Halophyte Research Articles

Gene metabolite relationships revealed metabolic adaptations of rice salt tolerance

Environmental stresses, particularly salinity, pose significant challenges to global crop production, notably impacting the growth and yield of rice. Integrating gene expression and metabolomics data offers valuable insights into the molecular mechanisms driving salt tolerance in plants. This study examined the effects of high salinity on the roots and shoots of rice genotypes with contrasting tolerances: CSR28 (tolerant) and IR28 (sensitive) at the seedling stage. Our phenotypic and physiological assessments indicated significant differences in response to prolonged salinity exposure between the two genotypes. Notably, osmoprotectants, including amino acids and sugars, exhibited increased accumulation, whereas most organic acids showed a decline. Linear regression analyses established significant correlations between the levels of proline, myoinositol, catalase (CAT), and superoxide dismutase (SOD) and their respective encoding genes: OsP5CS2, OsIMP, OsNCA1a, and OsSOD-Fe. Furthermore, a relationship was identified between H2O2 content and the expression of glycolate oxidase (GLO), highlighting its role in initiating defense mechanisms under salinity stress. Our findings indicated specific metabolites and genes associated with distinct organs, genotypes, and timepoints that can serve as biomarkers for the development of new salt-tolerant rice varieties.

Ion homeostasis and coordinated salt tolerance mechanisms in a barley (Hordeum vulgare L.)doubled haploid line

Salinization poses a significant challenge in agriculture. Identifying salt-tolerant plant germplasm resources and understanding their mechanisms of salt tolerance are crucial for breeding new salt-tolerant plant varieties. However, one of the primary obstacles to achieving this goal in crops is the physiological complexity of the salt-tolerance trait. In a previous study, we developed a salt-tolerant barley doubled haploid (DH) line, designated as DH20, through mutagenesis combined with microspore culture, establishing it as an idea model for elucidating the mechanisms of salt tolerance. In this study, ion homeostasis, key osmotic agents, antioxidant enzyme activities and gene expression were compared between Hua30 (the original material used as a control) and DH20. The results indicated that under salt treatment, DH20 exhibited significantly higher shoot fresh and dry weight, relative plant height, shoot K+/Na+ ratio, improved stomatal guard cell function, and better retention of chloroplast ultrastructure compared to Hua30. Notably, the K+ efflux in DH20 was significantly lower while the Na+ and H+ efflux was significantly higher than those in Hua30 under salt stress in mesophyll cells. Furthermore, the activities of ascorbate peroxidase, superoxide dismutase, and peroxidase, along with the levels of proline, betaine, malondialdehyde, and soluble protein, were correlated with ion efflux and played a vital role in the response of DH20 to salt stress. Compared to Hua30, the relative expression levels of the HvSOS1, HvSOS2, HvSOS3, HvHKT1;3, HvNHX1, HvNHX2, and HvNHX3 genes, which showed a strong correlation with Na+, K+, and H+ efflux, exhibited significant differences at 24 h under salt stress in DH20. These findings suggest that ion homeostasis, key osmolytes, antioxidant enzyme activities, and associated gene expression are coordinated in the salt tolerance of DH20, with K+ retention and Na+ and H+ efflux serving as important mechanisms for coping with salt stress. These findings present new opportunities for enhancing salinity tolerance, not only in barley but in other cereals as well, including wheat and rice, by integrating this trait with other traditional mechanisms. Furthermore, MIFE measurements of NaCl-induced ion fluxes from leaf mesophyll provide plant breeders with an efficient method to screen germplasm for salinity stress tolerance in barley and potentially other crops. Clinical trial number: Not applicable.

