Halophyte Research Articles

Identification of NAC Transcription Factors in Suaeda glauca and Their Responses to Salt Stress.

NAC (NAM/ATAF1/2/CUC2) transcription factors regulate plant growth and development and stress responses. Because NAC transcription factors are known to play important roles in the regulation of salt tolerance in many plants, we aimed to explore their roles in the halophyte Suaeda glauca. Based on transcriptome sequencing data, we identified 25 NAC transcription factor gene family members. In a phylogenetic tree analysis with Arabidopsis thaliana NAC transcription factors, the SgNACs were divided into 10 groups. The physicochemical properties and conserved domains of the putative proteins, as well as the transcript profiles of their encoding genes, were determined for the 25 SgNAC genes using bioinformatic methods. Most of the S. glauca NAC genes were upregulated to some extent after 24 h of salt stress, suggesting that they play an important role in regulating the salt tolerance of S. glauca. These findings lay the foundation for further research on the functions and mechanisms of the NAC gene family in S. glauca.

Isolation of the Endophytic Fungus Aspergillus terreus from a Halophyte (Tetraena qatarensis) and Assessment of Its Potential in Tomato Seedling Protection.

Living in diverse environmentally harsh conditions, the plant exhibits a unique survival mechanism. As a result, the endophytes residing within the plant produce specific compounds that promote the plant's growth and defend it against pathogens. Plants and algae symbiotically harbor endophytes, i.e., microbes and microorganisms living within them. The objective of this study is to isolate endophytic fungi, specifically strains of Aspergillus terreus, from the leaves of the salt-tolerant plant Tetraena qatarensis and to explore the salt tolerance, antagonistic activity, and growth promotion properties. Strain C A. terreus (ON117337.1) was screened for salt tolerance and antagonistic effects. Regarding salt tolerance, the isolate demonstrated the ability to thrive in a concentration of up to 10% NaCl. A. terreus showed inhibitory activity against four fungal phytopathogens, namely Fusarium oxysporum, Alternaria alternata, Colletotrichum gloeosporioides, and Botrytis cinerea. The GC-MS investigation of the fungal (strain C Aspergillus terreus) extract showed the presence of about 66 compounds (secondary metabolites). Secondary metabolites (SMs) are produced, like Hexadecanoic acid, which aids in controlling phytopathogens. Also produced is lovastatin, which is used to treat hypercholesterolemia. Strain C, which showed salinity tolerance and the highest inhibitory activity, was further analyzed for its effect on tomato seed germination under pathogen stress from Fusarium oxysporum. The greenhouse experiment indicated that the fungi increased the length of tomato seedlings and the plant biomass. Therefore, the selected endophytes derived from Tetraena qatarensis were scrutinized for their potential as biocontrol agents, aiming to thwart fungal pathogens and stimulate plant growth. The in vitro and in vivo assessments of strain C (Aspergillus terreus) against Fusarium oxysporum in this investigation indicate the promising role of endophytes as effective biological control agents. Investigating novel bio-products offers a sustainable approach to agriculture, gradually reducing dependence on chemical fungicides.

Genome-Wide Identification of Caffeic Acid O-Methyltransferase Gene Family in Medicago truncatula: MtCOMT13-Mediated Salt and Drought Tolerance Enhancement

Legumes are important grains and forages, providing high-quality proteins, vitamins, and micronutrients to humans and animals. Medicago truncatula is a close relative of alfalfa (Medicago sativa). Caffeic acid O-methyltransferase (COMT), a key gene that is identified to be essential for melatonin synthesis, plays a significant role in plant growth, development, and abiotic stress responses. However, a systematic study on the COMT gene family in M. truncatula has still not been reported. In this study, 63 MtCOMT genes were identified and categorized into three groups. Gene structure and conserved motif analyses revealed the relative conservation of closely clustered MtCOMTs within each group. Duplicated events in MtCOMT members were identified, and segmental duplication was the main mean. Cis-acting element prediction revealed the involvement of MtCOMTs in growth and development and response to light, stress, and plant hormones. RNA-seq data analysis showed that 57 MtCOMTs varied under salt and drought stresses. The RT-qPCR expression patterns showed that MtCOMT9, MtCOMT13, MtCOMT22, MtCOMT24, MtCOMT43, and MtCOMT46 were related to salt and drought responses in M. truncatula. Additionally, Arabidopsis thaliana overexpressing MtCOMT13 displayed superior plant growth phenotypes and enhanced tolerance to salt and drought stresses through higher photosynthetic parameters and activities of antioxidant enzymes, which indicated that MtCOMT13 played an important role in positively regulating plant salt and drought tolerance. These findings contribute to an improved understanding of MtCOMTs’ roles in abiotic stress responses in M. truncatula, providing an important theoretical basis and genetic resource for legume species resistance breeding in the future.

