Tolerance Of Tomato Plants Research Articles

Chrysin alleviates salt stress in tomato by physiological, biochemical, and genetic mechanisms

Soil salinity greatly reduces agricultural productivity, especially in dry and semi-arid regions, by interfering with physiological and biochemical processes. This research aimed to determine whether Chrysin (Chr) can mitigate the negative effects of salinity on growth parameters, antioxidant enzyme activity, and gene expression in tomato (Solanum lycopersicum L.) plants. Experiments were conducted in a semi-controlled greenhouse, with plants subjected to varying concentrations of sodium chloride (NaCl) (0 and 100 mM) and Chr (0, 0.1, 0.5, and 1.0 mM). Results revealed that salinity stress significantly reduced plant height, leaf area, and chlorophyll content while increasing hydrogen peroxide (H2O2), malondialdehyde (MDA), and proline levels, indicating oxidative stress. Chr application alleviated these detrimental effects by enhancing the activity of antioxidant enzymes such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), thereby reducing reactive oxygen species (ROS) accumulation. Additionally, Chr treatments improved plant water status and mineral content under salt stress. Gene expression analysis showed that Chr positively regulated the transcription of salt tolerance-related genes, including HKT1-1, HKT1-2, and PIP1-2, which are associated with sodium ion transport and water balance. These findings suggest that Chr can be an effective biostimulant for enhancing salt tolerance in tomato plants by modulating physiological, biochemical, and genetic mechanisms. This study provides insights into Chr's potential as a sustainable solution for improving crop resilience to salinity in agricultural practices. Further research is recommended to optimize Chr concentrations for maximum efficacy.

Mechanistic insights to Paenibacillus lentimorbus mediated biocontrol of Alternaria solani in Solanum lycopersicum L. through carbohydrate reallocation and sweet immunity suppression

Researchers envisaged that PGPR (plant growth promoting rhizobacteria) has vast possibilities as a bioinoculant that will lead to revolution. However, it's still very far from becoming commercially successful. Here, the information regarding the root colonization of PGPR in host plants and plant response towards PGPR is inadequate. It can provide valuable information for developing successful biofertilizers and biocontrol agents. PGPR (Paenibacillus lentimorbus NRRL B-30488 or CHM12) has been previously reported as a successful commercial biofertilizer and biocontrol agent. However, the exact mechanism of plant growth promotion and biocontrol is poorly studied. So, CHM12 was appraised for biotic stress amelioration of pathogen Alternaria solani in Tomato (Solanum lycopersicum L.) var. S-22 plants. PGPR CHM12 was assessed for various plant growth parameters such as proline, sugar content, etc. in pathogen A. solani (AS) challenged plants and compared with the CHM12 treated plants in a greenhouse study. Then, the metabolomics tool (GC-MS) was used to identify metabolites and their respective genes playing pivotal roles in colonization tactics availed by PGPR. Further, gene expression analysis was done to affirm the involvement of various genes related to metabolites providing biotic stress tolerance in Tomato plants. The current research discerned that PGPR CHM12 revealed significant differences in different plant growth parameters studied. There were 33 distinct metabolites identified, which stipulated the involvement of carbohydrate metabolism mainly in combating biotic stress in this study. Thus, our study reconfirmed very few reported previous results through gene expression analysis, suggesting the downregulation of carbohydrate metabolism genes in PGPR-treated plants. This downregulation of carbohydrate genes might be the critical factor for suppressing the plant's immune response to gaining entry inside the host plant. This also helps in retaining and reallocating carbohydrates in plant cells to reduce pathogen proliferation.