Evaluating the nutritional, therapeutic, and economic potential of Tetragonia decumbens Mill.: A promising wild leafy vegetable for bio-saline agriculture in South Africa

Abstract Global agriculture feeds over seven billion people and alarmingly, this number is expected to increase by a further 50% by 2050. To meet the additional food demand, the world development report has estimated that crop production should increase by 70–100% by 2050. However, climate change, expanding soil salinization, and the developing shortages of freshwater have negatively affected crop production of edible plants around the world. Current attempts to adapt to these conditions include the use of salt-tolerant plant species with potential economic value to fulfil the increasing food demand escalated by the increasing human population. The wild edible halophyte Tetragonia decumbens commonly known as dune spinach has the potential to be used as a leafy vegetable, a source of dietary salt, in phytoremediation and as a source of secondary metabolites. However, it remains underutilized in South Africa as commercial farming of this species has never been explored. This review examined the potential of domesticating the wild dune spinach as a leafy vegetable, describing its morphology and ecology, its propagation and cultivation requirements as well as its potential use on human health and in phytoremediation of saline soils. Furthermore, this analysis is expected to be useful towards further research and popularization of this underexploited halophyte.

Identification of significant SNPs for yield-related salt tolerant traits in rice through genome-wide association analysis.

Rice salt tolerance is highly anticipated to meet global demand in response to decreasing farmland and soil salinization. Therefore, dissecting the genetic loci controlling salt tolerance in rice for improving productivity is of utmost importance. Here, we evaluated six salt-tolerance-related traits of a biparental mapping population comprising 280 F2 rice individuals (Oryza sativa L.) at the seedling and reproductive stages. We performed a genome-wide association study (GWAS) to identify marker-trait associations under artificially induced salt stress using the 1K RICA chip (Agriplex Genomics, Cedar Avenue, Suite 250, Cleveland, 011444106, USA). We have identified 8 single nucleotide polymorphisms (SNPs) representing eight genomic regions on chromosomes 5, 8, 9, and 10. These were significantly associated with the six salt-tolerance-related traits, no. of tillers per plant (TPP), effective tillers per plant (ETP), spikelet fertility percentage (SFP), field grain number (FGN), grain length breadth ratio (LBR) and thousand-grain weight (TGW). FGN has two significant SNPs (SNP0758 and SNP0759) on Chromosome 9, whereas SFP on chromosomes 8 and 12 (SNP1127 and SNP0966, respectively). Similarly, for TPP (SNP0796), a significant SNP was detected on chromosome 10, and for ETP (SNP0414) on chromosome 5. Two significant SNPs were found in chromosome 12 for LBR (SNP0920) and TGW (SNP0976). Based on all loci, we screened 3 possible candidate genes in chromosomes 8, 9, and 12 between the genomic region of SNP0920 and SNP1127 under salt stress. Interestingly, these genes were involved in protein coding, none of which was previously reported as being involved in plant salt tolerance. Further, the genetic relationship between the mapping population and population structure was classified by STRUCTURE v 2.3. Genotypes with ≥ 80% of shared ancestry were explained into two major clusters (I and II), and < 80% of shared ancestry were categorized as admixtures. An unrooted alpha was developed by TASSEL 5.0, dividing the genotypes into three major groups where 97 individuals were in Cluster 1, cluster 2 consisted of 93 individuals, and the remaining Cluster 3 included 90 individuals. A kinship matrix developed from 860 SNPs indicated group formation and more substantial relatedness among the genotypes with a red zone. Our findings provide valuable information for enhancing the understanding of complicated salt tolerance mechanisms in rice seedlings and the identified candidates potentially used for breeding salt-tolerant genotypes.

LbHKT1;1 Negatively Regulates Salt Tolerance of Limonium bicolor by Decreasing Salt Secretion Rate of Salt Glands.

