NaCl Stress Research Articles

Differential biochemical and metabolic responses of contrast rice cultivars (<i>Oryza sativa</i> L.) under salt stress

More than half of the global population uses rice as the fundamental staple food; therefore, it is one of the most popular crops in the world. However, it is susceptible to salt stress, particularly among monocot crops, which reduces rice cultivation yield and threatens global food security. This research investigates the role of some factors, including amino acids, antioxidant enzymes, and sugars, in the response to the salinity stress of three contrasting rice cultivars, Dai Thom 8 (salt-sensitive), OC 10 (moderately salt-tolerant), and OM 9577 (salt-tolerant) in the seedling stage. The salt-tolerant varieties exhibited remarkable differences in physiological and biochemical traits, including enhancement of growth capacity, reduction of cell membrane damage via lowering lipid peroxidation, minimization of ROS generation, enhancement of free radical scavenging activity, and SOD, POD, and CAT enzyme activities. Additionally, the study analyzed the presence of 13 sugars using GC-MS and found that all three rice cultivars shared seven common sugars in similar quantities. However, OM 9577 had a higher content of the other six sugars compared to OC 10 and Dai Thom 8. It is one of the important biochemical factors responsible for the difference in the response mechanism to NaCl stress among rice varieties, specifically lyxofuranose (3.268%), a-D-xylopyranose (5.727%), mannopyranose (12.86%), α-D-glucopyranose (6.399%), ß-D-glucopyranose (5.509%), and D-arabinose (1.512%). Furthermore, the quantification of 20 amino acids through HPLC-DAD revealed that the salt-tolerant rice cultivars had higher concentrations of 11 amino acids than the salt-sensitive ones, including proline, isoleucine, serine, ornithine, histidine, glutamic acid, asparagine, alpha-alanine, aspartic acid, glutamine, and valine. These findings provide promising biochemical indicators for selecting salt-tolerant rice cultivars or improving existing varieties through traditional hybridization or gene transfer methods. Understanding these responses can significantly contribute to enhancing rice cultivation and ensuring food security in regions facing salinity challenges.

Computational and experimental analysis of foxtail millet under salt stress and selenium supplementation.

Salinity stress is a major threat to crop growth and productivity. Millets are stress-tolerant crops that can withstand the environmental constraints. Foxtail millet is widely recognized as a drought and salinity-tolerant crop owing to its efficient ROS scavenging mechanism. Ascorbate peroxidase (APX) is one of the reactive oxygen species (ROS) scavenging enzymes that leads to hydrogen peroxide (H2O2) detoxification and stabilization of the internal biochemical state of the cell under stress. This inherent capacity of the APX enzyme can further be enhanced by the application of an external mitigant. This study focuses on the impact of salt (NaCl) and selenium (Se) application on the APX enzyme activity of foxtail millet using in silico and in-vitro techniques and mRNA expression studies. The NaCl was applied in the concentrations, i.e., 150mM and 200mM, while the Se was applied in 1μM, 5μM, and 10μM concentrations. The in silico studies involved three-dimensional structure modeling and molecular docking. The in vitro studies comprised the morphological and biochemical parameters, alongside mRNA expression studies in foxtail millet under NaCl stress and Se applications. The in silico studies revealed that the APX enzyme showed better interaction with Se as compared to NaCl, thus suggesting the enzyme-modulating role of Se. The morphological and biochemical analysis indicated that Se alleviated the NaCl (150mM and 200mM) and induced symptoms at 1µM as compared to 5 and 10µM by enhancing the morphological parameters, upregulating the gene expression and enzyme activity of APX, and ultimately reducing the H2O2 content significantly. The transcriptomic studies confirmed the upregulation of chloroplastic APX in response to salt stress and selenium supplementation. Hence, it can be concluded that Se as a mitigant at lower concentrations can alleviate NaCl stress in foxtail millet.

