ABSTRACT
Cadmium (Cd) and lead (Pb) are among the most toxic heavy metals affecting human health and crop yield. Suaeda maritima (L.) Dumort is an obligate halophyte that is well adapted to saline soil. The inbuilt salinity tolerance mechanisms of halophytes help them to survive in heavy metal-contaminated rhizospheric soil. In the present study, growth and ionomic responses, reactive oxygen species (ROS) accumulation, modulations of phytochelatins, antioxidative defense, and metabolomic responses were studied in S. maritima imposed to Cd and Pb stresses with an aim to elucidate Cd and Pb tolerance mechanisms and phytoremediation potential of this halophyte. Our results showed a reduction of biomass in S. maritima, which may serve as an energy conservation strategy for survival under heavy metal stress. The increased accumulation of ROS with concomitant higher expression of various antioxidative enzymes suggests the efficient scavenging of ROS. The metabolite profiling revealed significant up-regulation of sugars, sugar alcohols, amino acids, polyphenols, and organic acids under Cd and Pb stresses suggesting their possible role in osmotic balance, ionic homeostasis, ROS scavenging, and signal transduction for stress tolerance. In S. maritima, the translocation factors (Tf) are <1 in both Cd and Pb treatments, which indicates that this halophyte has high phytostabilization potential for Cd and Pb in roots and through restricted translocation of heavy metal ions to the aboveground part. The findings of this study offer comprehensive information on Cd and Pb tolerance mechanisms in S. maritima and suggest that this halophyte can detoxify the HMs through physiological, ionic, antioxidative, and metabolic regulations.
Subject(s)
Biodegradation, Environmental , Cadmium , Chenopodiaceae , Lead , Reactive Oxygen Species , Salt-Tolerant Plants , Cadmium/metabolism , Cadmium/toxicity , Chenopodiaceae/metabolism , Chenopodiaceae/drug effects , Salt-Tolerant Plants/metabolism , Lead/metabolism , Reactive Oxygen Species/metabolism , Metabolomics , Antioxidants/metabolism , Metabolome/drug effects , Soil Pollutants/metabolism , Plant Roots/metabolism , Plant Roots/drug effects , Phytochelatins/metabolismABSTRACT
MAIN CONCLUSION: Arsenic tolerance in the halophyte Salvadora persica is achieved by enhancing antioxidative defense and modulations of various groups of metabolites like amino acids, organic acids, sugars, sugar alcohols, and phytohormones. Salvadora persica is a facultative halophyte that thrives under high saline and arid regions of the world. In present study, we examine root metabolic responses of S. persica exposed to individual effects of high salinity (750 mM NaCl), arsenic (600 µM As), and combined treatment of salinity and arsenic (250 mM NaCl + 600 µM As) to decipher its As and salinity resistance mechanism. Our results demonstrated that NaCl supplementation reduced the levels of reactive oxygen species (ROS) under As stress. The increased activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) maintained appropriate levels of ROS [superoxide (O2â¢-) and hydrogen peroxide (H2O2)] under salinity and/or As stress. The metabolites like sugars, amino acids, polyphenols, and organic acids exhibited higher accumulations when salt was supplied with As. Furthermore, comparatively higher accumulations of glycine, glutamate, and cystine under combined stress of salt and As may indicate its role in glutathione and phytochelatins (PCs) synthesis in root. The levels of phytohormones such as salicylate, jasmonate, abscisic acid, and auxins were significantly increased under high As with and without salinity stress. The amino acid metabolism, glutathione metabolism, carbohydrate metabolism, tricarboxylic acid cycle (TCA cycle), phenylpropanoid biosynthesis, and phenylalanine metabolism are the most significantly altered metabolic pathways in response to NaCl and/or As stress. Our study decoded the important metabolites and metabolic pathways involved in As and/or salinity tolerance in root of the halophyte S. persica providing clues for development of salinity and As resistance crops.