The HKT-type proteins have been extensively studied and have been shown to play important roles in long-distance Na+ transport, maintaining ion homoeostasis and improving salt tolerance in plants. However, there have been no reports on the types, characteristics and functions of HKT-type proteins in Limonium bicolor, a recretohalophyte species with the typical salt gland structure. In this study, five LbHKT genes were identified in L. bicolor, all belonging to subfamily 1 (HKT1). There are many cis-acting elements related to abiotic/biotic stress response on the promoters of the LbHKT genes. LbHKT1;1 was investigated in detail. Subcellular localization results showed that LbHKT1;1 is targeted to the plasma membrane. Functional analysis in yeast showed that LbHKT1;1 has a higher tolerance than AtHKT1;1 under high Na+ conditions. Silencing and overexpression of the LbHKT1;1 gene in L. bicolor showed that LbHKT1;1 negatively regulates salt secretion by the salt glands. Further experiments showed that LbbZIP52 can specifically bind to the ABRE element in the LbHKT1;1 promoter and regulate the expression of the LbHKT1;1 gene and is involved in the negative regulation of the salt secretion capacity of L. bicolor. This study demonstrates for the first time that the HKT-type protein is involved in salt secretion by salt glands and provides a new perspective on the function of HKT-type proteins under salt stress conditions.

Comprehensive In Silico Analysis of the NHX (Na+/H+ Antiporter) Gene in Rice (Oryza sativa L.)

The Na+/H+ antiporter (NHX) gene family plays a pivotal role in plant salt tolerance in regulating intracellular Na+ and H+ homeostasis. In this study, seven candidate OsNHX genes (OsNHX1 to OsNHX7) were identified in the rice genome and classified into three phylogenetic clusters (Vac, Endo, and PM) based on their predicted subcellular localization. Five OsNHX gene pairs (OsNHX1/OsNHX2, OsNHX1/OsNHX3, OsNHX1/OsNHX4, OsNHX2/OsNHX6, and OsNHX5/OsNHX6) were found to have arisen from dispersed duplication events and exhibited purifying selection, indicating functional conservation. Analysis of cis-regulatory elements (CREs) revealed a diverse range of elements associated with tissue-specific expression, hormone signaling, and stress responses, particularly to dehydration and salinity. Notably, CREs associated with tissue/organelle-specific expression and stress responses were the most abundant, suggesting a potential role for OsNHX genes in regulating growth, development, and stress tolerance in rice. Importantly, expression profiling revealed that OsNHX1, OsNHX2, OsNHX3, and OsNHX5 were upregulated under salt stress, with significantly higher expression levels in the salt-tolerant rice cultivar Pokkali compared to the salt-sensitive cultivar IR64. Our findings provide a comprehensive analysis of the evolutionary, structural, and functional features of the OsNHX gene family and highlights their critical role in rice salt tolerance, offering insights into potential applications for crop improvement.

Residual effects of biochar and nano-modified biochar on growth and physiology under saline environment in two different genotype of Oryza sativa L.

Soil salinity is represent a significant environmental stressor that profoundly impairs crop productivity by disrupting plant physiological functions. To mitigate this issue, the combined application of biochar and nanoparticles has emerged as a promising strategy to enhance plant salt tolerance. However, the long-term residual effects of this approach on cereal crops remain unclear. In a controlled pot experiment, rice straw biochar (BC) was applied in an earlier experiment at a rate of 20t/ha, in conjunction with ZnO and Fe2O3 nanoparticles at concentrations of 10mgL-1 and 20mgL-1. Two rice genotypes, Jing Liang You-534 (salt-sensitive) and Xiang Liang You-900 (salt-tolerant), were utilized under 0% NaCl (S1) and 0.6% NaCl (S2) conditions. Results showed that, application of residual ZnOBC-20 significantly enhanced rice biomass, photosynthetic assimilation, relative chlorophyll content, SPAD index, enzyme activities, K+/Na+ ratio, hydrogen peroxide (H2O2) levels, and overall plant growth. Specifically, ZnOBC-20 increased the tolerance index by 142.8% and 146.1%, reduced H2O2 levels by 27.11% and 35.8%, and decreased malondialdehyde (MDA) levels by 33% and 57.9% in V1 and V2, respectively, compared to their respective controls. Residual of ZnOBC-20 mitigated oxidative damage caused by salinity-induced over-accumulation of reactive oxygen species (ROS) by enhancing the activities of antioxidant enzymes (SOD, POD, CAT, and APX) and increasing total soluble protein (TSP) content. Xiang Liang You-900 exhibited a less severe response to salinity compared to Jing Liang You-534. Additionally, residual of ZnOBC-20 significantly enhanced the anatomical architecture of both root and leaf tissues and regulated the expression levels of salt-related genes. Residual of ZnOBC-20 also improved salt tolerance in rice plants by reducing sodium (Na+) accumulation and enhancing potassium (K+) retention, thereby increasing the K+/Na+ ratio under saline conditions. The overall results of this experiment demonstrate that, residual effects of ZnOBC-20 not only improved the growth and physiological traits of rice plants under salt stress but also provided insights into the mechanisms behind the innovative combination of biochar and nanoparticles residual impacts for enhancing plant salt tolerance.

