Enhanced Tolerance To Salt Stress Research Articles

Salt Stress Tolerance in Medicinal and Aromatic Plants: A Review

Soil salinity is a globally pervasive issue, significantly affecting crop productivity and quality. This review provides a comprehensive overview of salt stress tolerance in medicinal and aromatic plants, plants known for their unique metabolic capabilities and resilience to abiotic stress. The adverse impact of salt stress on plant development, growth, and chemical composition is examined, emphasizing the specific effects on medicinal and aromatic plants, such as reduced biomass, altered yield, and modification of chemical composition. We delve into the complex responses exhibited by plants under salt stress, including physiological, biochemical, and molecular mechanisms. Physiological responses such as osmotic adjustment and ion homeostasis, biochemical responses including antioxidant production and compatible solute synthesis, and molecular responses like the upregulation of salt stress-responsive genes and hormone modulation, all contribute to salt stress tolerance. Understanding these intricate mechanisms offers valuable insights into the plants' resilience under salt stress. This review also discusses strategies to enhance salt stress tolerance in medicinal and aromatic plants, encompassing breeding and genetic modification, management strategies, and the utilization of beneficial soil microbes. The potential of selective breeding and genetic engineering in developing salt-tolerant plants is explored, along with the implementation of efficient irrigation systems and the use of salt-tolerant rootstocks. Additionally, the potential role of beneficial soil microbes such as mycorrhizal fungi and plant growth-promoting rhizobacteria in alleviating salt stress is highlighted. Lastly, we present potential future directions and applications for this research. The findings and strategies elaborated upon in this review have far-reaching implications, including the improvement of salt stress tolerance in other crops, promoting sustainable agriculture in saline soils, and potential therapeutic implications due to altered biochemical composition under salt stress. The continuation of research in this field is critical to tackling soil salinity challenges and maximizing the medicinal and aromatic plants' potential under salt stress. This review underscores the importance of studying salt stress tolerance mechanisms in medicinal and aromatic plants to contribute to sustainable agricultural practices and the advancement of the pharmaceutical industry.

ZmEREB57 regulates OPDA synthesis and enhances salt stress tolerance through two distinct signalling pathways in Zea mays.

In plant, APETALA2/ethylene-responsive factor (AP2/ERF)-domain transcription factors are important in regulating abiotic stress tolerance. In this study, ZmEREB57 encoding a AP2/ERF transcription factor was identified and its function was investigated in maize. ZmEREB57 is a nuclear protein with transactivation activity induced by several abiotic stress types. Furthermore, two CRISPR/Cas9 knockout lines of ZmEREB57 showed enhanced sensitivity to saline conditions, whereas the overexpression of ZmEREB57 increased salt tolerance in maize and Arabidopsis. DNA affinity purification sequencing (DAP-Seq) analysis revealed that ZmEREB57 notably regulates target genes by binding to promoters containing an O-box-like motif (CCGGCC). ZmEREB57 directly binds to the promoter of ZmAOC2 involved in the synthesis of 12-oxo-phytodienoic acid (OPDA) and jasmonic acid (JA). Transcriptome analysis revealed that several genes involved in regulating stress and redox homeostasis showed differential expression patterns in OPDA- and JA-treated maize seedlings exposed to salt stress compared to those treated with salt stress alone. Analysis of mutants deficient in the biosynthesis of OPDA and JA revealed that OPDA functions as a signalling molecule in the salt response. Our results indicate that ZmEREB57 involves in salt tolerance by regulating OPDA and JA signalling and confirm early observations that OPDA signalling functions independently of JA signalling.

Genome-wide analysis of WD40 protein family and functional characterization of BvWD40-82 in sugar beet.

