Improving Plant Salt Tolerance Research Articles

Hydrogen peroxide as a mediator of 5-aminolevulinic acid-induced Na+ retention in roots for improving salt tolerance of strawberries.

To explore the mechanisms of 5-aminolevulinic acid (ALA)-improved plant salt tolerance, strawberries (Fragaria × ananassa Duch. cv. 'Benihoppe') were treated with 10mg l-1 ALA under 100 mmol l-1 NaCl stress. We found that the amount of Na+ increased in the roots but decreased in the leaves. Laser scanning confocal microscopy (LSCM) observations showed that ALA-induced roots had more Na+ accumulation than NaCl alone. Measurement of the xylem sap revealed that ALA repressed Na+ concentrations to a large extent. The electron microprobe X-ray assay also confirmed ALA-induced Na+ retention in roots. qRT-PCR showed that ALA upregulated the gene expressions of SOS1 (encoding a plasma membrane Na+ /H+ antiporter), NHX1 (encoding a vacuolar Na+ /H+ antiporter) and HKT1 (encoding a protein of high-affinity K+ uptake), which are associated with Na+ exclusion in the roots, Na+ sequestration in vacuoles and Na+ unloading from the xylem vessels to the parenchyma cells, respectively. Furthermore, we found that ALA treatment reduced the H2 O2 content in the leaves but increased it in the roots. The exogenous H2 O2 promoted plant growth, increased root Na+ retention and stimulated the gene expressions of NHX1, SOS1 and HKT1. Diphenyleneiodonium (DPI), an inhibitor of H2 O2 generation, suppressed the effects of ALA or H2 O2 on Na+ retention, gene expressions and salt tolerance. Therefore, we propose that ALA induces H2 O2 accumulation in roots, which mediates Na+ transporter gene expression and more Na+ retention in roots, thereby improving plant salt tolerance.

Effects of Ionic Components of Saline Water on Irrigated Sunflower Physiology

The characteristics of ions in saline water can be significantly different along the water salinity gradient. The physiologic processes of plants that are irrigated with this kind of water are remarkably influenced. Based on the field sampling data, the chemical components of irrigation water were studied, and their influence on sunflower nutrient uptake, water content, and dry weight were evaluated. The results demonstrated that irrigation water salinity was mainly controlled by Na, SO4, Mg, and Cl concentrations and the ionic characteristics changed as soon as water becomes saline. The concentrations of Na, Ca, Mg, and N in sunflower leaves changed slightly with increasing irrigation salinity, whereas the concentration of leaf C decreased steadily. The ions in irrigation water had significantly different effects on leaf nutrient uptake. The Ca and Cl concentrations in irrigation water significantly influenced the Ca-related ionic exchange and C- and N-assimilation processes in sunflower leaves. The water content in the stem rose positively with irrigation salinity, whereas we observed little response in the leaves, fruits, and roots, although they were all mainly affected by the concentrations of Ca, Cl, Na, NO3, and SO4 in irrigation water. The biomass in leaves, stems, flower discs, and seeds all significantly reduced with irrigation salinity increase, and a loss of about 25% in stem biomass was detected. The concentrations of Na, Ca, Mg, K, Cl, and SO4 in irrigation water influenced the dry weight of different organs. The results presented here demonstrate that the ionic effects of irrigation water on plant physiologic processes are complex, which is concerning in terms of improving plant salt tolerance and managing saline water resources.