Drought and Salinity Tolerance of the PtWRKY33 Gene in Populus

In this study, the PtWRKY33 gene sequence was cloned by PCR from cDNA, and systematic evolutionary analysis was performed. qRT–PCR was performed to measure the expression of the PtWRKY33 gene in the roots, stems and leaves of Populus tremuloides under drought and saline stresses, and overexpression vectors were constructed and genetically transformed into tobacco. The results showed that the WRKY transcription factors of Populus trichocarpa, Populus euphratica and Populus alba were in the same branch and were closely related to each other. Treating poplar seedlings with 20% PEG6000 solution to simulate drought stress showed that expression of the PtWRKY33 gene was induced and increased 1.89 times, 3.45 times and 11.6 times in leaves, stems and roots. The relative expression of the PtWRKY33 gene was slower to respond to 150 mM NaCl treatment but was nonetheless induced. At 48 h, the increase was 1–3 times in leaves, stems and roots, respectively. NaHCO3 (60 mM) was used to treat poplar seedlings with alkaline salt stress; the results indicated that the PtWRKY33 gene was sensitive to NaHCO3 stress treatment, and that its relative expression was significantly increased and increased 10.51 times (24 h), 6.56 times (6 h) and 5.16 times (24 h) in leaves, stems and roots, respectively. In this study, we found that NaCl and NaHCO3 stress treatments were able to induce an increase in the expression of the NtSOD1 and NtAPX2 genes using qRT–PCR, and the significant increase in expression under the treatments compared with WT may be caused by overexpression of the PtWRKY33 gene. Overexpression of the PtWRKY33 gene in tobacco enhanced the antioxidant stress capacity and improved the salinity tolerance of transgenic tobacco. These results indicate that the PtWRKY33 gene is a key gene for improved salinity-tolerant growth, which is important for future molecular breeding of tree resistance.

Rootstock mediated alteration in morphology and photosystem in sweet orange (Citrus sinensis) scion cv. Pusa Sharad under NaCl stress

There is a dearth of rootstock studies on how salinity stress imparts tolerance to the scion cultivar in citrus [Citrus sinensis (L.) Osbeck]. The impact of sodium chloride on sweet orange cv. Pusa Sharad (PS) grafted on 11 different rootstocks i.e. Jatti khatti (JK), X–639 (X9), CRH–12 (C12), NRCC–1 (N1), NRCC–2 (N2), NRCC–3 (N3), NRCC–4 (N4), NRCC–5 (N5), Troyer citrange (TC), CRH–47 (C47) and Cleopatra mandarin (CM) was evaluated at the nursery unit of ICAR-Indian Agricultural Research Institute, New Delhi, during 2019–22. Irrigation water containing 30 and 60 mM of sodium chloride (NaCl) was applied to scion/rootstock combinations in comparison to control (without NaCl) till the onset of salt injury symptoms i.e. 42 days. Under salinity stress, the PS scion grafted onto CM, X9, C47, N1, and N3 rootstocks exhibited minimum reduction in the scion height, leaf area ratio, root to shoot ratio, total chlorophyll content, total carotenoid content, transpiration rate, photosynthesis rate, internal CO2 concentration and stomatal conductance as compared to PS scions grafted onto JK, C12, N2, N4, N5, and TC rootstocks under 60 mM NaCl stress. Results showed that specific rootstock can enhance salt-tolerance potential by increasing pigment content and strengthening the photosystem. PS scions grafted onto CM, C47, X9, N1, and N3 demonstrated greater NaCl tolerance compared to those grafted onto JK, C12, N2, N4, N5, and TC and hence recommended for areas having salinity level up to 60 mM.

Comparative genomics reveals evidence of polycyclic aromatic hydrocarbon degradation in the moderately halophilic genus Pontibacillus

Polycyclic aromatic hydrocarbons (PAHs) are a common class of persistent organic pollutants (POPs) that are widely distributed in various environments and pose significant threats to both environmental and human health. The genus Pontibacillus, a type of moderately halophilic bacteria, has demonstrated potential for biodegrading aromatic compounds in high-salinity environments. However, no previous study has comprehensively investigated the PAH degradation mechanisms and environmental adaptability in the genus Pontibacillus. In this study, we sequenced the whole genome of the PAH-degrading strain Pontibacillus chungwhensis HN14 and conducted a comparative genomics analysis of genes associated with PAH degradation, as well as salt and arsenic tolerance using ten other Pontibacillus sp. strains. Here, we elucidated potential degradation pathways for benzo[a]pyrene and phenanthrene, which were initiated by cytochrome P450 monooxygenases, in most Pontibacillus strains. Moreover, four Pontibacillus strains were selected to investigate the biodegradation of benzo[a]pyrene and phenanthrene under high-salt (5% NaCl) stress, and all four strains exhibited exceptional degradation abilities. The results of comparative genomics and phenotypic analyses demonstrate that the genus Pontibacillus have the potential to degrade polycyclic aromatic hydrocarbons in high-salinity environments, thus providing valuable insights for biodegradation in extreme environments.