Bacterial Communities Associated with the Leaves and the Roots of Salt Marsh Plants of Bayfront Beach, Mobile, Alabama, USA.

Salt marshes are highly dynamic and biologically diverse ecosystems that serve as natural habitats for numerous salt-tolerant plants (halophytes). We investigated the bacterial communities associated with the roots and leaves of plants growing in the coastal salt marshes of the Bayfront Beach, located in Mobile, Alabama, United States. We compared external (epiphytic) and internal (endophytic) communities of both leaf and root plant organs. Using 16S rDNA amplicon sequencing methods, we identified 10 bacterial phyla and 59 different amplicon sequence variants (ASVs) at the genus level. Bacterial strains belonging to the phyla Proteobacteria, Bacteroidetes, and Firmicutes were highly abundant in both leaf and root samples. At the genus level, sequences of the genus Pseudomonas were common across all four sample types, with the highest abundance found in the leaf endophytic community. Additionally, Pantoea was found to be dominant in leaf tissue compared to roots. Our study revealed that plant habitat (internal vs. external for leaves and roots) was a determinant of the bacterial community structure. Co-occurrence network analyses enabled us to discern the intricate characteristics of bacterial taxa. Our network analysis revealed varied levels of ASV complexity in the epiphytic networks of roots and leaves compared to the endophytic networks. Overall, this study advances our understanding of the intricate composition of the bacterial microbiota in habitats (epiphytic and endophytic) and organs (leaf and root) of coastal salt marsh plants and suggests that plants might recruit habitat- and organ-specific bacteria to enhance their tolerance to salt stress.

The Arabidopsis thaliana ecotype Ct-1 achieves higher salt tolerance relative to Col-0 via higher tissue retention of K+ and NO3-

Agriculture is vital for global food security, and irrigation is essential for improving crop yields. However, irrigation can pose challenges such as mineral scarcity and salt accumulation in the soil, which negatively impact plant growth and crop productivity. While numerous studies have focused on enhancing plant tolerance to high salinity, research targeting various ecotypes of Arabidopsis thaliana has been relatively limited. In this study, we aimed to identify salt-tolerant ecotypes among the diverse wild types of Arabidopsis thaliana and elucidate their characteristics at the molecular level. As a result, we found that Catania-1 (Ct-1), one of the ecotypes of Arabidopsis, exhibits greater salt tolerance compared to Col-0. Specifically, Ct-1 exhibited less damage from reactive oxygen species (ROS) than Col-0, despite not accumulating antioxidants like anthocyanins. Additionally, Ct-1 accumulated more potassium ions (K+) in its shoots and roots than Col-0 under high salinity, which is crucial for water balance and preventing dehydration. In contrast, Ct-1 plants were observed to accumulate slightly lower levels of Na+ than Col-0 in both root and shoot tissues, regardless of salt treatment. These findings suggest that Ct-1 plants achieve high salinity resistance not by extruding more Na+ than Col-0, but rather by absorbing more K+ or releasing less K+. Ct-1 exhibited higher nitrate (NO3-) levels than Col-0 under high salinity conditions, which is associated with enhanced retention of K+ ions. Additionally, genes involved in NO3- transport and uptake, such as NRT1.5 and NPF2.3, showed higher transcript levels in Ct-1 compared to Col-0 when exposed to high salinity. However, Ct-1 did not demonstrate significantly greater resistance to osmotic stress compared to Col-0. These findings suggest that enhancing plant tolerance to salt stress could involve targeting the cellular processes responsible for regulating the transport of NO3- and K+. Overall, our study sheds light on the mechanisms of plant salinity tolerance, emphasizing the importance of K+ and NO3- transport in crop improvement and food security in regions facing salinity stress.

