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Abhijith Shankar PS, Parida P, Bhardwaj R, Yadav A, Swapnil P, Seth CS, Meena M. Deciphering molecular regulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) signalling networks in Oryza genus amid environmental stress. PLANT CELL REPORTS 2024; 43:185. [PMID: 38951279 DOI: 10.1007/s00299-024-03264-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 06/10/2024] [Indexed: 07/03/2024]
Abstract
The Oryza genus, containing Oryza sativa L., is quintessential to sustain global food security. This genus has a lot of sophisticated molecular mechanisms to cope with environmental stress, particularly during vulnerable stages like flowering. Recent studies have found key involvements and genetic modifications that increase resilience to stress, including exogenous application of melatonin, allantoin, and trehalose as well as OsSAPK3 and OsAAI1 in the genetic realm. Due to climate change and anthropogenic reasons, there is a rise in sea level which raises a concern of salinity stress. It is tackled through osmotic adjustment and ion homeostasis, mediated by genes like P5CS, P5CR, GSH1, GSH2, and SPS, and ion transporters like NHX, NKT, and SKC, respectively. Oxidative damage is reduced by a complex action of antioxidants, scavenging RONS. A complex action of genes mediates cold stress with studies highlighting the roles of OsWRKY71, microRNA2871b, OsDOF1, and OsICE1. There is a need to research the mechanism of action of proteins like OsRbohA in ROS control and the action of regulatory genes in stress response. This is highly relevant due to the changing climate which will raise a lot of environmental changes that will adversely affect production and global food security if certain countermeasures are not taken. Overall, this study aims to unravel the molecular intricacies of ROS and RNS signaling networks in Oryza plants under stress conditions, with the ultimate goal of informing strategies for enhancing stress tolerance and crop performance in this important agricultural genus.
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Affiliation(s)
- P S Abhijith Shankar
- School of Basic Sciences, Department of Botany, Central University of Punjab, Bathinda, 151401, Punjab, India
| | - Pallabi Parida
- School of Basic Sciences, Department of Botany, Central University of Punjab, Bathinda, 151401, Punjab, India
| | - Rupesh Bhardwaj
- School of Basic Sciences, Department of Botany, Central University of Punjab, Bathinda, 151401, Punjab, India
| | - Ankush Yadav
- School of Basic Sciences, Department of Botany, Central University of Punjab, Bathinda, 151401, Punjab, India
| | - Prashant Swapnil
- School of Basic Sciences, Department of Botany, Central University of Punjab, Bathinda, 151401, Punjab, India.
| | | | - Mukesh Meena
- Laboratory of Phytopathology and Microbial Biotechnology, Department of Botany, Mohanlal Sukhadia University, Udaipur, 313001, Rajasthan, India.
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Tian X, Zhang R, Yang Z, Zhu J, Fang W, Yang R, Yin Y. Melatonin mediates phenolic acids accumulation in barley sprouts under MeJA stress. Front Nutr 2024; 11:1403293. [PMID: 38899320 PMCID: PMC11186395 DOI: 10.3389/fnut.2024.1403293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/20/2024] [Indexed: 06/21/2024] Open
Abstract
Phenolic acids are secondary metabolites in higher plants, with antioxidant, anticancer, and anti-aging effects on the human body. Therefore, foods rich in phenolic acids are popular. Methyl jasmonate (MeJA) promoted phenolic acids accumulation but also inhibited sprout growth. Melatonin (MT) was a new type of plant hormone that not only alleviated plants' abiotic stress, but also promoted the synthesis of plant-stimulating metabolism. This study aimed to elucidate the mechanism of exogenous MT on the growth and development, and phenolic acids metabolism of barley sprouts under MeJA treatment. The results showed that MT increased the phenolic acids content in sprouts by increasing the activities of phenylalanine ammonia-lyase and cinnamic acid 4-hydroxylase, and up-regulating the gene expression of phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate: coenzyme a ligase, and ferulic acid-5-hydroxylase. MT attenuated the growth inhibition of barley sprouts under MeJA stress by increasing the activities of regulated antioxidant enzymes and the expression of their corresponding genes. Furthermore, MT increased the NO content and induced Ca2+ burst in barley sprouts under MeJA stress. These events were inhibited by DL-4-Chlorophenylalanine. These results suggested that MT ameliorated growth inhibition and promoted the biosynthesis of phenolic acids in barley sprouts under MeJA stress.