Improvement Salt Tolerance of Safflower Plants by Endophytic Bacteria

Salinity is one of the most dangerous environmental limiting factors of the plant productivity. A wide range of adaptation strategies is required to overcome salinity stress. However, such strategies seem to be long drawn and cost-intensive. It has been confirmed in recent years that plant growth promoting endophytes (PGPEs) that have the ability to further build a symbiotic association with their host to improve host plant salt tolerance. In our investigation try to improve plant salt tolerance using different species of endophytic bacteria. From the total eight endophytic bacterial species were isolated from root, stem, and leaf of Carthamustinctorius (safflower) plant, two isolates were capable of using 1-aminocyclopropane-1-carboxylic acid (ACC) as a sole nitrogen source, and they are of positive results for (ACC) deaminase activity and indole-3-acetic acid (IAA) production. The bacterial isolates were identified using 16S ribosomal DNA technique as Bacillus cereus and Bacillus aerius and had accession numbers MG708176 and MG711593 respectively, by submitting their sequences in GenBank database. This study showed that the bacterial strains B. cereus and B. aerius are valuable biological plant growth promoters that could enhance salt tolerance in Safflower plants under 100, 200, and 300mMNaCl levels resulting in an increase in plant growth and ascorbate-glutathione redox cycle, in comparison with the non-inoculated controls. Our findings reported that the co-inoculation of the two selected endophytic bacteria strains were successfully isolated from Safflower seedlings significantly alleviated the harmful effects of salt stress, promoted plant growth and biomass yield.

Exogenous application of gibberellic acid participates in up-regulation of lipid biosynthesis under salt stress in rice

Alterations in membrane lipid composition lead to improved plant salt tolerance. Gibberellic acid (GA3) has also been widely reported to reduce growth inhibition induced by increased salinity. However, little is known about whether exogenous application of GA3 participates in up-regulation of lipid biosynthesis under salt stress. In this study, one of the major lipid biosynthesis genes in rice (Oryza sativa L. cv. Nipponbare), monogalactosyldiacylglycerol synthase (OsMGD) was found to be significantly up-regulated by GA3 treatment. Lipid analysis showed that after salt disturbance, the concentrations of all the measured lipids, including monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and phospholipid lipids + sulfoquinovosyl diacylglycerol (PL + SQDG) were decreased significantly. However, GA3 treatment prior to salt disturbance caused those lipids to remain at high levels, as well as preserving a high DGDG/MGDG ratio. The desaturation of DGDG (DBI) was also increased in GA3 pre-treatment plants as compared with no GA3 pre-treatment, primarily due to a decrease of 16:0 fatty acids and an increase of 18:3 fatty acids in DGDG. Plants pre-treated with GA3 prior to salt disturbance had higher dry weights than those without pre-treatment. The chlorophyll concentration was also higher in GA3 treated plants than in untreated plants under salt disturbance. Taken together, these results indicate that exogenous application of GA3 participates in up-regulation of chloroplast lipid biosynthesis under salt disturbance in rice.

STRESS INDUCED FACTOR 2, a Leucine-Rich Repeat Kinase Regulates Basal Plant Pathogen Defense.

Protein kinases play fundamental roles in plant development and environmental stress responses. Here, we identified the STRESS INDUCED FACTOR (SIF) gene family, which encodes four leucine-rich repeat receptor-like protein kinases in Arabidopsis (Arabidopsis thaliana). The four genes, SIF1 to SIF4, are clustered in the genome and highly conserved, but they have temporally and spatially distinct expression patterns. We employed Arabidopsis SIF knockout mutants and overexpression transgenics to examine SIF involvement during plant pathogen defense. SIF genes are rapidly induced by biotic or abiotic stresses, and SIF proteins localize to the plasma membrane. Simultaneous knockout of SIF1 and SIF2 led to improved plant salt tolerance, whereas SIF2 overexpression enhanced PAMP-triggered immunity and prompted basal plant defenses, significantly improving pathogen resistance. Furthermore, SIF2 overexpression plants exhibited up-regulated expression of the defense-related genes WRKY53 and flg22-INDUCED RECEPTOR-LIKE KINASE1 as well as enhanced MPK3/MPK6 phosphorylation upon pathogen and elicitor treatments. The expression of the calcium signaling-related gene PHOSPHATE-INDUCED1 also was enhanced in the SIF2-overexpressing lines upon pathogen inoculation but repressed in the sif2 mutants. Bimolecular fluorescence complementation demonstrates that the BRI1-ASSOCIATED RECEPTOR KINASE1 protein is a coreceptor of the SIF2 kinase in the signal transduction pathway during pathogen invasion. These findings characterize a stress-responsive protein kinase family and illustrate how SIF2 modulates signal transduction for effective plant pathogenic defense.

