function as red/far-red photoreceptors in plants and are essential for light-regulated growth and development. Photomorphogenesis, the developmental program in light, is the default program in seed plants. In dark-grown seedlings, photomorphogenic growth is suppressed by the action of the CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)/SUPPRESSOR OF phyA-105 (SPA) complex, which targets positive regulators of photomorphogenic growth for degradation by the proteasome. Phytochromes inhibit the COP1/SPA complex, leading to the accumulation of transcription factors promoting photomorphogenesis; yet, the mechanism by which they inactivate COP1/SPA is still unknown. Here, we show that light-activated phytochrome A (phyA) and phytochrome B (phyB) interact with SPA1 and other SPA proteins. Fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy analyses show that SPAs and phytochromes colocalize and interact in nuclear bodies. Furthermore, light-activated phyA and phyB disrupt the interaction between COP1 and SPAs, resulting in reorganization of the COP1/SPA complex in planta. The light-induced stabilization of HFR1, a photomorphogenic factor targeted for degradation by COP1/SPA, correlates temporally with the accumulation of phyA in the nucleus and localization of phyA to nuclear bodies. Overall, these data provide a molecular mechanism for the inactivation of the COP1/SPA complex by phyA- and phyB-mediated light perception.
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Affiliation(s)
- David J Sheerin
- Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Chiara Menon
- Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Sven zur Oven-Krockhaus
- Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Beatrix Enderle
- Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Ling Zhu
- Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712
| | - Philipp Johnen
- Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Frank Schleifenbaum
- Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - York-Dieter Stierhof
- Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Enamul Huq
- Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712
| | - Andreas Hiltbrunner
- Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
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25
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Huang X, Ouyang X, Deng XW. Beyond repression of photomorphogenesis: role switching of COP/DET/FUS in light signaling. CURRENT OPINION IN PLANT BIOLOGY 2014; 21:96-103. [PMID: 25061897 DOI: 10.1016/j.pbi.2014.07.003] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/26/2014] [Accepted: 07/02/2014] [Indexed: 05/04/2023]
Abstract
Light is a pivotal environmental stimulus that promotes plant photomorphogenesis. Substantial progress has been achieved in defining the central repressors of photomorphogenesis, the CONSTITUTIVE PHOTOMORPHOGENIC/DE-ETIOLATED/FUSCA (COP/DET/FUS) loci, in the past 20 years. COP/DET/FUS proteins are well-conserved, and regulate a variety of biological processes in plants and animals. The fact that these proteins contribute to the repression of plant photomorphogenesis by regulating the ubiquitin-proteasome-dependent pathway has been well established. Recently, molecular insight has been gained into the functional diversity of COP/DET/FUS. Here, we review the current research on the roles of COP/DET/FUS, with a focus on the functional conversion of COP1 in photomorphogenesis.
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Affiliation(s)
- Xi Huang
- School of Life Sciences, Xiamen University, Xiamen 361102, China
| | - Xinhao Ouyang
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing 100871, China
| | - Xing Wang Deng
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing 100871, China; Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520-8104, USA.
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Casal JJ, Candia AN, Sellaro R. Light perception and signalling by phytochrome A. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:2835-45. [PMID: 24220656 DOI: 10.1093/jxb/ert379] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In etiolated seedlings, phytochrome A (phyA) mediates very-low-fluence responses (VLFRs), which initiate de-etiolation at the interphase between the soil and above-ground environments, and high-irradiance responses (HIR), which complete de-etiolation under dense canopies and require more sustained activation with far-red light. Light-activated phyA is transported to the nucleus by FAR-RED ELONGATED HYPOCOTYL1 (FHY1). The nuclear pool of active phyA increases under prolonged far-red light of relatively high fluence rates. This condition maximizes the rate of FHY1-phyA complex assembly and disassembly, allowing FHY1 to return to the cytoplasm to translocate further phyA to the nucleus, to replace phyA degraded in the proteasome. The core signalling pathways downstream of nuclear phyA involve the negative regulation of CONSTITUTIVE PHOTOMORPHOGENIC 1, which targets for degradation transcription factors required for photomorphogenesis, and PHYTOCHROME-INTERACTING FACTORs, which are transcription factors that repress photomorphogenesis. Under sustained far-red light activation, released FHY1 can also be recruited with active phyA to target gene promoters as a transcriptional activator, and nuclear phyA signalling activates a positive regulatory loop involving BELL-LIKE HOMEODOMAIN 1 that reinforces the HIR.
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Affiliation(s)
- J J Casal
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and CONICET, 1417 Buenos Aires, Argentina Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires-CONICET, C1405BWE Buenos Aires, Argentina
| | - A N Candia
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and CONICET, 1417 Buenos Aires, Argentina
| | - R Sellaro
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and CONICET, 1417 Buenos Aires, Argentina
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Xu D, Lin F, Jiang Y, Huang X, Li J, Ling J, Hettiarachchi C, Tellgren-Roth C, Holm M, Deng XW. The RING-Finger E3 Ubiquitin Ligase COP1 SUPPRESSOR1 Negatively Regulates COP1 Abundance in Maintaining COP1 Homeostasis in Dark-Grown Arabidopsis Seedlings. THE PLANT CELL 2014; 26:1981-1991. [PMID: 24838976 PMCID: PMC4079363 DOI: 10.1105/tpc.114.124024] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/13/2014] [Accepted: 04/28/2014] [Indexed: 05/18/2023]
Abstract
CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) functions as an E3 ubiquitin ligase in both plants and animals. In dark-grown Arabidopsis thaliana seedlings, COP1 targets photomorphogenesis-promoting factors for degradation to repress photomorphogenesis. Little is known, however, about how COP1 itself is regulated. Here, we identify COP1 SUPPRESSOR1 (CSU1), a RING-finger E3 ubiquitin ligase, as a regulator of COP1. Genetic evidence demonstrates that csu1 mutations suppress cop1-6 phenotypes completely in the dark. Furthermore, CSU1 colocalizes with COP1 in nuclear speckles and negatively regulates COP1 protein accumulation in darkness. CSU1 can ubiquitinate COP1 in vitro and is essential for COP1 ubiquitination in vivo. Therefore, we conclude that CSU1 plays a major role in maintaining COP1 homeostasis by targeting COP1 for ubiquitination and degradation in dark-grown seedlings.
