Enhanced Tolerance To Salt Stress Research Articles

Enhancing Salt Stress Tolerance in Tomato (Solanum lycopersicum L.) through Silicon Application in Roots.

Soil salinization poses a significant threat to agricultural productivity, necessitating innovative agronomic strategies to mitigate its impact. This study focuses on improving salt stress resistance in tomato plants through the application of silicon (Si) in roots. A greenhouse experiment was carried out under normal conditions (control, and 1 and 4 mM Si) and under salinity stress (salt control, and 1 and 4 mM Si). Various parameters were analyzed in leaves and roots. Under normal conditions, tomato plants grown in non-saline conditions exhibited some toxicity when exposed to Na2SiO3. As for the experiments under salt stress conditions, Si mitigated oxidative damage, preserving root cell membrane integrity. The concentration of malondialdehyde was reduced by 69.5%, that of proline was reduced by 56.4% and there was a 57.6% decrease in catalase activity for tomato plants treated with 1 mM Si under salt stress. Furthermore, Fe uptake and distribution, under salt conditions, increased from 91 to 123 mg kg-1, the same concentration as that obtained for the normal control. In all cases, the lower dose produced better results under normal conditions than the 4 mM dose. In summary, this research provides a potential application of Si in non-fertigated crop systems through a radicular pathway.

Overexpression of stress granule protein TZF1 enhances salt stress tolerance by targeting ACA11 mRNA for degradation in Arabidopsis.

Tandem CCCH zinc finger (TZF) proteins play diverse roles in plant growth and stress response. Although as many as 11 TZF proteins have been identified in Arabidopsis, little is known about the mechanism by which TZF proteins select and regulate the target mRNAs. Here, we report that Arabidopsis TZF1 is a bona-fide stress granule protein. Ectopic expression of TZF1 (TZF1 OE), but not an mRNA binding-defective mutant (TZF1H186Y OE), enhances salt stress tolerance in Arabidopsis. RNA-seq analyses of NaCl-treated plants revealed that the down-regulated genes in TZF1 OE plants are enriched for functions in salt and oxidative stress responses. Because many of these down-regulated mRNAs contain AU- and/or U-rich elements (AREs and/or UREs) in their 3'-UTRs, we hypothesized that TZF1-ARE/URE interaction might contribute to the observed gene expression changes. Results from RNA immunoprecipitation-quantitative PCR analysis, gel-shift, and mRNA half-life assays indicate that TZF1 binds and triggers degradation of the autoinhibited Ca2+-ATPase 11 (ACA11) mRNA, which encodes a tonoplast-localized calcium pump that extrudes calcium and dampens signal transduction pathways necessary for salt stress tolerance. Furthermore, this salt stress-tolerance phenotype was recapitulated in aca11 null mutants. Collectively, our findings demonstrate that TZF1 binds and initiates degradation of specific mRNAs to enhance salt stress tolerance.

The overexpression of OsMed 37_6, a mediator complex subunit enhances salt stress tolerance in rice

Mediator, a multisubunit co-activator complex, regulates transcription in eukaryotes and is involved in diverse processes in rice through its different subunits. Here, we have explored salt stress response of one of the rice Mediator subunit gene OsMED37_6. To unravel the possible mechanism of OsMed37_6 gene function, a detailed bioinformatics analysis was also followed. It was found that the gene has functional domains like Hsp70 (heat hock protein). Several salt tolerance up regulatory transcription factors are also predicted to be interacting with OsMed37_6 protein. To validate these understanding on the roles of OsMED37_6 in rice, we generated overexpression lines with OsMed37_6: pCAMBIA231: LBA4404 gene construct. It was observed that the overexpression enhances salt stress tolerance in transgenic lines. Therefore, it is a possibility that the mediator protein imparts salt tolerance by interacting with salt tolerance related transcription factors.