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Affiliation(s)
- Xin Tian
- College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, China
| | - Renjiao Zhang
- College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, China
| | - Zhengfei Yang
- College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, China
| | - Jiangyu Zhu
- College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, China
| | - Weiming Fang
- College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, China
| | - Runqiang Yang
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yongqi Yin
- College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu, China
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Khan Z, Jan R, Asif S, Farooq M, Jang YH, Kim EG, Kim N, Kim KM. Exogenous melatonin induces salt and drought stress tolerance in rice by promoting plant growth and defense system. Sci Rep 2024; 14:1214. [PMID: 38216610 PMCID: PMC10786868 DOI: 10.1038/s41598-024-51369-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 01/04/2024] [Indexed: 01/14/2024] Open
Abstract
Due to global climate change, crops are certainly confronted with a lot of abiotic and biotic stress factors during their growth that cause a serious threat to their development and overall productivity. Among different abiotic stresses, salt and drought are considered the most devastating stressors with serious impact on crop's yield stability. Here, the current study aimed to elucidate how melatonin works in regulating plant biomass, oxidative stress, antioxidant defense system, as well as the expression of genes related to salt and drought stress in rice plants. Eight groups of rice plants (3 replicates, 5 plants each) underwent varied treatments: control, melatonin, salt, drought, salt + drought, salt + melatonin, drought + melatonin, and salt + drought + melatonin. Melatonin (100 µM) was alternately applied a week before stress exposure; salt stress received 100 mM NaCl every 3 days for 3 weeks, and drought stress involved 10% PEG. Young leaves were randomly sampled from each group. The results showed that melatonin treatment markedly reduces salt and drought stress damage by promoting root, shoot length, fresh and dry weight, increasing chlorophyll contents, and inhibiting excessive production of oxidative stress markers. Salt and drought stress significantly decreased the water balance, and damaged cell membrane by reducing relative water contents and increasing electrolyte leakage. However, melatonin treated rice plants showed high relative water contents and low electrolyte leakage. Under salt and drought stress conditions, exogenous application of melatonin boosted the expression level of salt and drought stress responsive genes like OsSOS, OsNHX, OsHSF and OsDREB in rice plants. Taken together, our results reveal that melatonin treatment significantly increases salt and drought tolerance of rice plants, by increasing plant biomass, suppressing ROS accumulation, elevating antioxidants defense efficiency, and up-regulating the expression of salt and drought stress responsive genes.
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Affiliation(s)
- Zakirullah Khan
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea
| | - Rahmatullah Jan
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea.
- Coastal Agriculture Research Institute, Kyungpook National University, Daegu, 41566, South Korea.
| | - Saleem Asif
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea
| | - Muhammad Farooq
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea
| | - Yoon-Hee Jang
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea
| | - Eun-Gyeong Kim
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea
| | - Nari Kim
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea
| | - Kyung-Min Kim
- Department of Applied Biosciences, Graduate School, Kyungpook National University, Daegu, 41566, South Korea.
- Coastal Agriculture Research Institute, Kyungpook National University, Daegu, 41566, South Korea.
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Adhikari A, Aneefi AG, Sisuvanh H, Singkham S, Pius MV, Akter F, Kwon EH, Kang SM, Woo YJ, Yun BW, Lee IJ. Dynamics of Humic Acid, Silicon, and Biochar under Heavy Metal, Drought, and Salinity with Special Reference to Phytohormones, Antioxidants, and Melatonin Synthesis in Rice. Int J Mol Sci 2023; 24:17369. [PMID: 38139197 PMCID: PMC10743973 DOI: 10.3390/ijms242417369] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 12/06/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023] Open
Abstract
This study aimed to develop a biostimulant formulation using humic acid (HA), silicon, and biochar alone or in combination to alleviate the lethality induced by combined heavy metals (HM-C; As, Cd, and Pb), drought stress (DS; 30-40% soil moisture), and salt stress (SS; 150 mM NaCl) in rice. The results showed that HA, Si, and biochar application alone or in combination improved plant growth under normal, DS, and SS conditions significantly. However, HA increased the lethality of rice by increasing the As, Cd, and Pb uptake significantly, thereby elevating lipid peroxidation. Co-application reduced abscisic acid, elevated salicylic acid, and optimized the Ca2+ and Si uptake. This subsequently elevated the K+/Na+ influx and efflux by regulating the metal ion regulators (Si: Lsi1 and Lsi2; K+/Na+: OsNHX1) and increased the expressions of the stress-response genes OsMTP1 and OsNramp in the rice shoots. Melatonin synthesis was significantly elevated by HM-C (130%), which was reduced by 50% with the HA + Si + biochar treatment. However, in the SS- and DS-induced crops, the melatonin content showed only minor differences. These findings suggest that the biostimulant formulation could be used to mitigate SS and DS, and precautions should be taken when using HA for heavy metal detoxification.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - In-Jung Lee
- Department of Applied Biosciences, Kyungpook National University, Daegu 41566, Republic of Korea; (A.A.); (A.G.A.); (H.S.); (S.S.); (M.V.P.); (F.A.); (E.-H.K.); (S.-M.K.); (Y.-J.W.); (B.-W.Y.)