Plant salt-tolerance mechanism: A review

Almost all crops that are important to humans are sensitive to high salt concentration in the soil. The presence of salt in soil is one of the most significant abiotic stresses in farming. Therefore, improving plant salt tolerance and increasing the yield and quality of crops in salty land is vital. Transgenic technology is a fast and effective method to obtain salt-tolerant varieties. At present, many scholars have studied salt damage to plant and plant salt-tolerance mechanism. These scholars have cloned a number of salt-related genes and achieved high salt tolerance for transgenic plants, thereby showing attractive prospects.In this paper, the salt-tolerance mechanism of plants is described from four aspects: plant osmotic stress, ion toxicity, oxidative stress, and salt tolerance genes. This review may help in studies to reveal the mechanism of plant salt tolerance, screen high efficiency and quality salt tolerance crops.

Switchgrass PvDREB1C plays opposite roles in plant cold and salt tolerance in transgenic tobacco

BackgroundThe C-repeat-binding factors/DRE-binding factors (CBF/DREBs) comprise a key transcription factor family involved in plant stress tolerance. Yet, there is limited information about switchgrass DREB genes and their functional roles.ResultsIn this study, four cold-inducible PvDREB1s were identified from switchgrass (Panicum virgatum), among which PvDREB1C was the one responded to cold stress later than the other three PvDREB1s. Yet, ectopic overexpression of PvDREB1C led to significantly compromised, instead of improved cold tolerance in transgenic tobacco. On the other hand, PvDREB1C was transcriptionally down-regulated in response to salt stress, but overexpression of PvDREB1C improved plant salt tolerance in transgenic tobacco. The improved salt tolerance was associated with increased K+/Na+ ratio and Ca2+ content, higher cellular osmotic potential, and activation of stress-related functional genes in the leaves of transgenic plants under salt stress.ConclusionsThe current results implied that PvDREB1C played opposite roles in plant cold and salt tolerance. Although DREB1s were known as positive stress regulators, particular attentions shall be paid to their potential negative regulatory role(s).

Proteomics-Based Investigation of Salt-Responsive Mechanisms in Roots of Bradyrhizobium japonicum-Inoculated Glycine max and Glycine soja Seedlings

Salt stress is one of the environmental factors most limiting crop productivity worldwide. Plant roots are the primary site for salt sensing; therefore, a thorough understanding of molecular mechanisms of salt response in roots is critical for improving plant salt tolerance. In this study, Glycine max Lee68 cultivar (USA, the salt-tolerant) and Glycine soja N23227 accession (the relatively salt-sensitive) were used as the experimental materials. This work aims to further understand the molecular mechanisms occurring in the roots of B. japonicum-inoculated soybean seedlings in response to salt stress from a proteomic perspective using liquid chromatography technique coupled to tandem mass spectrometry (LC–MS/MS). Proteomic analysis showed that a total of 105 differentially expressed proteins in the roots of B. japonicum-inoculated soybean seedlings were successfully identified. Among them, 42 and 46 proteins were up-regulated in Lee68 and in N23227, respectively, where 34 were commonly up-regulated in both genotypes and eight were up-regulated in Lee68 and down-regulated in N23227. All of the bacteroid proteins were down-regulated in N23227, of which four were up-regulated in Lee68. These results indicated that salt stress could change the expression level of some proteins in the roots of B. japonicum-inoculated soybean seedlings which may in turn play a role in the adaption to salt stress; meanwhile, inoculation with B. japonicum might be more advantageous to salt-tolerant genotypes than the salt-sensitive ones.