Deciphering the role of SlWRKY36 and SlWRKY51 in salt stress tolerance via modulating ion homeostasis and proline biosynthesis

Soil salinity caused by NaCl is a major challenge to agricultural crops worldwide. For this, two WRKY transcription factors were evaluated for their role in salt stress tolerance in tomato plants (Solanum lycopersicum; Sl). SlWRKY36 and SlWRKY51 provided novel insight into the regulatory mechanism in tomato against salt stress via virus-induced gene silencing (VIGS). Salt stress significantly reduced chlorophyll-a, an abundant form of chlorophyll content to 6.0 and 5.1 mg/g and proline content to 0.06 mg/g and 0.09 mg/g respectively in SlWRKY36 and SlWRKY51 silenced tomato plants. This shows that salt stress affected proline content that act as osmo-protectant and damaged photosynthetic pigments in silenced SlWRKY36 and SlWRKY51 tomato plants. Similarly, the concentrations of Na+/ K+ ratio also showed a significantly higher trend 14 days after salt stress with 5.5 mg/g and 8.9 mg/g concentration at 200 mM for SlWRKY36 and SlWRKY51 showing silencing promotes Na+/K+ ion ratio under salt stress. Also, salt stress responsive genes such as salt overly sensitive SOS1 and Na+/H+ exchanger NHX1 displayed lower transcript level in silenced plants at 200 mM salt stress showing their negative regulation by SlWRKY36 and SlWRKY51 gene silencing. Collectively, these findings suggest for the first time the role of SlWRKY36 and SlWRKY51 as positive regulators of salt stress tolerance by managing ion homeostasis, proline content and photosynthetic machinery via transcriptional reprogramming. Overall, SlWRKY36 and SlWRKY51 were explored as potential candidates for engineering salt tolerance in tomato crop plants.

The Use of Compost and Arbuscular Mycorrhizal Fungi and Their Combination to Improve Tomato Tolerance to Salt Stress.

Salinity poses a significant challenge to tomato plant development and metabolism. This study explores the use of biostimulants as eco-friendly strategies to enhance tomato plant tolerance to salinity. Conducted in a greenhouse, the research focuses on the Solanum lycopersicum L. behavior under saline conditions. Tomato seeds were treated with arbuscular mycorrhizal fungi (AMF), compost, and their combination under both non-saline and saline conditions (0 and 150 mM NaCl). Plant height, number of flowers and fruits, shoot fresh weight, and root dry weight were negatively impacted by salt stress. The supplementation with compost affected the colonization of AMF, but the application of stress had no effect on this trait. However, the use of compost and AMF separately or in combination showed positive effects on the measured parameters. At the physiological level, compost played a beneficial role in increasing photosynthetic efficiency, whether or not plants were subjected to salinity. In addition, the application of these biostimulants led to an increase in nitrogen content in the plants, irrespective of the stress conditions. AMF and compost, applied alone or in combination, showed positive effects on photosynthetic pigment concentrations and protein content. Under salt stress, characterized by an increase in lipid peroxidation and H2O2 content, the application of these biostimulants succeeded in reducing both these parameters in affected plants through exhibiting an increase in antioxidant enzyme activity. In conclusion, incorporating compost, AMF, or their combined application emerges as a promising approach to alleviate the detrimental impacts of salt stress on both plant performances. These findings indicate optimistic possibilities for advancing sustainable and resilient agricultural practices.

Plant growth promoting activities of endophytic bacteria from Melia azedarach (Meliaceae) and their influence on plant growth under gnotobiotic conditions

