Silicon nutrition stimulates Salt-Overly Sensitive (SOS) pathway to enhance salinity stress tolerance and yield in rice

Sodium chloride-induced metabolic shifts and morpho-physiological responses in Bacopa monnieri (L.) Wettst. for enhanced bacoside-A production

This study investigated the impact of NaCl concentrations (50-200 mM) on Bacopa monnieri (BM) grown under natural environmental conditions. The results revealed significant enhancements (p < 0.05) in various traits under NaCl exposure. Maximum increase of up to 1.4× (plant height), 2.6× (leaf number), 6.6× (shoot no.), and 2× (root no.) was recorded in morphological parameters at 100 mM. Similarly, maximum chlorophyll content (1.8×), catalase (2.2×), and guaiacol peroxidase (GPX) (2.4×) enzyme activities were also recorded at 100 mM NaCl. Furthermore, HPLC analysis showed a substantial increase (∼1.5×) in bacoside-A content after treatment with 100 mM. GC-MS analysis revealed stimulation of specific metabolites influencing bacoside production. This study offers a practical approach to enhance biomass and bacoside-A synthesis in BM plants, eliminating the need for costly in vitro methods and benefiting both farmers and pharmaceutical sector. Further investigation at molecular level for mapping changes due to different salt levels in metabolic pathways could also be performed.

Photovoltaic cell-derived silicon fertilizer and its combined effect with silicate-dissolving bacteria Bacillus aryahattai on rice growing during the tillering stage

The widespread retirement of crystalline silicon solar cells in coming years poses a significant obstacle to sustainable development. Arable soils have experienced a gradual decline in available silicon levels due to intensive agricultural production. Therefore, it is feasible to repurpose recovered waste crystalline silicon cells below cell-reuse benchmark into agriculturally usable resources. This study investigates the impact of photovoltaic crystalline silicon-derived fertilizer (Si group), external silicate-dissolving bacteria (Bac group), and their combination (All group) on early rice nutrient uptake, growth development, and soil physical and chemical properties through a 45-day potting experiment. The combined addition of silicon fertilizer and bacteria significantly improved soil nitrification process (nitrate nitrogen NO3-N increased by 73.5%) and soil organic matter content by 16.2%. The increases in soil-available silicon (by 14.9%) and total potassium (by 19%) in the All and Si were significant. For rice growth, the addition of silicon fertilizer did not have a positive effect on dry matter accumulation and plant height possibly due to the Si threshold effect or K stress. However, the chlorophyll content of the Bac and All treatment groups was enhanced by 25% and 29%, respectively, suggesting the positive effect of bacteria on soil nitrogen utilization. The absorption of potassium by the plants was positively correlated with silicon, and the accumulation of silicon reduced the carbon content of the rice's aboveground parts by 7.3% to 9.0%. The study provides a feasible solution of recycling and reusing waste crystalline silicon in agricultural applications, and the results also have indicative significance for the sustainable rice production under non-stress environmental conditions.

Response of young rice panicles to salt stress: insights based on phenotype and transcriptome analysis

Saline-alkali soils limit rice growth and production. With an increasing global population, enhancing rice salt tolerance is crucial for improving yields in these areas. This study investigated the developmental characteristics of young panicles and pollen fertility in two rice varieties, 58M and 58L, under salt stress. Results showed that 58M had more substantial salt tolerance during panicle development. RNA sequencing of 18 samples from both varieties under high salt stress (0 h, 6 h, and 24 h) identified 469 common differentially expressed genes (DEGs) and 2,308 DEGs between the varieties. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment highlighted significant pathways such as phenylpropanoid biosynthesis, protein processing, and flavonoid biosynthesis. Six gene co-expression modules related to salt tolerance were identified, with six candidate genes (LOC_Os05g38530, LOC_Os04g07920, LOC_Os12g02105, LOC_Os01g06580, LOC_Os06g49250, and LOC_Os06g48300) potentially linked to salt tolerance. These findings provide insights into rice salt tolerance mechanisms and offer new genetic resources for breeding salt-tolerant rice.