Novel nucleus-localized GRAM protein encoding OsGRAM57 gene enhances salt tolerance through ABA-dependent pathway and modulated carbohydrate metabolism

GRAM (Glucosyltransferases-like GTPase activators and Myotubularin) domain-encoding proteins play pivotal roles in plant growth and responses to biotic stresses. Yet, their influence on abiotic stress responses has remained enigmatic. This study unveils a novel nucleus-localized OsGRAM57, a GRAM protein-encoding gene and its profound regulatory functions in enhancing salt stress tolerance using Arabidopsis thaliana as a model plant. OsGRAM57-OEX (OsGRAM57-OEX) lines displayed significant enhancement in salt tolerance, modulated physiological, biochemical, K+/Na+ ratios, and enzymatic indices as compared to their wild-type (WT). Furthermore, OsGRAM57-OEX seedlings demonstrate increased levels of endogenous abscisic acid (ABA) and other phytohormones, while metabolic profiling revealed enhanced carbohydrate metabolism. Delving into the ABA signaling pathway, OsGRAM57 emerged as a central regulator, orchestrating the expression of genes crucial for salt stress responses, carbohydrate metabolism, and ABA signaling. The observed interactions with target genes and transactivation assays provided additional support for OsGRAM57's pivotal role. These findings underscore OsGRAM57's positive influence on the ABA pathway and affirm its capacity to enhance salt tolerance through an ABA-dependent pathway and fine-tuned carbohydrate metabolism. In summary, this new study reveals the previously undiscovered regulatory roles of OsGRAM57 in Arabidopsis abiotic stress responses, offering promising ways for strengthening plant resilience in the face of adverse environmental conditions.

The fungus Acremonium alternatum enhances salt stress tolerance by regulating host redox homeostasis and phytohormone signaling.

While endophytic fungi offer promising avenues for bolstering plant resilience against abiotic stressors, the molecular mechanisms behind this biofortification remain largely unknown. This study employed a multifaceted approach, combining plant physiology, proteomic, metabolomic, and targeted hormonal analyses to illuminate the early response of Brassica napus to Acremonium alternatum during the nascent stages of their interaction. Notably, under optimal growth conditions, the initial reaction to fungus was relatively subtle, with no visible alterations in plant phenotype and only minor impacts on the proteome and metabolome. Interestingly, the identified proteins associated with the Acremonium response included TUDOR 1, Annexin D4, and a plastidic K+ efflux antiporter, hinting at potential processes that could counter abiotic stressors, particularly salt stress. Subsequent experiments validated this hypothesis, showcasing significantly enhanced growth in Acremonium-inoculated plants under salt stress. Molecular analyses revealed a profound impact on the plant's proteome, with over 50% of salt stress response proteins remaining unaffected in inoculated plants. Acremonium modulated ribosomal proteins, increased abundance of photosynthetic proteins, enhanced ROS metabolism, accumulation of V-ATPase, altered abundances of various metabolic enzymes, and possibly promoted abscisic acid signaling. Subsequent analyses validated the accumulation of this hormone and its enhanced signaling. Collectively, these findings indicate that Acremonium promotes salt tolerance by orchestrating abscisic acid signaling, priming the plant's antioxidant system, as evidenced by the accumulation of ROS-scavenging metabolites and alterations in ROS metabolism, leading to lowered ROS levels and enhanced photosynthesis. Additionally, it modulates ion sequestration through V-ATPase accumulation, potentially contributing to the observed decrease in chloride content.

Enhancing Salt Stress Tolerance in Rye with ZnO Nanoparticles: Detecting H2O2 as a Stress Biomarker by Nanostructured NiO Electrochemical Sensor

This article is devoted to the study of the effect of ZnO nanoparticles on the development of tolerance to salt stress in rye samples. As a quantitative criterion for assessing the degree of oxidative stress, the amount of H2O2 released in the samples during growth was determined. For these purposes, an electrochemical sensor based on hydrothermally synthesized wall-shaped NiO nanostructures was developed. This sensor has been proven to demonstrate high sensitivity (2474 µA·mM−1), a low limit of detection (1.59 µM), good selectivity against common interferents, and excellent long-term stability. The investigation reveals that the incorporation of ZnO nanoparticles in irrigation water notably enhances rye’s ability to combat salt stress, resulting in a decrease in detected H2O2 levels (up to 70%), coupled with beneficial effects on morphological traits and photosynthetic rates.

