•Growth reduction under high salinity is an energy conservation strategy in H. salicornicum.•Downregulation of stomata is a water conservation strategy in H. salicornicum.•Na+, total soluble sugars, ...and total free amino acids are major contributors for osmotic adjustment.•Coordination of enzymatic and non-enzymatic antioxidative components play vital role in salt tolerance of H. salicornicum.•Structural integrity of photosystems is maintained by efficient sequestration of ROS.
Salinity is a foremost environmental threat that challenges agriculture and food security worldwide. In the present work, physiological, biochemical and anatomical strategies adopted by the xero-halophyte Haloxylon salicornicum in response to salinity was investigated. H. salicornicum plant withstands a prolong treatment of salinity, even under high dose of NaCl (400 mM). Our results showed that both fresh and dry biomass of shoot, plant height, and shoot area increased under low salinity (100–200 mM NaCl), whereas these parameters remained unaffected under high salinity (300–400 mM NaCl). In H. salicornicum, shoot water content (SWC%) was maintained at all levels of salinity. Salt tolerance index of H. salicornicum did not decline with increasing doses of salinity indicating salt tolerance capability of the plant. Although, salinity caused an increase in Na+ content of shoot, but K+ content of shoot remained steady at all levels of salinity. The rate of photosynthesis (PN), stomatal conductance (gs), rate of transpiration (E), water use efficiency (WUE), quantum yield of PSII (ΦPSII), photochemical quenching (qP), and electron transport rate (ETR) remained at par to the control level under low salinity (100–200 mM NaCl) and then reduced significantly under high salinity (300–400 mM NaCl). Salinity had no significant impacts on maximum quantum efficiency of PSII (Fv/Fm) and non-photochemical quenching (NPQ) which implies that PS II remained unaffected by sanity-induced oxidative damage. The levels of H2O2 and NO increased significantly under salinity, whereas the level of O2•− remained unaffected under various levels of salinity. Higher level of H2O2 and NO indicates the signaling role of these molecules. Lipid peroxidation level remained unchanged under low salinity (0–300 mM NaCl), but increased significantly under extreme salinity (400 mM NaCl). Ratio of AsA/DHA (indicator of cellular redox potential) elevated under high salinity (300–400 mM NaCl). The activities of various enzymatic antioxidants like SOD, APX, POX, GR and CAT showed differential responses under salinity. The results propose that coordination between enzymatic and non-enzymatic antioxidative components regulates ROS levels in H. salicornicum and contribute in salt tolerance by maintaining water status, ion homeostasis, redox status of the cells, and efficient protection of PSII form salinity induced oxidative damage. Higher tolerance index, optimal growth and competent antioxidative system make this xero-halophyte a suitable candidate for reclamation of salt degraded agricultural lands and can be a potent genetic resource for the development of salinity tolerant crops.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Halophytes are plants which naturally survive in saline environment. They account for ∼1% 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.
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•Halophyte S. persica is an As-hyperaccumulator and can withstand high salinity and arsenic.•The salinity tolerance index was > 99 and As tolerance index was > 70 in S. ...persica.•In-built As-salinity cross tolerance mechanisms confer tolerance to metal toxicity in S. persica.•Higher root phytochelatin suggest higher vacuolar sequestration of arsenic in root.•Modulations of ROS-scavenging attributes safeguard the plant from As-induced oxidative stress.
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A total of 56 metabolites belonging to various functional classes changed in halophyte Salvadora persica under salinity.•Amino acids, sugars and sugar alcohols act as osmoprotectant ...under salinity.•Salinity decreased the TCA cycle activity for the synthesis of osmoprotectants.•The decreased TCA cycle activity indicates the decrease carbon flow from glycolysis.•Two important phytohormones ABA and JA act synergistically in stress signalling.