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Affiliation(s)
- Dongqing Xu
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden
| | - Fang Lin
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Yan Jiang
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden
| | - Xi Huang
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Jigang Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Junjie Ling
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Chamari Hettiarachchi
- Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden
| | - Christian Tellgren-Roth
- Uppsala Genome Center, National Genomics Infrastructure-Science for Life Laboratory, Department of Immunology, Genetics, and Pathology, Uppsala University, Rudbeck Laboratory, SE-751 85 Uppsala, Sweden
| | - Magnus Holm
- Department of Biological and Environmental Sciences, Gothenburg University, SE-405 30 Gothenburg, Sweden
| | - Xing Wang Deng
- Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
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Zhou P, Song M, Yang Q, Su L, Hou P, Guo L, Zheng X, Xi Y, Meng F, Xiao Y, Yang L, Yang J. Both PHYTOCHROME RAPIDLY REGULATED1 (PAR1) and PAR2 promote seedling photomorphogenesis in multiple light signaling pathways. PLANT PHYSIOLOGY 2014; 164:841-52. [PMID: 24335334 PMCID: PMC3912110 DOI: 10.1104/pp.113.227231] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 12/09/2013] [Indexed: 05/20/2023]
Abstract
Arabidopsis (Arabidopsis thaliana) seedlings undergo photomorphogenesis in the light and etiolation in the dark. Light-activated photoreceptors transduce the light signals through a series of photomorphogenesis promoting or repressing factors to modulate many developmental processes in plants, such as photomorphogenesis and shade avoidance. CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) is a conserved RING finger E3 ubiquitin ligase, which mediates degradation of several photomorphogenesis promoting factors, including ELONGATED HYPOCOTYL5 (HY5) and LONG HYPOCOTYL IN FAR-RED1 (HFR1), through a 26S proteasome-dependent pathway. PHYTOCHROME RAPIDLY REGULATED1 (PAR1) was first detected as an early repressed gene in both phytochrome A (phyA)-mediated far-red and phyB-mediated red signaling pathways, and subsequent studies showed that both PAR1 and PAR2 are negative factors of shade avoidance in Arabidopsis. However, the role of PAR1 and PAR2 in seedling deetiolation, and their relationships with other photomorphogenesis promoting and repressing factors are largely unknown. Here, we confirmed that both PAR1 and PAR2 redundantly enhance seedling deetiolation in multiple photoreceptor signaling pathways. Their transcript abundances are repressed by phyA, phyB, and cryptochrome1 under far-red, red, and blue light conditions, respectively. Both PAR1 and PAR2 act downstream of COP1, and COP1 mediates the degradation of PAR1 and PAR2 through the 26S proteasome pathway. Both PAR1 and PAR2 act in a separate pathway from HY5 and HFR1 under different light conditions, except for sharing in the same pathway with HFR1 under far-red light. Together, our results substantiate that PAR1 and PAR2 are positive factors functioning in multiple photoreceptor signaling pathways during seedling deetiolation.
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Bender KW, Rosenbaum DM, Vanderbeld B, Ubaid M, Snedden WA. The Arabidopsis calmodulin-like protein, CML39, functions during early seedling establishment. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:634-47. [PMID: 24033804 DOI: 10.1111/tpj.12323] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 08/26/2013] [Accepted: 09/02/2013] [Indexed: 05/10/2023]
Abstract
During Ca(2+) signal transduction, Ca(2+)-binding proteins known as Ca(2+) sensors function to decode stimulus-specific Ca(2+) signals into downstream responses. Plants possess extended families of unique Ca(2+) sensors termed calmodulin-like proteins (CMLs) whose cellular roles are not well understood. CML39 encodes a predicted Ca(2+) sensor whose expression is strongly increased in response to diverse external stimuli. In the present study, we explored the biochemical properties of recombinant CML39, and used a reverse genetics approach to investigate its physiological role. Our data indicate that Ca(2+) binding by CML39 induces a conformational change in the protein that results in an increase in exposed-surface hydrophobicity, a property that is consistent with its predicted function as a Ca(2+) sensor. Loss-of-function cml39 mutants resemble wild-type plants under normal growth conditions but exhibit persistent arrest at the seedling stage if grown in the absence of sucrose or other metabolizable carbon sources. Under short-day conditions, cml39 mutants display increased sucrose-induced hypocotyl elongation. When grown in the dark, cml39 mutants show impaired hypocotyl elongation in the absence of sucrose. Promoter-reporter data indicate that CML39 expression is prominent in the apical hook in dark-grown seedlings. Collectively, our data suggest that CML39 functions in Arabidopsis as a Ca(2+) sensor that plays an important role in the transduction of light signals that promote seedling establishment.
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Affiliation(s)
- Kyle W Bender
- Department of Biology, Queen's University, Kingston, ON, K7L 3N6, Canada
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