Molecular and metabolomics analysis reveals new insight into the mechanism underlying Iris halophila Pall. IhCHS1-mediated regulation of plant salt tolerance

Molecular and metabolomics analysis reveals new insight into the mechanism underlying Iris halophila Pall. IhCHS1-mediated regulation of plant salt tolerance

Exogenous 2,4-Epibrassinolide Alleviates Alkaline Stress in Cucumber by Modulating Photosynthetic Performance.

Brassinosteroids (BRs) are recognized for their ability to enhance plant salt tolerance. While considerable research has focused on their effects under neutral salt conditions, the mechanisms through which BRs regulate photosynthesis under alkaline salt stress are less well understood. This study investigates these mechanisms, examining plant growth, photosynthetic electron transport, gas exchange parameters, Calvin cycle dynamics, and the expression of key antioxidant and Calvin cycle genes under alkaline stress conditions induced by NaHCO3. The findings indicate that NaHCO3 stress substantially impairs cucumber growth and photosynthesis, significantly reducing chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (ΦPSII), antenna conversion efficiency (Fv'/Fm'), and photochemical quenching coefficient (qP). This disruption suggests a severe dysregulation of the photosynthetic electron transport system, impairing electron transfer from photosystem II (PSII) to photosystem I (PSI) and subsequently the Calvin cycle. Application of exogenous 24-epibrassinolide (EBR) alleviated these effects, reducing leaf chlorosis and growth inhibition and significantly enhancing the expression of key genes within the antioxidant system (AsA-GSH cycle) and the Calvin cycle. This intervention also led to a reduction in reactive oxygen species (ROS) accumulation and improved photosynthetic performance, as evidenced by enhancements in Pn, Gs, E, Fv/Fm, ΦPSII, Fv'/Fm', and qP. Moreover, NaHCO3 stress hindered chlorophyll synthesis, primarily by blocking the conversion from porphobilinogen (PBG) to uroporphyrinogen III (UroIII) and by increasing chlorophyllase (Chlase) and decreasing porphobilinogen deaminase (PBGD) activity. Exogenous EBR countered these effects by enhancing PBGD activity and reducing Chlase activity, thereby increasing chlorophyll content under stress conditions. In summary, EBR markedly mitigated the adverse effects of alkaline stress on cucumber leaf photosynthesis by stabilizing the photosynthetic electron transport system, accelerating photosynthetic electron transport, and promoting the Calvin cycle. This study provides valuable insights into the regulatory roles of BRs in enhancing plant resilience to alkaline stress.

CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 regulates salt tolerance through CATALASE 2 in Arabidopsis.

