151
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Hernández IG, Gomez FJV, Cerutti S, Arana MV, Silva MF. Melatonin in Arabidopsis thaliana acts as plant growth regulator at low concentrations and preserves seed viability at high concentrations. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2015; 94:191-6. [PMID: 26113158 DOI: 10.1016/j.plaphy.2015.06.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/04/2015] [Accepted: 06/08/2015] [Indexed: 05/18/2023]
Abstract
Since the discovery of melatonin in plants, several roles have been described for different species, organs, and developmental stages. Arabidopsis thaliana, being a model plant species, is adequate to contribute to the elucidation of the role of melatonin in plants. In this work, melatonin was monitored daily by UHPLC-MS/MS in leaves, in order to study its diurnal accumulation as well as the effects of natural and artificial light treatments on its concentration. Furthermore, the effects of exogenous application of melatonin to assess its role in seed viability after heat stress and as a regulator of growth and development of vegetative tissues were evaluated. Our results indicate that melatonin contents in Arabidopsis were higher in plants growing under natural radiation when compared to those growing under artificial conditions, and its levels were not diurnally-regulated. Exogenous melatonin applications prolonged seed viability after heat stress conditions. In addition, melatonin applications retarded leaf senescence. Its effects as growth promoter were dose and tissue-dependent; stimulating root growth at low concentrations and decreasing leaf area at high doses.
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Affiliation(s)
- Ismaél Gatica Hernández
- Instituto de Biología Agrícola de Mendoza (IBAM-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Federico José Vicente Gomez
- Instituto de Biología Agrícola de Mendoza (IBAM-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Soledad Cerutti
- Instituto de Química de San Luis (INQUISAL-CONICET), Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, San Luis, Argentina
| | - María Verónica Arana
- Instituto Nacional de Tecnología Agropecuaria (INTA-Bariloche), Estación Experimental Agropecuaria Bariloche, CONICET, Río Negro, Argentina
| | - María Fernanda Silva
- Instituto de Biología Agrícola de Mendoza (IBAM-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo, Mendoza, Argentina.
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152
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Liu N, Gong B, Jin Z, Wang X, Wei M, Yang F, Li Y, Shi Q. Sodic alkaline stress mitigation by exogenous melatonin in tomato needs nitric oxide as a downstream signal. JOURNAL OF PLANT PHYSIOLOGY 2015; 186-187:68-77. [PMID: 26412100 DOI: 10.1016/j.jplph.2015.07.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 06/30/2015] [Accepted: 07/03/2015] [Indexed: 05/03/2023]
Abstract
The present study was designed to determine the interactive effect of exogenous melatonin and nitric oxide (NO) on sodic alkaline stress mitigation in tomato seedlings. It was observed that exogenous melatonin treatment elevated NO levels in alkaline-stressed tomato roots. However, exogenous NO had little effects on melatonin levels. Importantly, melatonin-induced NO generation was accompanied by increased tolerance to alkaline stress. Chemical scavenging of NO reduced melatonin-induced alkaline stress tolerance and defense genes' expression. However, inhibition of melatonin biosynthesis had a little effect on NO-induced alkaline stress tolerance. These results strongly suggest that NO, acting as a downstream signal, is involved in the melatonin-induced tomato tolerance to alkaline stress. This process creates a new signaling pathway for improving stress tolerance in plant.
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Affiliation(s)
- Na Liu
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Biao Gong
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Zhiyong Jin
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Xiufeng Wang
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Min Wei
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Fengjuan Yang
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Yan Li
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China
| | - Qinghua Shi
- State Key Laboratory of Crop Biology, Scientific Observing and Experimental Station of Environment Controlled Agricultural Engineering in Huang-Huai-Hai Region, Ministry of Agriculture, PR China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, PR China.