Subject(s)
Arsenic , Salvadoraceae , Antioxidants/metabolism , Salt-Tolerant Plants/metabolism , Salvadoraceae/metabolism , Arsenic/toxicity , Reactive Oxygen Species/metabolism , Sodium Chloride/pharmacology , Salinity , Hydrogen Peroxide/metabolism , Plant Growth Regulators/pharmacology , Oxidative Stress , GlutathioneABSTRACT
Chromium (Cr) is a highly toxic element adversely affecting the environment, cultivable lands, and human populations. The present study investigated the effects of Cr (VI) (100-400 µM) on plant morphology and growth, photosynthetic pigments, organic osmolytes, ionomics, and metabolomic dynamics of the halophyte Suaeda maritima to decipher the Cr tolerance mechanisms. Cr exposure reduced the growth and biomass in S. maritima. The photosynthetic pigments content significantly declined at higher Cr concentrations (400 µM). However, at lower Cr concentrations (100-300 µM), the photosynthetic pigments remained unaffected or increased. The results suggest that a high concentration of Cr exposure might have adverse effects on PS II in S. maritima. The enhanced uptake of Na+ in S. maritima imposed to Cr stress indicates that Na+ might have a pivotal role in osmotic adjustment, thereby maintaining water status under Cr stress. The proline content was significantly upregulated in Cr-treated plants suggesting its role in maintaining osmotic balance and scavenging ROS. The metabolomic analysis of control and 400 µM Cr treated plants led to the identification of 62 metabolites. The fold chain analysis indicated the upregulation of several metabolites, including phytohormones (SA and GA3), polyphenols (cinnamic acid, sinapic acid, coumaric acid, vanillic acid, and syringic acid), and amino acids (alanine, leucine, proline, methionine, and cysteine) under Cr stress. The upregulation of these metabolites suggests the enhanced metal chelation and sequestration in vacuoles, reducing oxidative stress by scavenging ROS and promoting photosynthesis by maintaining the chloroplast membrane structure and photosynthetic pigments. Furthermore, in S. maritima, Cr tolerance index (Ti) was more than 60% in all the treatments, and Cr bio-concentration factor (BCF) and translocation factor (Tf) values were all greater than 1.0, which clearly indicates the Cr-hyperaccumulator characteristics of this halophyte.
Subject(s)
Chenopodiaceae , Chromium , Humans , Chromium/toxicity , Chromium/metabolism , Salt-Tolerant Plants , Reactive Oxygen Species , Oxidative Stress , Antioxidants/metabolism , Proline/metabolism , Proline/pharmacology , Chenopodiaceae/metabolism , Stress, PhysiologicalABSTRACT
Potassium (K) scarcity of arable land is one of the important factors that hamper the growth of the plants and reduce yield worldwide. In the current study, we examine the physiological, biochemical, and metabolome response of Arachis hypogaea (GG7 genotype: fast-growing, tall, early maturing, and high yielding) under low K either solitary or in combination with Si to elucidate the ameliorative role of Si. The reduced fresh and dry biomass of peanut and photosynthetic pigments content was significantly alleviated by Si. Si application did not affect the leaf and stem K+, although it enhanced root K+ in K-limitation, which is probably due to up-regulated expression of genes responsible for K uptake. Si improves the potassium use efficiency in K-limitation as compared to control. K-deficiency increased MDA, O2â¢-, and H2O2 levels in leaf and root of peanut. Si improved/maintained the activity of antioxidative enzymes, which significantly lowered the ROS accumulation in K-limitation. The AsA/DHA and GSH/GSSG ratio was approximately unaffected in both leaf and root, suggesting the maintained cellular redox potential in K-starved peanut. Si promotes accumulation of sugars and sugar alcohols, phytohormones indicating their probable involvement in signal transduction, osmotic regulation, and improvement of stress tolerance. Down-regulation of aspartic acid and glutamic acid while up-regulation of lysine, histidine, and arginine could maintain charge balance in K-deprived peanut. The significant accumulation of polyphenols under K limitation supplemented with Si suggests the role of polyphenols for ROS scavenging. Our results demonstrated that Si as a beneficial element can mitigate K-nutrient toxicity and improve KUE of peanut under K-limitation conditions. Moreover, our results demonstrate that Si application can improve crop yield, quality, and nutrient use efficiency under nutrient limitation conditions.
Subject(s)
Arachis , Potassium Deficiency , Antioxidants/metabolism , Arachis/genetics , Dietary Supplements , Homeostasis , Hydrogen Peroxide , Polyphenols , Potassium , Reactive Oxygen Species/metabolism , Silicon/pharmacologyABSTRACT
Arsenic (As) is a highly toxic metalloid adversely affecting the environment, human health, and crop productivity. The present study assessed the synergistic effects of salinity and As on photosynthetic attributes, stomatal regulations, and metabolomics responses of the xero-halophyte Salvadora persica to decipher the As-salinity cross-tolerance mechanisms and to identify the potential metabolites/metabolic pathways involved in cross-tolerance of As with salinity. Salinity and As stress-induced significant stomatal closure in S. persica suggests an adaptive response to decrease water loss through transpiration. NaCl supplementation improved the net photosynthetic rate (by +39%), stomatal conductance (by +190%), water use efficiency (by +55%), photochemical quenching (by +37%), and electron transfer rate (54%) under As stress as compared to solitary As treatment. Our results imply that both stomatal and non-stomatal factors account for a reduction in photosynthesis under high salinity and As stress conditions. A total of 64 metabolites were identified in S. persica under salinity and/or As stress, and up-regulation of various metabolites support early As-salinity stress tolerance in S. persica by improving antioxidative defense and ROS detoxification. The primary metabolites such as polyphenols (caffeic acid, catechin, gallic acid, coumaric acid, rosmarinic acid, and cinnamic acid), amino acids (glutamic acid, cysteine, glycine, lysine, phenylalanine, and tyrosine), citrate cycle intermediates (malic acid, oxalic acid, and α-ketoglutaric acid), and most of the phytohormones accumulated at higher levels under combined treatment of As + NaCl compared to solitary treatment of As. Moreover, exogenous salinity increased glutamate, glycine, and cysteine, which may induce higher synthesis of GSH-PCs in S. persica. The metabolic pathways that were significantly affected in response to salinity and/or As include inositol phosphate metabolism, citrate cycle, glyoxylate and dicarboxylate metabolism, amino acid metabolism, and glutathione metabolism. Our findings indicate that inflections of various metabolites and metabolic pathways facilitate S. persica to withstand and grow optimally even under high salinity and As conditions. Moreover, the addition of salt enhanced the arsenic tolerance proficiency of this halophyte.