Sugar beet is one of the most important sugar crops in the world. It contributes greatly to the global sugar production, but salt stress negatively affects the crop yield. WD40 proteins play important roles in plant growth and response to abiotic stresses through their involvement in a variety of biological processes, such as signal transduction, histone modification, ubiquitination, and RNA processing. The WD40 protein family has been well-studied in Arabidopsis thaliana, rice and other plants, but the systematic analysis of the sugar beet WD40 proteins has not been reported. In this study, a total of 177 BvWD40 proteins were identified from the sugar beet genome, and their evolutionary characteristics, protein structure, gene structure, protein interaction network and gene ontology were systematically analyzed to understand their evolution and function. Meanwhile, the expression patterns of BvWD40s under salt stress were characterized, and a BvWD40-82 gene was hypothesized as a salt-tolerant candidate gene. Its function was further characterized using molecular and genetic methods. The result showed that BvWD40-82 enhanced salt stress tolerance in transgenic Arabidopsis seedlings by increasing the contents of osmolytes and antioxidant enzyme activities, maintaining intracellular ion homeostasis and increasing the expression of genes related to SOS and ABA pathways. The result has laid a foundation for further mechanistic study of the BvWD40 genes in sugar beet tolerance to salt stress, and it may inform biotechnological applications in improving crop stress resilience.

Exploration of plant growth promoting traits and regulatory mechanisms of Bacillus anthracis PM21 in enhancing salt stress tolerance in maize.

Bacillus species have been reported to reduce the negative effects of salt stress on plants; the involvement of Bacillus anthracis PM21 and the internal mechanisms involved in this process are unclear. The effects of PM21 inoculation on maize plants under salt stress were investigated in this study. The study aimed to assess the ability of Bacillus anthracis PM21 to endure high levels of salinity stress while preserving the concentration of plant growth regulators. The biomass, photosynthetic pigments, relative water content (RWC), antioxidants, osmoprotectants, inorganic ion contents, regulation of plant hormones and expression of antioxidants enzyme encoded genes were investigated under normal and salinity stress conditions. Bacillus anthracis PM21 produced a significant amount of 1-aminocyclopropane-1-carboxylate deaminase enzyme (ACC deaminase) and exopolysaccharides (EPS) under salt stress and normal conditions. PM21 also produced plant growth stimulants including indole acetic acid, gibberellic acid (GA3), kinetin, and siderophore under salinity stress and normal conditions. Under salt stress, PM21 inoculation markedly increased plant growth indices, stimulate antioxidant enzyme mechanisms, osmoprotectants, and chlorophyll content. The use of qRT-PCR to analyze the transcription of targeted genes indicated greater expression of antioxidant-encoded genes and inferred their possible function in salinity stress tolerance. Our findings shed light on the functions of PM21 and its regulatory mechanisms in plant salt stress tolerance, as well as the importance of PM21 in this process. This study will provide a thorough analysis of the theoretical framework for adopting PM21 in agricultural production as an eco-friendly method to enhance crop growth and yield under salinity stress.

The Plant Growth-Promoting Bacteria Strain Bacillus mojavensis I4 Enhanced Salt Stress Tolerance in Durum Wheat.

Plant growth and production are adversely affected by soil salinity. A plant growth-promoting bacteria (PGPB) designated as the "I4 strain" of Bacillus mojavensis was isolated from Tunisian soil (Sfax, Tunisia) and showed the ability to be grown in the presence of NaCl concentrations ranging from 0 to 10% in Luria Bertani (LB) medium. The PGPB-mediated salt tolerance in durum wheat was evaluated. The physiological parameters such as growth, shoot and root length, dry and fresh weight were higher in I4-inoculated wheat plants in comparison with non-treated plants under salt stress. Results showed that this strain promoted wheat growth and preserved the membrane damage by notably lowering the electrolytes leakage and malondialdehyde content in contrast to non-inoculated plants. Moreover, leaf chlorophyll content, biochemical parameters and antioxidant enzyme activities measurement showed a better salt and heavy metal stress adaptation of the I4-inoculated plants. Due to these outcomes, it could be suggested that the inoculation of the PGPB I4 strain enhanced the wheat plant's growth, especially under salt stress conditions. This study confirms the ameliorative role played by PGPB in tolerating salt stress in wheat and their potential use as biofertilizers to enhance its growth in saline soil and help in promoting this plant's culture to provide food security under these perturbed global circumstances.