FaTEDT1L of Octoploid Cultivated Strawberry Functions as a Transcriptional Activator and Enhances Abiotic Stress Tolerance in Transgenic Arabidopsis

Plants may encounter abiotic stresses, such as drought, flooding, salinity, and extreme temperatures, thereby negatively affecting their growth, development, and reproduction. In order to enhance their tolerance to such stresses, plants have developed intricate signaling networks that regulate stress-responsive gene expression. For example, Arabidopsis Enhanced Drought Tolerance1/HOMEODOMAIN GLABROUS 11 (AtEDT1/HDG11), one of the transcription factor genes from the group IV of homeodomain-leucine zipper (HD-ZIP) gene family, has been shown to increase drought tolerance in various transgenic plants. However, the underlying molecular mechanisms of enhanced stress tolerance remain unclear. In this study, we identified a homologous gene related to AtEDT1/HDG11, named FaTEDT1L, from the transcriptome sequencing database of cultivated strawberry. Phylogenetic analysis revealed the close relationship of FaTEDT1L with AtEDT1/HDG11, which is one of the group IV members of the HD-ZIP gene family. Yeast one-hybrid analysis showed that FaTEDT1L functions as a transcriptional activator. Transgenic Arabidopsis plants overexpressing FaTEDT1L under the control of the cauliflower mosaic virus (CaMV) 35S promoter exhibited significantly enhanced tolerance to osmotic stress (both drought and salinity) when compared to the wild-type (WT) plants. Under osmotic stress, the average root length was 3.63 ± 0.83 cm, 4.20 ± 1.03 cm, and 4.60 ± 1.14 cm for WT, 35S::FaTEDT1L T2 #3, and 35S:: FaTEDT1L T2 #5, respectively. Substantially increased root length in 35S::FaTEDT1L T2 #3 and 35S::FaTEDT1L T2 #5 was noted when compared to the WT. In addition, the average water loss rates were 64%, 57.1%, and 55.6% for WT, 35S::FaTEDT1L T2 #3, and 35S::FaTEDT1L T2 #5, respectively, after drought treatment, indicating a significant decrease in water loss rate of 35S:: FaTEDT1L T2 #3 and 35S::FaTEDT1L T2 #5 is a critical factor in enhancing plant drought resistance. These findings thus highlight the crucial role of FaTEDT1L in mitigating drought and salt stresses and regulating plant osmotic stress tolerance. Altogether, FaTEDT1L shows its potential usage as a candidate gene for strawberry breeding in improving crop resilience and increasing agricultural productivity under adverse environmental conditions.

Silicon in paddy fields: Benefits for rice production and the potential of rice phytoliths for biogeochemical carbon sequestration

Silicon (Si) biogeochemical cycling is beneficial for crop productivity and carbon (C) sequestration in agricultural ecosystem, thus offering a nonnegligible role in alleviating global warming and food crisis. Compared with other crops, rice plants have a greater quantity of phytolith production, because they are able to take up a lot of Si. However, it remains unclear on Si supply capacity of paddy soils across the world, general rice yield-increasing effect after Si fertilizer addition, and factors affecting phytolith production and potential of phytolith C sequestration in paddy fields. This study used a meta-analysis of >3500 data from 87 studies to investigate Si supply capacity of global paddy soils and elaborate the benefits of Si regarding rice productivity and phytolith C sequestration in paddy fields. Analytical results showed that the Si supply capacity of paddy soils was insufficient in the major rice producing countries/regions. Dealing with this predicament, Si fertilization was an effective strategy to supply plant-available Si to improve rice productivity. Our meta-analysis results further revealed that Si fertilization led to the average increasing rate of 36 % and 39 % in rice yield and biomass, which could reach up to 52 % and 46 % with the increasing doses of Si fertilizer, respectively. Especially, this strategy also improved the potential of phytolith C sequestration through the increased phytolith content and rice biomass, despite that this potential might have a decline in old paddy soils (≥ 7000 year) compared to in young paddy soils (≤ 1000 year) due to the slow migration and dissolution of phytoliths at millennial scale. Our findings thus indicate that a deep investigation on the benefits of Si in agroecosystem will further improve our understanding on regulating crop production and the potential of biogeochemical C sequestration within phytoliths in global cropland.