Large-scale assessment of characteristic plant species on Eurasian saline and alkaline soda ecosystems

From an ecological standpoint, saline and alkaline habitats are considered as extreme environments for vascular plants because salinity and alkalinity serve as primary structuring factors that significantly influence the species richness of vegetation cover. The non-alkaline salinity stress on plants primarily results from interactions of NaCl, Na2SO4, and other neutral salts, whereas alkalinity stress is caused by NaHCO3 and Na2CO3, accompanied by an increase in pH. Some halophytes and salt-tolerant plants are well-adapted to such permanent abiotic stress. Surprisingly, they are able to survive and reproduce under environmental conditions of more than 200 mM NaCl concentration and are also able to live permanently in extreme conditions. The aim of this study was to identify characteristic and indicator plant species for permanently alkaline soda and non-alkaline saline wetland habitats, and to analyze the relationship between the chemical composition of water and the plant’s saturation index. Based on the obtained results we can conclude that plant species identified to live in high saline conditions may also grow under high alkaline conditions. Two groups were distinguished based on the salinity and alkalinity: “Saline group” includes all types of halophytes and halotolerant species, while “Soda group” includes obligate alkalophytes and alkalotolerant species. However, the diversity of plants in alkaline environment is bigger than in saline environment, and most of the halotolerant species grow in both alkaline soda and saline habitats. It is possible to identify three indicator species requiring alkaline soda habitats to live in (Aster tripolium, Puccinellia limosa, Suaeda pannonica) and three indicator species that dominantly grow in non-alkaline saline habitats (Juncus maritimus, Salicornia prostrata, Suaeda salsa). Different independent variables have been identified and analyzed to understand their influence on the species saturation index by calculating percentage of characteristic plant species of the entire region. It was identified that the plant saturation index has a significant positive relationship with the Mean Temperature of the Warmest Quarter, Topsoil Sand, and Clay fraction variables, and there is a significant negative relationship with the Solid Earth surface heat flow, as the heating can increase the extremity of the environment. Identification of indicator species of salinity and alkalization makes it possible to determine the type of soil, water bodies and habitats as a rapid biomonitoring method as a visual observation, without the use of expensive equipment and chemical laboratory tests.

Investigating the application of the aquaponic paradigm to Litopenaeus vannamei farming

Abstract Aquaponics, a sustainable farming system combining aquaculture and hydroponics, has been widely adopted, used, particularly in freshwater. This study explores the feasibility of adapting the aquaponic model to saltwater conditions, specifically for wastewater treatment from Litopenaeus vannamei farming using the salt-tolerant plant species Rhizophora apiculata Blume. It focuses on plant development and calculates the water treatment effectiveness in terms of nutrient removal in mg of NH4 +, NO2 −, NO3 −, and total phosphorus per gram of plant mass. The first phase involved seedling production, model creation, and testing the plant’s wastewater treatment capabilities. After three months of growth, the plants are subjected to shrimp wastewater, and their nutrient removal efficiency is determined. The obtained data provides essential parameters for the operation of the model during Phase 2. In Phase 1, R. apiculata Blume removed NH4 +, NO2 −, NO3 −, and total phosphorus at 95%, 97%, 59%, and 57% efficiency after seven days, respectively. It focuses on plant development and quantifies the efficiency of water treatment by measuring the removal of nutrients such as NH4 +, NO2 −, NO3 −, and total phosphorus per gram of plant mass.The calculated nutrient removal coefficients per gram of plant mass are NH4 +: 0.007, NO2 −: 0.005, NO3 −: 0.031 and total phosphorus: 0.121. In Phase 2, the designed aquaponic model was developed, which included a shrimp tank with 300 individuals per 1 m3, a fish tank with 50 individuals per 0.5 m3, and a plant growing system. The experimental aquaponic model demonstrates the technical feasibility of using R. apiculata Blume to recycle water in shrimp farming. The model shows potential for scaling up and offers additional benefits, as the leaves R. apiculata of can serve as an herbal source for aquatic species.