The CCCH-Type Zinc-Finger Protein GhC3H20 Enhances Salt Stress Tolerance in Arabidopsis thaliana and Cotton through ABA Signal Transduction Pathway

The CCCH zinc-finger protein contains a typical C3H-type motif widely existing in plants, and it plays an important role in plant growth, development, and stress responses. In this study, a CCCH zinc-finger gene, GhC3H20, was isolated and thoroughly characterized to regulate salt stress in cotton and Arabidopsis. The expression of GhC3H20 was up-regulated under salt, drought, and ABA treatments. GUS activity was detected in the root, stem, leaves, and flowers of ProGhC3H20::GUS transgenic Arabidopsis. Compared with the control, the GUS activity of ProGhC3H20::GUS transgenic Arabidopsis seedlings under NaCl treatment was stronger. Through the genetic transformation of Arabidopsis, three transgenic lines of 35S-GhC3H20 were obtained. Under NaCl and mannitol treatments, the roots of the transgenic lines were significantly longer than those of the wild-type (WT) Arabidopsis. The leaves of the WT turned yellow and wilted under high-concentration salt treatment at the seedling stage, while the leaves of the transgenic Arabidopsis lines did not. Further investigation showed that compared with the WT, the content of catalase (CAT) in the leaves of the transgenic lines was significantly higher. Therefore, compared with the WT, overexpression of GhC3H20 enhanced the salt stress tolerance of transgenic Arabidopsis. A virus-induced gene silencing (VIGS) experiment showed that compared with the control, the leaves of pYL156-GhC3H20 plants were wilted and dehydrated. The content of chlorophyll in pYL156-GhC3H20 leaves was significantly lower than those of the control. Therefore, silencing of GhC3H20 reduced salt stress tolerance in cotton. Two interacting proteins (GhPP2CA and GhHAB1) of GhC3H20 have been identified through a yeast two-hybrid assay. The expression levels of PP2CA and HAB1 in transgenic Arabidopsis were higher than those in the WT, and pYL156-GhC3H20 had expression levels lower than those in the control. GhPP2CA and GhHAB1 are the key genes involved in the ABA signaling pathway. Taken together, our findings demonstrate that GhC3H20 may interact with GhPP2CA and GhHAB1 to participate in the ABA signaling pathway to enhance salt stress tolerance in cotton.

RAP2.6 enhanced salt stress tolerance by reducing Na+ accumulation and stabilizing the electron transport in Arabidopsis thaliana

The transcription factors of the AP2/ERF family are involved in plant growth and development and responses to biotic and abiotic stresses. Here, we found RAP2.6, a transcription factor which belongs to the ERF subfamily, was responsive to salt stress in Arabidopsis. Under salt stress conditions, rap2.6 mutant seedlings were the sensitivity deficiency to salt stress which was reflected in higher germination rate and longer root length compared to the wild type. Also, the expressions of salt-related gene including SOS1, SOS2, SOS3, NHX1, NHX3, NHX5 and HKT1 in rap2.6 mutant seedlings were lower than the wild type under salt stress. rap2.6 mutant adult lacked salt stress tolerance based on the results of the phenotype, survival rates and ion leakage. Compared to wild type, rap2.6 mutant adult accumulated more Na+ in leaves and roots while the salt-related gene expressions were lower. In addition, the photosynthetic electron transport and PSII energy distribution in rap2.6 mutant plant leaves had been more seriously affected under salt stress conditions compared to the wild type. In summary, this study identified essential roles of RAP2.6 in regulating salt stress tolerance in Arabidopsis.

Methyl jasmonate enhances salt stress tolerance associated with antioxidant and cytokinin alteration in perennial ryegrass

