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Rhizobacteria play a crucial role in plant growth and yield, stimulating primary production and improving stress resistance. Climate change has several consequences worldwide that affect arable land and agriculture. Studies on plant–soil–microorganism interactions to enhance plant productivity and/or resistance to abiotic stress may open new perspectives. This strategy aims to make agricultural‐relevant plant species able to complete their biological cycle in extreme soils with the help of inoculated or primed plant growth‐promoting rhizobacteria (PGPR).We provide an overview of the evolution of interest in PGPR research in the last 30 years through: (i) a quantitative search on the Scopus database; (ii) keyword frequencies and clustering analysis, and (iii) a keyword network and time‐gradient analysis.The review of scientific literature on PGPR highlighted an increase in publications in the last 15 years, and a specific time gradient on subtopics, such as abiotic stresses. The rise in PGPR as a keyword co‐occurring with salinity and drought stresses aligns with the growing number of papers from countries directly or partly affected by climate change.The study of PGPR, its features, and related applications will be a key challenge in the next decades, considering climate change effects on agriculture. The increased interest in PGPR leads to deeper knowledge focused specifically on researching agriculturally sustainable solutions for soils affected by salinity and drought. [ABSTRACT FROM AUTHOR]

The continuous growth of the world's population has led to an increased demand for food. Biochar (BC) contains valuable functional groups and nutrients, which have been demonstrated to enhance soil properties and boost crop yield. Nonetheless, unmodified BC exhibits significant alkalinity and a large salt concentration; thus, its efficacy in improving saline-alkali soil remains a matter of contention. Therefore, scholars aim to address the aforementioned limitations by adapting BC. In this paper, a summary is given of the methods used to modify BC and the effects of modified BC on salt-affected soil and saline-alkali soil properties, including pH, nutrients and microbial activity. The effects and principles of different modifiers and modification methods on BC's physicochemical properties (porosity and functional group content and type, etc.) were revealed. Furthermore, the principle of soil improvement by modified BC varies depending on the modification method. Although modified BC can effectively enhance salt-affected soil, its excessive application and improper selection of modifiers can aggravate Na+ toxicity or introduce other pollutants into salt-affected soil. Therefore, using modified BC with care is imperative according to the actual situation. In this review, we provide a detailed introduction to the methods and principles of BC modification for saline-alkali soil. Furthermore, we identify the shortcomings and future research directions in this field. These insights are valuable when choosing proper BC modification methods for salt-affected soil. [ABSTRACT FROM AUTHOR]

Salinity is a major environmental constraint that limits growth and productivity of rice all over the world. Although rice plants are vulnerable to salt stress at both seedling and flowering stages, genetic dissection of salt tolerance at the flowering stage is challenging due to non‐uniformity of stress application at the appropriate growth stage. The present study was conducted to identify quantitative trait loci (QTLs) and candidate genes associated with the flowering stage salt tolerance and compare with those associated with the seedling stage using a high‐resolution genetic map. A population of advanced generation introgression lines with uniform flowering time was evaluated for salt tolerance at the seedling and flowering stages. A genetic map was constructed using 14,230 polymorphic single nucleotide polymorphism markers between donor parents (TCCP and FL478) and the recurrent parent (RP) (Jupiter). Seventeen and 28 QTLs were identified for traits associated with salt tolerance at the seedling and flowering stage, respectively. Important candidate genes present in the flowering stage salt responsive QTL regions were OsHAK13, OsCYP21‐4, GIF1, and OsRGG20, whereas the seedling stage QTL intervals harbored genes such OsHAK20, STRK1, and OsMADS25. Gene expression analysis revealed upregulation of OsHAK13 and OsCYP21‐4 in TCCP, 3 days after exposure to salt stress at the flowering stage. Similarly, expression of OsHAK20, STRK1, and OsMADS25 was highly upregulated in TCCP under salt stress at the seedling stage. Due to differences in genetic control of salt tolerance at both seedling and flowering stages, stacking of genes/QTLs for salt tolerance at both stages will be needed. Since some beneficial QTLs were also contributed by the RP, emphasis should be on targeting the desirable QTLs from donors while retaining the beneficial QTLs of the RP to improve salinity tolerance in rice using marker‐assisted selection. [ABSTRACT FROM AUTHOR]