Ectopic Overexpression of Barley PIP2;4 Confers Salt Tolerance in Arabidopsis

In the present study HvPIP2;4 was overexpressed in Arabidopsis thaliana to engineer enhanced salt tolerance. Barley Aquaporin was selected since barley shows fairly good tolerance to drought, salt stress and low temperature compared to many other crops including rice, and it was thought that analysis of barley aquaporin will provide a good insight into the molecular mechanisms involved in transport of water & their efficacy during abiotic stress condition. Arabidopsis line expressing HvPIP2;4 from annual crop plant Hordeum vulgare (Barley) under the control of constitutive promoter was used to analyze the expression of HvPIP2; 4 and its efficacy during salt stress when NaCl concentration gradually increased. The pattern of expression of HvPIP2; 4 were found to be NaCl dose dependent during salt stress. The constitutive expression of HvPIP2;4 enhanced salt stress tolerance in Arabidopsis. HvPIP2;4 played a dominant role in improving plant salt tolerance. It may be very well presumed that overexpression of HvPIP2;4 in crop plant might benefit them by enhancing their salt tolerance capacity.Int J Appl Sci Biotechnol, Vol 4(4): 498-512

Coordination between Bradyrhizobium and Pseudomonas alleviates salt stress in soybean through altering root system architecture

ABSTRACTIt is a well accepted strategy to improve plant salt tolerance through inoculation with beneficial microorganisms. However, its underlying mechanisms still remain unclear. In the present study, hydroponic experiments were conducted to evaluate the effects of Bradyrhizobium japonicum USDA 110 with salt-tolerant Pseudomonas putida TSAU1 on growth, protein content, nitrogen, and phosphorus uptake as well as root system architecture of soybean (Glycine max L.) under salt stress. The results indicated that the combined inoculation with USDA 110 and TSAU1 significantly improved plant growth, nitrogen and phosphorus contents, and contents of soluble leaf proteins under salt stress compared to the inoculation with the symbiont alone or compared to un-inoculated ones. The root architectural traits, like root length, surface area, project area, and root volume; as well as nodulation traits were also significantly increased by co-inoculation with USDA 110 and TSAU1. The plant-growth promoting rhizobacteria (PGPR) P. putida strain TSAU1 could improve the symbiotic interaction between the salt-stressed soybean and B. japonicum USDA 110. In conclusion, inoculation with B. japonicum and salt-tolerant P. putida synergistically improved soybean salt tolerance through altering root system architecture facilitating nitrogen and phosphorus acquisition, and nodule formation.

Iron deficiency response gene Femu2 plays a positive role in protecting Chlamydomonas reinhardtii against salt stress

BackgroundIron deficiency related gene, Femu2, encodes protein homologous to a C2H2-type zinc finger protein, which participates in the regulation of FOX1 gene induced by iron (Fe) deficiency in Chlamydomonas reinhardtii. In this study, we investigate the gene function of Femu2 in response to salt stress in C. reinhardtii. MethodsFemu2-overexpressing and Femu2-silencing transgenic cells were analyzed under salt stress. Several physiological indices were measured, and global changes in gene expression were investigated via RNA-seq. ResultsCompared with that of the non-treated control, the transcript levels of Femu2 were dramatically induced by iron deficiency and can also be significantly induced after algal cell exposure to Tris–acetate–phosphate (TAP) medium with 100 and 150mM NaCl. The promoter also responded to NaCl induction. Femu2-overexpressing transgenic algal cells exhibited significantly enhanced tolerance to salt stress. Conversely, Femu2-silencing cells showed higher sensitivity to salt stress than the control. Physiological analyses revealed that the overexpression of Femu2 increased the contents of proline and soluble sugars in transgenic cells under high salinity and that silencing Femu2 resulted in increased malondialdehyde level and decreased superoxide dismutase activity. RNA-seq results showed that a total of 248 genes have opposite expression profiles and that 5508 and 2120 genes were distinctly up-regulated or down-regulated in Femu2-overexpressing and Femu2-silencing transgenic cells under salt stress, respectively. ConclusionFemu2 may play an important positive role in protecting C. reinhardtii against salt stress. General SignificanceThe results of this study indicated that Femu2 may be useful in improving plant salt tolerance.