Jamonic acid (JA) and its derivatives such as methyl jasmonate (MJ) regulate stress tolerance but of the mechanism of MJ’s impact on turfgrass salt stress tolerance are not fully understood. The objectives of this experiment y was to investigate the responses of antioxidant and hormone metabolism to exogenous MJ in perennial ryegrass (<italic>Lolium perenne</italic> L<italic>.</italic>) subjected to salt stress. The MJ at 0, 25, 50, and 100 µM were applied to the ryegrass seedlings, and then the treated grass was exposed to salt stress at 250 mM NaCl. The grass plants serving as control were irrigated with regular water without MJ. Salt stress induced an increase in leaf electrolyte leakage (EL), and malondialdehyde (MDA) and reduction in turf visual quality rating and chlorophyll content. Exogenous MJ treatments suppressed EL and MDA, promoted chlorophyll content. The MJ treatments also improved superoxide dismutase (SOD) and catalase (CAT) and ascorbate peroxidase (APX) activity relative to salt treatment alone. Salt stress enhanced leaf gibberellin A4 (GA4) content but decreased indole-3-acetic acid (IAA), zeatin riboside (ZR), and isopentenyl adenosine (iPA). Exogenous MJ at 50 and 100 uM increased IAA, ZR, and iPA content under salt stress. Our data suggest that MJ treatment may enhance salt stress tolerance of perennial ryegrass by promoting the selected hormone level and antioxidant enzyme activity, and protecting cell membrane and photosynthetic function in perennial ryegrass.

Grape BES1 transcription factor gene VvBES1-3 confers salt tolerance in transgenic Arabidopsis

BRI1-EMS-Suppressor 1 (BES1) regulates plant growth, development, and stress resistance, and plays a pivotal role in the brassinosteroid (BR) signal transduction pathway. In this study, a total of 12 BES1 genes were identified in the grape (Vitis vinifera) genome. Phylogenetic, structure, and motif sequence analyses of these genes provided insights into their evolutionary characteristics. Hormone-, stress-, and light-responsive and organ-specific cis-acting elements were identified in VvBES1 gene promoters. Microarray data analysis showed that VvBES1 family members exhibit diverse expression patterns in different organs. Quantitative real-time PCR (qRT-PCR) analysis showed that the expression levels of VvBES1 genes differed in response to BR, methyl jasmonate (MeJA), cold (4 °C), NaCl, and polyethylene glycol (PEG) treatments. The expression of VvBES1-3 was 29-fold higher under salt stress than control at 12 h. Moreover, VvBES1-3-overexpessing Arabidopsis thaliana plants showed lower malondialdehyde content, higher proline content, enhanced antioxidant enzyme (catalase, superoxide dismutase, peroxidase) activities, and higher salt-responsive gene expression levels than wild-type plants under salt stress, indicating that VvBES1-3 overexpression enhances salt stress tolerance in transgenic Arabidopsis. These results will contribute to further understanding the functions of BES1 transcription factors in the abiotic stress response.

Salt stress proteins in plants: An overview.

Salinity stress is considered the most devastating abiotic stress for crop productivity. Accumulating different types of soluble proteins has evolved as a vital strategy that plays a central regulatory role in the growth and development of plants subjected to salt stress. In the last two decades, efforts have been undertaken to critically examine the genome structure and functions of the transcriptome in plants subjected to salinity stress. Although genomics and transcriptomics studies indicate physiological and biochemical alterations in plants, it do not reflect changes in the amount and type of proteins corresponding to gene expression at the transcriptome level. In addition, proteins are a more reliable determinant of salt tolerance than simple gene expression as they play major roles in shaping physiological traits in salt-tolerant phenotypes. However, little information is available on salt stress-responsive proteins and their possible modes of action in conferring salinity stress tolerance. In addition, a complete proteome profile under normal or stress conditions has not been established yet for any model plant species. Similarly, a complete set of low abundant and key stress regulatory proteins in plants has not been identified. Furthermore, insufficient information on post-translational modifications in salt stress regulatory proteins is available. Therefore, in recent past, studies focused on exploring changes in protein expression under salt stress, which will complement genomic, transcriptomic, and physiological studies in understanding mechanism of salt tolerance in plants. This review focused on recent studies on proteome profiling in plants subjected to salinity stress, and provide synthesis of updated literature about how salinity regulates various salt stress proteins involved in the plant salt tolerance mechanism. This review also highlights the recent reports on regulation of salt stress proteins using transgenic approaches with enhanced salt stress tolerance in crops.