AMPK activator 991 specifically activates SnRK1 and thereby affects seed germination in rice

Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) and AMP-activated protein kinase (AMPK) are highly conserved. Compound 991 is an AMPK activator in mammals. However, whether 991 also activates SnRK1 remains unknown. The addition of 991 significantly increased SnRK1 activity in desalted extracts from germinating rice seeds in vitro. To determine whether 991 has biological activity, rice seeds were treated with different concentrations of 991. Germination was promoted at low concentrations but inhibited at high concentrations. The effects of 991 on germination were similar to those of OsSnRK1a overexpression. To explore whether 991 affects germination by specifically affecting SnRK1, germination of an snrk1a mutant and the wild type under 1 μM 991 treatment was compared. The snrk1a mutant was insensitive to 991. Phosphoproteomic analysis showed that the differential phosphopeptides induced by 991 and OsSnRK1a overexpression largely overlapped. Furthermore, SnRK1 might regulate rice germination in a dosage-dependent manner by regulating the phosphorylation of three phosphosites, namely S285-PIP2;4, S1013-SOS1, and S110-ABI5. These results indicate that 991 is a specific SnRK1 activator in rice. The promotion and inhibition of germination by 991 also occurred in wheat seeds. Thus, 991 is useful for exploring SnRK1 function and the chemical regulation of growth and development in crops.

The Physiological and Molecular Mechanisms of Silicon Action in Salt Stress Amelioration

Salinity is one of the most common abiotic stress factors affecting different biochemical and physiological processes in plants, inhibiting plant growth, and greatly reducing productivity. During the last decade, silicon (Si) supplementation was intensively studied and now is proposed as one of the most convincing methods to improve plant tolerance to salt stress. In this review, we discuss recent papers investigating the role of Si in modulating molecular, biochemical, and physiological processes that are negatively affected by high salinity. Although multiple reports have demonstrated the beneficial effects of Si application in mitigating salt stress, the exact molecular mechanism underlying these effects is not yet well understood. In this review, we focus on the localisation of Si transporters and the mechanism of Si uptake, accumulation, and deposition to understand the role of Si in various relevant physiological processes. Further, we discuss the role of Si supplementation in antioxidant response, maintenance of photosynthesis efficiency, and production of osmoprotectants. Additionally, we highlight crosstalk of Si with other ions, lignin, and phytohormones. Finally, we suggest some directions for future work, which could improve our understanding of the role of Si in plants under salt stress.

cGMP functions as an important messenger involved in SlSAMS1-regulated salt stress tolerance in tomato

Salt stress adversely affects the growth, development, and yield of tomato (Solanum lycopersicum). SAM Synthetase (SAMS), which is responsible for the biosynthesis of S-adenosylmethionine (SAM, a precursor of polyamine biosynthesis), participates in plant response to abiotic stress. However, the regulatory mechanism of SAMS-mediated salt stress tolerance remains elusive. In this study, we characterized a SAMS homologue SlSAMS1 in tomato. We found that SlSAMS1 is highly expressed in tomato roots, and its expression can be induced by salt stress. Crucially, overexpression of SlSAMS1 in tomato enhances salt stress tolerance. Through metabolomic profiling, we identified some differentially accumulated metabolites, especially, a secondary messenger guanosine 3',5'-cyclic monophosphate (cGMP) which may play a key role in SlSAMS1-regulated salt tolerance. A series of physiological and biochemical data suggest that cGMP alleviates salt stress-induced growth inhibition, and potentially acts downstream of the polyamine-nitric oxide (PA-NO) signaling pathway to trigger H2O2 signaling in response to salt stress. Taken together, the study reveals that SlSAMS1 regulates tomato salt tolerance via the PA-NO-cGMP-H2O2 signal module. Our findings elucidate the regulatory pathway of SlSAMS1-induced plant response to salt stress and indicate a pivotal role of cGMP in salt tolerance.