Soil salinization threatens global crop production. Here, we report that a receptor-like cytoplasmic kinase (RLCK), CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 (CRCK3), plays an essential role in plant salt tolerance via CATALASE 2 (CAT2), a hydrogen peroxide (H2O2)-scavenging enzyme in Arabidopsis (Arabidopsis thaliana). CRCK3 was induced by salt stress, and its knockout mutant displayed a salt-sensitive phenotype compared to wild-type (WT) plants. CRCK3 was activated by salt stress in a calcium-dependent manner, and its kinase activity was required for plant salt tolerance. CRCK3 physically interacted with CAT2, and CRCK3-mediated salt tolerance depended on CAT2. Salt treatment significantly induced CAT2 phosphorylation via the action of CRCK3, and this phosphorylation was required for CAT2-mediated H2O2 scavenging to reduce ROS content and oxidative damage in plants under saline conditions. CRCK3 phosphorylated CAT2 at the Thr209 residue, resulting in elevated catalase activity to reduce reactive oxygen species (ROS) accumulation under saline conditions. Therefore, the CRCK3-CAT2 module mediates plant salt tolerance by maintaining redox homeostasis. This study expands our knowledge of how plants respond to salt stress.

Genome-Wide Identification and Characterization of the LEA Gene Family in Common Bean and the Role of the Dehydrin Gene PvHDN3 in Enhancing Salt and Drought Tolerance in Transgenic Tobacco Plant.

Genome-Wide Identification and Characterization of the LEA Gene Family in Common Bean and the Role of the Dehydrin Gene PvHDN3 in Enhancing Salt and Drought Tolerance in Transgenic Tobacco Plant.

Effects of Brassinosteroid on the Physiological Changes on Two Varieties of Tea Plants Under Salt Stress.

Salt stress is one of the abiotic stresses affecting crop quality and yield, and the application of exogenous brassinosteroids (BRs) can be used in response to salt stress. However, the function of BR in tea plants under salt stress remains to be elucidated. This study investigated the effects of exogenous spraying of BR on the malondialdehyde, soluble sugar, soluble protein, and antioxidant enzyme activities in tea plants under salt stress and explored the expression changes in genes related to the synthesis pathways of proline and secondary metabolites (flavonoids and theanine). The results show that 200 mM NaCl solution inhibits the physiology of tea plants, but 0.2 mg/L BR could partially reduce the damage by increasing photosynthetic pigments, osmoregulatory substances (such as soluble sugar, soluble protein, and proline), and the activity of antioxidant enzymes (including peroxidase, catalase, and superoxide dismutase), while decreasing the malondialdehyde content in salt-stressed leaves. The qRT-PCR experiment also shows that the genes related to the synthesis pathways of proline and secondary metabolites (flavonoids and theanine) were upregulated under salt stress, and the proline degradation genes were downregulated, thus promoting the accumulation of proline under salt stress in both varieties. When tea plants were subjected to salt stress, the expression of genes related to the synthesis of secondary metabolites was regulated accordingly to resist salt stress. Moreover, spraying BR had an obvious effect on improving the salt tolerance of tea plants. Therefore, exploring a way to improve the salt tolerance of tea trees provides a reference for the subsequent study of its salt tolerance mechanism, which is of great significance for expanding the introduction area of tea trees, increasing the planting area of tea trees, and improving the yield and quality of tea.

Identification of dehydrin family genes in three Medicago species and insights into their tolerant mechanism to salt stress.

All ten dehydrin genes from three Medicago species are responsive to different kinds of abiotic stress, and CAS31 confers transgenic plants salt tolerance by down-regulating HKT1 expression. Dehydrins are protective proteins playing crucial roles in the tolerance of plants to abiotic stresses. However, a full-scale and systemic analysis of total dehydrin genes in Medicago at the genome level is still lacking. In this study, we identified ten dehydrin genes from three Medicago species (M. truncatula, M. ruthenica, and M. sativa), categorizing the coding proteins into four types. Genome collinearity analysis among the three Medicago species revealed six orthologous gene pairs. Promoter regions of dehydrin genes contained various phytohormone- and stress-related cis-elements, and transcriptome analysis showed up-regulation of all ten dehydrin genes under different stress conditions. Transformation of dehydrin gene CAS31 increased the tolerance of transgenic seedlings compared with wild-type seedlings under salt stress. Our study demonstrated that transgenic seedlings maintained the more chlorophyll, accumulated more proline and less hydrogen peroxide and malondialdehyde than wild-type seedlings under salt stress. Further study revealed that CAS31 reduced Na+ accumulation by down-regulating HKT1 expression under salt stress. These findings enhance our understanding of the dehydrin gene family in three Medicago species and provide insights into their mechanisms of tolerance.

