title: Melatonin systemically ameliorates drought stress-induced damage in Medicago sativa plants by modulating nitro-oxidative homeostasis and proline metabolism.
abstract: Recent reports have uncovered the multifunctional role of melatonin in plant physiological responses under optimal and suboptimal environmental conditions. In this study, we explored whether melatonin pretreatment could provoke priming effects in alfalfa (Medicago sativa L.) plants subsequently exposed to prolonged drought stress (7 days), by withholding watering. Results revealed that the rhizospheric application of melatonin (10 μmol L-1) remarkably enhanced the drought tolerance of alfalfa plants, as evidenced by the observed plant tolerant phenotype, as well as by the higher levels of chlorophyll fluorescence and stomatal conductance, compared with nontreated drought-stressed plants. In addition, lower levels of lipid peroxidation (MDA content) as well as of both H2O2and NO contents in primed compared with nonprimed stressed plants suggest that melatonin pretreatment resulted in the systemic mitigation of drought-induced nitro-oxidative stress. Nitro-oxidative homeostasis was achieved by melatonin through the regulation of reactive oxygen (SOD, GR, CAT, APX) and nitrogen species (NR, NADHde) metabolic enzymes at the enzymatic and/or transcript level. Moreover, melatonin pretreatment resulted in the limitation of cellular redox disruption through the regulation of the mRNA levels of antioxidant and redox-related components (ADH, AOX, GST7, GST17), as well via osmoprotection through the regulation of proline homeostasis, at both the enzymatic (P5CS) and gene expression level (P5CS, P5CR). Overall, novel results highlight the importance of melatonin as a promising priming agent for the enhancement of plant tolerance to drought conditions through the regulation of nitro-oxidative and osmoprotective homeostasis.
authors.affiliation: Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus.
authors.forename: Chrystalla
authors.initials: C
authors.lastname: Antoniou
authors.affiliation: Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus.
authors.forename: Giannis
authors.initials: G
authors.lastname: Chatzimichail
authors.affiliation: Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus.
authors.forename: Rafaella
authors.initials: R
authors.lastname: Xenofontos
authors.affiliation: Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Pavlou
authors.affiliation: Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Panagiotou
authors.affiliation: Agricultural Research Institute, Ministry of Agriculture, Rural Development and Natural Recourses, Nicosia, Cyprus.
authors.forename: Anastasis
authors.initials: A
authors.lastname: Christou
authors.affiliation: Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus.
authors.forename: Vasileios
authors.identifier: http://orcid.org/0000-0003-1205-2070
authors.initials: V
authors.lastname: Fotopoulos
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D002492:Central Nervous System Depressants / Q000494:pharmacology; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D000455:Medicago sativa / Q000187:drug effects / Q000378:metabolism*; D008550:Melatonin / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002492:Central Nervous System Depressants; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D008550:Melatonin
keywords: alfalfa; antioxidants; hydrogen peroxide; nitric oxide; proline; redox regulation