Plant Na+/H+antiporter (NHX) genes enhance salt tolerance by preventing excessive Na+ accumulation in the cytosol through partitioning of Na+ ions into vacuoles or extracellular transport across the plasma membrane. However, there is limited detailed information regarding the salt stress responsive SlNHXs in the most recent tomato genome. We investigated the role of this gene family's expression patterns in the open flower tissues under salt shock in Solanum lycopersicum using a genome‐wide approach. A total of seven putative SlNHX genes located on chromosomes 1, 4, 6, and 10 were identified, but no ortholog of the NHX5 gene was identified in the tomato genome. Phylogenetic analysis revealed that these genes are divided into three different groups. SlNHX proteins with 10–12 transmembrane domains were hypothetically localized in vacuoles or cell membranes. Promoter analysis revealed that SlNHX6 and SlNHX8 are involved with the stress‐related MeJA hormone in response to salt stress signaling. The structural motif analysis of SlNHX1, −2, −3, −4, and −6 proteins showed that they have highly conserved amiloride binding sites. The protein–protein network revealed that SlNHX7 and SlNHX8 interact physically with Salt Overly Sensitive (SOS) pathway proteins. Transcriptome analysis demonstrated that the SlNHX2 and SlNHX6 genes were substantially expressed in the open flower tissues. Moreover, quantitative PCR analysis indicated that all SlNHX genes, particularly SlNHX6 and SlNHX8, are significantly upregulated by salt shock in the open flower tissues. Our results provide an updated framework for future genetic research and development of breeding strategies against salt stress in the tomato. [ABSTRACT FROM AUTHOR]

Aim: Mangrove canopy height is a key metric to assess tidal forests' resilience in the face of climate change. In terrestrial forests, tree height is primarily determined by water availability, plant hydraulic design, and disturbance regime. However, the role of water stress remains elusive in tidal environments, where saturated soils are prevalent, and salinity can substantially affect the soil water potential. Location: Global. Time Period: The canopy height dataset provides a global snapshot of the maximum mangrove height geographical distribution for the year 2000. Climate and environmental variables extend over the period 1970–2018. Major Taxa Studied: Mangroves. Methods: We use global observations of maximum canopy height, species richness, air temperature, and seawater salinity—a proxy of soil water salt concentration—to explore the causal link between salinity and mangrove stature. Results: Our findings suggest that salt stress limits mangrove height. High salinity favours more salt‐tolerant species, narrowing the spectrum of viable traits. Highly salt‐tolerant mangroves have evolved to cope with high salt concentrations in the soil, but this adaptation comes at a cost. They typically have lower rates of photosynthesis and growth, resulting in reduced productivity and smaller stature compared to more salt‐sensitive mangrove species. This suggests a causal link between salinity, biodiversity, and tree height, where high salinity selects for more salt‐tolerant species that tend to be less productive and shorter. Conclusions: We hypothesize that the salinity‐induced limit to mangrove canopy height is the direct result of a reduction of primary productivity, an increment in the risk of xylem cavitation, and an indirect consequence of the decrease in biodiversity. As sea‐level rise enhances coastal salinisation, failure to account for these effects can lead to incorrect estimates of future carbon stocks in Tropical coastal ecosystems and endanger preservation efforts. [ABSTRACT FROM AUTHOR]

In plant, APETALA2/ethylene‐responsive factor (AP2/ERF)‐domain transcription factors are important in regulating abiotic stress tolerance. In this study, ZmEREB57 encoding a AP2/ERF transcription factor was identified and its function was investigated in maize. ZmEREB57 is a nuclear protein with transactivation activity induced by several abiotic stress types. Furthermore, two CRISPR/Cas9 knockout lines of ZmEREB57 showed enhanced sensitivity to saline conditions, whereas the overexpression of ZmEREB57 increased salt tolerance in maize and Arabidopsis. DNA affinity purification sequencing (DAP‐Seq) analysis revealed that ZmEREB57 notably regulates target genes by binding to promoters containing an O‐box‐like motif (CCGGCC). ZmEREB57 directly binds to the promoter of ZmAOC2 involved in the synthesis of 12‐oxo‐phytodienoic acid (OPDA) and jasmonic acid (JA). Transcriptome analysis revealed that several genes involved in regulating stress and redox homeostasis showed differential expression patterns in OPDA‐ and JA‐treated maize seedlings exposed to salt stress compared to those treated with salt stress alone. Analysis of mutants deficient in the biosynthesis of OPDA and JA revealed that OPDA functions as a signalling molecule in the salt response. Our results indicate that ZmEREB57 involves in salt tolerance by regulating OPDA and JA signalling and confirm early observations that OPDA signalling functions independently of JA signalling. SUMMARY STATEMENT: As an important cereal crop worldwide, however, the yield and quality of maize are severely affected by salt stress. This study identified that ZmEREB57, a AP2/ERF transcription factor, contributes to salt tolerance in maize. The ZmEREB57‐mediated salt stress response can be achieved by binding to the ZmAOC2 promoter, which is a positive regulator of OPDA biosynthesis. Although as being a precursor for JA synthesis, OPDA functions independently of JA as a signalling molecule in the salt response. [ABSTRACT FROM AUTHOR]