Subject(s)
Arsenic , Salvadoraceae , Arsenic/toxicity , Humans , Metabolomics , Photosynthesis , Salinity , Salt-Tolerant PlantsABSTRACT
Drought stress considered as a major environmental constraint that frequently limits crop production globally. In the current investigation, drought stress-induced alterations in growth, ion homeostasis, photosynthetic pigments, organic osmolytes, reactive oxygen species (ROS) generation, antioxidative components, and metabolic profile were examined in order to assess the role of silicon (Si) in mitigation of drought effects and to understand the drought adaptive mechanism in two contrasting peanut genotypes (GG7: fast growing and tall, TG26: slow growing and semi-dwarf). Si application significantly improved the leaf chlorophyll content, relative water content % (RWC %), growth and biomass in GG7 compared with TG26 genotype under water stress. Si supplementation considerably promotes the uptake and transport of mineral nutrients under drought condition in both the genotypes, which eventually promote plant growth. Exogenous application of Si protects the photosynthetic pigments from oxidative damage by reducing membrane lipid peroxidation and either maintained or reduced H2O2 accumulation in both the genotypes. The activity of enzymatic antioxidants like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and glutathione reductase (GR) and non-enzymatic antioxidants like ascorbate (AsA) and glutathione (GSH) were either maintained or increased in both the genotypes in response to Si under drought as compared to those without Si. Silicon-induced higher accumulation of metabolites mainly sugars and sugar alcohols (talose, mannose, fructose, sucrose, cellobiose, trehalose, pinitol, and myo-inositol), amino acids (glutamic acid, serine, histidine, threonine, tyrosine, valine, isoleucine, and leucine) in GG7 genotype as compared to TG26, provides osmo-protection. Moreover, Si application increased phytohormones levels such as indole-3-acetic acid (IAA), gibberellic acid (GA3), jasmonic acid (JA), and zeatin in GG7 genotype under drought stress compared to non-Si treated seedlings suggesting its involvement in signaling pathways for drought adaptation and tolerance. Noteworthy increment in polyphenols (chlorogenic acid, caffeic acid, ellagic acid, rosmarinic acid, quercetin, coumarin, naringenin, and kaempferol) in the Si treated seedlings of GG7 genotype as compared to TG26 under drought stress suggests an efficient mechanism of ROS sequestration in GG7 genotype. Our findings provide comprehensive information on physiological, biochemical, and metabolic dynamics associated with Si-mediated water stress tolerance in peanut. This study indicates that the drought tolerance efficacy of peanut genotypes can be improved by Si application.
Subject(s)
Antioxidants , Droughts , Arachis/genetics , Genotype , Homeostasis , Hydrogen Peroxide , Oxidative Stress , Silicon/pharmacologyABSTRACT
Drought is one of the most catastrophic abiotic stresses that affects global food production severely. The present work investigates the metabolic and physiological adaptation mechanisms in the xero-halophyte Haloxylon salicornicum to counter the effects of drought. This xero-halophyte can withstand a prolonged drought period of 14 days and recovered within 7 days of irrigation with minimal effects of drought on growth and physiological parameters. Photosynthetic parameters such as PN , gs , and E decreased significantly, whereas WUE increased under drought condition. Drought induces a significant decline in the Fv/Fm ratio. However, the value of Fv/Fm ratio successfully recovered within 7 days of the recovery period. Differential regulations of various antioxidative enzymes increase the drought tolerance potential of H. salicornicum. The metabolomic analysis of H. salicornicum shoot identified 63 metabolites: 43 significantly increased and 20 significantly decreased under drought conditions. These metabolites mainly include amino acids, organic acids, amines, sugar alcohols, sugars, fatty acids, alkaloids, and phytohormones. The metabolites that have a significant contribution towards drought tolerance include citric acid, malic acid, tartaric acid, d-erythrose, glyceric acid, sucrose, pentanoic acid, d-mannitol, ABA, and palmitic acid. KEGG pathway enrichment analysis showed that the vital drought-responsive metabolic pathways mainly include galactose metabolism, aminoacyl-tRNA biosynthesis, glyoxylate and dicarboxylate metabolism, citrate cycle (TCA cycle), alanine, aspartate, and glutamate metabolism. This study offers comprehensive information on physiological, antioxidative and metabolic adaptations and overall drought tolerance mechanisms in H. salicornicum. The information gained from this study will provide guidance to plant breeders and molecular biologists to develop drought-tolerant crop varieties.