Bacteria that live asymptomatically within plant tissues are known as endophytes. Because of the close relation with the plant host, they have been a matter of interest for application as plant growth promoters. Melia azedarach is a widely distributed medicinal tree with proven insecticidal, antimicrobial, and antiviral activity. The aim of this study was to isolate and characterize endophytic bacteria from M. azedarach and analyze their plant growth promoting activities for the potential application as biological products. Bacteria were isolated from roots and leaves of trees growing in two locations of Northeastern Argentina. The isolates were characterized by repetitive extragenic palindromic sequence PCR and 16S rDNA sequence analysis. The plant growth-promoting activities were assayed in vitro, improvement of plant growth of selected isolates was tested on M. azedarach plantlets, and the effect of selected ACC deaminase producing isolates was tested on tomato seedlings under salt-stress conditions. The highest endophytic bacterial abundance and diversity were obtained from the roots. All isolates had at least one of the assayed plant growth-promoting activities and 80 % of them had antagonistic activity. The most efficient bacteria were Pseudomonas monteilii, Pseudomonas farsensis, Burkholderia sp. and Cupriavidus sp. for phosphate solubilization (2064 μg P ml−1), IAA production (94.7 μg ml−1), siderophore production index (5.5) and ACC deaminase activity (1294 nmol α-ketobutyrate mg−1 h−1). M. azedarach inoculation assays revealed the bacterial growth promotion potential, with Pseudomonas monteilii, Pseudomonas farsensis and Cupriavidus sp. standing out for their effect on leaf area, leaf dry weight, specific leaf area, and total Chl, Mg and N content, with increases of up to 149 %, 58 %, 65 %, 178 %, 76 % and 97.7 %, respectively, compared to NI plants. Efficient ACC deaminase-producing isolates increased stress tolerance of tomato plants under saline condition. Overall, these findings indicate the potential of the endophytic isolates as biostimulant and biocontrol agents.

Computational Analysis of Albaflavenone Interaction with SlMAPK1 for Drought Resistance in Tomato.

As global agricultural challenges intensify, particularly drought stress, the exploration of innovative strategies for crop resilience has become crucial. This study focuses on the role of the microbial endophyte metabolite Albaflavenone in enhancing drought resistance in tomato (Solanum lycopersicum L.) through the activation of the SlMAPK1 protein in the MAPK pathway. To computationally analyze the interaction between Albaflavenone and SlMAPK1 and to elucidate the potential enhancement of drought tolerance in tomato plants through this interaction. We utilized molecular docking, homology modeling, and molecular dynamics simulations to investigate the binding affinities and interaction dynamics between SlMAPK1 and Albaflavenone. Functional network analysis was employed to examine protein-protein interactions within the MAPK pathway, while the MM-GBSA method was used to calculate binding free energies. Our computational analyses revealed that Albaflavenone exhibited a high binding affinity to SlMAPK1 with a binding energy of - 8.9kcal/mol. Molecular dynamics simulations showed this interaction significantly stabilized SlMAPK1, suggesting enhanced activity. Specifically, the root mean square deviation (RMSD) of the Albaflavenone-SlMAPK1 complex stabilized at around 3.1Å, while the root mean square fluctuations (RMSF) indicated consistent amino acid conformations. Additionally, the radius of gyration (Rg) analysis demonstrated minimal variance, suggesting a compact and stable protein-ligand complex. The significant binding affinity between Albaflavenone and SlMAPK1 highlights the potential of leveraging plant-microbe interactions in developing sustainable agricultural practices. These findings also demonstrate the effectiveness of computational methods in dissecting complex biological interactions, contributing to a deeper understanding of plant resilience strategies against environmental stresses.

Plasma membrane intrinsic proteins SlPIP2;5 gene regulates tolerance to high VPD in tomato