Optimizing cotton growth in saline soil: Compound microbial agent modulates indigenous bacteria to enhance photosynthesis and vegetative-reproductive balance

Salt-tolerant composite plant growth-promoting rhizobacteria (STC-PGPR) can alleviate salt stress, though its complexity makes its stability and mechanisms in indeterminate-growing crops unclear. We tested STC-PGPR on two cotton (Gossypium hirsutum L.) varieties (G1: Xinluzao 72, G2: Zhongmiansuo 49), with two microbial treatments (B1: none, B2: with STC-PGPR) and three salinity levels (S1: 0 g NaCl kg−1, S2: 4 g NaCl kg−1, S3: 8 g NaCl kg−1). The pot experiment used a three-factor completely randomized design in a greenhouse, with NaCl mixed into the soil before transplanting. STC-PGPR (Paenibacillus polymyxa SC2, Bacillus velezensis DSYZ, Lactobacillus casei DY-3, and Saccharomyces cerevisiae DY-4) was applied 14 days post-transplant and during flowering and boll development. STC-PGPR was diluted with water and applied to the rhizosphere. Results showed that under S1, STC-PGPR increased G2’s seed cotton dry matter accumulation (Sc) by 25.1 %. Under S2, STC-PGPR increased G1’s boll dry matter accumulation (Bo) from 0.21 g to 7.7 g per pot. Other STC-PGPR treatments were less effective due to overdeveloped vegetative organs, highlighting the need for balanced vegetative and reproductive growth. High salinity reduced STC-PGPR effectiveness under S3. Random forest analysis identified crucial indicators regulated by STC-PGPR that significantly affected reproductive organ dry matter accumulation (P<0.001). Bioinformatics and correlation analyses showed biomarkers enriched by STC-PGPR influenced these indicators, not STC-PGPR directly. In S1, G2B2’s biomarkers enhanced stomatal conductance, increasing the net photosynthetic rate (Pn) and promoting dry matter accumulation. They also increased stem diameter and inhibited vegetative growth, enhancing transport and channeling energy to reproductive organs. In S2, G1B2’s biomarkers reduced leaf thickness, increased chlorophyll content to enhance Pn, and extended the maturation period. This enabled cotton to accumulate more photosynthetic products and allocate them to reproductive organs. This study demonstrates that STC-PGPR enhances productivity under salt stress, providing insights for optimizing saline soil cultivation.

Application of Trichoderma asperellum spore powder helps maintain ionic balance and photosystem II activity in wolfberry in saline soil

The mechanisms how Trichoderma enhances plant salt tolerance remain to be further dissected. Trichoderma asperellum spore powder (TS) was supplemented to saline soil around the stem base of potted wolfberry (Lycium chinense), and the role of Trichoderma asperellum in ameliorating salt tolerance of wolfberry was investigated with emphasis on ionic balance and photosystems II (PSII) activity. Plant dry weight was significantly increased by TS supplement, suggesting that Trichoderma asperellum promoted wolfberry growth in saline soil. As TS supplement elevated leaf and root K+/Na+ by increasing K+ content and decreasing Na+ content, Trichoderma asperellum improved ionic balance in wolfberry under saline soil stress, and the mechanism depended on that Trichoderma asperellum raised root Na+ exclusion and blocked root K+ loss. Consequentially, oxidative stress was ameliorated by Trichoderma asperellum according to lower leaf lipid peroxidation and H2O2 content in plants with TS supplement. Moreover, PSII was protected against oxidative injury and could maintain higher photochemical efficacy with TS supplement. K and J steps in prompt chlorophyll fluorescence transients were lowered by TS supplement, suggesting that Trichoderma asperellum alleviated salt-induced inhibition on electron transport at both PSII donor and acceptor sides, and consistently, more PSII centers became reactive. In addition, higher delayed chlorophyll fluorescence transients under TS supplement corroborated that Trichoderma asperellum enhanced whole PSII performance. Overall, Trichoderma asperellum helped maintain ionic balance by preventing K+ loss and elevating Na+ exclusion in roots and protect PSII by alleviating oxidative stress in wolfberry cultivated in saline soil.