Summary: Crop loss due to soil salinization is a global threat to agriculture. Nitric oxide (NO) and ethylene involve in multiple plant tolerance. However, their interaction in salt resistance remains largely elusive.We tested the mutual induction between NO and ethylene, and then identified an 1‐aminocyclopropane‐1‐carboxylate oxidase homolog 4 (ACOh4) that influences ethylene synthesis and salt tolerance through NO‐mediated S‐nitrosylation.Both NO and ethylene positively responded to salt stress. Furthermore, NO participated in salt‐induced ethylene production. Salt tolerance evaluation showed that function of NO was abolished by inhibiting ethylene production. Conversely, function of ethylene was little influenced by blocking NO generation. ACO was identified as the target of NO to control ethylene synthesis. In vitro and in vivo results suggested that ACOh4 was S‐nitrosylated at Cys172, resulting in its enzymatic activation. Moreover, ACOh4 was induced by NO through transcriptional manner. Knockdown of ACOh4 abolished NO‐induced ethylene production and salt tolerance. At physiological status, ACOh4 positively regulates the Na+ and H+ efflux, and keeps K+/Na+ homeostasis by promoting salt‐resistive genes' transcripts.Our findings validate a role of NO‐ethylene module in salt tolerance and uncover a novel mechanism of how NO promoting ethylene synthesis against adversity. [ABSTRACT FROM AUTHOR]

Eukaryotic genomes are pervasively transcribed by RNA polymerase II. Yet, the molecular and biological implications of such a phenomenon are still largely puzzling. Here, we describe noncoding RNA transcription upstream of the Arabidopsis thaliana DOG1 gene, which governs salt stress responses and is a key regulator of seed dormancy. We find that expression of the DOG1 gene is induced by salt stress, thereby causing a delay in seed germination. We uncover extensive transcriptional activity on the promoter of the DOG1 gene, which produces a variety of lncRNAs. These lncRNAs, named PUPPIES, are co‐directionally transcribed and extend into the DOG1 coding region. We show that PUPPIES RNAs respond to salt stress and boost DOG1 expression, resulting in delayed germination. This positive role of pervasive PUPPIES transcription on DOG1 gene expression is associated with augmented pausing of RNA polymerase II, slower transcription and higher transcriptional burst size. These findings highlight the positive role of upstream co‐directional transcription in controlling transcriptional dynamics of downstream genes. Synopsis: DOG1 is a key regulator of plant seed dormancy, whose expression is regulated by multiple mechanisms. Here, salt stress is found to induce pervasive lncRNA transcription within the DOG1 promoter region, resulting in augmented RNA Polymerase II pausing, slower transcription and increased DOG1 expression. The DOG1 gene restricts seed germination under salt stress independently of its function in primary dormancy.The DOG1 promoter region gives rise to salt stress‐responsive PUPPIES lncRNAs, which regulate DOG1 expression in cis to delay germination.Co‐directional pervasive transcription of PUPPIES activates DOG1 expression through augmented RNA polymerase II pausing and enhanced transcriptional bursting.The identified regulatory mechanism involves an increase of RNA molecules produced per DOG1 transcriptional burst, augmented pausing and slower transcription. [ABSTRACT FROM AUTHOR]

Summary: Legumes form a symbiotic association with rhizobia and fix atmospheric nitrogen in specialized root organs known as nodules. It is well known that salt stress inhibits root nodule symbiosis by decreasing rhizobial growth, rhizobial infection, nodule number, and nitrogenase activity in diverse legumes. Despite this knowledge, the genetic and molecular mechanisms governing salt stress's inhibition of nodulation and nitrogen fixation are still elusive. In this Viewpoint, we summarize the most recent knowledge of the genetic mechanisms that shape this symbiosis according to the salt levels in the soil. We emphasize the relevance of modulating the activity of the transcription factor Nodule Inception to properly shape the symbiosis with rhizobia accordingly. We also highlight the knowledge gaps that are critical for gaining a deeper understanding of the molecular mechanisms underlying the adaptation of the root nodule symbiosis to salt‐stress conditions. We consider that filling these gaps can help to improve legume nodulation and harness its ecological benefits even under salt‐stress conditions. [ABSTRACT FROM AUTHOR]

Wheat plants are ubiquitously simultaneously exposed to salinity and limited iron availability caused by soil saline‐alkalisation. Through this study, we found that both low Fe and NaCl severely inhibited the growth of seminal roots in wheat seedlings; however, sufficient Fe caused greater growth cessation of seminal roots than low Fe under salt stress. Low Fe improved the root meristematic division activity, not altering the mature cell sizes compared with sufficient Fe under salt stress. Foliar Fe spray and split‐root experiments showed that low Fe‐alleviating the salinity‐induced growth cessation of seminal roots was dependent on local low Fe signals in the roots. Ionomics combined with TEM/X‐ray few differences in the root Na+ uptake and vacuolar Na+ sequestration between two Fe levels under salt stress. Phytohormone profiling and metabolomics revealed salinity‐induced overaccumulation of ACC/ethylene and tryptophan/auxin in the roots under sufficient Fe than under low Fe. Differential gene expression, pharmacological inhibitor addition and the root growth performance of transgenic wheat plants revealed that the rootward auxin efflux and was responsible for the low Fe‐mediated amelioration of the salinity‐induced growth cessation of seminal roots. Our findings will provide novel insights into the modulation of crop root growth under salt stress. Summary statement: We found that low Fe ameliorated the salinity‐induced growth cessation of wheat seminal roots, and our findings will provide novel insights into the understanding of Fe involved nutrient interactions and the modulation of crop root growth under salt stress. [ABSTRACT FROM AUTHOR]