Elevated osmolytes accumulation helps in combating NaCl stress causing negative impacts on growth and metabolism of Vigna radiata (L.)

Salinity stress is one of the main abiotic stresses that have a negative impact on the growth performance of green gram. The current study was carried out as a result to find out growth, and morpho-biochemical changes in Vigna radiata CO7 variety cultivated under NaCl stress treatments. The V. radiata CO7 variety was selected and the experiment was carried out in pot culture under varying NaCl concentrations viz., 0, 50, 75, 100, and 125 mM respectively to assess maximum tolerance range of the CO7 variety. The salt stress was given on 15th days after sowing and sampling was done after 10 days of treatment on the 25th, 35th, and 45th day respectively. Salt stress results in a steep decline in shoot length, biomass, chlorophyll contents a and b, and soluble protein contents with increased NaCl treatments on all sampling days. However, carotenoid contents, and compatible solutes including proline, Glycine-betaine, Amino acids and total soluble sugars contents were found to be upregulated under varying NaCl concentrations in V. radiata CO7 variety on all sampling days. Thus, increased carotenoid contents, and osmolytes, provide stress tolerance to V. radiata CO7 variety by maintaining the turgor pressure of cells and preventing further water loss under varying NaCl concentrations. Hence, this variety shows maximum surveillance at 75 mM and beyond this plant performance is restricted and further study is needed to access CO7 variety for a breeding program to enhance salt stress tolerance.

The PbbHLH62/PbVHA-B1 module confers salt tolerance through modulating intracellular Na+/K+ homeostasis and reactive oxygen species removal in pear

The vacuolar H+-ATPase (V-ATPase) is a multi-subunit membrane protein complex, which plays pivotal roles in building up an electrochemical H+-gradient across tonoplast, energizing Na+ sequestration into the central vacuole, and enhancing salt stress tolerance in plants. In this study, a B subunit of V-ATPase gene, PbVHA-B1 was discovered and isolated from stress-induced P. betulaefolia combining with RT-PCR method. The RT-qPCR analysis revealed that the expression level of PbVHA-B1 was upregulated by salt, drought, cold, and exogenous ABA treatment. Subcellular localization analyses showed that PbVHA-B1 was located in the cytoplasm and nucleus. Moreover, overexpression of PbVHA-B1 gene noticeably increased the ATPase activity and the tolerance to salt in transgenic Arabidopsis plants. In contrast, knockdown of PbVHA-B1 gene in P.betulaefolia by virus-induced gene silencing had reduced resistance to salt stress. In addition, using yeast one-hybride (Y1H) and yeast two-hybride (Y2H) screens, PbbHLH62, a bHLH transcription factor, was identified as a partner of the PbVHA-B1 promoter and protein. Then, we also found that PbbHLH62 positively regulate the expression of PbVHA-B1 and the ATPase activity after salt stress treatment. These findings provide evidence that PbbHLH62 played a critical role in the salt response. Collectively, our results demonstrate that a PbbHLH62/PbVHA-B1 module plays a positive role in salt tolerance by maintain intracellular ion and ROS homeostasis in pear.

Microbacterium azadirachtae CNUC13 Enhances Salt Tolerance in Maize by Modulating Osmotic and Oxidative Stress.