SaTDT enhanced plant tolerance to NaCl stress by modulating the levels of malic acid and citric acid in cells.

The issue of soil salinization is a global concern that significantly impairs crop productivity, quality, and distribution. Tonoplast Dicarboxylate Transporter (TDT) is a pivotal malic acid transporter localized on the vacuolar membrane, involving in maintaining intracellular pH homeostasis in plants. However, the molecular mechanisms and regulatory pathways underlying plant salt tolerance through TDT remain elusive. In this study, we cloned a gene encoding vacuolar membrane dicarboxylic acid transporter designated as SaTDT from the halophyte Spartina alterniflora. Subsequently, its role in regulating salt stress was investigated. The heterologous expression of SaTDT in Arabidopsis thaliana was observed to enhance the transgenic plants' tolerance to salt stress and alleviate the growth damage caused by this stress. The overexpression of SaTDT can simultaneously enhance plant photosynthetic efficiency by regulating the cellular contents of malic acid and citric acid, or by increasing the activity of MDH and PEPC enzymes. It also regulates and balances energy utilization during carbon assimilation under salt-stressed conditions, thereby establishing an energetic foundation for enhancing plant tolerance to stress. SaTDT also has the capacity to enhance the plant cells' ability in regulating antioxidant enzyme activity or osmotic accumulation, thereby playing a crucial role in maintaining intracellular redox homeostasis. In conclusion, our findings establish a foundation basis for elucidating the regulatory role of the SaTDT gene in S.alterniflora's adaptation to high-salinity habitats.

Adaptive Strategy of the Perennial Halophyte Grass Puccinellia tenuiflora to Long-Term Salinity Stress.

Salinity stress influences plants throughout their entire life cycle. However, little is known about the response of plants to long-term salinity stress (LSS). In this study, Puccinellia tenuiflora, a perennial halophyte grass, was exposed to 300 mM NaCl for two years (completely randomized experiment design with three biological replicates). We measured the photosynthetic parameters and plant hormones and employed a widely targeted metabolomics approach to quantify metabolites. Our results revealed that LSS induced significant metabolic changes in P. tenuiflora, inhibiting the accumulation of 11 organic acids in the leaves and 24 organic acids in the roots and enhancing the accumulation of 15 flavonoids in the leaves and 11 phenolamides in the roots. The elevated accumulation of the flavonoids and phenolamides increased the ability of P. tenuiflora to scavenge reactive oxygen species. A comparative analysis with short-term salinity stress revealed that the specific responses to long-term salinity stress (LSS) included enhanced flavonoid accumulation and reduced amino acid accumulation, which contributed to the adaptation of P. tenuiflora to LSS. LSS upregulated the levels of abscisic acid in the leaves and ACC (a direct precursor of ethylene) in the roots, while it downregulated the levels of cytokinins and jasmonic acids in both the organs. These tolerance-associated changes in plant hormones would be expected to reprogram the energy allocation among growth, pathogen defense, and salinity stress response. We propose that abscisic acid, ethylene, cytokinins, and jasmonic acids may interact with each other to construct a salinity stress response network during the adaptation of P. tenuiflora to LSS, which mediates salinity stress response and significant metabolic changes. Our results provided novel insights into the plant hormone-regulated metabolic response of the plants under LSS, which can enhance our understanding of plant salinity tolerance.

The Growth and Ion Absorption of Sesbania (Sesbania cannabina) and Hairy Vetch (Vicia villosa) in Saline Soil Under Improvement Measures.