A novel TaSST gene from wheat contributes to enhanced resistance to salt stress in Arabidopsis thaliana and Oryza sativa

In this research, through the analyzing of the Triticum aestivum salt-tolerant mutant gene expression profile, under salt stress. A brand new gene with unknown functions induced by salt was cloned. The cloned gene was named Triticum aestivum salt stress protein (TaSST). GenBank accession number of TaSST is ACH97119. Quantitative polymerase chain reaction (qPCR) results exhibited that the expression TaSST was induced by salt, abscisic acid (ABA), and polyethylene glycol (PEG). TaSST could improve salt tolerance of Arabidopsis-overexpressed TaSST. After salt stress, physiological indexes of transgenic Arabidopsis were better compared with WT (wild-type) plants. TaSST was mainly located in the cytomembrane. qPCR analyzed the expression levels of nine tolerance-related genes of Arabidopsis in TaSST-overexpressing Arabidopsis. Results showed that the expression levels of SOS3, SOS2, KIN2, and COR15a significantly increased, whereas the expression of the five other genes showed no obvious change. OsI_01272, the homologous gene of TaSST in rice, was interfered using RNA interference (RNAi) technique. RNAi plants became more sensitive to salt than control plants. Thus, we speculate that TaSST can improve plant salt tolerance.

Molecular cloning of Phosphoethanolamine N-methyltransferase (PEAMT) gene and its promoter from the halophyte Suaeda liaotungensis and their response to salt stress

Phosphoethanolamine N-methyltransferase (encoded by the PEAMT gene) catalyzes the methylation of phosphoethanolamine to produce phosphocholine, which is dephosphorylated to free choline. Choline is the substrate for glycine betaine synthesis, which can improve the salt tolerance of plants. A 1688 bp cDNA of SlPEAMT was isolated from the halophyte Suaeda liaotungensis. Real-time quantitative PCR showed that SlPEAMT expression was induced in S. liaotungensis under salt stress. An 897 bp fragment of the 5′ flanking region of SlPEAMT (designated pP) was isolated from S. liaotungensis. This fragment contained the transcription start site and a number of stress-responsive elements, such as MBS, GT-1 elements, and a W-box. The fragment was inserted into the pCAMBIA1301 plasmid by replacing the CaMV35S promoter. The pP-GUS construct was introduced into tobacco. β-glucuronidase (GUS) histochemical staining and quantitative fluorescence analysis showed an 18.6-fold increase in GUS activity in pP-GUS transgenic tobacco treated with 200 mmol NaCl l−1. Thus, SlPEAMT and its promoter are responsive to salt stress and may be useful in genetic engineering to improve plant salt tolerance.

Molecular Character, Phylogeny and Expression of Tomato LeNHX3 Gene Involved in Multiple Adverse Stress Responses

Crop production is severely affected by high salt stress. To obtain more salt-tolerant crops by genetic modification, it is crucial to explore some key genes associated with salt tolerance. LeNHX3 gene is considered one putative Na+/H+ antiporter with the ability of improving plant salt tolerance by maintaining intracellular ionic balance in tomato, however, limited information about it has been reported. Here, we report the structure, phylogenetic evolution and expression of LeNHX3 gene from wild type tomato (Lycopersicon esculentum Mill cv. Ailsa Craig). Sequence analysis showed that LeNHX3 encodes a protein containing 10 transmembrane domains, with a typical conserved amiloride binding domain presented in the third transmembrane domain. An interesting discovery also showed that sequence of LeNHX3 was more conserved than its allele protein collected by GenBank (designated as LeNHX3-GB in this study) when compared with others Na+/H+ antiporters. Homology modeling results showed that the structure of LeNHX3 protein consists mainly of α-helix and random coil, it has similar tertiary structure to that of LeNHX3-GB, however, inter-residue interactions were found to be further strengthened in LeNHX3. Phylogenetic analysis showed LeNHX3 was clustered with vacuolar Na+/H+ antiporters and has distant relationship to plasma membrane Na+/H+ antiporters. Expression profiles analysis indicated LeNHX3 gene was constitutively expressed in roots, stems and leaves, its expression was also induced by salt, low temperature and abscisic acid. The results presented in this work provide new insights into LeNHX3 gene, it is particularly important that one new LeNHX3 allele from wild tomato was mined, which can serve as a candidate gene for improving plant stress tolerance by genetic engineering.

Global Identification of MicroRNAs and Their Targets in Barley under Salinity Stress.