Subject(s)
Droughts , Salt-Tolerant Plants , Adaptation, Physiological , Metabolomics , Stress, PhysiologicalABSTRACT
Heavy metal(loid)s contamination in soil is a major environmental concern that limits agricultural yield and threatens human health worldwide. Arsenic (As) is the most toxic non-essential metalloid found in soil which comes from various natural as well as human activities. S. persica is a facultative halophyte found abundantly in dry, semiarid and saline areas. In the present study, growth, mineral nutrient homeostasis, MDA content, phytochelatin levels, and ROS-scavenging attributes were examined in S. persica imposed to solitary treatments of salinity (250 mM and 750 mM NaCl), solitary treatments of arsenic (200 µM and 600 µM As), and combined treatments of As with 250 mM NaCl with an aim to elucidate salinity and As tolerance mechanisms. The results demonstrated that S. persica plants sustained under high levels of As (600 µM As) as well as NaCl (750 mM). The activity of superoxide dismutase, catalase, peroxidase, and glutathione reductase were either elevated or unaffected under salt or As stress. However, ascorbate peroxidase activity declined under both solitary and combination of As with NaCl. Furthermore, the cellular redox status measured in terms of reduced ascorbate/dehydroascorbate, and reduced glutathione/oxidized glutathione ratios also either increased or remained unaffected in seedlings treated with both solitary and combined treatments of As + NaCl. Significant accumulation of various oxidative stress indicators (H2O2 and O2-) were observed under high As stress condition. However, presence of salt with high As significantly reduced the levels of ROS. Furthermore, exogenous salt improved As tolerance index (Ti) under high As stress condition. The values of translocation factor (Tf) and As bioaccumulation factor (BF) were >1 in all the treatments. From this study, it can be concluded that the facultative halophyte S. persica is a potential As accumulator and may find application for phytoextraction of arsenic-contaminated saline soil.
Subject(s)
Arsenic , Salvadoraceae , Antioxidants , Arsenic/toxicity , Humans , Hydrogen Peroxide , Oxidative Stress , Reactive Oxygen Species , Salinity , Salt-Tolerant Plants , SeedlingsABSTRACT
Haloxylon salicornicum is a xero-halophyte growing in saline and arid regions of the world. Metabolite profiling was carried out in shoot of both control and salinity treated (400 mM NaCl) samples by GC-QTOF-MS and HPLC-DAD analysis to decipher the salinity tolerance mechanism in this xero-halophyte. The present study investigates the alteration in metabolite profile of H. salicornicum that support the salinity tolerance of the plant. The metabolomic analysis of H. salicornicum shoot identified 56 metabolites, of which 47 metabolites were significantly changed in response to salinity. These metabolites were mainly included in the category of amino acids, organic acids, amines, sugar alcohols, sugars, fatty acids, alkaloids, and phytohormones. In response to salinity, most of the amino acids were down-regulated except alanine, phenylalanine, lysine, and tyramine, which were up-regulated in H. salicornicum. In contrast to amino acids, most sugars and organic acids were up-regulated in response to salinity. Correlation and pathway enrichment analysis identified important biological pathways playing significant roles in conferring salt tolerance of H. salicornicum. These biological pathways include amino sugar and nucleotide sugar metabolism, citrate cycle (TCA cycle), starch and sucrose metabolism, phenylalanine metabolism, cysteine, methionine, glycine, serine, and threonine metabolism, etc. The data presented here suggest that the modulations of various metabolic pathways facilitate H. salicornicum to survive and grow optimally even under high salinity condition. This study offers comprehensive information on metabolic adaptations and overall salt tolerance mechanisms in H. salicornicum. The information gained through this study will provide guidance to plant breeders and molecular biologists to develop salinity tolerant crop varieties.