A novel PGPF Penicillium olsonii isolated from the rhizosphere of Aeluropus littoralis promotes plant growth, enhances salt stress tolerance, and reduces chemical fertilizers inputs in hydroponic system.

The hydroponic farming significantly enhances the yield and enables multiple cropping per year. These advantages can be improved by using plant growth-promoting fungi (PGPF) either under normal or stress conditions. In this study, the fungal strain (A3) isolated from the rhizosphere of the halophyte plant Aeluropus littoralis was identified as Penicillium olsonii based on sequence homology of its ITS region. The A3 fungus was shown to be halotolerant (up to 1 M NaCl) and its optimal growth was at 27°C, but inhibited at 40°C. In liquid culture medium, the A3 produced indole acetic acid (IAA) especially in the presence of L-tryptophan. Tobacco plants grown under hydroponic farming system were used to evaluate the promoting activity of the direct effect of A3 mycelium (DE) and the indirect effect (IDE) of its cell-free culture filtrate (A3CFF). The results showed that for the two conditions (DE or IDE) the tobacco seedlings exhibited significant increase in their height, leaf area, dry weight, and total chlorophyll content. Interestingly, the A3CFF (added to the MS liquid medium or to nutrient solution (NS), prepared from commercial fertilizers) induced significantly the growth parameters, the proline concentration, the catalase (CAT) and the superoxide dismutase (SOD) activities of tobacco plants. The A3CFF maintained its activity even after extended storage at 4°C for 1 year. Since the A3 is a halotolerant fungus, we tested its ability to alleviate salt stress effects. Indeed, when added at 1:50 dilution factor to NS in the presence of 250 mM NaCl, the A3CFF enhanced the plant salt tolerance by increasing the levels of total chlorophyll, proline, CAT, and SOD activities. In addition, the treated plants accumulated less Na+ in their roots but more K+ in their leaves. The A3CFF was also found to induce the expression of five salt stress related genes (NtSOS1, NtNHX1, NtHKT1, NtSOD, and NtCAT1). Finally, we proved that the A3CFF can reduce by half the chemical fertilizers inputs. Indeed, the tobacco plants grown in a hydroponic system using 0.5xNS supplemented with A3CFF (1:50) exhibited significantly higher growth than those grown in 0.5xNS or 1xNS. In an attempt to explain this mechanism, the expression profile of some growth related genes (nitrogen metabolism (NR1, NRT1), auxin (TRYP1, YUCCA6-like), and brassinosteroid (DET2, DWF4) biosynthesis) was performed. The results showed that all these genes were up-regulated following plant treatment with A3CFF. In summary the results revealed that the halotolerant fungus P. olsonii can stimulates tobacco plant growth, enhances its salt tolerance, and reduces by half the required chemical fertilizer inputs in a hydroponic farming system.

Astaxanthin synthesized gold nanoparticles enhance salt stress tolerance in rice by enhancing tetrapyrrole biosynthesis and scavenging reactive oxygen species in vitro

One of the most common abiotic stresses, high salinity stress, has strictly inhibited plant growth all over the world. Rice is a common food crop, while saline soil has a bad impact on its quality and yield. Nanoparticles (NPs) have been found as an alleviation strategy against abiotic stresses, including salt stress. Astaxanthin is a natural antioxidative oxycarotenoid found in a variety of seafood and microorganisms. We first synthesized astaxanthin gold nanoparticles (Ast-AuNPs) using astaxanthin and chloroauric acid, and then found that 100 mg/L Ast-AuNPs effectively reduced the stress of high salinity (150 mM NaCl) for seven days in hydroponically grown 10-days-old rice seedlings to a greater extent than astaxanthin (100 mg/L) alone. We discovered that supplementing with Ast-AuNPs induced tetrapyrrole biosynthesis while decreasing oxidative stress caused by high salinity. Free proline, malondialdehyde, and hydrogen peroxide levels were dramatically reduced by 45.9%∼51.8%, while antioxidant enzyme activities (peroxidase, catalase, and superoxide dismutase) were expressively increased by 1.85∼3.85 fold with the addition of Ast-AuNPs under salt stress. Furthermore, we found that supplementing rice with Ast-AuNPs induced the expression of ROS-scavenging genes (OsCATA, OsCATB, OsPRX65, OsPRX89, OsCu/ZnSOD1, and OsCu/ZnSOD2) by 2.19∼9.92 fold in leaves. Consequently, these results showed that Ast-AuNPs can benefit rice seedlings coping with high salinity stress by inducing tetrapyrrole biosynthesis, scavenging ROS, and increasing antioxidant activity, and it also expanded the use of functional gold nanoparticles in the treatment of high salinity stress in crops.