Soil salinization is one of the leading threats to global ecosystems, food security, and crop production. Plant growth-promoting rhizobacteria (PGPRs) are potential bioinoculants that offer an alternative eco-friendly agricultural approach to enhance crop productivity from salt-deteriorating lands. The current work presents bacterial strain CNUC13 from maize rhizosphere soil that exerted several PGPR traits and abiotic stress tolerance. The strain tolerated up to 1000 mM NaCl and 30% polyethylene glycol (PEG) 6000 and showed plant growth-promoting (PGP) traits, including the production of indole-3-acetic acid (IAA) and siderophore as well as phosphate solubilization. Phylogenetic analysis revealed that strain CNUC13 was Microbacterium azadirachtae. Maize plants exposed to high salinity exhibited osmotic and oxidative stresses, inhibition of seed germination, plant growth, and reduction in photosynthetic pigments. However, maize seedlings inoculated with strain CNUC13 resulted in significantly improved germination rates and seedling growth under the salt-stressed condition. Specifically, compared with the untreated control group, CNUC13-treated seedlings exhibited increased biomass, including fresh weight and root system proliferation. CNUC13 treatment also enhanced photosynthetic pigments (chlorophyll and carotenoids), reduced the accumulation of osmotic (proline) and oxidative (hydrogen peroxide and malondialdehyde) stress indicators, and positively influenced the activities of antioxidant enzymes (catalase, superoxide dismutase, and peroxidase). As a result, CNUC13 treatment alleviated oxidative stress and promoted salt tolerance in maize. Overall, this study demonstrates that M. azadirachtae CNUC13 significantly enhances the growth of salt-stressed maize seedlings by improving photosynthetic efficiency, osmotic regulators, oxidative stress resilience, and antioxidant enzyme activity. These findings emphasize the potential of utilizing M. azadirachtae CNUC13 as a bioinoculant to enhance salt stress tolerance in maize, providing an environmentally friendly approach to mitigate the negative effects of salinity and promote sustainable agriculture.

Enhancing salt stress tolerance in kidney beans: The synergistic effects of biochar and salicylic acid in arid and semi-arid regions

Salt stress is one of the most damaging environmental stresses of recent times and poses a significant threat to food security. Here, we conducted an experimental study over two consecutive years (2022–2023) to evaluate the physiological and biochemical characteristics of kidney beans. The study used a randomized complete block design with 4 replications (n = 4). The experiment included three levels of salicylic acid (SA): SA0 (0 mM), SA0.5 (0.5 mM) and SA1 (1 mM). The study also used biochar in four levels, without biochar as the control treatment (B0), regular biochar (Rb) by 2.5 % per soil weight, modified biochar with phosphoric acid (PA) by 1.25 % per soil weight, and modified biochar with sulfuric acid (Sb) by 1.25 % per soil weight. Additionally, salt stress (SS) was induced using NaCl in three levels, SS0 (distilled water), SS4 (4 4 dS m−1), and SS8 (8 dS m−1). The results showed that salt stress, biochar, and salicylic acid significantly affected the measured parameters. Salt stress (SS4 and SS8) negatively affected the measured parameters compared to the control. However, the application of biochar and salicylic acid regulated the alleviation of the impact of salt stress. Under SS4, the application of Rb along with SA1 resulted in the highest value of proline content. The highest enzymatic activity of catalase was observed due to the use of PA in combination with SA0.5 under non-saline soil conditions. The use of PA under SS8 increased the hydrogen peroxide and caused the highest activity, while the lowest activity was obtained under non-saline soil conditions with the application of Sb. In the first year of the experiment, it was found that the use of SA1 without biochar under non-stress conditions resulted in the highest levels of malondialdehyde. Likewise, in the second year, the highest malondialdehyde activity was observed by applying Rb and SA1 under SS8. The research concludes that kidney bean plants are significantly impacted by salt stress, which affects their biochemical characteristics. Nonetheless, the combined application of biochar and salicylic acid showed promise in addressing these challenges. This approach could be particularly effective in managing salinity issues in arid and semi-arid regions, highlighting the potential of biochar and salicylic acid for improving plant resilience under such conditions.

In silico analysis and expression profiling reveal the presence of abiotic stress and developmental stage specific Aconitase genes in rice (Oryza sativa L.)