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153
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Hasan MK, Ahammed GJ, Yin L, Shi K, Xia X, Zhou Y, Yu J, Zhou J. Melatonin mitigates cadmium phytotoxicity through modulation of phytochelatins biosynthesis, vacuolar sequestration, and antioxidant potential in Solanum lycopersicum L. FRONTIERS IN PLANT SCIENCE 2015; 6:601. [PMID: 26322055 PMCID: PMC4531246 DOI: 10.3389/fpls.2015.00601] [Citation(s) in RCA: 173] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 07/21/2015] [Indexed: 05/17/2023]
Abstract
Melatonin is a ubiquitous signal molecule, playing crucial roles in plant growth and stress tolerance. Recently, toxic metal cadmium (Cd) has been reported to regulate melatonin content in rice; however, the function of melatonin under Cd stress, particularly in higher plants, still remains elusive. Here, we show that optimal dose of melatonin could effectively ameliorate Cd-induced phytotoxicity in tomato. The contents of Cd and melatonin were gradually increased over time under Cd stress. However, such increase in endogenous melatonin was incapable to reverse detrimental effects of Cd. Meanwhile, supplementation with melatonin conferred Cd tolerance as evident by plant biomass and photosynthesis. In addition to notable increase in antioxidant enzymes activity, melatonin-induced Cd stress mitigation was closely associated with enhanced H(+)-ATPase activity and the contents of glutathione and phytochelatins. Although exogenous melatonin had no effect on root Cd content, it significantly reduced leaf Cd content, indicating its role in Cd transport. Analysis of Cd in different subcellular compartments revealed that melatonin increased cell wall and vacuolar fractions of Cd. Our results suggest that melatonin-induced enhancements in antioxidant potential, phytochelatins biosynthesis and subsequent Cd sequestration might play a critical role in plant tolerance to Cd. Such a mechanism may have potential implication in safe food production.
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Affiliation(s)
| | | | - Lingling Yin
- Department of Horticulture, Zhejiang University, HangzhouChina
| | - Kai Shi
- Department of Horticulture, Zhejiang University, HangzhouChina
- Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative BiologyHangzhou, China
| | - Xiaojian Xia
- Department of Horticulture, Zhejiang University, HangzhouChina
- Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative BiologyHangzhou, China
| | - Yanhong Zhou
- Department of Horticulture, Zhejiang University, HangzhouChina
- Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative BiologyHangzhou, China
- Key Laboratory of Horticultural Plants Growth, Development and Quality Improvement, Agricultural Ministry of ChinaHangzhou, China
| | - Jingquan Yu
- Department of Horticulture, Zhejiang University, HangzhouChina
- Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative BiologyHangzhou, China
- Key Laboratory of Horticultural Plants Growth, Development and Quality Improvement, Agricultural Ministry of ChinaHangzhou, China
| | - Jie Zhou
- Department of Horticulture, Zhejiang University, HangzhouChina
- Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative BiologyHangzhou, China
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154
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Zhao H, Xu L, Su T, Jiang Y, Hu L, Ma F. Melatonin regulates carbohydrate metabolism and defenses against Pseudomonas syringae pv. tomato DC3000 infection in Arabidopsis thaliana. J Pineal Res 2015; 59:109-19. [PMID: 25958775 DOI: 10.1111/jpi.12245] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 05/05/2015] [Indexed: 01/06/2023]
Abstract
Melatonin has been reported to promote plant growth and development. Our experiments with Arabidopsis thaliana showed that exogenous applications of this molecule mediated invertase inhibitor (C/VIF)-regulated invertase activity and enhanced sucrose metabolism. Hexoses were accumulated in response to elevated activities by cell wall invertase (CWI) and vacuolar invertase (VI). Analyses of sugar metabolism-related genes revealed differential expression during plant development that was modulated by melatonin. In particular, C/VIF1 and C/VIF2 were strongly down-regulated by exogenous feeding. We also found the elevated CWI activity in melatonin-treated Arabidopsis improved the factors (cellulose, xylose, and galactose) for cell wall reinforcement and callose deposition during Pseudomonas syringae pv. tomato DC3000 infection, therefore, partially induced the pathogen resistance. However, CWI did not involve in salicylic acid (SA)-regulated defense pathway. Taken together, this study reveals that melatonin plays an important role in invertase-related carbohydrate metabolism, plant growth, and pathogen defense.