SsDHN, a dehydrin protein from Suaeda salsa, enhances salt stress tolerance in transgenic tobacco plants

SsDHN, a dehydrin protein from Suaeda salsa, enhances salt stress tolerance in transgenic tobacco plants

B2, an abscisic acid mimic, improves salinity tolerance in winter wheat seedlings via improving activity of antioxidant enzymes.

Salinity severely inhibits growth and reduces yield of salt-sensitive plants like wheat, and this effect can be alleviated by plant growth regulators and phytohormones, among which abscisic acid (ABA) plays a central role in response to various stressful environments. ABA is highly photosensitive to light disruption, which this limits its application. Here, based on pyrabactin (a synthetic ABA agonist), we designed and synthesized a functional analog of ABA and named B2, then evaluated its role in salt resistance using winter wheat seedlings. The phenotypes showed that B2 significantly improved the salt tolerance of winter wheat seedlings by elevating the biomass. The physiological analysis found that B2 treatment reduced the generation rate of O2–, electrolyte leakage, the content of proline, and the accumulation of malonaldehyde (MDA) and H2O2 and also significantly increased the contents of endogenous hormones zeatin riboside (ZA) and gibberellic acid (GA). Further biochemical analysis revealed that the activities of various antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), were enhanced by B2, and the activities of antioxidase isozymes SOD3, POD1/2, and APX1/2 were particularly increased, largely resembling ABA treatment. The abiotic stress response-related gene TaSOS1 was significantly upregulated by B2, while the TaTIP2;2 gene was suppressed. In conclusion, an ABA analog B2 was capable to enhance salt stress tolerance in winter wheat seedlings by stimulating the antioxidant system, providing a novel regulator for better survival of crops in saline soils and improving crop yield.

Effect of a Biostimulant Based on Polyphenols and Glycine Betaine on Tomato Plants’ Responses to Salt Stress

Climate change accentuates abiotic stress conditions putting at risk several commercial cultivars particularly vulnerable to salinity in the early stages of development, which makes adopting new technologies in tune with the environment necessary to mitigate its impact. In this study, we tested the possible effects of a commercial biostimulant (BALOX®) on enhancing salt stress tolerance in salt-treated tomato plants, analysing plant growth and several stress biochemical markers: photosynthetic pigments, ion contents in roots and leaves, leaf concentrations of different osmolytes, oxidative stress markers, non-enzymatic antioxidants, and the specific activities of major antioxidant enzymes. The experimental design consisted of three soil salinity levels (non-saline, saline, and very saline), two biostimulant doses (0.4 mL and 0.8 mL of the BALOX® stock per litre of irrigation water), and the non-treated control (without biostimulant), evaluated at 30 and 60 days of treatment. The biostimulant favoured plant growth, especially at the root level and in saline soils. In addition, it helped reduce Na+ and Cl− uptake by the roots and seemed to stimulate, to some extent, K+ and Ca2+ transport to the aerial part of the plant. The BALOX® application significantly reduced the level of stress affecting the plants in saline soils, as shown by the decrease in the contents of proline and oxidative stress biomarkers and the activity of salt-induced antioxidant enzymes. Some of the biostimulant effects were also observed under low salinity conditions; therefore, in addition to enhancing salt stress responses, BALOX® appears to stimulate the growth of tomato plants through a general improvement of photosynthesis and primary metabolism.