The growth and yield of crops have been significantly affected by abiotic stresses. Although respiratory metabolism is integral to plants, its understanding within the context of stress adaptation remains limited . While the rice genome contains three Aconitase genes, their specific roles in abiotic stress tolerance and plant development remain largely unexplored. This study aimed to characterize the Aconitase gene family in rice, shedding light on the evolution of Aconitase and its involvement in diverse developmental processes, as well as its response under various abiotic stress conditions. Phylogenetic analysis indicated the evolutionary relationship between rice Aconitase genes and those of other plant species. The prediction of promoter cis-elements revealed the presence of diverse cis-acting elements associated with the response to abiotic stress within the Aconitase gene family. In addition, an analysis of public RNA-seq data indicated the potential involvement of Aconitase genes in various developmental processes and mechanisms related to stress tolerance. Further, qRT-PCR confirmed the expression patterns of Aconitase genes. Expression analysis revealed differential expression of Aconitase genes under cold, drought, ABA, and salt stresses. Elevated levels of the OsAco1 transcript resulted in a phenotype that exhibited increased tolerance to salt stress. Biochemical analysis revealed higher Aconitase activity in the overexpressed line compared to the control plant. Furthermore, the overexpressed line exhibited improved growth and lower H2O2 levels than the control plant following a 2-hour exposure to 200 mM salt stress. These findings suggest a potential role of Aconitase in enhancing salt stress tolerance. Moreover, they lay the foundation for further exploration into the precise involvement of Aconitase in plant developmental processes under various stress conditions, with the ultimate aim of developing salt-tolerant rice cultivars.

Calcineurin B-like protein ZmCBL8-1 promotes salt stress resistance in Arabidopsis.

ZmCBL8-1 enhances salt stress tolerance in maize by improving the antioxidant system to neutralize ROS homeostasis and inducing Na+/H+ antiporter gene expressions of leaves. Calcineurin B-like proteins (CBLs) as plant-specific calcium sensors have been explored for their roles in the regulation of abiotic stress tolerance. Further, the functional variations in ZmCBL8, encoding a component of the salt overly sensitive pathway, conferred the salt stress tolerance in maize. ZmCBL8-1 is a transcript of ZmCBL8 found in maize, but its function in the salt stress response is still unclear. The present study aimed to characterize the protein ZmCBL8-1 that was determined to be composed of 194 amino acids (aa) with three conserved EF hands responsible for binding Ca2+. However, a 20-aa fragment was found to be missing from its C-terminus relative to another transcript of ZmCBL8. Results indicated that it harbored a dual-lipid modification motif MGCXXS at its N-terminus and was located on the cell membrane. The accumulation of ZmCBL8-1 transcripts was high in the roots but relatively lower in the leaves of maize under normal condition. In contrast, its expression was significantly decreased in the roots, while increased in the leaves under NaCl treatment. The overexpression of ZmCBL8-1 resulted in higher salt stress resistance of transgenic Arabidopsis in a Ca2+-dependent manner relative to that of the wild type (WT). In ZmCBL8-1-overexpressing plants exposed to NaCl, the contents of malondialdehyde and hydrogen peroxide were decreased in comparison with those in the WT, and the expression of key genes involved in the antioxidant defense system and Na+/H+ antiporter were upregulated. These results suggested that ZmCBL8-1 played a positive role in the response of leaves to salt stress by inducing the expression of Na+/H+ antiporter genes and enhancing the antioxidant system to neutralize the accumulation of reactive oxygen species. These observations further indicate that ZmCBL8-1 confers salt stress tolerance, suggesting that transcriptional regulation of the ZmCBL8 gene is important for salt tolerance.

Mycorrhizal colonization and calcium spraying modulate physiological and antioxidant responses to improve pepper growth and yield under salinity stress