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Nie M, Ning N, Chen J, Zhang Y, Li S, Zheng L, Zhang H. Melatonin enhances salt tolerance in sorghum by modulating photosynthetic performance, osmoregulation, antioxidant defense, and ion homeostasis. Open Life Sci 2023; 18:20220734. [PMID: 37872968 PMCID: PMC10590611 DOI: 10.1515/biol-2022-0734] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 08/23/2023] [Accepted: 08/29/2023] [Indexed: 10/25/2023] Open
Abstract
Melatonin is a potent antioxidant that can prevent plant damage caused by adverse stresses. It remains unclear whether exogenous melatonin can mitigate the effects of salt stress on seed germination and seedling growth of sorghum (Sorghum bicolor (L.) Moench). The aim of this study was to decipher the protective mechanisms of exogenous melatonin (100 μmol/L) on sorghum seedlings under NaCl-induced salt stress (120 mmol/L). Plant morphological, photosynthetic, and physiological characteristics were analyzed at different timepoints after sowing. Results showed that salt stress inhibited seed germination, seedling growth, and plant biomass accumulation by reducing photosynthetic pigment contents, photosynthetic efficiency, root vigor, and mineral uptake. In contrast, seed priming with melatonin enhanced photosynthetic pigment biosynthesis, photosynthetic efficiency, root vigor, and K+ content under salt stress. Melatonin application additionally enhanced the activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and increased the levels of non-enzymatic antioxidants (reduced glutathione, ascorbic acid) in the leaves. These changes were accompanied by increase in the leaf contents of soluble sugars, soluble proteins, and proline, as well as decrease in hydrogen peroxide accumulation, malondialdehyde content, and electrolyte leakage. Our findings indicate that exogenous melatonin can alleviate salt stress-induced damage in sorghum seedlings through multifaceted mechanisms, such as improving photosynthetic performance and root vigor, facilitating ion homeostasis and osmoregulation, and promoting antioxidant defense and reactive oxygen species scavenging.
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Affiliation(s)
- Mengen Nie
- College of Agronomy, Shanxi Agricultural University, 81 Longcheng Street, Taiyuan, Shanxi, 030000, China
| | - Na Ning
- College of Resources Environment and Chemistry, Chuxiong Normal University, 546 Lucheng South Road, Chuxiong, Yunnan, 675000, China
| | - Jing Chen
- College of Agronomy, Shanxi Agricultural University, 81 Longcheng Street, Taiyuan, Shanxi, 030000, China
| | - Yizhong Zhang
- Shanxi Key Laboratory of Sorghum Genetic and Germplasm Innovation, Sorghum Research Institute, Shanxi Agricultural University,238 Yunhua West Street, Jinzhong, Shanxi, 030600, China
| | - Shuangshuang Li
- College of Resources Environment and Chemistry, Chuxiong Normal University, 546 Lucheng South Road, Chuxiong, Yunnan, 675000, China
| | - Lue Zheng
- College of Resources Environment and Chemistry, Chuxiong Normal University, 546 Lucheng South Road, Chuxiong, Yunnan, 675000, China
| | - Haiping Zhang
- Center for Agricultural Gene Resources Research, Shanxi Agricultural University, 81 Longcheng Street, Taiyuan, Shanxi, 030000, China
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Tang Y, Li J, Song Q, Cheng Q, Tan Q, Zhou Q, Nong Z, Lv P. Transcriptome and WGCNA reveal hub genes in sugarcane tiller seedlings in response to drought stress. Sci Rep 2023; 13:12823. [PMID: 37550374 PMCID: PMC10406934 DOI: 10.1038/s41598-023-40006-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 08/03/2023] [Indexed: 08/09/2023] Open
Abstract
Drought stress can severely affect sugarcane growth and yield. The objective of this research was to identify candidate genes in sugarcane tillering seedlings in response to drought stress. We performed a comparative phenotypic, physiological and transcriptomic analysis of tiller seedlings of drought-stressed and well-watered "Guire 2" sugarcane, in a time-course experiment (5 days, 9 days and 15 days). Physiological examination reviewed that SOD, proline, soluble sugars, and soluble proteins accumulated in large amounts in tiller seedlings under different intensities of drought stress, while MDA levels remained at a stable level, indicating that the accumulation of osmoregulatory substances and the enhancement of antioxidant enzyme activities helped to limit