A transcriptomic study reveals salt stress alleviation in cotton plants upon salt tolerant PGPR inoculation

Soil salinity is a major constraint for reducing crop productivity worldwide. To combat this situation, the current project was aimed to examine the effect of plant growth-promoting rhizobacteria (PGPR) inoculation on the growth of cotton ( Gossypium hirsutum, var. Jin668) plants during salt stress and to identify salt stress-responsive genes in cotton plants. For this purpose, two bacteria, Bacillus subtilis and Bacillus pumilus were selected among the 20 strains isolated from the cotton rhizosphere under the salt stress (200 mM NaCl) and identified by 16 S rRNA sequencing. B. subtilis and B. pumilus were applied to Jin668 plants under salt stress which enhanced resistance to salt stress (leaf and root growth) compared to only salt-treated plants and control plants. Transcriptomic analysis revealed 556 differentially expressed genes (481 up-regulated and 75 down-regulated) in the B. subtilis + Salt versus Salt treatments and 943 (536 up-regulated and 407 down-regulated) genes in the B. pumilus + Salt versus Salt treatments. KEGG analysis of B. pumilus + Salt versus Salt and B. pumilus + Salt versus Salt revealed the pathways plant-pathogen interaction and plant hormone signal transduction were expressed in both treatments, while ascorbate and aldarate metabolism pathways and glyoxylate and dicarboxylate metabolism pathways were uniquely expressed in the B. pumilus + Salt versus Salt comparison, and the pentose and glucuronate interconversions pathway was uniquely expressed in the B. pumilus + Salt treatment versus Salt comparison. These data showed that B. subtilis and B. pumilus significantly enhance salt stress tolerance in cotton plants during salt stress conditions. • Two Bacteria, Bacillus subtilis and Bacillus pumilus were selected from the cotton rhizosphere under the salt stress. • B. subtilis and B. pumilus were applied to cottonplants under salt stress which enhanced resistance to salt stress. • Transcriptomic analysis revealed 556 DEGs in the B.subtilis vs Salt and 943 DEGS in the B.pumilus vs Salt treatments. • KEGG analysis of B. subtilis and B. pumilus versus Salt revealed the variouspathways were expressed in both treatments. • In conclusion, B. subtilis and B. pumilus significantly enhancetolerance in cotton plants during salt stress conditions.

Comparative transcriptome analysis of synthetic and common wheat in response to salt stress

Salt stress reduces wheat yield. Therefore, improvement for enhanced salt stress tolerance is necessary for stable production. To understand the molecular mechanism of salt tolerance in common wheat and synthetic hexaploid (SH) wheat, RNA sequencing was performed on the roots of three wheat lines salt-tolerant SH wheat, salt-tolerant common wheat, and salt-sensitive common wheat. Differentially expressed genes (DEGs) in response to salt stress were characterized using gene ontology enrichment analysis. Salt tolerance in common wheat has been suggested to be mainly regulated by the activation of transporters. In contrast, salt tolerance in SH wheat is enhanced through up-regulation of the reactive oxygen species signaling pathway, other unknown pathways, and different ERF transcription factors. These results indicate that salt tolerance is differentially controlled between common wheat and SH wheat. Furthermore, QTL analysis was performed using the F2 population derived from SH and salt-sensitive wheat. No statistically significant QTL was detected, suggesting that numerous QTLs with negligible contributions are involved in salt tolerance in SH wheat. We also identified DEGs specific to each line near one probable QTL. These findings show that SH wheat possesses salt tolerance mechanisms lacking in common wheat and may be potential breeding material for salt tolerance.

Characterization of Siccibacter sp. Strain C2 a Novel Rhizobacterium that Enhances Tolerance of Barley to Salt Stress.