Plasma membrane intrinsic proteins (PIPs) play important roles in plant growth, development, and abiotic stress responses. However, the functions and regulatory mechanisms of PIPs under high vapor pressure deficit (VPD) stress are not yet well understood. In this study, we used tobacco rattle virus (TRV) - mediated virus-induced gene silencing (VIGS) technology to discover that SlPIP2;5 is involved in the acclimation process of tomato plants to high VPD. Under high VPD, the TRV-SlPIP2;5 strain exhibited improved growth compared to the TRV strain, and silencing SlPIP2;5 increased the enzyme activities of the antioxidant system of tomato plants and reduced the sensitivity of plants to atmospheric drought stress by eliminating reactive oxygen species produced by the plants. Additionally, leaf structure was improved, with decreased thickness of the epidermis and spongy tissue, leading to enhanced water transport efficiency. Furthermore, the TRV-SlPIP2;5 strain had increased stomatal length and individual stomatal area, which changed net assimilation rate and stomatal conductance to air drought. In addition, SlPIP2;5 was localized on the plasma membrane, and its promoter region contained numerous core elements and V-myb avian myeloblastosis viral oncogene homolog (MYB) binding sites. Yeast One-Hybrid Assay (Y1H) and Dual Luciferase (LUC) assays showed that the transcription factor SlMYB110 can bind to SlPIP2;5 and regulate its expression. qRT-PCR analysis revealed that high VPD inhibited the expression of SlMYB110, consistent with the expression pattern of SlPIP2;5. Therefore, we speculate that under high VPD, SlMYB110 negatively regulates the expression of SlPIP2;5, thereby modulating the tolerance of tomato plants to atmospheric drought. These findings provide a theoretical basis for improving tomato response to high VPD, and SlPIP2;5 was added to the high VPD-responsive gene pool as a valuable gene that could be used to improve high VPD tolerance in tomato through genetic engineering.

Jasmonates Promote β-Amylase-Mediated Starch Degradation to Confer Cold Tolerance in Tomato Plants.

Cold stress severely restricts growth and development, reduces yields, and impairs quality in tomatoes (Solanum lycopersicum). Amylase-associated starch degradation and soluble sugar accumulation have been implicated in adaptation and resistance to abiotic stress. Here, we report a β-amylase (BAM) gene, SlBAM3, which plays a central role in tomato cold tolerance. The expression of SlBAM3 was triggered by cold stress. SlBAM3 knockout using the CRISPR/Cas9 system retarded starch degradation and reduced soluble sugar accumulation in tomato plants, eventually attenuating cold tolerance. Expression analysis revealed that the SlBAM3 transcript level was boosted by MeJA. Furthermore, MYC2, an essential component of the JA signaling pathway, could bind to the SlBAM3 promoter and directly activate SlBAM3 transcription, as revealed by yeast one-hybrid and dual LUC assays. In addition, the suppression of MYC2 resulted in increased starch accumulation, decreased soluble sugar content, and reduced tolerance to cold stress in tomato plants. Taken together, these findings demonstrate that JA positively regulates β-amylase-associated starch degradation through the MYC2-SlBAM3 module in tomato during cold stress. The results of the present work expand our understanding of the mechanisms underlying BAM gene activation and starch catabolism under cold stress. The regulatory module of SlBAM3 can be further utilized to breed tomato cultivars with enhanced cold tolerance.

Chitosan from Mushroom Improves Drought Stress Tolerance in Tomatoes.

Chitosan is a derivative of chitin that is one of the most abundant biopolymers in nature, found in crustacean shells as well as in fungi cell walls. Most of the commercially available chitosans are produced from the exoskeletons of crustaceans. The extraction process involves harsh chemicals, has limited potential due to the seasonal and limited supply and could cause allergic reactions. However, chitosan has been shown to alleviate the negative effect of environmental stressors in plants, but there is sparse evidence of how chitosan source affects this bioactivity. The aim of this study was to investigate the ability of chitosan from mushroom in comparison to crustacean chitosan in enhancing drought stress tolerance in tomato plants (cv. MicroTom). Chitosan treatment was applied through foliar application and plants were exposed to two 14-day drought stress periods at vegetative and fruit set growth stages. Phenotypic (e.g., fruit number and weight), physiological (RWC) and biochemical-stress-related markers (osmolytes, photosynthetic pigments and malondialdehyde) were analyzed at different time points during the crop growth cycle. Our hypothesis was that this drought stress model will negatively impact tomato plants while the foliar application of chitosan extracted from either crustacean or mushroom will alleviate this effect. Our findings indicate that drought stress markedly decreased the leaf relative water content (RWC) and chlorophyll content, increased lipid peroxidation, and significantly reduced the average fruit number. Chitosan application, regardless of the source, improved these parameters and enhanced plant tolerance to drought stress. It provides a comparative study of the biostimulant activity of chitosan from diverse sources and suggests that chitosan sourced from fungi could serve as a more sustainable and environmentally friendly alternative to the current chitosan from crustaceans.