Subject(s)
Chenopodiaceae/metabolism , Metabolic Networks and Pathways , Salt Tolerance , Salt-Tolerant Plants/metabolism , Metabolomics , SalinityABSTRACT
Haloxylon salicornicum is a xero-halophyte which grow predominantly in dry saline areas. However, the proteomic approach for revealing the regulatory network involved in salt adaptation of this important xerohalophyte has not been studied so far. In the present investigation, the label-free quantitative proteomic analysis was carried out in shoot of H. salicornicum to get an insight into the functional network of proteins involved in salt tolerance. Comparative proteomic analysis in control and salt treated plants of H. salicornicum by nano-ESI-LC-MS and MS/MS, and data base searching led to the identification of 723 proteins. Pathway enrichment analysis by KEGG uncovered various biological pathways to which salinity induced differentially regulated proteins are involved. In H. salicornicum, out of 723 identified proteins, 187 proteins were differentially regulated in response to salinity. In addition to significant up-regulation of stress responsive proteins, other proteins involved in carbohydrate metabolism, TCA cycle, protein synthesis, antioxidative defense systems, energy transfer, ion transport, nucleotide binding, and proteosomal proteins also significantly up-regulated under salinity in H. salicornicum. The major photosynthetic proteins up-regulated were RuBisCo, D1 protein, photosystem II-CP47, and cytochrome b599. TCA cycle component proteins such as citrate synthase, succinate dehydrogenase, and malate dehydrogenase upregulated indicating their significant roles in providing vital energy for salinity tolerance. Salinity induced higher expressions of ion transporters in H. salicornicum suggest efficient compartmentalization of toxic sodium ions. In addition, up-regulation of antioxidative defense system can be correlated with effective scavenging of salinity induced ROS, hence imparting salt tolerance. In H. salicornicum, protein synthesis was boosted under salinity as confirmed from the salinity-induced up-regulation of the ribosome associated proteins. Salinity induced significantly changed proteins of the ribosomal pathway include ribosomal protein components such as elongation factor-Tu (EF-Tu), initiation factor 1 and 2 (IF1, 2), Rpo cluster C and B, etc. Functional integrity of protein synthesis machinery in H. salicornicum is maintained under high salinity by higher abundance of ribosomal subunit proteins in NaCl-treated plants. We assume that consistent energy supply by the up-regulation of TCA cycle along with uninterrupted protein synthesis and maintenance of structural integrity of the photosynthetic machinery are the primary mechanism of salinity tolerance of H. salicornicum. In the present study, we comprehensively elucidated possible mechanisms associated with systematic salt tolerance of H. salicornicum employing proteomic approach. The information from this study will contribute to the genetic improvement of crop plants that can be grown in saline marginal lands.
Subject(s)
Chenopodiaceae , Salt-Tolerant Plants , Plant Proteins/genetics , Proteomics , Salinity , Salt Tolerance , Salt-Tolerant Plants/genetics , Stress, Physiological , Tandem Mass SpectrometryABSTRACT
Arachis hypogaea L. (peanut) is a major oil yielding crop and its productivity is largely affected by the availability of nitrogen and phosphorus. The present study aims to elucidate the differential physiological and biochemical mechanisms involved in two contrasting genotypes of peanut for mitigation of N and/or P deficiency. The plants of two contrasting genotypes of peanut (GG7 and TG26) were subjected to N and/or P deficiency under hydroponic culture condition. After 15 d of N and/or P deficiency, various growth parameters, mineral nutrient status, nutrient use efficiency, photosynthesis, transpiration, water use efficiency, chlorophyll fluorescence, ROS level, and changes in enzymatic and non-enzymatic antioxidative components were measured in control and nutrient deficient plants. Our results showed that GG7 is fast-growing genotype than TG26 under control condition, whereas under N and/or P deficiency growth performance of GG7 was significantly declined as compared to TG26. The levels of photosynthetic pigments, net photosynthesis activity (PN), and stomatal conductance (gs) declined in N and/or P deficient plants of both the genotypes. However, quantum efficiency of photosystem II (Fv/Fm) did not change significantly under N and/or P starvation in both the genotypes. In the present investigation, most of the antioxidative enzymes either remained in steady state or downregulated in both the genotypes of peanut under N and/or P deficiency condition. N and/or P deficiency did not influence the levels of ROS and oxidative stress indicators such as O2·-, H2O2, and MDA in both the genotypes. In the present investigation, the decline in growth in both the genotypes under N and/or P deficiency might be due to the reduced photosynthetic performance. Our results suggest that TG26 is more resistant to N and P deficiency than GG7 genotype. Higher NUE value of GG7 as compared to TG26 suggests that GG7 can utilize N more efficiently to promote biomass production than TG26 under sufficient nutrient condition. On the other hand, mineral resource allocation to leaf and higher PUE are key adaptive features of the TG26 genotype under N, and P deficiency conditions. The differential regulations of various enzymatic and non-enzymatic antioxidative components in peanut genotypes maintain the cellular redox homeostasis under mineral deficiency conditions and prevent the peanut plants from oxidative stress, thereby maintaining PSII efficiency. The information from the present study can be useful for the improvement of traits in peanut that can maintain the productivity under N and P deficient environment with minimum input of fertilizers.