Abiotic stresses, such as salt and drought, limit plant growth, reduce crop production, and pose the greatest challenge to the sustainability of agricultural development in arid and semi-arid countries. Arbuscular mycorrhizal fungi (AMF) and calcium can play an important role in alleviating the adverse effects of abiotic stresses on plants. Therefore, this study was conducted to evaluate the effect of two levels of mycorrhizal inoculation (inoculated seedlings and non-inoculated seedlings) and three levels of foliar spraying with calcium (0, 0.5%, and 1%), separately or in combination, on growth, physiology, and yield of salt-stressed pepper (Capsicum annuum L.). The experiment was conducted in an open field with saline soil and irrigation water, in a randomized complete block design with split plot arrangement. Mycorrhizal inoculation and calcium spray have been shown to facilitate nutrient uptake, modulate physiological responses, and activate the antioxidant system, enhancing salt stress tolerance and improving the growth and yield of salt-stressed pepper. Combined treatment plants grown from inoculated seedlings and sprayed with 1% Ca recorded the best results, alleviating salt stress-induced oxidative damage by activating the antioxidant system including antioxidant enzymes [Superoxide dismutase (SOD) and catalase (CAT)], and non-enzymatic antioxidants (ascorbic acid and phenols), reducing H2O2 and malondialdehyde (MDA) accumulation, enhancing physiological activities (relative water content (RWC %) and chlorophyll content), and improving nutrient balance (increasing N, P, K and reducing Na content), leading to increased pepper growth and yield parameters. Our results indicated that mycorrhizal inoculation and calcium spray can be recommended as a practical alternative and environmentally friendly approach to enhance plant tolerance to salt stress by improving nutritional status, physiological processes, and antioxidant activities, thus increasing the morphological and yield traits of stressed plants.

Responsive Alternative Splicing Events of Opisthopappus Species against Salt Stress.

Salt stress profoundly affects plant growth, prompting intricate molecular responses, such as alternative splicing (AS), for environmental adaptation. However, the response of AS events to salt stress in Opisthopappus (Opisthopappus taihangensis and Opisthopappus longilobus) remains unclear, which is a Taihang Mountain cliff-dwelling species. Using RNA-seq data, differentially expressed genes (DEGs) were identified under time and concentration gradients of salt stress. Two types of AS, skipped exon (SE) and mutually exclusive exons (MXE), were found. Differentially alternative splicing (DAS) genes in both species were significantly enriched in "protein phosphorylation", "starch and sucrose metabolism", and "plant hormone signal transduction" pathways. Meanwhile, distinct GO terms and KEGG pathways of DAS occurred between two species. Only a small subset of DAS genes overlapped with DEGs under salt stress. Although both species likely adopted protein phosphorylation to enhance salt stress tolerance, they exhibited distinct responses. The results indicated that the salt stress mechanisms of both Opisthopappus species exhibited similarities and differences in response to salt stress, which suggested that adaptive divergence might have occurred between them. This study initially provides a comprehensive description of salt responsive AS events in Opisthopappus and conveys some insights into the molecular mechanisms behind species tolerance on the Taihang Mountains.

Polysaccharides Produced by Plant Growth-Promoting Rhizobacteria Strain Burkholderia sp. BK01 Enhance Salt Stress Tolerance to Arabidopsis thaliana.

Salt stress is one of the most serious abiotic stresses leading to reduced agricultural productivity. Polysaccharides from seaweed have been used as biostimulants to promote crop growth and improve plant resistance to abiotic stress. In this study, PGPR strain Burkholderia sp. BK01 was isolated from the rhizosphere of wheat, and it was characterized for phosphorus (Pi) dissolution, indole-3-acetic acid (IAA) production, ammonia (NH3) and exopolysaccharides (EPS). In particular, strain BK01 can efficiently produce extracellular polysaccharide with a yield of 12.86 g/L, using sorbitol as carbon source. BK01 EPS was identified as an heteropolysaccharide with Mw 3.559 × 106 Da, composed of (D)-galactose (75.3%), (D)-glucose (5.5%), (L)-rhamnose (5.5%), (D)-galactouronic acid (4.9%) and (D)-glucuronic acid (8.8%). The present work aims to highlight the effect of the BK01 EPS on growth and biochemical changes in Arabidopsis thaliana under salt stress (100 mM). The purified BK01 EPS at a concentration of 100 mg/L efficiently promoted the growth of plants in pot assays, improved the chlorophyll content, enhanced the activities of SOD, POD and CAT, and decreased the content of MDA. This results suggested that the polysaccharides produced by PGPR strain Burkholderia sp. BK01 can be used as biostimulants to promote plant growth and improve plant resistance to salt stress.