Carbohydrate distribution via SWEET17 is critical for Arabidopsis inflorescence branching under drought.

Sugars Will Eventually be Exported Transporters (SWEETs) are the most recently discovered family of plant sugar transporters. By acting as uniporters, SWEETs facilitate the diffusion of sugars across cell membranes and play an important role in various physiological processes such as abiotic stress adaptation. AtSWEET17, a vacuolar fructose facilitator, was shown to be involved in the modulation of the root system during drought. In addition, previous studies have shown that overexpression of an apple homolog leads to increased drought tolerance in tomato plants. Therefore, SWEET17 might be a molecular element involved in plant responses to drought. However, the role and function of SWEET17 in above-ground tissues of Arabidopsis under drought stress remain elusive. By combining gene expression analysis and stem architecture with the sugar profiles of different above-ground tissues, we uncovered a putative role for SWEET17 in carbohydrate supply and thus cauline branch elongation, especially during periods of carbon limitation, as occurs under drought stress. Thus, SWEET17 seems to be involved in maintaining efficient plant reproduction under drought stress conditions.

Hydrogen Sulfide Alleviates Oxidative Damage under Chilling Stress through Mitogen-Activated Protein Kinase in Tomato.

Tomato is the vegetable with the largest greenhouse area in China, and low temperature is one of the main factors affecting tomato growth, yield, and quality. Hydrogen sulfide (H2S) plays an important role in regulating plant chilling tolerance, but its downstream cascade reaction and mechanism remain unclear. Mitogen-activated protein kinases (MAPK/MPKs) are closely related to a variety of signaling substances in stress signal transmission. However, whether H2S is related to the MPK cascade pathway in response to low-temperature stress is rarely reported. In this study, NaHS treatment significantly decreased the electrolyte leakage (EL), superoxide anion (O2-) production rate, and hydrogen peroxide (H2O2) content of seedlings at low temperatures. In addition, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were obviously increased; and the photochemical efficiency of PSII (Fv/Fm) was enhanced with treatment with NaHS, indicating that NaHS improved the seedlings' cold tolerance by alleviating the degree of membrane lipid peroxidation and oxidative damage. However, H2S scavenger hypotaurine (HT) treatment showed the opposite effect. We found that H2S content, L-cysteine desulfhydrase (LCD) activity, and mRNA expression were increased by chilling stress but reduced by MPK inhibitor PD98059; PD98059 reversed the alleviating effect of H2S via increasing the EL and H2O2 contents. The expression levels of MPK1-MPK7 at low temperatures showed that SlMPK4 was significantly induced by exogenous NaHS and showed a trend of first increasing and then decreasing, while the expression level of SlMPK4 in HT-treated seedlings was lower than that of the control. After SlMPK4 was silenced by virus-induced gene silencing, the H2S-induced upregulation of C-repeat-Binding Factor (CBF1), inducer of CBF expression 1 (ICE1), respiratory burst oxidase homologs (RBOH1, RBOH2) at low temperatures disappeared, and tomato cold tolerance decreased. In conclusion, H2S improves the cold tolerance of tomato plants by increasing the activity of antioxidant enzymes and reducing reactive oxygen species (ROS) accumulation and membrane lipid peroxidation. MPK4 may act as a downstream signaling molecule in this process.

Tomato SlMAPK3 Modulates Cold Resistance by Regulating the Synthesis of Raffinose and the Expression of SlWRKY46.