Salvadora persica L. (Miswak) is a facultative halophyte growing under high saline conditions. It has developed the adaptive characteristics to cope with high salinity because of its extreme habitat. The present study investigates the metabolomic responses of the halophyte S. persica imposed to long term salinity. This study will provide a systematic framework for understanding the underlying mechanisms and metabolic plasticity of S. persica for adaptation under high saline conditions. S. persica seedlings were imposed to various levels of salinity for 60 d. The metabolic profiling was carried out in leaf samples collected from control and NaCl-treated plants using GC–MS and HPLC analysis. The principal component analysis (PCA) and partial least squares-discriminate analysis (PLS-DA) were used for identifying the variations among control and treated groups. Furthermore, correlation based networking and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were employed for elucidation of metabolic pathways involved in salt tolerance of S. persica. In S. persica, a total of 56 metabolites belonging to different functional classes such as amino acids, TCA cycle intermediates, organic acids, sugars, sugar alcohols, phytohormones and fatty acids were changed by salinity. The fold change analysis showed that salinity induced major metabolic differences were noted for proline, methionine, phenylalanine, phosphonic acid, citric acid, galactaric acid, mandelic acid, caffeic acid, shikimic acid, gulonic acid, d-xylose, d-mannose, d-tagatose, d-mannitol, ABA, jasmonic acid, stearic acid and benzyl amine. Further assessment by correlation-based networking and KEGG pathway enrichment analysis demonstrated that the salinity-induced metabolites are associated with the major biological pathways related to amino acid biosynthesis, energy metabolism, carbohydrate metabolism, glycolysis, gluconeogenesis, pyruvate metabolism, TCA cycle, inositol phosphate metabolism, galactose metabolism and alkaloid biosynthesis. The present study is the first report on metabolomic responses to salinity in the halophyte S. persica. From our study, it was concluded that the coordination between various metabolic processes and pathways in S. persica enable the plant to adapt under extreme saline environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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.
•Salinity and As interaction confer tolerance to As toxicity in S. persica.•S. persica reduces transpirational water loss through stomatal closure.•WUE and efficiency of PS II is maintained under high salinity and/or As.•Increased TCA cycle intermediates deliver carbon skeleton for osmolyte synthesis.•Glutamate and cysteine are involved in osmotic balance, and GSH and PCs synthesis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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 (O
2
•−
) and hydrogen peroxide (H
2
O
2
) 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.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
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•Peanut genotypes imposed to PEG-mediated drought under Si-supplementation.•Si promotes absorption of mineral nutrients under drought in both the genotypes.•Si improved biomass, leaf chlorophyll content, and RWC% in GG7 compared to TG26.•Si provides osmoprotection by higher accumulation of metabolites in GG7 than TG26.•Si improved IAA, GA3, JA, and zeatin levels in GG7 genotype under drought.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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•Cd and Pb are immobilized in root of S. maritima by synthesis of PCs, GSH, and OAs.•Water status is maintained under Cd and Pb stress by ionic and osmotic homeostasis.•Cd and Pb-induced ROS is scavenged by synchronized antioxidative defense system.•Metabolomics revealed key metabolites and metabolic pathways involved in HM stress.•S. maritima phytostabilizes Cd and Pb ions via exclusion or avoidance strategy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Mangroves are woody plants which form the dominant vegetation in tidal, saline wetlands along tropical and subtropical coasts. The current knowledge concerning the most striking feature of mangroves ...i.e., their unique ability to tolerate high salinity is summarized in the present review. In this review, we shall discuss recent studies that have focused on morphological, anatomical, physiological, biochemical, molecular and genetic attributes associated with the response to salinity, some of which presumably function to mediate salt tolerance in the mangroves. Here we shall also review the major advances recently made at both the genetic and the genomic levels in mangroves. Salinity tolerance in mangroves depends on a range of adaptations, including ion compartmentation, osmoregulation, selective transport and uptake of ions, maintenance of a balance between the supply of ions to the shoot, and capacity to accommodate the salt influx. The tolerance of mangroves to a high saline environment is also tightly linked to the regulation of gene expression. By integrating the information from mangroves and performing comparisons among species of mangroves and non-mangroves, we could give a general picture of salt tolerance mechanisms of mangroves, thus providing a new avenue for development of salt tolerance in crop plants through effective breeding strategies and genetic engineering techniques.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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