Genome‐wide characterization of trihelix genes reveals Cqtrihelix23 enhances the salt tolerance in quinoa (Chenopodium quinoa)

AbstractSoil salinity poses an escalating threat to global environmental sustainability, agricultural productivity, and food safety. Quinoa (Chenopodium quinoa), recognized as a halophyte, has emerged as a promising crop due to its high nutritional value and stress resistance. Nevertheless, the current understanding of salt tolerance genes in quinoa remains incomplete. This comprehensive study aimed to identify the quinoa trihelix family and families associated with salt stress, including Na+/H+ antiporter (NHX) and calcineurin B‐like (CBL). Through expression analysis, Cqtrihelix23 was identified as responsive to salt stress. Subsequent transient transformation experiments revealed that Cqtrihelix23 enhanced quinoa's tolerance to salt stress by promoting root development, maintaining the antioxidant system, and reducing the Na+/K+ ratio. Additionally, it was discovered that Cqtrihelix23 upregulated the expression of CqCBL10 and CqNHX4. Further protein interaction experiments confirmed the interaction between Cqtrihelix23, CqCBL10, and CqNHX4. Notably, CqCBL10 and CqNHX4 also contributed to salt stress resistance, and in combination with Cqtrihelix23, they synergistically enhanced salt stress tolerance. In conclusion, this study highlights the significance of Cqtrihelix23, CqCBL10, and CqNHX4 as key contributors within the regulatory network associated with quinoa's salt tolerance. These findings lay a solid groundwork for the development of salt‐tolerant quinoa varieties.

Humic acids enhance salt stress tolerance associated with pyrroline 5-carboxylate synthetase gene expression and hormonal alteration in perennial ryegrass (Lolium perenne L.).

Humic acid (HA) has been used as an important component in biostimulant formulations to enhance plant tolerance to salt stress, but the mechanisms underlying are not fully understood. This study was to investigate the physiological and molecular mechanisms of HA's impact on salt stress tolerance in perennial ryegrass (Lolium perenne L.). The two types of HA were extracted from weathered coal samples collected from Wutai County (WTH) and Jingle County (JLH) of Shanxi Province, China. The grass seedlings subjected to salt stress (250 mM NaCl) were treated with HA solutions containing 0.01% WTH (W/V) or 0.05% JLH (W/V), respectively. The HA treatments improved leaf photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) and reduced leaf oxidative injury (lower malondialdehyde content) and Pro and intercellular CO2 concentrations in salt-stressed perennial ryegrass. The HA treatments also reversed the decline in antioxidative enzymes ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activity and improved growth and anti-senescence hormones indole-3-acetic acid (IAA) and brassinosteroid (BR). The HA treatments reduced the relative expression of P5CS and its downstream products proline (Pro) and the stress defense hormones abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), and polyamines (PA). The results of this study indicate that the application of HAs may improve salt stress tolerance by regulating P5CS gene expression related to osmotic adjustment and increasing the activity of antioxidant enzymes and anti-senescence hormones in perennial ryegrass.

PagMYB73 enhances salt stress tolerance by regulating reactive oxygen species scavenging and osmotic maintenance in poplar

The MYB transcription factor (TF) family, widely recognized for its involvement in multiple biological processes, holds a significant position among plant TF families due to its substantial size. The R2R3-MYB TF has been extensively studied and known for its pivotal role in regulating the synthesis of anthocyanin, lignin, and secondary wall components in plants. However, there is currently limited information available regarding the function of R2R3-MYB genes in response to salt stress specifically in poplar. Here, we focused on a specific R2R3-MYB gene, PagMYB73, which belongs to the 84K poplar (Populus alba × P. glandulosa) species. We aimed to investigate the role of PagMYB73 in the regulatory mechanisms involved in salt stress response. PagMYB73 showed strong induction in leaves under salt stress conditions. Transgenic poplar plants overexpressing PagMYB73 exhibited enhanced salt tolerance, while suppression of the gene resulted in increased sensitivity to high salt levels. PagMYB73 can regulate the expression of several stress-related genes, including PagGSTU19, PagLEA51, PagSODs, PagPODs, and PagP5CS2. It achieves this by binding to the promoter regions of these genes that orchestrate adaptive responses to salt stress by modulating the osmotic balance and reducing the levels of reactive oxygen species (ROS). Indeed, overexpression of PagGSTU19 and PagLEA51 has been shown to enhance the salt tolerance of poplar. In conclusion, PagMYB73 regulates the expression of stress-related genes to improve ROS scavenging ability and osmotic maintenance, thereby improving the salt tolerance of the transgenic poplar.