Overexpression of JsFLS5 in calli improves salinity tolerance by maintaining active oxygen balance and reducing Na+ toxicity in Juglans sigillata

The escalating global climate change significantly threatens plant growth, development, and production through salinity stress. Flavonoids, a crucial category of secondary metabolites, have been extensively studied for their role in modulating plant growth and development mechanisms in the face of biological and abiotic stress. The flavonol synthetase (FLS) gene plays a key role in the biosynthesis and accumulation of flavonoids. To investigate the correlation between salt tolerance and flavonol synthesis, JsFLS5 was overexpressed in the callus of Juglans sigillata cv. "Qianhe-7." This study shows that the upregulation of JsFLS5 significantly elevates the overall flavonoid content by modulating the expression of genes associated with flavonoid synthesis under salinity stress conditions. Additionally, the overexpressing callus exhibited enhanced resistance to salt stress compared to the wild-type callus, as evidenced by reduced levels of reactive oxygen species accumulation, electrolyte leakage, and malondialdehyde content in the overexpressing callus relative to the wild type (WT). Moreover, the overexpressing callus showed higher antioxidant enzyme activity and a more efficient ascorbic acid-glutathione cycle. Furthermore, the concentration of Na+ in the overexpressing callus was lower than WT, resulting in a decreased Na+ /K+ ratio. These findings suggest that JsFLS5 overexpression in calli effectively mitigates the oxidative damage induced by osmotic stress and reduces Na+ toxicity by enhancing flavonoid synthesis under salt stress conditions. Consequently, this study offers a novel perspective for comprehending the role of JsFLS5 in the response to abiotic stress in J. sigillata.

Genome-wide characterization of SOS1 gene family in potato (Solanum tuberosum) and expression analyses under salt and hormone stress

Salt Overly Sensitive 1 (SOS1) is one of the members of the Salt Overly Sensitive (SOS) signaling pathway and plays critical salt tolerance determinant in plants, while the characterization of the SOS1 family in potato (Solanum tuberosum) is lacking. In this study, 37 StSOS1s were identified and found to be unevenly distributed across 10 chromosomes, with most of them located on the plasma membrane. Promoter analysis revealed that the majority of these StSOS1 genes contain abundant cis-elements involved in various abiotic stress responses. Tissue specific expression showed that 21 of the 37 StSOS1s were widely expressed in various tissues or organs of the potato. Molecular interaction network analysis suggests that 25 StSOS1s may interact with other proteins involved in potassium ion transmembrane transport, response to salt stress, and cellular processes. In addition, collinearity analysis showed that 17, 8, 1 and 5 of orthologous StSOS1 genes were paired with those in tomato, pepper, tobacco, and Arabidopsis, respectively. Furthermore, RT-qPCR results revealed that the expression of StSOS1s were significant modulated by various abiotic stresses, in particular salt and abscisic acid stress. Furthermore, subcellular localization in Nicotiana benthamiana suggested that StSOS1-13 was located on the plasma membrane. These results extend the comprehensive overview of the StSOS1 gene family and set the stage for further analysis of the function of genes in SOS and hormone signaling pathways.

Tolerance with High Yield Potential Is Provided by Lower Na+ Ion Accumulation and Higher Photosynthetic Activity in Tolerant YNU31-2-4 Rice Genotype under Salinity and Multiple Heat and Salinity Stress

The yield-reduction effect of abiotic stressors such as salinity and heat stresses with the growing world population threatens food security. Although adverse effects of salinity and heat stress on plant growth and production parameters have been documented, in nature, abiotic stresses occur sequentially or simultaneously. In this study, the stress tolerance and yield capacity of Yukinkomai, YNU31-2-4, and YNU SL rice genotypes tested under control (26 °C, 0 mM NaCl), salinity (26 °C, 75 mM NaCl), heat (31 °C, 0 mM NaCl), and heat and salinity (31 °C, 75 mM NaCl) stress combinations at vegetative and reproductive stages with six different scenarios. The results show that salinity and the heat and salinity combination stresses highly reduce plant growth performance and yield capacity. Heat stress during reproduction does not affect the yield but reduces the grain quality. The YNU31-2-4 genotype performs better under heavy salt and heat and salinity stress then the Yukinkomai and YNU SL genotypes. YNU31-2-4 genotypes accumulate less Na⁺ and more K⁺ under salt and multiple stresses. In the YNU31-2-4 genotype, low Na⁺ ion accumulation increases photosynthetic activity and pigment deposition, boosting the yield. Stress lowers the glucose accumulation in dry seeds, but the YNU31-2-4 genotype has a higher glucose accumulation.