Integration of light signaling and diverse abiotic stress responses contribute to plant survival in a changing environment. Some reports have indicated that light signals contribute a plant's ability to deal with heat, cold, and stress. However, the molecular link between light signaling and the salt‐response pathways remains unclear. We demonstrate here that increasing light intensity elevates the salt stress tolerance of plants. Depletion of HY5, a key component of light signaling, causes Arabidopsis thaliana to become salinity sensitive. Interestingly, the small heat shock protein (sHsp) family genes are upregulated in hy5‐215 mutant plants, and HsfA2 is commonly involved in the regulation of these sHsps. We found that HY5 directly binds to the G‐box motifs in the HsfA2 promoter, with the cooperation of HISTONE DEACETYLASE 9 (HDA9), to repress its expression. Furthermore, the accumulation of HDA9 and the interaction between HY5 and HDA9 are significantly enhanced by salt stress. On the contrary, high temperature triggers HY5 and HDA9 degradation, which leads to dissociation of HY5‐HDA9 from the HsfA2 promoter, thereby reducing salt tolerance. Under salt and heat stress conditions, fine tuning of protein accumulation and an interaction between HY5 and HDA9 regulate HsfA2 expression. This implies that HY5, HDA9, and HsfA2 play important roles in the integration of light signaling with salt stress and heat shock response. [ABSTRACT FROM AUTHOR]

Christoph-Martin holds a doctoral degree and a Habilitation in Plant Nutrition and was a postdoctoral fellow at Hohenheim University (Germany, 2016) and at the University of Kiel (Germany, 2011-2014). Keywords: chlorine; drought; guard cells; magnesium; plant nutrition; salt stress EN chlorine drought guard cells magnesium plant nutrition salt stress 1998 1999 2 02/07/22 20220301 NES 220301 What inspired your interest in plant science? Chlorine, drought, guard cells, magnesium, salt stress, plant nutrition. [Extracted from the article]

SUMMARY: Soil salinity is a significant threat to global agriculture. Understanding salt exclusion mechanisms in halophyte species may be instrumental in improving salt tolerance in crops. Puccinellia tenuiflora is a typical salt‐excluding halophytic grass often found in potassium‐deprived saline soils. Our previous work showed that P. tenuiflora possesses stronger selectivity for K+ than for Na+; however, the mechanistic basis of this phenomenon remained elusive. Here, P. tenuiflora PutHKT1;5 was cloned and the functions of PutHKT1;5 and PutSOS1 were characterized using heterologous expression systems. Yeast assays showed that PutHKT1;5 possessed Na+ transporting capacity and was highly selective for Na+ over K+. PutSOS1 was located at the plasma membrane and operated as a Na+/K+ exchanger, with much stronger Na+ extrusion capacity than its homolog from Arabidopsis. PutHKT2;1 mediated high‐affinity K+ and Na+ uptake and its expression levels were upregulated by mild salinity and K+ deprivation. Salinity‐induced changes of root PutHKT1;5 and PutHKT1;4 transcript levels matched the expression pattern of root PutSOS1, which was consistent with root Na+ efflux. The transcript levels of root PutHKT2;1 and PutAKT1 were downregulated by salinity. Taken together, these findings demonstrate that the functional activity of PutHKT1;5 and PutSOS1 in P. tenuiflora roots is fine‐tuned under saline conditions as well as by operation of other ion transporters/channel (PutHKT1;4, PutHKT2;1, and PutAKT1). This leads to the coordination of radial Na+ and K+ transport processes, their loading to the xylem, or Na+ retrieval and extrusion under conditions of mild salinity and/or K+ deprivation. Significance Statement: P. tenuiflora is considered an important model halophyte due to its strong salt tolerance and close genetic relationship with cereals. Here, We aimed to elucidate the coordinated physiological and molecular mechanism for P. tenuiflora adapt to severe salinity and K+ starvation conditions. [ABSTRACT FROM AUTHOR]

Complex bacterial communities in the rhizosphere play a crucial role in plant growth and stress tolerance. These communities vary across cultivars and external environments. However, the influences of salt stress on the structural composition of bacterial microbiome and gene expression of salt‐sensitive and salt‐tolerant sweet sorghum (Sorghum bicolor L. Moench) cultivars have not been studied sufficiently. Here, we employed a combination of 16S rRNA gene profiling and RNA‐seq analysis to characterize changes in root‐associated microbiomes and determine differentially expressed genes (DEG) in the roots of salt‐tolerant M‐81E and salt‐sensitive 'Roma' var. sweet sorghum cultivars under soil conditions with/without salinity. Results revealed that the two contrasting sweet sorghum genotypes selectively filtered and recruited distinct root microbiota in response to salt stress. M‐81E‐enriched bacterial taxa were more diverse and exhibited a higher abundance of metabolic functions than Roma‐enriched taxa. M‐81E‐associated bacterial co‐occurrence networks were more complex and harboured more positive links than Roma‐associated bacterial networks. Furthermore, nine DEG were identified as core salt‐responsive genes and were central to the salt tolerance of sweet sorghum. Correlation analysis revealed that the expression of HSP70, a molecular chaperone, is linked to the recruitment of numerous M‐81E‐enriched bacteria; their relationship needs further exploration. The study supplements the comprehension of the potential role of host–microbe interactions in the response of sweet sorghum to salt stress. [ABSTRACT FROM AUTHOR]