Soil salinization is a serious threat to the ecological environment and sustainable agricultural development in the arid regions of northwest China. Optimal soil salinization amelioration methods were eagerly explored under different soil salinity levels. Sesbania and hairy vetch are salt-tolerant plants, and green manure improved the saline environment. In this study, two leguminous halophytic crops, sesbania (Sesbania cannabina) and hairy vetch (Vicia villosa), were planted under different salinity levels, combined with three saline soil improvement measures, namely gravel mulching, manure application, and straw returning. No improvement measures and no salinity treatment was set as the control (CK). This study was conducted to analyze the effects of soil salinization improvement measures on the growth and ion uptake of sesbania and hairy vetch as biological measures under different soil salinity levels. Sesbania under manure application absorbed the highest soil Na+ (2.71 g kg-1) and Cl- (2.66 g kg-1) amounts at a soil salinity of 3.2 g kg-1, which was 14.7% and 10.95% higher than under gravel mulching and straw returning, respectively. Na+ and Cl- absorption of hairy vetch under manure application reached the highest value of 1.39 g kg-1 and 1.38 g kg-1 at a soil salinity of 1.6 g kg-1, which was 24.46% and 22.31% higher than under gravel mulching and straw returning, respectively. Plant height and stem diameter as well as root growth and development of sesbania and hairy vetch were limited at soil salinities greater than 1.6 g kg-1 and 0.8 g kg-1. Overall, sesbania and hairy vetch effectively absorbed both soil Na+ and Cl- under manure application, thus regulating soil salinity and reducing soil salinization. However, soil salinity levels greater than 3.2 g kg-1 and 1.6 g kg-1 not only weakened the ionic absorption capacity but also inhibited the growth and development of sesbania and hairy vetch. This study provides evidence that soil salt ion absorption by sesbania and hairy vetch is promoted effectively, ameliorating soil salinity, under manure application as compared to under gravel mulching and straw returning.

The antisense CircRNA VvcircABH controls salt tolerance and the brassinosteroid signaling response by suppressing cognate mRNA splicing in grape.

Soil salinization is a major factor limiting the sustainable development of the grape industry. Circular RNAs (circRNAs) are more stable than linear mRNAs and are involved in stress responses. However, the biological functions and molecular mechanisms underlying antisense circRNAs in plants remain unclear. We identified the antisense circRNA VvcircABH through high-throughput sequencing. Using genetic transformation methods and molecular biological techniques, we analyzed the effects of VvcircABH on the response to salt stress and the mechanisms underlying its effects. VvcircABH was located in the nucleus and upregulated by salt stress, while the expression level of its cognate gene VvABH (alpha/beta-hydrolase) was downregulated. VvcircABH overexpression or VvABH silencing greatly enhanced grape salt tolerance. VvcircABH could bind to the overlapping region and inhibits VvABH pre-mRNA splicing, thereby decreasing the expression level of VvABH. Additionally, VvcircABH repressed the additive effect of VvABH on the interaction between VvBRI1 (brassinosteroid-insensitive 1) and VvBKI1 (BRI1 kinase inhibitor 1), thus influencing the plant's response to BR, which plays important roles in plant salt tolerance. We conclude that VvcircABH and VvABH play distinct roles in the salt tolerance and brassinosteroid signaling response, and VvcircABH could govern the expression of VvABH by inhibiting its splicing.

Global Insights into the Lysine Acetylome Reveal the Role of Lysine Acetylation in the Adaptation of Bacillus altitudinis to Salt Stress.