Regulation of thermodynamics and kinetics of silica nucleation during the silicification process in higher plants

The formation mechanism of SiO₂ aggregates is controversial because two contrasting hypotheses are often proposed to explain plant silicification. In this review, we summarize the physicochemical fundamentals of amorphous silica nucleation and discuss how plants regulate the process of silicification by influencing the thermodynamics and kinetics of silica nucleation. At silicification positions, plants overcome the thermodynamic barrier by establishing the supersaturation of the H₄SiO₄ solution and reducing the interfacial free energy. Among the thermodynamic-drivers, the establishment of supersaturation of H₄SiO₄ solution mainly depends on the expression of Si transporters for H₄SiO₄ supply, evapotranspiration for concentrating Si, and the other solutes in H₄SiO₄ solution for influencing the dissolution equilibrium of SiO₂; while the interfacial free energy was reduced seemingly by the overexpression Na⁺/H⁺ antiporter SOS1 in high NaCl-stressed rice. Moreover, some kinetic-drivers, such as silicification-related proteins (Slp1 and PRP1) and new cell wall components, are actively expressed or synthesized by plants to interact with silicic acid, thereby reducing the kinetic barrier. According to classical nucleation theory, when the thermodynamic barrier is overcome, the super-saturated silicic acid solution (such as H₄SiO₄ in xylem sap) does not necessarily have to precipitate, just has the potential ability to precipitation. Thus, based on the mediators of SiO₂ deposition at the thermodynamic-driven stage, it is difficult to evaluate whether the process of plant silicification is active or passive. We conclude that the characteristics of kinetic-drivers determine the mechanism of plant silicification.

Plant salt response: Perception, signaling, and tolerance

Salt stress is one of the significant environmental stressors that severely affects plant growth and development. Plant responses to salt stress involve a series of biological mechanisms, including osmoregulation, redox and ionic homeostasis regulation, as well as hormone or light signaling-mediated growth adjustment, which are regulated by different functional components. Unraveling these adaptive mechanisms and identifying the critical genes involved in salt response and adaption are crucial for developing salt-tolerant cultivars. This review summarizes the current research progress in the regulatory networks for plant salt tolerance, highlighting the mechanisms of salt stress perception, signaling, and tolerance response. Finally, we also discuss the possible contribution of microbiota and nanobiotechnology to plant salt tolerance.

Brassinolide improves the tolerance of Malus hupehensis to alkaline stress

Malus hupehensis is one of the most widely used apple rootstocks in china but is severely damaged by alkaline soil. Alkaline stress can cause more serious harmful effects on apple plants than salt stress because it also induces high pH stress except for ion toxicity, osmotic stress, and oxidative damage. Brassinolide (BL) plays important roles in plant responses to salt stress. However, its role and function mechanism in apple plants in response to alkaline stress has never been reported. This study showed that applying exogenous 0.2 mg/L BL significantly enhanced the resistance of M. hupehensis seedlings to alkaline stress. The main functional mechanisms were also explored. First, exogenous BL could decrease the rhizosphere pH and promote Ca²⁺ and Mg²⁺ absorption by regulating malic acid and citric acid contents and increasing H⁺ excretion. Second, exogenous BL could alleviate ion toxicity caused by alkaline stress through enhancing Na⁺ efflux and inhibiting K⁺ expel and vacuole compartmentalization. Last, exogenous BL could balance osmotic stress by accumulating proline and reduce oxidative damage through increasing the activities of antioxidant enzymes and antioxidants contents. This study provides an important theoretical basis for further analyzing the mechanism of exogenous BL in improving alkaline tolerance of apple plants.