The growth and development of maize is affected in a crucial way by the salinity of the soil it grows in. Therefore, if we want to improve the salt tolerance of maize, it is of paramount importance to understand how it responds to salt stress. To explore how maize adapts to a saline environment, we chose one salt-tolerant maize variety, Jingnongyu 658 (JNY658), and one salt-sensitive variety, Yunyu7 (YY7), and treated the seedlings of both varieties with a 100 mM NaCl solution. After harvesting them, we analysed the adaptive responses to salt stress with respect to various characteristics of the root architecture and water and nutrient acquisition. We found that when subjected to salt stress, both varieties exhibited a reduction in biomass, root activity, 15N and H2O uptake amount, lateral root branching density, lateral root length, total root length, root surface area and root volume, where the YY7 suffered a greater reduction than the JNY658. Salt stress also induced a decreased absorption of K+, passively promoted the absorption of Na18 and gave rise to an increased Na+/K+ ratio in the roots of both varieties. It should be noted that JNY658 exposed to salt stress developed a lower Na+ and gave rise to an increased Na+/K+ ratio in the roots of both varieties. It should be noted that JNY658 exposed to salt stress developed a lower Na+ ratio than YY7. Compared with the control group, the expression of ZmSOS1, ZmSOS2 and ZmNHX genes in the roots of JNY658 subjected to salt stress was significantly upregulated, which enabled them to maintain a lower Na+ ratio than YY7. Compared with the control group, the expression of ZmSOS1, ZmSOS2 and ZmNHX genes in the roots of JNY658 subjected to salt stress was significantly upregulated, which enabled them to maintain a lower Na+ content. In both varieties, the salicylic acid (SA) and gibberellin19) content increased significantly, but the auxin (IAA), jasmonic acid (JA) and trans-zeatin (TZ) content was reduced. In addition, JNY658 in salt stress significantly increased their abscisic acid (ABA) content, due to the increased expression of its key biosynthesis genes, NCED. Compared with JNY658, the reductions in IAA, JA and TZ content in YY7 were greater, while the increases in ABA and SA content were smaller. The varieties in the ABA, JA, SA and IAA of roots subjected to salt stress significantly or extremely significantly correlated with the lateral root branching density, lateral root length, root surface area, Na19) content increased significantly, but the auxin (IAA), jasmonic acid (JA) and trans-zeatin (TZ) content was reduced. In addition, JNY658 in salt stress significantly increased their abscisic acid (ABA) content, due to the increased expression of its key biosynthesis genes, NCED. Compared with JNY658, the reductions in IAA, JA and TZ content in YY7 were greater, while the increases in ABA and SA content were smaller. The varieties in the ABA, JA, SA and IAA of roots subjected to salt stress significantly or extremely significantly correlated with the lateral root branching density, lateral root length, root surface area, Na+ content, K+ content and Na+/K+ ratio. We conclude that the salt-tolerant maize variety mitigated the toxic effect of salinity on maize root growth and development by regulating the hormone content and enhancing its expression of stress-responsive genes while maintaining ion homeostasis and promoting water and nutrient acquisition, which ultimately resulted in a less pronounced decrease in plant biomass. [ABSTRACT FROM AUTHOR]

SUMMARY: Polyploidy provides an opportunity for evolutionary innovation and species diversification, especially under stressful conditions. In allopolyploids, the conditional dynamics of homoeologous gene expression can be either inherited from ancestral states pre‐existing in the parental diploids or novel upon polyploidization, the latter potentially permitting a wider range of phenotypic responses to stresses. To gain insight into regulatory mechanisms underlying the diversity of salt resistance in Gossypium species, we compared global transcriptomic responses to modest salinity stress in two allotetraploid (AD‐genome) cotton species, Gossypium hirsutum and G. mustelinum, relative to their model diploid progenitors (A‐genome and D‐genome). Multivariate and pairwise analyses of salt‐responsive changes revealed a profound alteration of gene expression for about one third of the transcriptome. Transcriptional responses and associated functional implications of salt acclimation varied across species, as did species‐specific coexpression modules among species and ploidy levels. Salt responsiveness in both allopolyploids was strongly biased toward the D‐genome progenitor. A much lower level of transgressive downregulation was observed in the more salt‐tolerant G. mustelinum than in the less tolerant G. hirsutum. By disentangling inherited effects from evolved responses, we show that expression biases that are not conditional upon salt stress approximately equally reflect parental legacy and regulatory novelty upon allopolyploidization, whereas stress‐responsive biases are predominantly novel, or evolved, in allopolyploids. Overall, our work suggests that allopolyploid cottons acquired a wide range of stress response flexibility relative to their diploid ancestors, most likely mediated by complex suites of duplicated genes and regulatory factors. Significance Statement: Investigating the salt response of cotton is needed to provide insight into breeding‐improved salt‐tolerant cottons and for better understanding long‐standing questions regarding how polyploids differ from their diploid progenitors with respect to abiotic stresses. We found that salt responses in allopolyploid cottons were evolved following polyploidy rather than being inherited from diploids. This novelty might reflect the complex interactions of homoeologous regulatory factors with their duplicated target genes in allopolyploids. [ABSTRACT FROM AUTHOR]