NaCl stress enhances pigment accumulation and synthesis in red rice during the germination stage

Red rice has become increasingly popular as a viable dietary choice due to its nutritional value. The germination process has been found to enhance the nutritional content of grains, particularly anthocyanins, and proanthocyanidins, and the presence of salt stress can further intensify this effect. In this study, the changes in bioactive phenolic compounds during the germination of red rice under salt stress were evaluated via chemical methods and UPLC-QToF/MS. The PLS-DA was used to analyze the upstream synthesis substrates of pigments in red rice treated with different NaCl concentrations. The results showed that NaCl stress inhibited red rice germination compared to the untreated group but that the total polyphenol content of red rice increased significantly after NaCl stress. Three anthocyanins and two proanthocyanidins were identified, and proanthocyanidins were the main components in pigment compounds. All these pigments tended to increase under 60 mmol/L NaCl treatment. Furthermore, upstream pigment substrates such as L-phenylalanine, cinnamic acid, p-coumaric acid, and leucocyanidin were also increased under NaCl stress. The activities of phenylalanine ammonia-lyase, leucoanthocyanidin reductase, and anthocyanin reductase related to these upstream metabolic substrates were up-regulated after NaCl stress. This study showed that NaCl stress effectively stimulated the accumulation of red rice pigments and their upstream substrates.

Salicylic Acid- and Potassium-Enhanced Resilience of Quinoa (Chenopodium quinoa Willd.) against Salinity and Cadmium Stress through Mitigating Ionic and Oxidative Stress.

Salinity and cadmium (Cd) contamination of soil are serious environmental issues threatening food security. This study investigated the role of salicylic acid (SA) and potassium (K) in enhancing the resilience of quinoa against the combined stress of salinity and Cd. Quinoa plants were grown under NaCl (0, 200 mM) and Cd (0, 100 µM) stress, with the addition of 0.1 mM SA and 10 mM K, separately or in combination. The joint stress of Cd and NaCl caused >50% decrease in plant growth, chlorophyll contents, and stomatal conductance compared to the control plants. The higher accumulation of Na and Cd reduced the uptake of K in quinoa tissues. The joint stress of salinity and Cd caused an 11-fold increase in hydrogen peroxide and 13-fold increase in thiobarbituric acid reactive substances contents, and caused a 61% decrease in membrane stability. An external supply of 0.1 mM SA and 10 mM K helped plants to better adapt to salinity and Cd stress with less of a reduction in plant biomass (shoot 19% and root 24%) and less accumulation of Na and Cd in plant tissues. The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) were enhanced by 11-fold, 10-fold, 7.7-fold, and 7-fold, respectively, when SA and K were applied together to the plants subjected to the joint stress of Cd and salinity. Based on the values of the bioconcentration factor (>1), the translocation factor (<1), and the higher tolerance index, it was clear that Cd-contaminated, salty soils could be stabilized with quinoa under the combined supply of SA and K.

Citric Acid and Hydro-Priming and Exogenous Application Alleviate Salt-Inhibited Seed Germination and Seedling Growth of Chilli (Capsicum annuum L.)