Effects of Prolonged High Salinity Stress on Alfalfa (Medicago sativa L.) Cultivars and Populations

Background: Alfalfa is a promising crop for improving soil structure and restoring agricultural land, particularly in areas affected by salinity. However, high and continuing salinity in soil and irrigation water can pose a significant challenge to the growth and productivity of alfalfa. The objective of this study was to investigate the effects of prolonged high salinity stress on alfalfa cultivars and populations. Methods: The material used in this study included 16 alfalfa populations and four alfalfa cultivars that exhibit salt tolerance during germination and early seedling development. The materials were exposed to 17.52 dS m-1 saline irrigation water stress for three months. As well as the morphology, survival at three months and crude ash, sodium and chloride ions were measured. Result: Salt-tolerant plants showed a slowdown in growth compared to control conditions, although they were still able to maintain growth. Duration and severity of stress affected the salt tolerance of the genotypes. The survival rates of the materials remained relatively unchanged for the first two months, but decreased significantly by the end of the third month. Furthermore, the survival rate of the materials increased as the amount of sodium and chloride ions absorbed by the plant decreased under high salinity conditions. Genetic material demonstrating long-term high salinity tolerance is crucial for resistance breeding and holds promise for the development of tolerant cultivars that can be grown under field conditions in the future. The properties of this material need to be determined and its long-term performance in field conditions needs to be tested.

Antioxidant Properties of Lippia alba Essential Oil: A Potential Treatment for Oxidative Stress-Related Conditions in Plants and Cancer Cells.

Lippia alba (Mill.) N.E.Br. ex Britton and P. Wilson is used in folk medicine of Central and South America for its biological activities: i.e., antifungal, antibacterial, antiviral, and anti-inflammatory. Based on ethnopharmacological information and the increasing interest in this species, this work aimed to test a possible wide use of its essential oil (EO) in pharmaceutical and horticultural applications. Therefore, we focused the attention on the antioxidant activity of the oil as a possible tool to overcome the oxidative stress in both applications. For this purpose, we have chosen three aggressive breast cancer cell lines and two horticultural species (Solanum lycopersicum L. and Phaseolus acutifolius L.) that are very sensitive to salt stress. We determined the antioxidant activity of L. alba EO through the quantification of phenols and flavonoids. Regarding tomato and bean plants under salt stress, L. alba EO was used for the first time as a seed priming agent to enhance plant salt tolerance. In this case, the seed treatment enhanced the content of phenolic compounds, reduced power and scavenger activity, and decreased membrane lipid peroxidation, thus mitigating the oxidative stress induced by salt. While in breast cancer cells the EO treatment showed different responses according to the cell lines, i.e., in SUM149 and MDA-MB-231 the EO decreased proliferation and increased antioxidant activity and lipid peroxidation, showing high cytotoxic effects associated with the release of lactate dehydrogenase, vice versa no effect was observed in MDA-MB-468. Such antioxidant activity opens a new perspective about this essential oil as a possible tool to counteract proliferation in some cancer cell lines and in horticulture as a seed priming agent to protect from oxidative damage in crops sensitive to salinity.

Silicon improves salt resistance by enhancing ABA biosynthesis and aquaporin expression in Nicotiana tabacum L

Silicon (Si) can significantly improve the salt tolerance of plants, but its mechanism remains unclear. In this study, role of abscisic acid (ABA) in Si derived salt resistance in tobacco seedling was investigated. Under salt stress, the photosynthetic rate, stomatal conductance, and transpiration rate of tobacco seedlings were reduced by 86.17%, 80.63%, and 67.54% respectively, resulting in a decrease in biomass. The application of Si found to mitigate these stress-induced markers. However, positive role of Si was mainly attributed to the enhanced expression of aquaporin genes, which helped in enhancing root hydraulic conductance (Lpr) and ultimately maintaining the leaf relative water content (RWC). Moreover, sodium tungstate, an ABA biosynthesis inhibitor, was used to test the role of ABA on Si-regulating Lpr. The results indicated that the improvement of Lpr by Si was diminished in the presence of ABA inhibitor. In addition, it was observed that the ABA content was increased due to the Si-upregulated of ABA biosynthesis genes, namely NtNCED1 and NtNCED5. Conversely, the expression of ABA metabolism gene NtCYP7O7A was found to be reduced by Si. Together, this study suggested that Si increased ABA content, leading to enhanced efficiency of water uptake by the roots, ultimately facilitating an adequate water supply to maintain leaf water balance. As a result, there was an improvement in salt resistance in tobacco seedling.