The intensification of global soil salinization has seriously decreased crop yield. At the same time, the rapid increase in population has raised the demand for crop yields. Reasonable use of saline‐alkali land and cultivation of salt‐tolerant crops through transgenic technology becomes more important. Sweet sorghum [Sorghum bicolor (L.)], as an important energy crop, resists abiotic stress effectively. In our previous salt tolerance gene‐screening experiment of sweet sorghum, it was found that applying calcium ions could alleviate salt stress of sweet sorghum to some extent. Therefore, 10 and 20 mM CaCl2 were applied to explore the effect of exogenous calcium application on salt stress. Compared with the sweet sorghum treated by salt stress, the dry and fresh weight of the plants were significantly increased, and the content of malondialdehyde (MDA) was decreased after applying calcium ions. At the same time, diaminobenzidine and nitro blue tetrazolium chloride monohydrate staining results showed that the contents of H2O2 and O2−• in the plants after calcium application were lower than those only treated with salt stress. To investigate the regulation mechanism of exogenous calcium application alleviating salt stress, RNA‐seq analysis was performed using libraries established in Roma roots under normal and NaCl treatment. Combined with Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes analysis, we found that calcium‐related genes were more involved in the oxidation‐reduction process and carbohydrate metabolism pathway. Among all differentially expressed genes, 12 known functional genes were further explored based on functional annotations and existing studies. To detect whether these 12 genes are related to salt response, we treated the Arabidopsis mutants of their homologous genes with 150 mM NaCl for 7 days. Among them, atglr3.5, atgad4, atiqm4, atglr2.8 and annat7 showed worse growth, lower survival rate and higher MDA content than WT under salt stress. This indicates that applying exogenous calcium can affect the expression of SbGR3.4, SbGADX1, SbIQM4, SbGR2.8 and SbAnnD7, which can regulate the expression of genes related to the lignin degradation, absorption of NH4+, and ubiquitination‐proteasome pathway, energy metabolism and cleaning of ROS accumulation in sweet sorghum under salt stress, so as to enhance the salt tolerance of plants. [ABSTRACT FROM AUTHOR]

SUMMARY: Phosphoenolpyruvate carboxylase (PEPC) is a carboxylating enzyme with important roles in plant metabolism. Most studies in C4 plants have focused on photosynthetic PEPC, but less is known about non‐photosynthetic PEPC isozymes, especially with respect to their physiological functions. In this work, we analyzed the precise roles of the sorghum (Sorghum bicolor) PPC3 isozyme by the use of knock‐down lines with the SbPPC3 gene silenced (Ppc3 lines). Ppc3 plants showed reduced stomatal conductance and plant size, a delay in flowering time, and reduced seed production. In addition, silenced plants accumulated stress indicators such as Asn, citrate, malate, and sucrose in roots and showed higher citrate synthase activity, even in control conditions. Salinity further affected stomatal conductance and yield and had a deeper impact on central metabolism in silenced plants compared to wild type, more notably in roots, with Ppc3 plants showing higher nitrate reductase and NADH‐glutamate synthase activity in roots and the accumulation of molecules with a higher N/C ratio. Taken together, our results show that although SbPPC3 is predominantly a root protein, its absence causes deep changes in plant physiology and metabolism in roots and leaves, negatively affecting maximal stomatal opening, growth, productivity, and stress responses in sorghum plants. The consequences of SbPPC3 silencing suggest that this protein, and maybe orthologs in other plants, could be an important target to improve plant growth, productivity, and resistance to salt stress and other stresses where non‐photosynthetic PEPCs may be implicated. Significance Statement: Knock‐down of a non‐photosynthetic phosphoenolpyruvate carboxylase gene affects plant growth and productivity and increases sensitivity to salt stress. [ABSTRACT FROM AUTHOR]