Salinity is a major barrier for seed germination, plant growth and production. Seed pre-treatment and exogenous chemical usage can effectively confer salt tolerance. We evaluated the potential of citric acid (CA) as priming and exogenous agents to ameliorate salt-inhibited germination and growth of Chilli (Capsicum annuum L.) in this study. The seeds were primed with 0.5 mM and 1 mM CA, and soaked in distilled water (hydro-priming) for 30 min. In addition, untreated seeds were used for the control experiment. Finally, primed seeds were subjected to 100 mM NaCl stress. Our results demonstrated that salinity significantly reduced the germination percentage (GP), germination index (GI), germination energy (GE), seed vigor index (SVI), root length (RL), shoot length (SL), shoot–root fresh and dry weight, and plant height and increased mean germination time (MGT). The results also indicated that salinity stress considerably decreased the relative water content (RWC) and photosynthetic pigments such as chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids, and increased relative water loss (RWL). The CA- and hydro-priming improved the GP, GI, GE SL, RL, SVI, and growth of seedlings, and reduced MGT under salt stress. Data also demonstrated that the supplementation of CA enhanced RWC and photosynthetic pigments and lowered RWL in the state of saline condition. When compared to other treatments, pretreatment, and exogenous use of 1 mM CA was determined to be comparatively more effective at imparting the salt tolerance of Chilli.

Physiological responses and adoptive mechanisms in oat against three levels of salt stress

To identify the propagation mechanisms and the adaptive strategies of oat seedlings exposed to NaCl, NaHCO3 and Na2CO3 the main salts in the soils of the salt-alkali grasslands of the Songnen Plain of China, growth rates and physiological indices of oat seedlings were measured in plants grown in soils with different concentrations (48-144 mmol L-1) of the three salts. The results demonstrated that although oat seedlings survival rates were unaffected by NaCl stress, the tiller number, plant height, and shoot and root dry weights decreased with increasing salt concentration, in the order of Na2CO3＞NaHCO3＞NaCl. In addition, propagation mechanisms higher concentrations of Na+ accumulated in the shoots and roots of oat seedlings under Na2CO3 stress and NaHCO3 stress than in seedlings under NaCl stress. Reductions in concentrations of K+ were also greater under both Na2CO3 and NaHCO3 stress than NaCl, especially in the roots. Large amounts of Cl－ and proline were found to accumulate in oat seedlings, most likely as a strategy for maintaining osmotic and ionic homeostasis under NaCl stress.

Molecular Mechanism of Response and Adaptation of Antioxidant Enzyme System to Salt Stress in Leaves of Gymnocarpos przewalskii.

The antioxidant enzyme system is the main defense system responsible for maintaining cellular reactive oxygen species (ROS) homeostasis and normal plant growth and development after saline stress. In this study, we identified and characterized the members of the SOD, APX and CAT gene families of the antioxidant enzyme system in Gymnocarpos przewalskii, using plant physiology and molecular biology methods, and analyzed the pattern of enzyme activity in response to NaCl stress. It was found that seven, six and two genes of SOD, APX and CAT gene families, respectively, were expressed in the leaf tissue of G. przewalskii, in which most of the genes were significantly upregulated under NaCl stress, and the enzymatic activities were in accordance with the gene expression. Three positive selection sites in the GpCAT1 gene can increase the hydrophilicity of the GpCAT1 protein, increase the volume of the active site and increase the affinity for H2O2, thus improving the catalytic efficiency of GpCAT1. The results of the present study provide new insights for further investigations of the evolution and function of the SOD, APX and CAT gene families in G. przewalskii and their essential roles under salt stress, and the findings will be useful for revealing the molecular mechanism of salt tolerance and breeding of salt-tolerant plants.

Chitosan modulated antioxidant activity, inorganic ions homeostasis and endogenous melatonin to improve yield of Pisum sativum L. accessions under salt stress

Effects of NaCl stress and foliar treatment of chitosan (CTS) on growth, antioxidant activity, inorganic ions and yield attributes of two pea (Pisum sativum L.) accessions were analyzed in this study. Experimentation was done in total 36 pots with 2 accessions and in three way completely randomized design (CRD) with 3 replicates. P. sativum plants were supplied with three salt concentrations (0, 60 and 120 mM) and two concentrations of CTS (0 and 120 mg/L). Both P. sativum accessions performed notably different from each other under salt stress. On the basis of remarkable reduction in biomass and yield parameters of ccession 200–03 under NaCl stress, it is assumed that this accession might be sensitive against salt stress. Whereas accession 200–06 under NaCl stress showed non-significant reduction in yield and biomass indicating that this accession might be resistant against salt stress. Foliar treatment of CTS boosted antioxidant enzyme activities, enhanced secondary metabolites (leaf proline and total phenolics), lowered the level of H2O2 and improved the RMP and yield in both ccessions. Salt stress resulted in enhanced content of endogenous melatonin. Chitosan treatment further boosted melatonin synthesis. It is concluded that foliar treatment of CTS mitigated the deleterious effects of salt stress and modulated growth in P. sativum plants under salt stress. Therefore, it is recommended that chitosan induced growth modulation in plants may be exploited.