Subject(s)
Antioxidants/metabolism , Genotype , Homeostasis , Nutrients , Phosphorus/metabolism , Photosynthesis/physiology , Arachis/physiology , Biomass , Chlorophyll , Fertilizers , Hydrogen Peroxide , Nitrogen , Plant Leaves/physiology , Plant Stomata/physiologyABSTRACT
Water deficit severely limits productivity of plants, and pose a major threat to modern agriculture system. Therefore, understanding drought adaptive mechanisms in drought-tolerant plants is imperative to formulate strategies for development of desiccation tolerance in crop plants. In present investigation, metabolic profiling employing GC-QTOF-MS/MS and HPLC-DAD was carried out to evaluate metabolic adjustments under drought stress in the xero-halophyte Salvadora persica. The metabolite profiling identified a total of 68 metabolites in S. persica leaf, including organic acids, amino acids, sugars, sugar alcohols, hormones, and polyphenols. The results showed that higher cellular osmolality under drought stress was accompanied by accumulations of several osmoprotectants like sugars and polyols (sucrose, glucose, mannose, galactose, erythrose, sorbose, glycerol, and myoinositol), organic acids (galactaric acid, tartaric acid, malic acid, oxalic acid, and citric acid), and amino acids (alanine, phenylalanine, tyrosine). Upregulation of ABA and JA support to achieve early drought tolerance in S. persica. Moreover, accumulation of coumarin, gallic acid, and chlorogenic acid provide antioxidative defense to S. persica. KEGG pathway enrichment analysis showed that altered metabolites were associated with starch and sucrose metabolism, galactose metabolism, inositol phosphate metabolism, and phenylalanine metabolism. While during recovery, metabolites associated with lysine biosynthesis and alanine, aspartate and glutamate metabolism were significantly altered. The results of the present study imply that coordinated regulations between various metabolites, metabolic processes, and pathways empower the xerohalophyte S. persica to adapt under drought environment. The knowledge from this study will enable the development of drought tolerance in crops using genetic engineering and breeding approaches.
Subject(s)
Adaptation, Physiological , Salvadoraceae , Stress, Physiological , Water , Droughts , Metabolomics , Salvadoraceae/metabolism , Tandem Mass Spectrometry , Water/metabolismABSTRACT
The present study evaluated the phytochemical constituents, nutritional attributes, and the antioxidant capacity of the medicinal halophyte Thespesia populnea. The metabolite profiling by GC-QTOF-MS analysis identified 37 metabolites among which sucrose, malic acid, and turanose were the most abundant. A total of 18 polyphenols and 17 amino acids were identified by the HPLC-DAD analysis. The most abundant polyphenols in T. populnea were gallic acid, catechin, and myricetin. Other polyphenols like protocatechuic acid, epigallocatechin gallate, rosmarinic acid, ellagic acid, rutin, and naringenine were also detected in ample amounts. The leaf extract demonstrated higher antioxidant as well as lipid peroxidation inhibition activities. A correlation analysis revealed a positive correlation between the antioxidant capacity and the phenolic compounds viz. gallic acid, catechin, myricetin, quercetin, apigenin, cinnamic acid, and coumarin which indicates that these phenolic compounds are the main contributors of the antioxidant potential of T. populnea. The results of this study establish T. populnea as a potential source of nonconventional functional food. PRACTICAL APPLICATIONS: The data presented here indicate that T. populnea can be considered as a nonconventional functional food and potential source of energy, antioxidants, minerals, essential amino acids, and bioactive compounds in herbal formulations, food supplements, or nutraceuticals. The metabolites identified from this halophyte have pharmacological and nutraceutical potentials, suggesting T. populnea as an ideal candidate for application in the food and phytopharmaceutical industries to produce health-promoting products, functional foods, and herbal medicines.