Salinity is a major limiting factor for agricultural production worldwide. A better understanding of the mechanisms of salinity stress response will aid efforts to improve plant salt tolerance. In this study, a combination of small RNA and mRNA degradome sequencing was used to identify salinity responsive-miRNAs and their targets in barley. A total of 152 miRNAs belonging to 126 families were identified, of which 44 were found to be salinity responsive with 30 up-regulated and 25 down-regulated respectively. The majority of the salinity-responsive miRNAs were up-regulated at the 8h time point, while down-regulated at the 3h and 27h time points. The targets of these miRNAs were further detected by degradome sequencing coupled with bioinformatics prediction. Finally, qRT-PCR was used to validate the identified miRNA and their targets. Our study systematically investigated the expression profile of miRNA and their targets in barley during salinity stress phase, which can contribute to understanding how miRNAs respond to salinity stress in barley and other cereal crops.

The beta subunit of glyceraldehyde 3-phosphate dehydrogenase is an important factor for maintaining photosynthesis and plant development under salt stress—Based on an integrative analysis of the structural, physiological and proteomic changes in chloroplasts in Thellungiella halophila

Thellungiella halophila, a new model halophyte, can survive under highly saline conditions. We performed comparative proteomics of chloroplasts from plants grown under different saline conditions. Seventy-five salt-responsive proteins were positively identified by mass spectrometry, which represented 43 unique ones. These proteins were categorized into 7 main pathways: light reaction, carbon fixation, energy metabolism, antenna proteins, cell structure, and protein degradation and folding. Saline conditions increased the abundance of proteins involved in photosynthesis, energy metabolism and cell structure. The results indicated that Thellungiella could withstand high salinity by maintaining normal or high photosynthetic capacity, reducing ROS production, as well as enhancing energy usage. Meanwhile, the ultrastructural and physiological data also agree with chloroplast proteomics results. Subsequently, the glyceraldehydes 3-phosphate dehydrogenase beta subunit (GAPB) involved in carbon fixation was selected and its role in salt tolerance was clarified by over-expressing it in Arabidopsis. ThGAPB-overexpressing plants had higher total chlorophyll contents, dry weights, water contents and survival rates than that of wild type plants. These results indicated that ThGAPB might improve plant salt tolerance by maintaining higher recycling rates of ADP and NADP+ to decrease ROS production, helping to maintain photosynthetic efficiency and plant development under saline conditions.

Study on salt tolerance with YHem1 transgenic canola (Brassica napus).

5-Aminolevulinic acid (5-ALA) has been suggested for improving plant salt tolerance via exogenous application. In this study, we used a transgenic canola (Brassica napus), which contained a constituted gene YHem1 and biosynthesized more 5-ALA, to study salt stress responses. In a long-term pot experiment, the transgenic plants produced higher yield under 200 mmol L(-1) NaCl treatment than the wild type (WT). In a short-term experiment, the YHem1 transformation accelerated endogenous 5-ALA metabolism, leading to more chlorophyll accumulation, higher diurnal photosynthetic rates and upregulated expression of the gene encoding Rubisco small subunit. Furthermore, the activities of antioxidant enzymes, including superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase, were significantly higher in the transgenic plants than the WT, while the levels of O2 ·(-) and malondialdehyde were lower than the latter. Additionally, the Na(+) content was higher in the transgenic leaves than that in the WT under salinity, but K(+) and Cl(-) were significantly lower. The levels of N, P, Cu, and S in the transgenic plants were also significantly lower than those in the WT, but the Fe content was significantly improved. As the leaf Fe content was decreased by salinity, it was suggested that the stronger salt tolerance of the transgenic plants was related to the higher Fe acquisition. Lastly, YHem1 transformation improved the leaf proline content, but salinity decreased rather than increased it. The content of free amino acids and soluble sugars was similarly decreased as salinity increased, but it was higher in the transgenic plants than that in the WT.