Genome-wide identification and expression profiling analysis of DIR gene family in Setaria italica.

Dirigent (DIR) proteins play essential roles in regulating plant growth and development, as well as enhancing resistance to abiotic and biotic stresses. However, the whole-genome identification and expression profiling analysis of DIR gene family in millet (Setaria italica (Si)) have not been systematically understood. In this study, we conducted genome-wide identification and expression analysis of the S. italica DIR gene family, including gene structures, conserved domains, evolutionary relationship, chromosomal locations, cis-elements, duplication events, gene collinearity and expression patterns. A total of 38 SiDIR members distributed on nine chromosomes were screened and identified. SiDIR family members in the same group showed higher sequence similarity. The phylogenetic tree divided the SiDIR proteins into six subfamilies: DIR-a, DIR-b/d, DIR-c, DIR-e, DIR-f, and DIR-g. According to the tertiary structure prediction, DIR proteins (like SiDIR7/8/9) themselves may form a trimer to exert function. The result of the syntenic analysis showed that tandem duplication may play the major driving force during the evolution of SiDIRs. RNA-seq data displayed higher expression of 16 SiDIR genes in root tissues, and this implied their potential functions during root development. The results of quantitative real-time PCR (RT-qPCR) assays revealed that SiDIR genes could respond to the stress of CaCl2, CdCl, NaCl, and PEG6000. This research shed light on the functions of SiDIRs in responding to abiotic stress and demonstrated their modulational potential during root development. In addition, the membrane localization of SiDIR7/19/22 was confirmed to be consistent with the forecast. The results above will provide a foundation for further and deeper investigation of DIRs.

Morpho-physiological profiling of rice (Oryza sativa) genotypes at germination stage with contrasting tolerance to salinity stress.

Salinity is among the harshest environmental stress conditions that negatively affects productivity of salt-sensitive rice. Since, germination is the most crucial phase in the life-cycle of plants, the present study was carried out to study the morpho-physiological traits associated with salinity stress. Evaluation of tolerance in four contrasting rice genotypes was assessed on the basis of specific morpho-physiological parameters including radicle emergence, seedling vigour index, germination index, mean germination time, radicle and plumule growth and seedling water uptake. Largely, our findings revealed that mean germination time (MGT) and seedling vigour index (SVI) are fast-screening procedures to test seedling performance in salt stress conditions. Salt sensitive genotypes showed higher MGT and lower SVI, confirming that these indices are good indicators of poor germination response. Salt-tolerant genotypes were shown to be inhibited to a lesser extent in alpha-amylase activity in spite of high concentrations of imposed NaCl stress, that correlated with better regulation of water-uptake and increased accumulation of total soluble sugar content. Exogenous supplementation of soluble sugars improved the germination rate in a salt sensitive genotype, Jyothi, confirming the importance of soluble sugars in signaling under NaCl stress conditions. Increased total phenols and flavonoids were observed to be relative to higher Total Antioxidant Capacity in salt tolerant genotypes underlying the significance of seed phenolic compounds in early germination response in NaCl stress conditions. Kagga, a landrace grown in coastal Karnataka performed comparably with that of salt tolerant rice, Pokkali. In conclusion, the determination of early seedling response may be utilized as a useful strategy to uncover genetic variation in rice germplasm to salinity stress.