Development of a Reference Transcriptome and Identification of Differentially Expressed Genes Linked to Salt Stress in Salt Marsh Grass (Sporobolus alterniflorus) along Delaware Coastal Regions.

Salt marsh grass (Sporobolus alterniflorus) plays a crucial role in Delaware coastal regions by serving as a physical barrier between land and water along the inland bays and beaches. This vegetation helps to stabilize the shoreline and prevent erosion, protecting the land from the powerful forces of the waves and tides. In addition to providing a physical barrier, salt marsh grass is responsible for filtering nutrients in the water, offering an environment for aquatic species and presenting a focal point of study for high salt tolerance in plants. As seawater concentrations vary along the Delaware coast from low to medium to high salinity, our study seeks to identify the impact of salt tolerance in marsh grass and to identify genes associated with salt tolerance levels. We developed more than 211,000 next-generation-sequencing (Illumina) transcriptomic reads to create a reference transcriptome from low-, medium-, and high-salinity marsh grass leaf samples collected from the Delaware coastline. Contiguous sequences were annotated based on a homology search using BLASTX against rice (Oryza sativa), foxtail millet (Setaria italica), and non-redundant species within the Viridiplantae database. Additionally, we identified differentially expressed genes related to salinity stress as candidates for salt stress qPCR analysis. The data generated from this study may help to elucidate the genetic signatures and physiological responses of plants to salinity stress, thereby offering valuable insight into the use of innovative approaches for gene expression studies in crops that are less salt tolerant.

Comparative Transcriptomic Analysis Reveals Transcriptional Differences in the Response of Quinoa to Salt and Alkali Stress Responses

Soil salinization is a global agro-ecological problem and a major factor impeding agricultural development. Planting salt-tolerant plants to improve saline soils offers both ecological and economic benefits. Currently, there are few studies addressing the combined effects of salt and alkali stress. Quinoa is known for its salinity tolerance. However, research has predominantly focused on the effects of salinity stress on quinoa’s morphology and physiology, with its molecular mechanisms remaining unclear. To better understand quinoa’s response mechanisms to salinity and alkali stress, we employed RNA-seq technology to analyze transcriptomes under these conditions. We identified 1833 differentially expressed genes (DEGs) under salt stress and 2233 DEGs under alkali stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations revealed that quinoa responds to salt and alkali stress through similar mechanisms. Both stresses promoted sucrose synthesis, starch synthesis and catabolism, which increased the osmotic potential of quinoa leaves. Additionally, there was a regulation of the down-regulated expression of the abscisic acid receptor PYR/PYL and the up-regulated expression of the serine/threonine protein kinase (PP2C) gene in the ABA signaling pathway. Contrasting with salt tolerance, the mechanism specific to quinoa’s alkalinity tolerance involves the up-regulation of the citric acid cycle via an active γ-aminobutyric acid (GABA) branch, enhancing quinoa’s energy metabolism. In summary, our transcriptome analysis revealed key regulatory mechanisms in quinoa’s response to saline and alkaline stress. This study deepens the understanding of quinoa’s stress response mechanisms and provides theoretical references for the biological improvement of salinized soils.

Genome-wide re-identification of the CrRLK1L family in soybean and functional characterization of GmCrRLK1L2 in salt stress response

The Catharanthus roseus receptor-like kinase 1-like (CrRLK1L), a member of the plant receptor-like kinase family, plays crucial roles in plant development and stress response. Despite previous screenings of soybean CrRLK1Ls, their specific function in stress response remains unclear. Utilizing recent soybean whole genome sequencing data, a comprehensive genome-wide analysis was performed to identify CrRLK1Ls in soybean. This study identified 45 CrRLK1L members in soybean, with CrRLK1L2 singled out for further functional investigation. Phylogenetic analysis categorized GmCrRLK1L genes into six classes, some of which exhibited homologs in Arabidopsis. Gene structure and motif analysis revealed a predominance of intron-lacking and relatively conserved GmCrRLK1L genes, with conserved motif patterns across members. Collinearity analysis indicated that both gene tandem and segmental duplication events drove the expansion of the GmCrRLK1L gene family, with segmental duplications being the primary driver. Expression profiling under salt treatment revealed significant up or downregulation of several GmCrRLK1L genes. Overexpression of GmCrRLK1L2 in soybean resulted in reduced plant height and salt tolerance, while knockout did not affect salt tolerance, suggesting potential genetic compensations by other genes. RNA-seq data showed that GmCrRLK1L2 overexpression influenced the expression of metabolic pathways and salt stress-responsive genes, including ACS3, ACO1, PER64, PER53, SAT3, and BCAT2. These findings lay the groundwork for elucidating the biological roles of GmCrRLK1Ls in soybean growth, development, and response to salinity stress.