Mitogen-activated protein kinase (MAPK) cascades and raffinose have been observed to increase in plants exposed to cold. However, it remains elusive whether and how MAPK regulates raffinose synthesis under cold stress. Here, overexpression of SlMAPK3 promoted the accumulation of galactinol and raffinose under cold stress, while CRISPR/Cas9-mediated mutants showed the opposite results. Moreover, SlMAPK3 promoted the expression of SlWRKY46 at low temperatures and interacted with SlWRKY46 protein. Overexpression of SlWRKY46 enhanced cold resistance. Furthermore, SlWRKY46 directly bound to the promoter of SlGols1 to enhance its expression and promoted the accumulation of raffinose. Virus-induced gene-silencing (VIGS)-mediated knockdown of SlGols1 remarkably elevated cold sensitivity and reduced raffinose content. Meanwhile, exogenous supplementation of raffinose could improve the cold tolerance of tomato plants. Thus, our data indicates that SlMAPK3 modulates cold resistance by regulating raffinose content and SlWRKY46 expression. SlWRKY46 also promotes the accumulation of raffinose by inducing the expression of SlGols1.

Native rhizobacteria improve drought tolerance in tomato plants by increasing endogenous melatonin levels and photosynthetic efficiency

Global food productivity is a growing concern due to increasing agricultural losses caused by biotic and abiotic stresses. Drought is one of the biggest threats to crop productivity. A promising alternative to maintain crop yields is the use of plant growth promoting rhizobacteria (PGPR). A recently found phytohormone produced by PGPR, melatonin, has an important role in the tolerance of plant to abiotic stress. The aim of this study was to evaluate the effects of the inoculation with Pseudomonas 42P4 and Enterobacter 64S1 on the growth, biochemical, and physiology of tomato plants under drought stress. The results showed that PGPR inoculation increased growth parameters, total chlorophyll content, and chlorophyll fluorescence parameters of tomato plants under drought stress. Native PGPR inoculation increased endogenous melatonin and the accumulation of proline levels and reduced lipid peroxidation, thus improving the drought tolerance of tomato plants. The findings of this study suggest that these native strains are able to reduce the impact of drought and could be a potent alternative to maintain crop productivity.

Effects of combined application of selenium and various plant hormones on the cold stress tolerance of tomato plants

Effects of combined application of selenium and various plant hormones on the cold stress tolerance of tomato plants

Exogenous application of silicon and selenium improves the tolerance of tomato plants to calcium nitrate stress

Silicon (Si) and selenium (Se) can improve the tolerance of plants to NaCl-induced salt stress. However, few studies are available on their regulatory effects on plants’ tolerance to calcium nitrate stress, which often occurs in protected facilities, causing secondary soil salinization. In this study, we report the effects of Si (6 mM) and Se (20 μM) applied separately or in combination on the growth, photosynthesis, oxidative damage, and nitrogen metabolism of tomato plants, as well as fruit quality under calcium nitrate stress. The results showed that applications of Si or Se alone or in combination improved the plant growth and photosynthetic performance and reduced oxidative damage of the stressed plants. Applications of Si and Se did not decrease the calcium accumulation in leaves of the stressed plants. Under calcium nitrate stress, the concentrations of NO3−, NO2− and NH4+ in leaves were significantly increased, while the activities of nitrogen assimilation-related enzymes (including nitrate reductase, nitrite reductase, glutamine synthase, glutamine-2-oxoglutarate aminotransferase and glutamate dehydrogenase) were decreased. Applications of Si and Se, especially their combined treatment, decreased the NO3−, NO2−, and NH4+ concentrations and enhanced the activities of nitrogen assimilation-related enzymes in the stressed plants. Applied Si and Se also decreased the nitrate and titratable acid concentrations and increased vitamin levels in tomato fruits under calcium nitrate stress. It is suggested that Si and Se improved the tomato plant growth and fruit quality under calcium nitrate stress by alleviating oxidative damage and promoting both photosynthesis and nitrogen assimilation.