Alleviation of NaCl stress in tomato varieties by promoting morpho-physiological attributes and biochemical characters

Salinity is a significant abiotic stress, affecting plant growth and productivity during all plant developmental stages. Soil salinization due to climate change is increasing crop loss every year. Salinity is considered the most important abiotic stress limiting crop production and plants are known to be able to continue to survive under this stress by involving many mechanisms. Vegetable crops face huge yield losses due to abiotic stress. Salt stress creates physiological drought in plants affecting morphology and alters physiological functions that harm plants through various processes. Tomato is an essential annual crop providing human food worldwide. It is estimated that by the year 2050 > 50% of the arable land will become saline and, in this respect, in recent years, researchers have focused their attention on studying how tomato plants behave under various saline conditions. This study was conducted to observe the effects of NaCl salinity on four tomato (Lycopersicum esculentum L.) varieties in a pot experiment. Morphological and physio-biochemical properties of four tomato varieties (Rio Grande, Nadir, Bonita, and 19299) were exposed to NaCl-salinity (0, 100, 200, and 300 mM) through irrigation. All the varieties have differential responses to different levels of salt. Salinity stress reduced growth parameters in all varieties as compared to control plants. Plant Variety 4 (19299) showed significantly increased growth (root length, shoot length, number of roots, number of leaves, leaf area, plant fresh and dry weight) and physiological attributes (photosynthetic pigments, total soluble sugars, and total proteins) as compared to other varieties. Variety 4 (19299) has better protection against salt stress by increasing pigment content and enzymatic activity under salt stress. Antioxidants (peroxidase, catalase, and superoxide dismutase) were increased to maximum in variety 3 (Bonita) which is the most susceptible variety among all other varieties. Malondialdehyde (MDA) content, lycopene, anthocyanin, and H2O2 also increased in Variety 3 as compared to other varieties and control plants. Bonita variety showed maximum reduction in root length, shoot length, number of roots, fresh and dry matter content as well as in leaf area while comparing with other three varieties. The study revealed that the 19299 variety is salt tolerant, Rio Grande and Nadir are intermediates while the Bonita variety is susceptible to salt stress.

Physiological and biochemical traits positively modulate tissue-specific withanolides and untargeted metabolites in Withania somnifera (L.) dunal under salinity stress

Withania somnifera (L.) Dunal (Ashwagandha) has been used in herbal medicines worldwide and in the Indian traditional medicinal system for 3000 years. It is a member of the Solanaceae family distributed across Asia, Africa, Australia, and Europe. Its bioactive secondary metabolite (withanolide) biosynthesis is sensitive to salinity stress, though the mechanism remains unexplored. Therefore, we investigated the effect of Sodium chloride (NaCl) on growth, photosynthesis, biochemical traits, tissue-specific withanolide, and untargeted metabolites in W. somnifera. Ashwagandha plants were raised in pots containing soil mixture and treated with different NaCl concentrations (0 as control, 10, 30, and 50 mM) for one month inside the greenhouse. NaCl stress significantly enhanced withaferin A (WFA) (3.79 mg/g), withanolide A (WA) (0.51 mg/g), and withanone (WN) (0.022 mg/g) at 50 mM NaCl groups in the shoot. Similarly, in the root, a significant increase in WFA (0.19 mg/g) and WN (0.0016 mg/g) were observed at 10 mM, WA (0.059 mg/g) at 30 mM, and withanolide B (WB) (0.013 mg/g) at 50 mM NaCl groups compared to control. LC-MS-based untargeted metabolite profiling revealed 37 differentially accumulated metabolites in all groups. Maximum abundance of glycyl-hydroxyproline (8X) followed by tyrosyl-valine (2X) and 3-hydroxy-beta-ionone (2X) were recorded at 50 mM NaCl groups compared to the control. This study showed for the first time that low NaCl stress enhances the biosynthesis of tissue-specific withanolides through physio-biochemical and metabolites adjustment. Overall, we demonstrated a multifaceted approach for cultivating medicinal crops in salt-affected areas with enhanced bioactive metabolites for healthcare and pharmaceutical industries.