Plant growth promoting rhizobacteria (PGPR) arouse an increasing interest as an eco-friendly solution for improving crop tolerance to environmental stresses. In this study, we report the characterization of a novel halotolerant PGPR strain (named C2) identified in a screen of rhizospheric bacterial isolates from southeast of Tunisia. Phylogenetic analysis showed that strain C2 is most likely affiliated to the genus Siccibacter with Siccibacter turicensis as the closest species (98.19%). This strain was able to perform phosphate solubilization and production of indole acetic acid (IAA), siderophores, hydrogen cyanide (HCN), as well as different hydrolytic enzymes (proteases, amylases, cellulases, and lipases). The potential of strain C2 in enhancing salt stress tolerance of Hordeum vulgare was also investigated. Our greenhouse inoculation assays showed that strain C2 promotes barley growth in the presence of 400mM NaCl by increasing biomass, root length, and chlorophyll contents. It has a positive effect on the photosynthetic efficiency, concomitantly with lower intercellular CO2 contents, compared to non-inoculated plants. Moreover, barley inoculation with strain C2 under salt stress, resulted in higher accumulation of proline and soluble sugars and alleviate the oxidative stress by decreasing hydrogen peroxide and malondialdehyde contents. Remarkably, this positive effect corroborates with a significant activation in the expression of a subset of barley stress responsive genes, including HVA1, HvDREB1, HvWRKY38 and HvP5CS. In summary, Siccibacter sp. strain C2 is able to enhance barley salt stress tolerance and should be leveraged in developing sustainable practices for cereal crop production.

Systemin peptide application improves tomato salt stress tolerance and reveals common adaptation mechanisms to biotic and abiotic stress in plants

Plants are continuously challenged by several environmental stresses that impair their growth and production performances. Stresses encountered by plants can be caused by biotic agents (e.g., herbivores, parasitic microorganisms, weeds) and abiotic factors (e.g., cold, drought, soil and water salinity). Despite these differences, plants respond to biotic and abiotic stresses with shared adaptive mechanisms resulting in complex and interlinked cross-talks. Systemin is a hormone peptide, playing a central role in the regulation of plant response against a wide range of stress agents, including wound, phytopathogenic fungi and phytophagous and sucking insects. It has also been shown that upregulation of prosystemin, the precursor protein of systemin, enhanced the tolerance of tomato plants to salt stress, indicating that systemin induced molecular adaptations to biotic stress can also be beneficial to plants exposed to salt stress. Considering that systemin is a small peptide that can be sensed by plants both as soil drench and foliar applications, we hypothesized that exogenous applications of systemin may increase salt stress tolerance in tomato plants through the activation of multiple adaptation mechanisms. Here we report that a soil drench picomolar solution of systemin increases tomato salt stress tolerance by i) activating of SOS1 , NHX and HKT Na + transporters in leaves ii) enhancing the cellular antioxidant power, and iii) balancing the protease activity induced by salt stress. Activation of these responses upon exogeneous application of systemin was highly correlated to an improved tomato growth under salt stress, suggesting that systemin may represent an important component of the crosstalk between biotic and abiotic stress responses in plants. • Exogenous treatment with systemin enhances salt stress tolerance in tomato plants. • Systemin improved osmotic balance, antioxidant activity, and protein stability. • Systemin mediates common adaptation mechanisms to biotic/abiotic stresses. • Biotic/abiotic stress crosstalk could be the target for future plant protection.

A C2H2-type zinc finger transcription factor, MdZAT17, acts as a positive regulator in response to salt stress

Salt stress restricts plant growth and productivity worldwide. Zinc finger proteins play important roles in response to various abiotic plant stresses. In this research, we identified and characterized the ZAT17 gene in Malus domestica, which encodes a C2H2-type zinc finger protein. MdZAT17 has two typical conserved zinc finger domains and an ERF-associated amphiphilic repression (EAR) motif. Promoter analysis showed that MdZAT17 contains several stress-related response elements (ABRE, CGTCA-motif, and TC-rich repeats), and qRT-PCR analysis showed that the expression level of MdZAT17 was induced by various abiotic stress treatments. The overexpression of MdZAT17 improved tolerance to salt stress in apple calli. The ectopic expression of MdZAT17 in Arabidopsis enhanced salt stress tolerance and led to lower malondialdehyde (MDA) content, lower reactive oxygen species (ROS) accumulation, and greater anthocyanin accumulation under salt stress. Moreover, the overexpression of MdZAT17 transgenic apple calli and Arabidopsis reduced the sensitivity to abscisic acid (ABA). In conclusion, our results indicate that MdZAT17 plays a positive regulatory role in salt tolerance, providing a theoretical basis for further research on its molecular mechanisms.