Background and aims: Determination of sodium (Na), potassium (K), and chloride (Cl) content in plant tissue is required for research related to salinity resistance in plants. Standard methods are available to extract these elements from dried plant material, but these methods are often costly, relatively dangerous, or time consuming. Many authors modify extraction methods substantially without proof of comparability across methods. Methods: Here, dried tissues of two varieties of rice and three varieties of sweet potato subjected to salt stress were extracted for Na and K using six different extraction methods (1–6) and for Cl using three Cl‐free extraction methods (2, 4, 5) for Cl: (1) the VDLUFA standard method, consisting of ashing, and heat extraction in hydrochloric acid (HCl), (2) hot water pressure extraction via autoclave, (3) extraction with 1 M HCl overnight, (4) hot water extraction at 90°C for 1 h, (5) acetic acid extraction in hot 1 M acetic acid for 2 h, and (6) extraction with a microwave using nitric acid. Na and K were determined via flame photometer and Cl via automated flow analysis. Results: Na and K concentrations varied little among different extraction methods as compared to the VDLUFA standard method, and for Cl, all extractions resulted in similar tissue Cl concentrations. Conclusions: Ultimately, the choice of extraction method depends on the instrumentation and lab equipment necessary, available budget, the available amount of sample, and time constraints which should be decided according to the experiment. For reasons of comparability among publications, methods applied should be clearly described since results vary depending on the method chosen. [ABSTRACT FROM AUTHOR]

High salt concentrations can restrict or inhibit microorganism activity, which can detrimentally influence pollutant degradation. In this study, intertidal wetland sediments (IWS) are introduced into constructed wetlands (CWs) as sources of microorganisms. The richness and evenness of bacterial and archaeal microbial communities in the presence of 150 × 10−3m NaCl are evaluated by high‐throughput sequencing. The distinction of dominant functional microorganisms in CWs with and without IWS is also analyzed. Anaerolineales and thermomicrobia are the dominant microorganisms in IWS–CWs in the saline condition and are related to methane production. The abundance of Alphaproteobacteria, Myxococcales, and Xanthomonadales, related to dehydrogenation, is relatively high in IWS–CWs. The addition of IWS induces further production of Anaerolineaceae and Geobacteraceae, which is positively correlated with the phosphorus‐accumulating and sulfate‐reducing stages. The dominant archaea phyla in IWS–CWs in the saline condition are Thaumarchaeota (87.5%) and Euryarchaeota (12.2%), which are involved in ammonia‐oxidizing and methane‐producing processes, respectively. These functional microbial communities are beneficial to the degradation and transformation of pollutants in the CWs. Thus, IWS with various halophilic and pollutant‐degrading microorganisms can be considered effective microbial sources to enhance the pollutant removal abilities of CWs. [ABSTRACT FROM AUTHOR]

SUMMARY: Plants that have experienced certain abiotic stress may gain tolerance to a similar stress in subsequent exposure. This phenomenon, called priming, was observed here in soybean (Glycine max) seedlings exposed to salt stress. Time‐course transcriptomic profiles revealed distinctively different transcriptional responses in the primed seedlings from those in the non‐primed seedlings under high salinity stress, indicating a stress response strategy of repressing unhelpful biotic stress responses and focusing on the promotion of those responses important for salt tolerance. To identify histone marks altered by the priming salinity treatment, a genome‐wide profiling of histone 3 lysine 4 dimethylation (H3K4me2), H3K4me3, and histone 3 lysine 9 acetylation (H3K9ac) was performed. Our integrative analyses revealed that priming induced drastic alterations in these histone marks, which coordinately modified the stress response, ion homeostasis, and cell wall modification. Furthermore, transcriptional network analyses unveiled epigenetically modified networks which mediate the strategic downregulation of defense responses. Altering the histone acetylation status using a chemical inhibitor could elicit the priming‐like transcriptional responses in non‐primed seedlings, confirming the importance of histone marks in forming the priming response. Significance Statement: Understanding how plants adapt to stress conditions is important for developing strategies for crop improvement. In this study, a mild salt treatment of soybean (Glycine max) seedlings primed them for a more effective response against subsequent high salinity stress, by altering the genome‐wide distribution of histone marks to upregulate osmotic stress response genes and downregulate those for defense responses. [ABSTRACT FROM AUTHOR]

Summary: Cell wall polysaccharide biosynthesis enzymes play important roles in plant growth, development and stress responses. The functions of cell wall polysaccharide synthesis enzymes in plant growth and development have been well studied. In contrast, their roles in plant responses to environmental stress are poorly understood. Previous studies have demonstrated that the rice cell wall cellulose synthase‐like D4 protein (OsCSLD4) is involved in cell wall polysaccharide synthesis and is important for rice growth and development. This study demonstrated that the OsCSLD4 function‐disrupted mutant nd1 was sensitive to salt stress, but insensitive to abscisic acid (ABA). The expression of some ABA synthesis and response genes was repressed in nd1 under both normal and salt stress conditions. Exogenous ABA can restore nd1‐impaired salt stress tolerance. Moreover, overexpression of OsCSLD4 can enhance rice ABA synthesis gene expression, increase ABA content and improve rice salt tolerance, thus implying that OsCSLD4‐regulated rice salt stress tolerance is mediated by ABA synthesis. Additionally, nd1 decreased rice tolerance to osmotic stress, but not ion toxic tolerance. The results from the transcriptome analysis showed that more osmotic stress‐responsive genes were impaired in nd1 than salt stress‐responsive genes, thus indicating that OsCSLD4 is involved in rice salt stress response through an ABA‐induced osmotic response pathway. Intriguingly, the disruption of OsCSLD4 function decreased grain width and weight, while overexpression of OsCSLD4 increased grain width and weight. Taken together, this study demonstrates a novel plant salt stress adaptation mechanism by which crops can coordinate salt stress tolerance and yield. [ABSTRACT FROM AUTHOR]