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Affiliation(s)
- Hongbo Zhao
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Lingfei Xu
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Tao Su
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Yang Jiang
- Centre for Organismal Studies Heidelberg, Heidelberg university, Heidelberg, Germany
| | - Lingyu Hu
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Fengwang Ma
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
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155
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Liang C, Zheng G, Li W, Wang Y, Hu B, Wang H, Wu H, Qian Y, Zhu XG, Tan DX, Chen SY, Chu C. Melatonin delays leaf senescence and enhances salt stress tolerance in rice. J Pineal Res 2015; 59:91-101. [PMID: 25912474 DOI: 10.1111/jpi.12243] [Citation(s) in RCA: 176] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Accepted: 04/23/2015] [Indexed: 12/16/2022]
Abstract
Melatonin, an antioxidant in both animals and plants, has been reported to have beneficial effects on the aging process. It was also suggested to play a role in extending longevity and enhancing abiotic stress resistance in plant. In this study, we demonstrate that melatonin acts as a potent agent to delay leaf senescence and cell death in rice. Treatments with melatonin significantly reduced chlorophyll degradation, suppressed the transcripts of senescence-associated genes, delayed the leaf senescence, and enhanced salt stress tolerance. Genome-wide expression profiling by RNA sequencing reveals that melatonin is a potent free radical scavenger, and its exogenous application results in enhanced antioxidant protection. Leaf cell death in noe1, a mutant with over-produced H2O2, can be relieved by exogenous application of melatonin. These data demonstrate that melatonin delays the leaf senescence and cell death and also enhances abiotic stress tolerance via directly or indirectly counteracting the cellular accumulation of H2O2.
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Affiliation(s)
- Chengzhen Liang
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
| | - Guangyong Zheng
- CAS Key Laboratory for Computational Biology, CAS-MPG Partner Institute for Computational Biology, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Wenzhen Li
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
| | - Yiqin Wang
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
| | - Bin Hu
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
| | - Hongru Wang
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
| | - Hongkai Wu
- School of Agriculture and Food Science, Zhejiang A & F University, Hangzhou, China
| | - Yangwen Qian
- Biogle Genome Editing Research Center, Hangzhou, China
| | - Xin-Guang Zhu
- CAS Key Laboratory for Computational Biology, CAS-MPG Partner Institute for Computational Biology, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Dun-Xian Tan
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Shou-Yi Chen
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
| | - Chengcai Chu
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences (CAS), Beijing, China
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156
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Shi H, Chen Y, Tan DX, Reiter RJ, Chan Z, He C. Melatonin induces nitric oxide and the potential mechanisms relate to innate immunity against bacterial pathogen infection in Arabidopsis. J Pineal Res 2015; 59:102-8. [PMID: 25960153 DOI: 10.1111/jpi.12244] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 05/05/2015] [Indexed: 12/17/2022]
Abstract
Melatonin (N-acetyl-5-methoxytryptamine) is a naturally occurring small molecule, serving as important secondary messenger in the response of plants to various biotic and abiotic stresses. However, the interactions between melatonin and other important molecules in the plant stress response, especially in plant immunity, are largely unknown. In this study, we found that both melatonin and nitric oxide (NO) levels in Arabidopsis leaves were significantly induced by bacterial pathogen (Pst DC3000) infection. The elevated NO production was caused by melatonin as melatonin application enhanced endogenous NO level with great efficacy. Moreover, both melatonin and NO conferred improved disease resistance against Pseudomonas syringe pv. tomato (Pst) DC3000 infection in Arabidopsis. NO scavenger significantly suppressed the rise of NO which was induced by exogenous application of melatonin. As a result, the beneficial effects of melatonin on the expression of salicylic acid (SA)-related genes and disease resistance against bacterial pathogen infection were jeopardized by use of a NO scavenger. Consistently, melatonin application significantly lost its effect on the innate immunity against P. syringe pv. tomato (Pst) DC3000 infection in NO-deficient mutants of Arabidopsis. The results indicate that melatonin-induced NO production is responsible for innate immunity response of Arabidopsis against Pst DC3000 infection.