Subject(s)
Antioxidants/analysis , Dietary Supplements/analysis , Malvaceae/chemistry , Phytochemicals/analysis , Plant Extracts/analysis , Polyphenols/analysis , Chromatography, High Pressure Liquid , Plant Leaves/chemistry , Plants, Medicinal/chemistryABSTRACT
The facultative halophyte Salvadora persica L. grow in arid, semiarid and saline areas. In present study, drought induced alterations in growth, ion homeostasis, photosynthesis, chlorophyll fluorescence, ROS regulation and antioxidative defense components were analyzed in S. persica with an aim to elucidate the drought tolerance mechanisms. In response to drought, significant reductions in growth, photosynthesis, and photosynthetic pigments were observed in S. persica. However, leaf relative water content (RWC %) did not change significantly. In S. persica seedlings, the growth, photosynthetic pigment contents and photosynthesis were resumed to control level within 7 d, when the drought treated plants were re-irrigated. However, quantum yield of PSII (ΦPSII), rate of electron transport (ETR), maximum efficiency of PSII (Fv/Fm), and photochemical quenching (qP) remained unaffected under water deficit stress. The results suggest that both non-stomatal as well as stomatal limitations can account for photosynthetic reduction. The ionomics studies revealed no significant alterations in levels of Na+, K+, Ca2+, B, Cu2+, Fe2+, Mo, and Zn2+ in leaf tissue during drought. However, there was increase in levels of Na+, K+, Ca2+ and Mg2+ in root tissue in response to drought. The activity of different enzymatic antioxidants like SOD, APX, and GR remained unaffected during drought, whereas POX activity increased and CAT activity declined under drought stress in comparison to control. This result proposes that vital ROS scavenging enzymes like SOD, APX and GR are at threshold levels to maintain the appropriate concentration of ROS. In S. persica, the ratio of AsA/DHA and GSH/GSSG (which are the indicators of redox potential of cell) remained steady or increased under drought which indicates that cellular redox level is maintained in this halophyte. Although ROS levels (H2O2 and O2â¢-) increased significantly under drought stress, electrolyte leakage and lipid peroxidation level remained unchanged in response to water deficit condition which indicates that minimal increase in ROS level under drought stress act in signaling for activation of ROS scavenging enzymes. Our results propose that decline in growth and photosynthesis is a vital energy conservation strategy of S. persica under drought condition. The rapid recovery of growth, photosynthesis and water relations in S. persica following drought seems to be a critical mechanism permitting this plant to withstand and survive under drought environment. In addition, our results implicate that efficient regulations of antioxidative enzymes in leaf tissue contribute in regulating the ROS level and cellular redox status, thereby protecting the plant from drought induced oxidative damage in S. persica. Consequently ion homeostasis, plant water status, and integrity of photosynthetic apparatus is maintained in S. persica subjected to drought. The results of present study propose that S. persica is a drought tolerant halophyte and it can be a potential candidate for restoration of degraded saline lands of coastal ecosystem.
Subject(s)
Adaptation, Physiological , Antioxidants/metabolism , Droughts , Reactive Oxygen Species/metabolism , Salvadoraceae/physiology , Ions/metabolism , Oxidation-Reduction , Photosynthesis , Photosynthetic Reaction Center Complex ProteinsABSTRACT
Halophytes are plants which naturally survive in saline environment. They account for â¼1% of the total flora of the world. They include both dicots and monocots and are distributed mainly in arid, semi-arid inlands and saline wet lands along the tropical and sub-tropical coasts. Salinity tolerance in halophytes depends on a set of ecological and physiological characteristics that allow them to grow and flourish in high saline conditions. The ability of halophytes to tolerate high salt is determined by the effective coordination between various physiological processes, metabolic pathways and protein or gene networks responsible for delivering salinity tolerance. The salinity responsive proteins belong to diverse functional classes such as photosynthesis, redox homeostasis; stress/defense, carbohydrate and energy metabolism, protein metabolism, signal transduction and membrane transport. The important metabolites which are involved in salt tolerance of halophytes are proline and proline analog (4-hydroxy-N-methyl proline), glycine betaine, pinitol, myo-inositol, mannitol, sorbitol, O-methylmucoinositol, and polyamines. In halophytes, the synthesis of specific proteins and osmotically active metabolites control ion and water flux and support scavenging of oxygen radicals under salt stress condition. The present review summarizes the salt tolerance mechanisms of halophytes by elucidating the recent studies that have focused on proteomic, metabolomic, and ionomic aspects of various halophytes in response to salinity. By integrating the information from halophytes and its comparison with glycophytes could give an overview of salt tolerance mechanisms in halophytes, thus laying down the pavement for development of salt tolerant crop plants through genetic modification and effective breeding strategies.
ABSTRACT
Plants exposed to salt stress undergo changes in their environment. The ability of plants to tolerate salt is determined by multiple biochemical pathways that facilitate retention and/or acquisition of water, protect chloroplast functions, and maintain ion homeostasis. Essential pathways include those that lead to synthesis of osmotically active metabolites, specific proteins, and certain free radical scavenging enzymes that control ion and water flux and support scavenging of oxygen radicals or chaperones. The ability of plants to detoxify radicals under conditions of salt stress is probably the most critical requirement. Many salt-tolerant species accumulate methylated metabolites, which play crucial dual roles as osmoprotectants and as radical scavengers. Their synthesis is correlated with stress-induced enhancement of photorespiration. In this paper, plant responses to salinity stress are reviewed with emphasis on physiological, biochemical, and molecular mechanisms of salt tolerance. This review may help in interdisciplinary studies to assess the ecological significance of salt stress.