Genome-wide identification of flowering Chinese cabbage BPC family genes and BcBPC9 functional analysis in Cd stress tolerance

Flowering Chinese cabbage is an important vegetable crop widely cultivated in southern China. However, flowering Chinese cabbage plants are susceptible to diverse environmental influences that mainly affect crop quality and production. The BASIC PENTACYSTEINE (BPC) transcription factor is an essential regulator of plant development and abiotic stress responses. However, the function and molecular mechanism of the BPC family genes in flowering Chinese cabbage remain unclear. This study aimed to investigate the molecular mechanisms of the BcBPC gene in abiotic stress tolerance. In flowering Chinese cabbage, 12 BcBPC family genes have been identified and found to be unequally distributed on eight chromosomes. Comprehensive analyses of BcBPC gene structure, motif analysis, cis-regulatory elements, and subcellular localization were performed. BcBPC genes were classified into three groups based on their sequence composition, phylogenetic relationships, and conserved domains, which were highly linked to those of other species. BcBPC family gene promoter consists 69.92% stress-responsive, 32.38% hormone-responsive, and 5.30%, related to growth- and biological process-responsive cis-regulatory elements. Subsequent qRT-PCR results showed that BcBPC genes were highly upregulated under abiotic stress, especially under NaCl and Cd stress. The overexpression of BcBPC9 increases Cd stress tolerance in yeast. BcBPC9 is located in the nucleus, but moves to the cell wall when exposed to Cd stress. BcBPC9 transient overexpression tobacco were improved growth and upregulated the antioxidant enzymes genes expression when exposed to Cd stress. These findings facilitate further investigation of the functional and molecular characteristics of BcBPC9 in response to abiotic stress. The outcomes of this study provide a crucial foundation for future research on improving plant growth and protecting vegetable production.

Na+ and K+ compartmentalization in Spinacea oleracea and their effects on growth, water relations, endogenous melatonin, and non-structural carbohydrates

Spinacea oleracea is an economically important vegetable crop. Its growth and nutrition are impacted by the changes in its hydraulic traits due to soil salinity caused by the fluxes of Na+ and K+ which need further investigations to promote its cultivation in degraded agriculture lands. The objective of this study was to assess the impact of different concentrations of NaCl on water relations and non-structural carbohydrates of S. oleracea. For which the hydraulic traits such as rate of photosynthesis, transpiration, stomatal conductance, relative water content, stomatal and vein anatomy, non-structural carbohydrates, and growth were assessed. The compartmentalization of Na+ and K+ was analyzed in both the above and below ground parts. We found that the application of NaCl significantly reduced K+ concentrations, growth, stomatal conductance, photosynthesis, relative water content and also impacted the veins and stomata. The maximum amount of Na+ was compartmentalized in leaf-blade while the minimum was in roots. Meanwhile, maximum K+ was compartmentalized in the mid-rib and minimum in the stem. The K+ and K+: Na+ decreased significantly with the increasing salinity in the treatments. Non-structural carbohydrates also decreased with an increase in sodium concentration. Further, some significant linear relationships were also found between Na+, K+ and the studied hydraulic traits. Endogenous melatonin exhibits an elevated concentration in response to the application of stress. Furthermore, the concentration of melatonin was found to be further increased with the administration of treatment T1 to T4. We conclude that S. oleracea can tolerate NaCl stress up to 80 mML−1. The findings can be helpful to cultivate S. oleracea in excessive sodic soil and can also be useful to cultivate other crops when successive cultivation of S. oleracea is carried out and Na+ is absorbed by the crop from the soil. This can help to promote the sustainable agriculture in some degraded lands.

Physiological and Molecular Responses of Apocynum venetum L. (Apocynaceae) on Salt Stress