Summary: Drought and salt stresses impose major constraints on soybean production worldwide. However, improving agronomically valuable soybean traits under drought conditions can be challenging due to trait complexity and multiple factors that influence yield. Here, we identified a nuclear factor Y C subunit (NF‐YC) family transcription factor member, GmNF‐YC14, which formed a heterotrimer with GmNF‐YA16 and GmNF‐YB2 to activate the GmPYR1‐mediated abscisic acid (ABA) signalling pathway to regulate stress tolerance in soybean. Notably, we found that CRISPR/Cas9‐generated GmNF‐YC14 knockout mutants were more sensitive to drought than wild‐type soybean plants. Furthermore, field trials showed that overexpression of GmNF‐YC14 or GmPYR1 could increase yield per plant, grain plumpness, and stem base circumference, thus indicating improved adaptation of soybean plants to drought conditions. Taken together, our findings expand the known functional scope of the NF‐Y transcription factor functions and raise important questions about the integration of ABA signalling pathways in plants. Moreover, GmNF‐YC14 and GmPYR1 have potential for application in the improvement of drought tolerance in soybean plants. [ABSTRACT FROM AUTHOR]

Soybean is an important crop worldwide, but its production is severely affected by salt stress. Understanding the regulatory mechanism of salt response is crucial for improving the salt tolerance of soybean. Here, we reveal a role for nuclear factor Y subunit GmNFYA in salt tolerance of soybean likely through the regulation of histone acetylation. GmNFYA is induced by salt stress. Overexpression of GmNFYA significantly enhances salt tolerance in stable transgenic soybean plants by inducing salt‐responsive genes. Analysis in soybean plants with transgenic hairy roots also supports the conclusion. GmNFYA interacts with GmFVE, which functions with putative histone deacetylase GmHDA13 in a complex for transcriptional repression possibly by reducing H3K9 acetylation at target loci. Under salt stress, GmNFYA likely accumulates and competes with GmHDA13 for interaction with GmFVE, leading to the derepression and maintenance of histone acetylation for activation of salt‐responsive genes and finally conferring salt tolerance in soybean plants. In addition, a haplotype I GmNFYA promoter is identified with the highest self‐activated promoter activity and may be selected during future breeding for salt‐tolerant cultivars. Our study uncovers the epigenetic regulatory mechanism of GmNFYA in salt‐stress response, and all the factors/elements identified may be potential targets for genetic manipulation of salt tolerance in soybean and other crops. [ABSTRACT FROM AUTHOR]

Cytokinins are phytohormones that regulate plant development, growth, and responses to stress. In particular, cytokinin has been reported to negatively regulate plant adaptation to high salinity; however, the molecular mechanisms that counteract cytokinin signaling and enable salt tolerance are not fully understood. Here, we provide evidence that salt stress induces the degradation of the cytokinin signaling components Arabidopsis (Arabidopisis thaliana) response regulator 1 (ARR1), ARR10 and ARR12. Furthermore, the stress‐activated mitogen‐activated protein kinase 3 (MPK3) and MPK6 interact with and phosphorylate ARR1/10/12 to promote their degradation in response to salt stress. As expected, salt tolerance is decreased in the mpk3/6 double mutant, but enhanced upon ectopic MPK3/MPK6 activation in an MKK5DD line. Importantly, salt hypersensitivity phenotypes of the mpk3/6 line were significantly alleviated by mutation of ARR1/12. The above results indicate that MPK3/6 enhance salt tolerance in part via their negative regulation of ARR1/10/12 protein stability. Thus, our work reveals a new molecular mechanism underlying salt‐induced stress adaptation and the inhibition of plant growth, via enhanced degradation of cytokinin signaling components. Synopsis: MKK5‐MPK3/6 signaling positively regulates salt tolerance in Arabidopsis, via phosphorylation and degradation of cytokinin signaling components ARR1/10/12. Salinity stress results in MPK3/6‐mediated phosphorylation and degradation of ARR1/10/12 proteins.MPK3/6 act upstream of ARR1/10/12 to promote the plant's adaption to high‐salinity.MPK3/6 are not involved in the regulation of cytokinin signaling under normal growth conditions. [ABSTRACT FROM AUTHOR]