Subject(s)
Adaptation, Physiological , Plant Physiological Phenomena , Sodium Chloride , Plant Physiological Phenomena/drug effects , Sodium Chloride/pharmacologyABSTRACT
A significant decrease in the amount of a protein, whose migration in two-dimensional gel electrophoresis corresponds to an apparent molecular mass of 23 kDa and pI = 6.5, was observed in leaves of NaCl-treated Bruguiera parviflora (Roxb.) Wt. & Arn. ex Griff. seedlings. This particular salt-sensitive protein, designated as SSP-23, almost disappeared after 45 days of treatment in 400 mM NaCl as compared to untreated seedlings (0 mM NaCl) where the presence of the protein was significant. A polyclonal antibody raised against the 23-kDa protein was used to determine the subcellular localization of this protein in leaves by cross-reaction with proteins from isolated chloroplasts, mitochondria, peroxisomes and cytosol fractions on Western blots. SSP-23 was confirmed to be localized in the cytosol by immunoblotting. The disappearance of SSP-23 as a result of high NaCl treatment suggests that this protein is salt-sensitive and has a possible role in salt adaptation.
Subject(s)
Plant Proteins/metabolism , Rhizophoraceae/metabolism , Sodium Chloride/pharmacology , Blotting, Western , Chloroplasts/chemistry , Chloroplasts/metabolism , Electrophoresis, Polyacrylamide Gel , Molecular Weight , Osmolar Concentration , Plant Leaves/drug effects , Plant Leaves/metabolism , Plant Proteins/isolation & purification , Rhizophoraceae/drug effectsABSTRACT
The influence of varying levels of salinity (0, 100, 200 and 400 mM) on the activities of nitrate reductase (NR, E.C. 1.6.6.1), acid phosphatase (ACP, E.C. 3.1.3.2), and alkaline phosphatase (ALP, EC 3.1.3.1 ) as well as on nitrate and phosphate uptake and total nitrogen levels in leaves of a true mangrove Bruguiera parviflora was investigated under hydroponic culture conditions. NR activity increased in 100mM NaCl treated plants, whereas it decreased gradually in 200 and 400 mM treated plants, relative to the controls. Decreased activity of NR by NaCl stress was also accompanied by a decrease in total nitrogen level and nitrate uptake. Decreases in NR activity, nitrate (NO3-), and total nitrogen level due to high salinity may be responsible for a decrease in growth and biomass production in this plant. However, salinity caused an increase in both ACP and ALP activity. Activity staining of ACP by native polyacrylamide gel electrophoresis revealed three isoforms: ACP-1, ACP-2, and ACP-3. We observed a preferential enhancement in the ACP-3 isoform by salinity. In order to understand whether the salinity-induced increase in phosphatase activity was due to inhibition in phosphate uptake, we monitored phosphate (Pi) levels in leaves and noted that phosphate levels decreased significantly under salinity. These results suggest that the induction of acid and ALP under salt stress may be due to a phosphorous deficiency.
Subject(s)
Hydroponics , Nitrogen/metabolism , Phosphorus/metabolism , Rhizophoraceae/metabolism , Sodium Chloride/pharmacology , Acid Phosphatase/metabolism , Alkaline Phosphatase/metabolism , Kinetics , Nitrate Reductase , Nitrate Reductases/metabolism , Rhizophoraceae/drug effects , Rhizophoraceae/growth & developmentABSTRACT
In order to assess the role of the antioxidative defense system against salt treatment, the activities of some antioxidative enzymes and levels of antioxidants were monitored in a true mangrove, Bruguiera parviflora, subjected to varying levels of NaCl under hydroponic culture. In the leaves of B. parviflora, salt treatment preferentially enhanced the content of H2O2 as well as the activity of ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione reductase (GR), and superoxide dismutase (SOD), whereas it induced the decrease of total ascorbate and glutathione (GSH+GSSG) content as well as catalase (CAT) activity. Analysis of isoforms of antioxidative enzymes by native PAGE and activity staining revealed that leaves of B. parviflora had one isoform each of Mn-SOD and Cu/Zn-SOD and three isoforms of Fe-SOD. Expression of Mn-SOD and Fe-SOD-2 was preferentially elevated by NaCl. Similarly, out of the six isoforms of GPX, the GPX-1, 2, 3 and 6 were enhanced by salt treatment but the levels of GPX-4 and -5 changed minimally as compared to those of a control. Activity staining gel revealed only one prominent isoform of APX and two isoforms of GR (GR-1 and GR-2), all of these isoforms increased upon salt exposure. Four CAT-isoforms were identified, among which the prominent CAT-2 isoform level was maximally reduced, suggesting differential down regulation of CAT isoforms by NaCl. The concentrations of malondialdehyde (MDA), a product of lipid peroxidation, remained unchanged in leaves of the plant treated with different concentrations of NaCl. This suggests that plants are protected against activated oxygen species by the elevated levels of certain antioxidative enzymes, thus avoiding lipid peroxidation during salt exposure. The differential changes in the levels of the isoforms due to NaCl treatment may be useful as markers for recognizing salt tolerance in mangroves.