Silicon enhances the submergence tolerance of rice by regulating quiescence strategy and alleviating oxidative damage

The safety of rice production under submergence is one of the research hotspots worldwide. Although the effects of silicon (Si) on enhancing plant stress tolerance have been widely investigated, the underlying mechanisms mediated by Si under submergence remains poorly understood. In this study, wild type (WT) and Si-defective mutant (lsi1) rice were chosen to investigate the mechanisms of Si-mediated rice resistance to submergence. Our results showed that Si addition effectively mitigated oxidative damages under submergence by reducing the content of hydrogen peroxide (H₂O₂) and superoxide (O₂^.-) in WT rice plants. Moreover, Si treatment increased rice yield by 21.5% for WT rice under submergence. The application of Si significantly inhibited the elongation and internode length in WT rice under submergence, through the synergistic regulation of endogenous hormones ethylene (ET), gibberellic acid (GA) and jasmonic acid (JA). Further investigation showed that the ethylene-responsive factor (ERF) SUB1A gene was expressed under submergence in WT and lsi1 rice, but Si addition did not influence the expression of SUB1A. Interestingly, exogenous Si down-regulated the relative expression levels of Si transporter genes Lsi1 and Lsi2 in WT rice roots by 51.7% and 48.0%, respectively. However, the physiological characteristics and genes expression of lsi1 rice were not affected by Si application regardless of submergence. The present study indicated that Si enhances the submergence tolerance and reduce the adverse effects of yield loss through the removal of reactive oxygen species and the adjustment of quiescence strategy.

Screening DHHCs of S-acylated proteins using an OsDHHC cDNA library and bimolecular fluorescence complementation in rice

S-acylation is an important lipid modification that primarily involves DHHC proteins (DHHCs) and associated S-acylated proteins. No DHHC-S-acylated protein pair has been reported so far in rice (Oryza sativa L.) and the molecular mechanisms underlying S-acylation in plants are largely unknown. We constructed an OsDHHC cDNA library for screening corresponding pairs of DHHCs and S-acylated proteins using bimolecular fluorescence complementation assays. Five DHHC-S-acylated protein pairs (OsDHHC30-OsCBL2, OsDHHC30-OsCBL3, OsDHHC18-OsNOA1, OsDHHC13-OsNAC9, and OsDHHC14-GSD1) were identified in rice. Among the pairs, OsCBL2 and OsCBL3 were S-acylated by OsDHHC30 in yeast and rice. The localization of OsCBL2 and OsCBL3 in the endomembrane depended on S-acylation mediated by OsDHHC30. Meanwhile, all four OsDHHCs screened complemented the thermosensitive phenotype of an akr1 yeast mutant, and their DHHC motifs were required for S-acyltransferase activity. Overexpression of OsDHHC30 in rice plants improved their salt and oxidative tolerance. Together, these results contribute to our understanding of the molecular mechanism underlying S-acylation in plants.

Ion transporters and their regulatory signal transduction mechanisms for salinity tolerance in plants

Soil salinity is one of the most serious threats to plant growth and productivity. Due to global climate change, burgeoning population and shrinking arable land, there is an urgent need to develop crops with minimum reduction in yield when cultivated in salt-affected areas. Salinity stress imposes osmotic stress as well as ion toxicity, which impairs major plant processes such as photosynthesis, cellular metabolism, and plant nutrition. One of the major effects of salinity stress in plants includes the disturbance of ion homeostasis in various tissues. In the present study, we aimed to review the regulation of uptake, transport, storage, efflux, influx, and accumulation of various ions in plants under salinity stress. We have summarized major research advancements towards understanding the ion homeostasis at both cellular and whole-plant level under salinity stress. We have also discussed various factors regulating the function of ion transporters and channels in maintaining ion homeostasis and ionic interactions under salt stress, including plant antioxidative defense, osmo-protection, and osmoregulation. We further elaborated on stress perception at extracellular and intracellular levels, which triggers downstream intracellular-signaling cascade, including secondary messenger molecules generation. Various signaling and signal transduction mechanisms under salinity stress and their role in improving ion homeostasis in plants are also discussed. Taken together, the present review focuses on recent advancements in understanding the regulation and function of different ion channels and transporters under salt stress, which may pave the way for crop improvement.