Unveiling the influence of salinity on bacterial microbiome assembly of halophytes and crops

BackgroundClimate change and anthropogenic activities intensify salinity stress impacting significantly on plant productivity and biodiversity in agroecosystems. There are naturally salt-tolerant plants (halophytes) that can grow and withstand such harsh conditions. Halophytes have evolved along with their associated microbiota to adapt to hypersaline environments. Identifying shared microbial taxa between halophyte species has rarely been investigated. We performed a comprehensive meta-analysis using the published bacterial 16S rRNA gene sequence datasets to untangle the rhizosphere microbiota structure of two halophyte groups and non-halophytes. We aimed for the identification of marker taxa of plants being adapted to a high salinity using three independent approaches.ResultsFifteen studies met the selection criteria for downstream analysis, consisting of 40 plants representing diverse halophyte and non-halophyte species. Microbiome structural analysis revealed distinct compositions for halophytes that face high salt concentrations in their rhizosphere compared to halophytes grown at low salt concentrations or from non-halophytes. For halophytes grown at high salt concentrations, we discovered three bacterial genera that were independently detected through the analysis of the core microbiome, key hub taxa by network analysis and random forest analysis. These genera were Thalassospira, Erythrobacter, and Marinobacter.ConclusionsOur meta-analysis revealed that salinity level is a critical factor in affecting the rhizosphere microbiome assembly of plants. Detecting marker taxa across high-halophytes may help to select Bacteria that might improve the salt tolerance of non-halophytic plants.

Regulation of nitro-oxidative homeostasis: an effective approach to enhance salinity tolerance in plants.

Soil salinity is a major constraint for sustainable agricultural productivity, which together with the incessant climate change may be transformed into a severe threat to the global food security. It is, therefore, a serious concern that needs to be addressed expeditiously. The overproduction and accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are the key events occurring during salt stress, consequently employing nitro-oxidative stress and programmed cell death in plants. However, very sporadic studies have been performed concerning different aspects of nitro-oxidative stress in plants under salinity stress. The ability of plants to tolerate salinity is associated with their ability to maintain the cellular redox equilibrium mediated by both non-enzymatic and enzymatic antioxidant defense mechanisms. The present review emphasizes the mechanisms of ROS and RNS generation in plants, providing a detailed evaluation of how redox homeostasis is conserved through their effective removal. The uniqueness of this article stems from its incorporation of expression analyses of candidate genes for different antioxidant enzymes involved in ROS and RNS detoxification across various developmental stages and tissues of rice, utilizing publicly available microarray data. It underscores the utilization of modern biotechnological methods to improve salinity tolerance in crops, employing different antioxidants as markers. The review also explores how various transcription factors contribute to plants' ability to tolerate salinity by either activating or repressing the expression of stress-responsive genes. In summary, the review offers a thorough insight into the nitro-oxidative homeostasis strategy for extenuating salinity stress in plants.

Salinity-induced variations in wheat biomass are regulated by the Na+:K+ ratio, root exudates, and keystone species