PHENOTYPIC EVALUATION OF 'THOMPSON SEEDLESS' GRAPES TRANSFORMED WITH ATNHX1 GROWING IN HYDROPONICS AND POTTED SOILS

Overexpression of vacuolar Na+/H+ antiport AtNHX1 has been reported to improve plant salt tolerance. We produced transgenic plants of Vitis vinifera ?Thompson Seedless? via Agrobacterium tumefaciens carrying the gene encoding for AtNHX1 under the control of the constitutive promoter CaMV35S. Independent transgenic lines with improved tolerance to salt stress were selected in first round evaluations. The objective of this study was to analyze the response of the selected lines to NaCl stress in hydroponics and potted soils. Untransformed and transgenic plants were acclimated to greenhouse conditions and grown hydroponically using Long Ashton nutrient solution. In the salinity treatments, NaCl concentrations were increased stepwise by 25 mM every 10 days up to 150 mM. In addition, untransformed and transgenic plants were grown in a mix of 7-3 grape pomace-sand soil and watered with Long Ashton nutrient solution with and without increasing concentrations of NaCl. Analysis of plant growth variables confirmed the improved tolerance of the transgenic lines, which showed higher shoot length, leaf number, leaf area, and fresh and dry weight of shoots and roots. However, their improved performance was not correlated with higher Na accumulation in root and/or shoot tissue compared to the untransformed controls. Na and Cl tissue contents were higher in plants grown in hydroponics; and roots accumulated 1.5-2.5 times more NaCl than aerial parts

Physiological adaptive mechanisms of plants grown in saline soil and implications for sustainable saline agriculture in coastal zone

There is large area of saline abandoned and low-yielding land distributed in coastal zone in the world. Soil salinity which inhibits plant growth and decreases crop yield is a serious and chronic problem for agricultural production. Improving plant salt tolerance is a feasible way to solve this problem. Plant physiological and biochemical responses under salinity stress become a hot issue at present, because it can provide insights into how plants may be modified to become more tolerant. It is generally known that the negative effects of soil salinity on plants are ascribed to ion toxicity, oxidative stress and osmotic stress, and great progress has been made in the study on molecular and physiological mechanisms of plant salinity tolerance in recent years. However, the present knowledge is not easily applied in the agronomy research under field environment. In this review, we simplified the physiological adaptive mechanisms in plants grown in saline soil and put forward a practical procedure for discerning physiological status and responses. In our opinion, this procedure consists of two steps. First, negative effects of salt stress are evaluated by the changes in biomass, crop yield and photosynthesis. Second, the underlying reasons are analyzed from osmotic regulation, antioxidant response and ion homeostasis. Photosynthesis is a good indicator of the harmful effects of saline soil on plants because of its close relation with crop yield and high sensitivity to environmental stress. Particularly, chlorophyll a fluorescence transient has been accepted as a reliable, sensitive and convenient tool in photosynthesis research in recent years, and it can facilitate and enrich photosynthetic research under field environment.

Proteomics-based investigation of salt-responsive mechanisms in plant roots

Salinity is one of the major abiotic stresses that limits agricultural productivity worldwide. Plant roots function as the primary site of salinity perception. Salt responses in roots are essential for maintaining root functionality, as well as for transmitting the salt signal to shoot for proper salt response and adaptation in the entire plant. Therefore, a thorough understanding of signaling and metabolic mechanisms of salt response in roots is critical for improving plant salt tolerance. Current proteomic studies have provided salt-responsive expression patterns of 905 proteins in 14 plant species. Through integrative analysis of salt-responsive proteins and previous physiological and molecular findings, this review summarizes current understanding of salt responses in roots and highlights proteomic findings on the molecular mechanisms in the fine-tuned salt-responsive networks. At the proteome level, the following processes become dominant in root salt response: (i) salt signal perception and transduction; (ii) detoxification of reactive oxygen species (ROS); (iii) salt uptake/exclusion and compartmentalization; (iv) protein translation and/or turnover dynamics; (v) cytoskeleton/cell wall dynamics; (vi) carbohydrate and energy metabolism; and (vii) other salt-responsive metabolisms. These processes work together to gain cellular homeostasis in roots and determine the overall phenotype of plant growth and development under salt stress.