Multidimensional Role of Silicon to Activate Resilient Plant Growth and to Mitigate Abiotic Stress

Sustainable agricultural production is critically antagonistic by fluctuating unfavorable environmental conditions. The introduction of mineral elements emerged as the most exciting and magical aspect, apart from the novel intervention of traditional and applied strategies to defend the abiotic stress conditions. The silicon (Si) has ameliorating impacts by regulating diverse functionalities on enhancing the growth and development of crop plants. Si is categorized as a non-essential element since crop plants accumulate less during normal environmental conditions. Studies on the application of Si in plants highlight the beneficial role of Si during extreme stressful conditions through modulation of several metabolites during abiotic stress conditions. Phytohormones are primary plant metabolites positively regulated by Si during abiotic stress conditions. Phytohormones play a pivotal role in crop plants' broad-spectrum biochemical and physiological aspects during normal and extreme environmental conditions. Frontline phytohormones include auxin, cytokinin, ethylene, gibberellin, salicylic acid, abscisic acid, brassinosteroids, and jasmonic acid. These phytohormones are internally correlated with Si in regulating abiotic stress tolerance mechanisms. This review explores insights into the role of Si in enhancing the phytohormone metabolism and its role in maintaining the physiological and biochemical well-being of crop plants during diverse abiotic stresses. Moreover, in-depth information about Si's pivotal role in inducing abiotic stress tolerance in crop plants through metabolic and molecular modulations is elaborated. Furthermore, the potential of various high throughput technologies has also been discussed in improving Si-induced multiple stress tolerance. In addition, a special emphasis is engrossed in the role of Si in achieving sustainable agricultural growth and global food security.

GR24-mediated enhancement of salt tolerance and roles of H2O2 and Ca2+ in regulating this enhancement in cucumber

This study investigated the regulation of the exogenous strigolactone (SL) analog GR24 in enhancing the salt tolerance and the effects of calcium ion (Ca2+) and hydrogen peroxide (H2O2) on GR24's regulation effects in cucumber. The seedlings were sprayed with (1) distilled water (CK), (2) NaCl, (3) GR24, then NaCl, (4) GR24, then H2O2 scavenger, then NaCl, and (5) GR24, then Ca2+ blocker, then NaCl. The second true leaf was selected for biochemical assays. Under the salt stress, the exogenous GR24 maintained the ion balance, increased the activity of antioxidant enzymes, reduced the membrane lipid peroxidation, and increased the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), accompanied by a decrease in relative conductivity, an increase in the proline content, and elevated gene expression levels of antioxidant enzymes, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, calcium-dependent protein kinases (CDPKs), salt overly sensitive SOS1, CBL-interacting protein kinase 2 (CIPK2), and calcineurin B-like protein 3 (CBL3). Such protective effects triggered by GR24 were attenuated or almost abolished by ethylene glycol tetraacetic acid (EGTA), lanthanum chloride (LaCl3, Ca2+ channel blocker), diphenyleneiodonium (DPI, NADPH oxidase inhibitor), and dimethylthiourea (DMTU, hydroxyl radical scavenger). Our data suggest that exogenous GR24 is highly effective in alleviating salt-induced damages via modulating antioxidant capabilities and improving ionic homeostasis and osmotic balance and that H2O2 and Ca2+ are required for GR24-mediated enhancement of salt tolerance.

Unraveling the contribution of OsSOS2 in conferring salinity and drought tolerance in a high-yielding rice

Abiotic stresses are emerging as a potential threat to sustainable agriculture worldwide. Soil salinity and drought will be the major limiting factors for rice productivity in years to come. The Salt Overly Sensitive (SOS) pathway plays a key role in salinity tolerance by maintaining the cellular ion homeostasis, with SOS2, a S/T kinase, being a vital component. The present study investigated the role of the OsSOS2, a SOS2 homolog from rice, in improving salinity and drought tolerance. Transgenic plants with either overexpression (OE) or knockdown (KD) of OsSOS2 were raised in one of the high-yielding cultivars of rice-IR64. Using a combined approach based on physiological, biochemical, anatomical, microscopic, molecular, and agronomic assessment, the evidence presented in this study advocates the role of OsSOS2 in improving salinity and drought tolerance in rice. The OE plants were found to have favorable ion and redox homeostasis when grown in the presence of salinity, while the KD plants showed the reverse pattern. Several key stress-responsive genes were found to work in an orchestrated manner to contribute to this phenotype. Notably, the OE plants showed tolerance to stress at both the seedling and the reproductive stages, addressing the two most sensitive stages of the plant. Keeping in mind the importance of developing crops plants with tolerance to multiple stresses, the present study established the potential of OsSOS2 for biotechnological applications to improve salinity and drought stress tolerance in diverse cultivars of rice.