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Affiliation(s)
- Haitao Shi
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University, Haikou, China
| | - Yinhua Chen
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University, Haikou, China
| | - Dun-Xian Tan
- Department of Cellular and Structural Biology, The University of Texas Health Science Center, San Antonio, TX, USA
| | - Russel J Reiter
- Department of Cellular and Structural Biology, The University of Texas Health Science Center, San Antonio, TX, USA
| | - Zhulong Chan
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
| | - Chaozu He
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University, Haikou, China
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157
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Byeon Y, Lee HY, Back K. Chloroplastic and cytoplasmic overexpression of sheep serotonin N-acetyltransferase in transgenic rice plants is associated with low melatonin production despite high enzyme activity. J Pineal Res 2015; 58:461-9. [PMID: 25782973 DOI: 10.1111/jpi.12231] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 03/13/2015] [Indexed: 01/05/2023]
Abstract
Serotonin N-acetyltransferase (SNAT), the penultimate enzyme in melatonin biosynthesis, catalyzes the conversion of serotonin into N-acetylserotonin. Plant SNAT is localized in chloroplasts. To test SNAT localization effects on melatonin synthesis, we generated transgenic rice plants overexpressing a sheep (Ovis aries) SNAT (OaSNAT) in their chloroplasts and compared melatonin biosynthesis with that of transgenic rice plants overexpressing OaSNAT in their cytoplasm. To localize the OaSNAT in chloroplasts, we used a chloroplast targeting sequence (CTS) from tobacco protoporphyrinogen IX oxidase (PPO), which expresses in chloroplasts. The purified recombinant CTS:OaSNAT fusion protein was enzymatically functional and localized in chloroplasts as confirmed by confocal microscopic analysis. The chloroplast-targeted CTS:OaSNAT lines and cytoplasm-expressed OaSNAT lines had similarly high SNAT enzyme activities. However, after cadmium and butafenacil treatments, melatonin production in rice leaves was severalfold lower in the CTS:OaSNAT lines than in the OaSNAT lines. Notably, enhanced SNAT enzyme activity was not directly proportional to the production of N-acetylserotonin, melatonin, or 2-hydroxymelatonin, suggesting that plant SNAT has a role in the homeostatic regulation of melatonin rather than in accelerating melatonin synthesis.
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Affiliation(s)
- Yeong Byeon
- Department of Biotechnology, Bioenergy Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea
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158
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Byeon Y, Lee HY, Hwang OJ, Lee HJ, Lee K, Back K. Coordinated regulation of melatonin synthesis and degradation genes in rice leaves in response to cadmium treatment. J Pineal Res 2015; 58:470-8. [PMID: 25783167 DOI: 10.1111/jpi.12232] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 03/13/2015] [Indexed: 12/14/2022]
Abstract
We investigated the expression patterns of genes involved in melatonin synthesis and degradation in rice leaves upon cadmium (Cd) treatment and the subcellular localization sites of melatonin 2-hydroxylase (M2H) proteins. The Cd-induced synthesis of melatonin coincided with the increased expression of melatonin biosynthetic genes including tryptophan decarboxylase (TDC), tryptamine 5-hydroxylase (T5H), and N-acetylserotonin methyltransferase (ASMT). However, the expression of serotonin N-acetyltransferase (SNAT), the penultimate gene in melatonin biosynthesis, was downregulated, suggesting that melatonin synthesis was counter-regulated by SNAT. Notably, the induction of melatonin biosynthetic gene expression was coupled with the induction of four M2H genes involved in melatonin degradation, which suggests that genes for melatonin synthesis and degradation are coordinately regulated. The induced M2H gene expression was correlated with enhanced M2H enzyme activity. Three of the M2H proteins were localized to the cytoplasm and one M2H protein was localized to chloroplasts, indicating that melatonin degradation occurs both in the cytoplasm and in chloroplasts. The biological activity of 2-hydroxymelatonin in the induction of the plant defense gene expression was 50% less than that of melatonin, which indicates that 2-hydroxymelatonin may be a metabolite of melatonin. Overall, our data demonstrate that melatonin synthesis occurs in parallel with melatonin degradation in both chloroplasts and cytoplasm, and the resulting melatonin metabolite 2-hydroxymelatonin also acts as a signaling molecule for defense gene induction.