further damage caused by drought stress. RNA-seq and weighted gene co-expression network analysis (WGCNA) were performed to identify genes and modules associated with sugarcane tillering seedlings in response to drought stress. Drought stress induced huge down-regulated in gene expression profiles, most of down-regulated genes were mainly associated with photosynthesis, sugar metabolism and fatty acid synthesis. We obtained four gene co-expression modules significantly associated with the physiological changes under drought stress (three modules positively correlated, one module negatively correlated), and found that LSG1-2, ERF1-2, SHKA, TIL, HSP18.1, HSP24.1, HSP16.1 and HSFA6A may play essential regulatory roles as hub genes in increasing SOD, Pro, soluble sugar or soluble protein contents. In addition, one module was found mostly involved in tiller stem diameter, among which members of the BHLH148 were important nodes. These results provide new insights into the mechanisms by which sugarcane tillering seedlings respond to drought stress.
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Affiliation(s)
- Yuwei Tang
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
| | - Jiahui Li
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China.
| | - Qiqi Song
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
| | - Qin Cheng
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
| | - Qinliang Tan
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
| | - Quanguang Zhou
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
| | - Zemei Nong
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
| | - Ping Lv
- Guangxi Subtropical Crops Research Institute, 22 Yongwu Road, Xingning District, Nanning, 530001, Guangxi Province, China
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Ahmed S, Khan MT, Abbasi A, Haq IU, Hina A, Mohiuddin M, Tariq MAUR, Afzal MZ, Zaman QU, Ng AWM, Li Y. Characterizing stomatal attributes and photosynthetic induction in relation to biochemical changes in Coriandrum sativum L. by foliar-applied zinc oxide nanoparticles under drought conditions. FRONTIERS IN PLANT SCIENCE 2023; 13:1079283. [PMID: 36714745 PMCID: PMC9879579 DOI: 10.3389/fpls.2022.1079283] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 11/28/2022] [Indexed: 06/18/2023]
Abstract
Abiotic stress, particularly drought, will remain an alarming challenge for sustainable agriculture. New approaches have been opted, such as nanoparticles (NPs), to reduce the negative impact of drought stress and lessen the use of synthetic fertilizers and pesticides that are an inevitable problem these days. The application of zinc oxide nanoparticles (ZnO NPs) has been recognized as an effective strategy to enhance plant growth and crop production during abiotic stress. The aim of the current study was to investigate the role of ZnO NPs in drought stress management of drought-susceptible Coriandrum sativum L. (C. sativum) in two consecutive seasons. Drought regimes (moderate drought regime-MDR and intensive drought regime-IDR) were developed based on replenishment method with respect to 50% field capacity of fully irrigated (control) plants. The results showed that foliar application of 100 ppm ZnO NPs improved the net photosynthesis (Pn), stomatal conductance (C), and transpiration rate (E) and boosted up the photosynthetic capacity associated with photosynthetic active radiation in MDR. Similarly, 48% to 30% improvement of chlorophyll b content was observed in MDR and onefold to 41% in IDR during both seasons in ZnO NP-supplemented plants. The amount of abscisic acid in leaves showed a decreasing trend in MDR and IDR in the first season (40% and 30%) and the second season (49% and 33%) compared with untreated ZnO NP plants. The ZnO NP-treated plants showed an increment in total soluble sugars, total phenolic content, and total flavonoid content in both drought regimes, whereas the abaxial surface showed high stomatal density and stomatal index than the adaxial surface in foliar-supplied NP plants. Furthermore, ZnO NPs improve the magnitude of stomata ultrastructures like stomatal length, stomatal width, and pore length for better adaptation against drought. Principal component analysis revealed the efficacy of ZnO NPs in inducing drought tolerance in moderate and intensive stress regimes. These results suggest that 100 ppm ZnO NPs can be used to ameliorate drought tolerance in C. sativum plants.