Bacillus altitudinis is a well-known beneficial microorganism in plant rhizosphere, capable of enhancing plant growth and salt tolerance in saline soils. However, the mechanistic changes underlying salt tolerance in B. altitudinis at the level of post-translational modifications remain unclear. Here, diverse lysine modifications including acetylation, succinylation, crotonylation, and malonylation were determined in the B. altitudinis response to salt stress by immunodetection, and the acetylation level greatly increased under salt stress. The in-depth acetylome landscape showed that 1032 proteins in B. altitudinis were differentially acetylated under salt stress. These proteins were involved in many physiological aspects closely related to salt tolerance like energy generation and conversion, amino acid synthesis and transport, cell motility, signal transduction, secretion system, and repair system. Moreover, we also identified the differential acetylation of key enzymes involved in the major osmolyte biosynthesis and conversion and antioxidant defenses. Thiol peroxidase (TPX), a key protective antioxidant enzyme, had 3 upregulated acetylation sites (K7/139/157) under salt stress. Site-specific mutations demonstrated that K7/139/157 acetylation strongly regulated TPX function in scavenging intracellular ROS, thereby impacting bacterial growth under salt stress. To our knowledge, this is the first study showing that bacteria adaptation to salt stress occurs at the level of PTMs.

A bHLH Transcription Factor Confers Salinity Stress Tolerance in Betula platyphylla.

Basic helix-loop-helix (bHLH) proteins comprise a large family of transcription factors that are involved in plant growth and development, as well as responses to various types of environmental stress. Betula platyphylla (birch) is a pioneer tree species in secondary forest that plays a key role in maintaining ecosystem stability and forest regeneration, but few bHLHs involved in abiotic stress responses have been unveiled in birch. In this study, nine BpbHLH TFs related to stress responses in the birch genome were identified. Quantitative real-time polymerase chain reaction (RT-PCR) analysis indicated that the expression of these TFs can be induced by salt stress, and the expression of BpbHLH1 was higher than that of other BpbHLH genes. Particle bombardment analysis revealed that BpbHLH1 was localized to the nucleus. Yeast transformation found that BpbHLH1 has transcriptional activation activity. We generated BpbHLH1-overexpressing and silencing transgenic birch plants and subjected them to salt stress analysis. BpbHLH1 can enhance the salt tolerance of birch plants by increasing the reactive oxygen species scavenging ability and inhibiting cell death. Yeast one-hybrid, ß-glucuronidase, and chromatin immunoprecipitation assays revealed that BpbHLH1 can regulate the expression of target genes involved in stress resistance by binding to the E-box-1, E-box-2 and G-box elements in their promoters. The results of this study enhanced our understanding of the salt tolerance conferred by BpbHLH TFs in B. platyphylla and identified useful genes for the breeding of novel birch germplasm.

ZmGolS1 underlies natural variation of raffinose content and salt tolerance in maize.

Salt stress significantly inhibits crop growth and development, and mitigating this can enhance salt tolerance in various crops. Previous studies have shown that regulating saccharide biosynthesis is a key aspect of plant salt tolerance; however, the underlying molecular mechanisms remain largely unexplored. In this study, we demonstrate that overexpression of a salt-inducible galactinol synthase gene, ZmGolS1, alleviates salt-induced growth inhibition, likely by promoting raffinose synthesis. Additionally, we show that natural variation in ZmGolS1 transcript levels contributes to the diversity of raffinose content and salt tolerance in maize. We further reveal that ZmRR18, a type-B response regulator transcription factor, binds to the AATC element in the promoter of ZmGolS1, with this binding increases the transcript levels of ZmGolS1 under salt conditions. Moreover, a single nucleotide polymorphism (termed SNP-302T) within the ZmGolS1 promoter significantly reduces its binding affinity for ZmRR18, resulting in decreased ZmGolS1 expression and diminished raffinose content, ultimately leading to a salt-hypersensitive phenotype. Collectively, our findings reveal the molecular mechanisms by which the ZmRR18-ZmGolS1 module enhances raffinose biosynthesis, thereby promoting maize growth under salt conditions. This research provides important insights into salt tolerance mechanisms associated with saccharide biosynthesis and identifies valuable genetic loci for breeding salt-tolerant maize varieties.