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Affiliation(s)
- Yeong Byeon
- Department of Biotechnology, Bioenergy Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea
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159
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Shi H, Tan DX, Reiter RJ, Ye T, Yang F, Chan Z. Melatonin induces class A1 heat-shock factors (HSFA1s) and their possible involvement of thermotolerance in Arabidopsis. J Pineal Res 2015; 58:335-42. [PMID: 25711624 DOI: 10.1111/jpi.12219] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 02/20/2015] [Indexed: 12/14/2022]
Abstract
Melatonin (N-acetyl-5-methoxytryptamine) serves as an important signal molecule during plant developmental processes and multiple abiotic stress responses. However, the involvement of melatonin in thermotolerance and the underlying molecular mechanism in Arabidopsis were largely unknown. In this study, we found that the endogenous melatonin level in Arabidopsis leaves was significantly induced by heat stress treatment, and exogenous melatonin treatment conferred improved thermotolerance in Arabidopsis. The transcript levels of class A1 heat-shock factors (HSFA1s), which serve as the master regulators of heat stress responses, were significantly upregulated by heat stress and exogenous melatonin treatment in Arabidopsis. Notably, exogenous melatonin-enhanced thermotolerance was largely alleviated in HSFA1s quadruple knockout (QK) mutants, and HSFA1s-activated transcripts of heat-responsive genes (HSFA2, heat stress-associated 32 (HSA32), heat-shock protein 90 (HSP90), and 101 (HSP101)) might be contributed to melatonin-mediated thermotolerance. Taken together, this study provided direct link between melatonin and thermotolerance and indicated the involvement of HSFA1s-activated heat-responsive genes in melatonin-mediated thermotolerance in Arabidopsis.
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Affiliation(s)
- Haitao Shi
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University, Haikou, China; Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
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160
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Lee HY, Byeon Y, Tan DX, Reiter RJ, Back K. Arabidopsis serotonin N-acetyltransferase knockout mutant plants exhibit decreased melatonin and salicylic acid levels resulting in susceptibility to an avirulent pathogen. J Pineal Res 2015; 58:291-9. [PMID: 25652756 DOI: 10.1111/jpi.12214] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 01/30/2015] [Indexed: 12/14/2022]
Abstract
Serotonin N-acetyltransferase (SNAT) is the penultimate enzyme in the melatonin biosynthesis pathway in plants. We examined the effects of SNAT gene inactivation in two Arabidopsis T-DNA insertion mutant lines. After inoculation with the avirulent pathogen Pseudomonas syringe pv. tomato DC3000 harboring the elicitor avrRpt2 (Pst-avrRpt2), melatonin levels in the snat knockout mutant lines were 50% less than in wild-type Arabidopsis Col-0 plants. The snat knockout mutant lines exhibited susceptibility to pathogen infection that coincided with decreased induction of defense genes including PR1, ICS1, and PDF1.2. Because melatonin acts upstream of salicylic acid (SA) synthesis, the reduced melatonin levels in the snat mutant lines led to decreased SA levels compared to wild-type, suggesting that the increased pathogen susceptibility of the snat mutant lines could be attributed to decreased SA levels and subsequent attenuation of defense gene induction. Exogenous melatonin treatment failed to induce defense gene expression in nahG Arabidopsis plants, but restored the induction of defense gene expression in the snat mutant lines. In addition, melatonin caused translocation of NPR1 (nonexpressor of PR1) protein from the cytoplasm into the nucleus indicating that melatonin-elicited pathogen resistance in response to avirulent pathogen attack is SA-dependent in Arabidopsis.