Selenium nanoparticles conferred drought tolerance in tomato plants by altering the transcription pattern of microRNA-172 (miR-172), bZIP, and CRTISO genes, upregulating the antioxidant system, and stimulating secondary metabolism.

Drought stress is one of the major limiting factors for the production of tomato in Iran. In this study, the efficiency of selenate and Se nanoparticle (SeNP) foliar application on tomato plants was assessed to vestigate mitigating the risk associated with water-deficit conditions. Tomato plants were treated with SeNPs at the concentrations of 0 and 4mg L-1; after the third sprays, the plants were exposed to water-deficit conditions. The foliar spraying with SeNPs not only improved growth, yield, and developmental switch to the flowering phase but also noticeably mitigated the detrimental risk associated with the water-deficit conditions. Gene expression experiments showed a slight increase in expression of microRNA-172 (miR-172) in the SeNP-treated plants in normal irrigation, whereas miR-172 displayed a downregulation trend in response to drought stress. The bZIP transcription factor and CRTISO genes were upregulated following the SeNP and drought treatments. Drought stress significantly increased the H2O2 accumulation that is mitigated with SeNPs. The foliar spraying with Se or SeNPs shared a similar trend to alleviate the negative effect of drought stress on the membrane integrity. The applied supplements also conferred drought tolerance through noticeable improvements in the non-enzymatic (ascorbate and glutathione) and enzymatic (catalase and peroxidase) antioxidants. The SeNP-mediated improvement in drought stress tolerance correlated significantly with increases in the activity of phenylalanine ammonia-lyase, proline, non-protein thiols, and flavonoid concentrations. SeNPs also improved the fruit quality regarding K, Mg, Fe, and Se concentrations. It was concluded that foliar spraying with SeNPs could mitigate the detrimental risk associated with the water-deficit conditions.

A transcriptional regulation of ERF15 contributes to ABA-mediated cold tolerance in tomato.

Cold stress is a major meteorological threat to crop growth and yield. Abscisic acid (ABA) plays important roles in plant cold tolerance by activating the expression of cold-responsive genes; however, the underlying transcriptional regulatory module remains unknown. Here, we demonstrated that the cold- and ABA-responsive transcription factor ETHYLENE RESPONSE FACTOR 15 (ERF15) positively regulates ABA-mediated cold tolerance in tomato. Exogenous ABA treatment significantly enhanced cold tolerance in wild-type tomato plants but failed to rescue erf15 mutants from cold stress. Transcriptome analysis showed that ERF15 was associated with the expression of cold-responsive transcription factors such as CBF1 and WRKY6. Further RT-qPCR assays confirmed that the ABA-induced increased in CBF1 and WRKY6 transcripts was suppressed in erf15 mutants when the plants were subjected to cold treatment. Moreover, yeast one-hybrid assays, dual-luciferase assays and electrophoretic mobility shift assays demonstrated that ERF15 activated the transcription of CBF1 and WRKY6 by binding their promoters. Silencing CBF1 or WRKY6 significantly decreased cold tolerance. Overall, our study identified the role of ERF15 in conferring ABA-mediated cold tolerance in tomato plants by activating CBF1 and WRKY6 expression. This study not only broadens our knowledge of the mechanism of ABA-mediated cold tolerance in plants but also highlights ERF15 as an ideal target gene for cold-tolerant crop breeding.

The Role of Tubulin and Thaumatin Genes and Osmotic Factors in Salinity Tolerance of Tomato Plants