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Affiliation(s)
- Shakil Ahmed
- Institute of Botany, University of the Punjab Quaid, Lahore, Pakistan
| | - Muhammad Tajammal Khan
- Institute of Botany, University of the Punjab Quaid, Lahore, Pakistan
- Division of Science and Technology, Department of Botany, University of Education, Lahore, Pakistan
| | - Asim Abbasi
- Department of Environmental Sciences, Kohsar University, Murree, Pakistan
| | - Inzamam Ul Haq
- College of Plant Protection, Gansu Agricultural University, Lanzhou, China
| | - Aiman Hina
- Department of Botany, Kohsar University, Murree, Pakistan
| | - Muhammad Mohiuddin
- Department of Environmental Sciences, Kohsar University, Murree, Pakistan
| | - Muhammad Atiq Ur Rehman Tariq
- Department of Environmental Sciences, Comsats University Islamabad (CUI), Abbottabad, Pakistan
- Center of Excellence in Water Resources Engineering, University of Engineering and Technology, Lahore, Pakistan
| | | | - Qamar uz Zaman
- Department of Environmental Sciences, The University of Lahore, Lahore, Pakistan
| | - Anne Wai Man Ng
- College of Engineering, IT and Environment, Charles Darwin University, Darwin, NT, Australia
| | - Yong Li
- National Engineering Laboratory for Applied Forest Ecological Technology in Southern China, Faculty of Life Science and Technology, Central South University of Forestry and Technology, Changsha, China
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Shreya S, Supriya L, Padmaja G. Melatonin induces drought tolerance by modulating lipoxygenase expression, redox homeostasis and photosynthetic efficiency in Arachis hypogaea L. FRONTIERS IN PLANT SCIENCE 2022; 13:1069143. [PMID: 36544878 PMCID: PMC9760964 DOI: 10.3389/fpls.2022.1069143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
Melatonin (N-acetyl-5-hydroxy tryptamine), a multipotent biomolecule is well known for its ability to confer tolerance to several abiotic and biotic stresses. The regulation of melatonin-mediated drought tolerance in drought-distinguished varieties can be different due to discriminating redox levels. The present study was focused on assessing the effects of melatonin priming against polyethylene glycol (PEG)-induced stress with respect to the antioxidant system, photosynthetic parameters, lipoxygenase expression, JA and ABA levels in drought-sensitive (Kadiri-7) and drought-tolerant (Kadiri-9) varieties. Exogenous melatonin alleviated the drought stress effects in sensitive variety (Kadiri-7) by increasing the endogenous melatonin content with an improved antioxidant system and photosynthetic attributes. The primed stressed plants of the sensitive variety exhibited reduced expression and activity of the chlorophyll degrading enzymes (Chl-deg PRX, pheophytinase and chlorophyllase) with a concomitant increase in chlorophyll content in comparison to unprimed controls. Interestingly, melatonin priming stimulated higher expression and activity of lipoxygenase (LOX) as well as enhanced the expression of genes involved in the synthesis of jasmonic acid (JA) including its content in drought stressed plants of the sensitive variety. The expression of NCED3 (involved in ABA-biosynthesis) was upregulated while CYP707A2 (ABA-degradation) was downregulated which corresponded with higher ABA levels. Contrastingly, priming caused a decrease in endogenous melatonin content under drought stress in tolerant variety (Kadiri-9) which might be due to feedback inhibition of its synthesis to maintain intracellular redox balance and regulate better plant metabolism. Furthermore, the higher endogenous melatonin content along with improved antioxidant system, photosynthetic efficiency and LOX expression associated with the increased levels of JA and ABA in unprimed stressed plants of the tolerant variety (Kadiri-9) is pointing towards the effectiveness of melatonin in mediating drought stress tolerance. Overall, exogenous melatonin alleviated the adverse effects of drought stress in sensitive variety while having no add-on effect on drought stress responses of tolerant variety which is inherently equipped to withstand the given duration of drought stress treatment.
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