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Affiliation(s)
- Hyoung Yool Lee
- Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, Korea
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161
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Byeon Y, Back K. Molecular cloning of melatonin 2-hydroxylase responsible for 2-hydroxymelatonin production in rice (Oryza sativa). J Pineal Res 2015; 58:343-51. [PMID: 25728912 DOI: 10.1111/jpi.12220] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 02/20/2015] [Indexed: 12/26/2022]
Abstract
Although melatonin biosynthetic genes from plants have been cloned, the melatonin catabolism mechanisms remain unclear. To clone the genes responsible for melatonin metabolism, we ectopically expressed 35 full-length cDNAs of rice 2-oxoglutarate-dependent dioxygenase (2-ODD) in Escherichia coli and purified the corresponding recombinant proteins. In vitro 2-ODD assays showed four independent 2-ODD proteins that were able to catalyze melatonin into 2-hydroxymelatonin, exhibiting melatonin 2-hydroxylase (M2H). These M2H proteins had peak activities at pH 8.0 and 30°C. The Km ranged from 121 μm to 371 μm with the Vmax ranging from 1.7 to 18.5 pkat/mg protein, respectively. The M2H enzyme activities were dependent on cofactors such as α-ketoglutarate, ascorbate, and Fe(2+), similar to the 2-ODD enzymes. M2H activity was inhibited by prohexadione-Ca, an inhibitor of 2-ODD, in a dose-dependent manner. M2H activity was high in the roots of rice seedlings, concurrent with high transcription levels of 2-ODD 21, suggesting that 2-ODD 21 was a major gene for M2H activity. Analogous to the high M2H activity in the roots, 2-hydroxymelatonin was found in large quantities in roots treated with melatonin. These results suggest that melatonin was metabolized into 2-hydroxymelatonin by the M2H genes in plants, but the physiological significance of 2-hydroxymelatonin remains to be examined in the future.
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Affiliation(s)
- Yeong Byeon
- Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, South Korea
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162
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163
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Lee HY, Byeon Y, Lee K, Lee HJ, Back K. Cloning of Arabidopsis serotonin N-acetyltransferase and its role with caffeic acid O-methyltransferase in the biosynthesis of melatonin in vitro despite their different subcellular localizations. J Pineal Res 2014; 57:418-26. [PMID: 25250906 DOI: 10.1111/jpi.12181] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 09/19/2014] [Indexed: 12/13/2022]
Abstract
Serotonin N-acetyltransferase (SNAT) is the penultimate enzyme in melatonin biosynthesis. We cloned SNAT from Arabidopsis thaliana (AtSNAT) and functionally characterized this enzyme for the first time from dicotyledonous plants. Similar to rice SNAT, AtSNAT was found to localize to chloroplasts with peak enzyme activity at 45 °C (Km , 309 μm; Vmax , 1400 pmol/min/mg protein). AtSNAT also catalyzed 5-methoxytryptamine (5-MT) into melatonin with high catalytic activity (Km , 51 μm; Vmax , 5300 pmol/min/mg protein). In contrast, Arabidopsis caffeic acid O-methyltransferase (AtCOMT) localized to the cytoplasm. Interestingly, AtCOMT can methylate serotonin into 5-MT with low catalytic activity (Km , 3.396 mm; Vmax , 528 pmol/min/mg protein). These data suggest that serotonin can be converted into either N-acetylserotonin by SNAT or into 5-MT by COMT, after which it is metabolized into melatonin by COMT or SNAT, respectively. To support this hypothesis, serotonin was incubated in the presence of both AtSNAT and AtCOMT enzymes. In addition to melatonin production, the production of major intermediates depended on incubation temperatures; N-acetylserotonin was predominantly produced at high temperatures (45 °C), while low temperatures (37 °C) favored the production of 5-MT. Our results provide biochemical evidence for the presence of a serotonin O-methylation pathway in plant melatonin biosynthesis.
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Affiliation(s)
- Hyoung Yool Lee
- Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, South Korea
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