Salt stress can limit crop productivity, and there are differences in salt tolerance among plant varieties; however, we lack a comprehensive understanding of how keystone species obtained from different plant varieties under salt stress change plant biomass by driving root exudate secretion and regulating the Na+:K+ ratio. We conducted a pot experiment for three wheat varieties (JiMai32 (JM32), XiaoYan60 (XY60), and ShanRong3 (SR3)) under saline/nonsaline soil conditions. Salt stress tended to significantly reduce wheat biomass, and the biomass reduction rates of the different varieties decreased in the order JM32 < XY60 < SR3. The compositions of the bacterial and fungal communities in the root endosphere, rhizosphere and bulk soil were measured, and salt-induced microbial taxa were isolated to identify keystone species from the co-occurrence networks and to study their effects on physiological responses to salinity in wheat varieties. We observed that root exudates participated in the regulation of the Na+:K+ ratio, thereby affecting wheat biomass, and this process was regulated by keystone species. JM32 was enriched in microorganisms that promote plant growth and resistance to salt stress, such as Burkholderiales, Sordariomycetes, Alteromonadaceae, Acremonium, and Dokdonella, and inhibited microorganisms that are sensitive to the environment (salt, nutrients) and plant pathogens, such as Nocardioidaceae, Nitrospira, Cytophagaceae, Syntrophobacteriaceae, and Striaticonidium. XY60 inhibited microorganisms with biological control and disease inhibition potential, such as Agromyces and Kaistobacter. SR3-enriched pathogens, such as Aurantimonadaceae and Pseudogymnoascus, as well as microorganisms with antagonistic pathogen potential and the ability to treat bacterial infections, such as RB41 and Saccharothrix, were inhibited. Our results confirmed the crucial function of salt-induced keystone species in enhancing plant adaptation to salt stress by driving root exudate secretion and regulating the Na+:K+ ratio, with implications for exploring reasonable measures to improve plant salt tolerance.

Comprehensive Identification and Expression Profiling of Epidermal Pattern Factor (EPF) Gene Family in Oilseed Rape (Brassica napus L.) under Salt Stress.

Rapeseed is a crucial oil crop globally, and in recent years, abiotic stress has increasingly affected its growth, development, yield, and quality. Salt stress is a significant abiotic factor that restricts crop production. The EPF gene family is vital in managing salt stress by controlling stomatal development and opening, which reduces water loss and increases plant salt tolerance. To explore the features of the EPF gene family in Brassica napus and their expression under salt stress, this study utilized Arabidopsis EPF protein sequences as seed sequences, including their PF17181 and PF16851 domains. A total of 27 members of the EPF gene family were detected within the rapeseed genome. The study examined the physicochemical properties, gene structure, phylogenetic relationships, and collinearity of BnEPFs. Through transcriptomes, we employed the qPCR method to determine the relative expression levels of BnEPF genes potentially associated with rapeseed stress resistance under both non-salt and salt stress conditions. Subsequently, we assessed their influence on rapeseed plants subjected to salt stress. During salt stress conditions, all BnEPF genes displayed a downregulation trend, indicating their potential impact on stomatal development and signal transduction pathways, consequently improving rapeseed's resistance to salt stress. The study findings establish a basis for exploring the roles of BnEPFs and offer candidate genes for breeding stress-resistant varieties and enhancing the yield in rapeseed.

Combined genome and transcriptome provides insight into the genetic evolution of an edible halophyte Suaeda salsa adaptation to high salinity.

Suaeda salsa L. is a typical halophyte with high value as a vegetable. Here, we report a 447.98 Mb, chromosomal-level genome of S. salsa, assembled into nine pseudomolecules (contig N50 = 1.36 Mb) and annotated with 27,927 annotated protein-coding genes. Most of the assembled S. salsa genome, 58.03%, consists of transposable elements. Some gene families including HKT1, NHX, SOS and CASP related to salt resistance were significantly amplified. We also observed expansion of genes encoding protein that bind the trace elements Zn, Fe, Cu and Mn, and genes related to flavonoid and α-linolenic acid metabolism. Many expanded genes were significantly up-regulated under salinity, which might have contributed to the acquisition of salt tolerance in S. salsa. Transcriptomic data showed that high salinity markedly up-regulated salt-resistance related genes, compared to low salinity. Abundant metabolic pathways of secondary metabolites including flavonoid, unsaturated fatty acids and selenocompound were enriched, which indicates that the species is a nutrient-rich vegetable. Particularly worth mentioning is that there was no significant difference in the numbers of cis-elements in the promoters of salt-related and randomly selected genes in S. salsa when compared with Arabidopsis thaliana, which may affirm that plant salt tolerance is a quantitative rather than a qualitative trait in terms of promoter evolution. Our findings provide deep insight into the adaptation of halophytes to salinity from a genetic evolution perspective.