Soil salinity is a drastic abiotic factor that affects many physiological processes and whole plants’ activities, as well as up- and down-regulating gene expression. Studying the effect of salinity on tubulin and thaumatin relative gene expression as DNA markers for salinity stress in tomato plants is a scarcely studied topic. Tubulin regulates and plays an important role in the immunolocalization of xylem and phloem fibers in stems and additionally maintains the concept of heavy microtubule contribution during cellulose microfibril confession in secondary cell walls under abiotic and biotic stresses. Like tubulin, thaumatin-like proteins are concomitant with plant defense responses against both biotic and abiotic stresses. The expression of the thaumatin gene can be meaningfully induced after plants' exposure to either drought, freezing, or salinity stresses. Thus, the present investigation was conducted to study the impact of different salinity levels (0, 75, 100, and 120 mM NaCl) on the tomato plants’ growth, osmotic adjustment, and relative gene expression of both antioxidant and salt tolerance genes. As the salt concentration intensified, the fresh and dry weight of the shoots and the roots reduced significantly, accompanied by a reduction in chlorophyll a and carotenoids. On the other hand, salinity stress significantly decreased the level of osmotica (e.g., soluble sugars and soluble proteins) in tomato tissues compared to non-saline-grown plants, while a significant accumulation of free amino acids was recorded. At the molecular level, it was observed that the relative expression of the polyphenol oxidase, peroxidase, and thaumatin genes was high at the level of 100 mM NaCl, but it was suppressed at 120 mM NaCl. In contrast, salinity down-regulated tubulin gene expression in stressed tomato plants relative to controls, revealing various mechanisms that instigated salinity tolerance, which is concentration-dependent. The study recommended the importance of amino acids as osmotica as well as the relative expressions of PPO, peroxidase, and thaumatin genes in conferring salt tolerance at low to moderate salt levels.

Exogenous Sucrose Confers Low Light Tolerance in Tomato Plants by Increasing Carbon Partitioning from Stems to Leaves.

Low light (LL) stress adversely affects plant growth and productivity. The role of exogenous sucrose in enhancing plant LL tolerance was investigated by spraying sucrose on tomato (Solanum lycopersicum L.) leaves. This study employed physiological and molecular approaches to identify the underlying mechanisms. Exogenous sucrose activated sucrose hydrolysis-related enzyme activity and upregulated genes encoding sucrose and hexose transporters in mature leaves, decreasing endogenous sucrose levels and promoting sucrose unloading during LL. Stem-related genes associated with sucrose synthesis and transport were also upregulated, enhancing sucrose phloem loading. Furthermore, sucrose from stems activated sucrose unloading in sink leaves, forming a feed-forward loop to sustain sucrose flow during LL. This led to increased nonstructural carbohydrates (NSCs), improved energy metabolism, and enhanced protein synthesis in leaves, ultimately boosting photosynthesis and fruit yield after light recovery. These findings highlight how exogenous sucrose enhances LL tolerance in tomatoes by increasing the transport of NSCs from stems to leaves.

The synergy of halotolerant PGPB and mauran mitigates salt stress in tomato (Solanum lycopersicum) via osmoprotectants accumulation.

Salinity stress is one of the major abiotic factors limiting sustainable agriculture. Halotolerant plant growth-promoting bacteria (PGPB) increased salt stress tolerance in plants, but the mechanisms underlying the tolerance are poorly understood. This study investigated the PGP activity of four halotolerant bacteria under salinity stress and the tomato salt-tolerance mechanisms induced by the synergy of these bacteria with the exopolysaccharide (EPS) mauran. All PGPB tested in this study were able to offer a significant improvement of tomato plant biomass under salinity stress; Peribacillus castrilensis N3 being the most efficient one. Tomato plants treated with N3 and the EPS mauran showed greater tolerance to NaCl than the treatment in the absence of EPS and PGPB. The synergy of N3 with mauran confers salt stress tolerance in tomato plants by increasing sodium transporter genes' expression and osmoprotectant content, including soluble sugars, polyols, proline, GABA, phenols and the polyamine putrescine. These osmolytes together with the induction of sodium transporter genes increase the osmotic adjustment capacity to resist water loss and maintain ionic homeostasis. These findings suggest that the synergy of the halotolerant bacterium N3 and the EPS mauran could enhance tomato plant growth by mitigating salt stress and could have great potential as an inductor of salinity tolerance in the agriculture sector.