Soil salinization is a crucial factor that impacts plant distribution and growth. Apocynum venetum, an ornamental plant with medicinal value, has shown remarkable salt tolerance. However, the specific mechanisms through which A. venetum responds to salt stress are not yet fully understood. To address this gap, we conducted a study where 10-week-old A. venetum seedlings were subjected to salt stress by irrigating them with a nutrient solution containing varying concentrations of NaCl (0, 100, 200, and 350 mmol·L−1). After the salt stress treatment, various growth indicators (such as plant height, root length, root fresh weight, root dry weight, leaf fresh weight, leaf dry weight, root water content, leaf water content, and root–leaf ratio) as well as physiological indicators (including SOD and CAT activities in both leaves and roots, soluble protein contents in leaves and roots, and chlorophyll and carotene contents in leaves) were determined. In addition, the gene expression profile of roots under salt stress was examined by transcriptome sequencing to explore the mechanism of salt response in A. venetum. Our results show that salt stress led to yellowing and wilting of A. venetum seedling leaves. Furthermore, the chlorophyll and carotenoid contents in the leaves of the 350 mmol·L−1 NaCl-treated group were significantly reduced. Although the leaf and root biomass gradually decreased with an increase in the salt concentration, the root–leaf ratio exhibited a decreasing trend. NaCl stress also caused significant changes in physiological indices in the A. venntum leaves and roots. The activities of superoxide dismutase (SOD) and catalase (CAT) increased in both leaves and roots of the 100 mmol·L−1 NaCl-treated group. The soluble protein content in both leaves and roots increased under the 200 mmol·L−1 NaCl stress. To screen changes in root gene expression, transcriptome sequencing and qRT-PCR were performed. GO and KEGG enrichment analyses revealed that salt stress primarily affects carbohydrate metabolism, MAPK signaling transduction, phytohormone signaling pathways, glyoxylate and dicarboxylate metabolism, and other pathways. This study provides a novel understanding of the growth and physiological response of A. venetum leaf and root to NaCl stress, as well as the changes in the transcription levels in A. venetum root. The results serve as a reference for future research on salt-tolerant mechanisms and molecular breeding of A. venetum.

Exogenous foliar application of melatonin mitigates salt induced oxidative stress and promotes growth in Gerbera jamosonii

Salt stress is a major abiotic stress factor that is increasing at a continuos pace and pressurizing global food security in view of climate change. Therefore, plant scientists are developing strategies to ameliorate the negative effects of salt stress on crop production. Melatonin (N-acetyl-5-methoxytryptamine; MT) is a vital biological hormone in plants that modulates growth, development, and tolerance to extreme environmental conditions. Its exogenous application is used to improve resistance to various stressors. Gerbera (Gerbera jamosonii L. cv. Yunnanhong) is a vital ornamental flower crop moderately sensitive against salt stress. A series of experiments were conducted on gerbera plants grown under NaCl stress (150 mM) with or in the absence of MT at 0.1 and 0.2 mM. It was shown that salt stress reduced growth and physiological traits but also caused oxidative stress, as recorded by the induction of oxidative stress markers in cell tissues. Foliar application of MT, especially at the concentration of 0.2 mM, boosted plant growth, biomass production, photosynthetic pigments, and ameliorated oxidative stress. The decrease in oxidative stress was associated with improved antioxidant activity linked to the production of the enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Exogenous MT also improved potassium (K+) uptake and restricted sodium (Na+) uptake in the leaves of gerbera. In conclusion, optimal MT application may serve as a potential ameliorator of salt-induced oxidative stress and help in the regulation of salinity for gerbera production under the threat of climate change.

Exopolysaccharides from endophytic Glutamicibacter halophytocota KLBMP 5180 functions as bio-stimulants to improve tomato plants growth and salt stress tolerance

Microbial exopolysaccharides (EPSs) can promote plants growth and protect them against various abiotic stresses, but the role of actinobacteria-produced EPSs in plant growth promoting is still less known. Here, we aim to explore the effect of EPSs from an endophyte Glutamicibacter halophytocota KLBMP 5180 on tomato seeds germination and seedlings growth under salt stress. Our study revealed that 2.0 g/L EPSs resulted in increased seed germination rate by 23.5 % and 11.0 %, respectively, under 0 and 200 mM NaCl stress conditions. Further pot experiment demonstrated that EPSs significantly promoted seedlings growth under salt stress, with increased height, root length and fibrous roots number. Plant physiological traits revealed that EPSs increased chlorophyll content, enhanced the activity of antioxidant enzymes, soluble sugar, and K+ concentration in seedlings; malondialdehyde and Na+ contents were reduced. Additionally, auxin, abscisic acid, jasmonic acid, and salicylic acid were accumulated significantly in seedlings after EPSs treatment. Furthermore, we identified 1233 differentially expressed genes, and they were significantly enriched in phytohormone signal transmission, phenylpropanoid biosynthesis, and protein processing in endogenous reticulum pathways, etc. Our results suggest that KLBMP 5180-produced EPSs effectively ameliorated NaCl stress in tomato plants by triggering complex regulation mechanism, and showed application potentiality in agriculture.