Jeongeuplla avenae gen. nov., sp. nov., a novel β-carotene-producing bacterium that alleviates salinity stress in Arabidopsis.

A novel endophytic bacterium, designated DY-R2A-6T, was isolated from oat (Avena sativa L.) seeds and found to produces β-carotene. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain DY-R2A-6T had 96.3% similarity with Jiella aquimaris LZB041T, 96.0% similarity with Aurantimonas aggregate R14M6T and Aureimonas frigidaquae JCM 14755T, and less than 95.8% similarity with other genera in the family Aurantimonadaceae. The complete genome of strain DY-R2A-6T comprised 5,929,370 base pairs, consisting of one full chromosome (5,909,198 bp) and one plasmid (20,172 bp), with a G + C content was 69.1%. The overall genome-related index (OGRI), including digital DNA-DNA hybridization (<20.5%), ANI (<79.2%), and AAI (<64.2%) values, all fell below the thresholds set for novel genera. The major cellular fatty acids (>10%) of strain DY-R2A-6T were C16:0, C19:0 cyclo ω8c, and summed feature 8 (C18:1ω7c and/or C18:1ω6c). Ubiquinone-10 was the main respiratory quinone. We identified the gene cluster responsible for carotenoid biosynthesis in the genome and found that the pink-pigment produced by strain DY-R2A-6T is β-carotene. In experiment with Arabidopsis seedlings, co-cultivation with strain DY-R2A-6T led to a 1.4-fold increase in plant biomass and chlorophyll content under salt stress conditions, demonstrating its capacity to enhance salt stress tolerance in plants. Moreover, external application of β-carotene to Arabidopsis seedlings under salt stress conditions also mitigated the stress significantly. Based on these findings, strain DY-R2A-6T is proposed to represent a novel genus and species in the family Aurantimonadaceae, named Jeongeuplla avenae gen. nov., sp. nov. The type strain is DY-R2A-6T (= KCTC 82985T = GDMCC 1.3014T). This study not only identified a new taxon but also utilized genome analysis to predict and confirm the production of β-carotene by strain DY-R2A-6T. It also demonstrated the ability of this strain to enhance salt stress tolerance in plants, suggesting potential application in agriculture to mitigate environmental stress in crops.

ZmELF6-ZmPRR37 module regulates maize flowering and salt response.

The control of flowering time in maize is crucial for reproductive success and yield, and it can be influenced by environmental stresses. Using the approaches of Ac/Ds transposon and transposable element amplicon sequencing techniques, we identified a Ds insertion mutant in the ZmPRR37 gene. The Ds insertion showed a significant correlation with days to anthesis. Further research indicated that ZmPRR37-CR knockout mutants exhibited early flowering, whereas ZmPRR37-overexpression lines displayed delayed flowering compared to WT under long-day (LD) conditions. We demonstrated that ZmPRR37 repressed the expression of ZmNF-YC2 and ZmNF-YA3 to delay flowering. Association analysis revealed a significant correlation between flowering time and a SNP2071-C/T located upstream of ZmPRR37. The SNP2071-C/T impacted the binding capacity of ZmELF6 to the promoter of ZmPRR37. ZmELF6 also acted as a flowering suppressor in maize under LD conditions. Notably, our study unveiled that ZmPRR37 can enhance salt stress tolerance in maize by directly regulating the expression of ABA-responsive gene ZmDhn1. ZmDhn1 negatively regulated maize salt stress resistance. In summary, our findings proposed a novel pathway for regulating photoperiodic flowering and responding to salt stress based on ZmPRR37 in maize, providing novel insights into the integration of abiotic stress signals into floral pathways.