Nitric Oxide (NO) Improves Wheat Growth under Dehydration Conditions by Regulating Phytohormone Levels and Induction of the Expression of the TADHN Dehydrin Gene.

Nitric oxide (NO) is a universal signaling molecule with important regulatory functions in the plant's life cycle and adaptation to a wide spectrum of environmental stresses including drought. The effect of pre-sowing seed treatment with the donor of NO sodium nitroprusside (SNP, 200 µM) on wheat Triticum aestivum L. plants subjected to dehydration (PEG-8000, 12%) was investigated. SNP pretreatment stimulated germination and seedling growth in normal conditions and protected them under dehydration. These effects were confirmed by percentage of seed germination, changes in fresh and dry weight of 5-6-day-old seedlings, as well as by seedlings' linear dimensions, visual appearance, and mitotic index of the root apical meristem. Assessment of the transpiration intensity (TI) and relative water content (RWC) showed that SNP pretreatment helped to maintain the water status of seedlings subjected to dehydration stress. The data obtained by enzyme-linked immunosorbent assay (ELISA) suggested that the positive effects of SNP may be due to its influence on the phytohormonal system. SNP pretreatment induced an increase in the level of indolylacetic acid (IAA) and especially cytokinins (CK), while essential changes in ABA content were not detected. Water deficiency caused a substantial increase in ABA content and a decrease in the levels of CK and IAA. Pre-sowing SNP treatment decreased stress-induced fluctuations in the content of all studied phytohormones. Using reverse-transcription PCR (RT-PCR), we obtained data on the increase in expression of the TADHN dehydrin gene in SNP-pretreated seedlings under normal and, especially, under dehydration conditions. These findings may indicate the participation of dehydrins in NO-induced defense reactions in wheat plants under water stress. Furthermore, exogenous NO had a stabilizing effect on membrane cellular structures, as evidenced by the reduction of electrolyte leakage (EL) levels and malondialdehyde (MDA) content in dehydrated wheat seedlings under the influence of pre-sowing SNP treatment.

The Contribution of Hormonal Changes to the Protective Effect of Endophytic Bacterium Bacillus subtilis on Two Wheat Genotypes with Contrasting Drought Sensitivities under Osmotic Stress.

A comparative analysis was conducted to evaluate the effects of seed priming with endophytic bacterium Bacillus subtilis 10-4 (BS) on the hormonal system and cell wall tolerance (lipid peroxidation (LPO), electrolyte leakage (EL), and root lignin deposition) of two Triticum aestivum L. (wheat) varieties with contrasting drought sensitivities (Ekada 70-drought-tolerant (DT); Salavat Yulaev-drought-sensitive (DS)) under normal conditions and 12% polyethylene glycol-6000 (PEG)-induced osmotic stress. The results showed that under normal conditions, the growth stimulation in wheat plants by BS was attributed to changes in the hormonal balance, particularly an increase in endogenous indole-3-acetic acid (IAA) accumulation. However, under stress, a significant hormonal imbalance was observed in wheat seedlings, characterized by a pronounced accumulation of abscisic acid (ABA) and a decrease in the levels of IAA and cytokinins (CK). These effects were reflected in the inhibition of plant growth. BS exhibited a protective effect on stressed plants, as evidenced by a significantly lower amplitude of stress-induced changes in the hormonal system: maintaining the content of IAA at a level close to the control, reducing stress-induced ABA accumulation, and preventing CK depletion. These effects were further reflected in the normalization of growth parameters in dehydrated seedlings, as well as a decrease in leaf chlorophyll degradation, LPO, and EL, along with an increase in lignin deposition in the basal part of the roots in both genotypes. Overall, the findings demonstrate that BS, producing phytohormones, specifically IAA and ABA, had a more pronounced protective effect on DT plants, as evidenced by a smaller amplitude of stress-induced hormonal changes, higher leaf chlorophyll content, root lignin deposition, and lower cell membrane damage (LPO) and permeability (EL) compared to DS plants.

Seed Treatment with Sodium Nitroprusside Ensures a Long-Term Physiological and Protective Effect on Wheat under Salinity.

Although salinity inhibits plant growth, the use of a nitric oxide (NO) gasotransmitter can reduce its negative effects. In this study, the influence of 200 µM sodium nitroprusside (SNP) (donor of NO) on wheat plants (Triticum aestivum L., cv. Salavat Yulaev) in conditions of salinization (100 mM NaCl) was analyzed in pot experiments. Seed priming regulated the level of endogenous NO in normal and salinity conditions throughout the entire experiment (30 and 60 days). Salinity led to the strong accumulation of NO and H2O2, which is negative for plants, and significantly reduced leaf area and photosynthetic pigments (chlorophyll a and b and carotenoids). In addition, stress caused a drop in the content of reduced glutathione (GSH) and ascorbic acid (ASA), an accumulation of oxidized glutathione (GSSG), and significantly activated glutathione reductase (GR), ascorbate peroxidase (APX), and lipid peroxidation (LPO) in wheat leaves. SNP treatment significantly attenuated the negative effects of salinity on leaf area and photosynthetic pigments. An important indicator of reducing the damaging effect of salinity on treated plants is the stabilization of the content of GSH and ASA throughout the experiment (60 days). This condition has been associated with long-term modulation of GR and APX activity. Such an effect of 200 µM SNP may be related to its ability to reduce stress-induced accumulation of NO. Additional accumulation of proline also mitigated the negative effect of salinity on plants, and this also evidenced decreased LPO and H2O2 in them. For the first time, in natural growing conditions (small-scale field experiments), it was found that pre-sowing seed treatment with 200 µM SNP led to an improvement in the main yield indicators and an increase in the content of essential amino acids in wheat grains. Thus, SNP treatment can be used as an effective approach for prolonged protection of wheat plants under salinity and to improve grain yield and its quality.

Endophytic Plant Growth-Promoting Bacterium Bacillus subtilis Reduces the Toxic Effect of Cadmium on Wheat Plants.

Heavy metal ions, in particular cadmium (Cd), have a negative impact on the growth and productivity of major crops, including wheat. The use of environmentally friendly approaches, in particular, bacteria that have a growth-stimulating and protective effect, can increase the resistance of plants. The effects of the pre-sowing seed treatment with the plant growth-promoting endophyte Bacillus subtilis 10-4 (BS) on cadmium acetate (Cd)-stressed Triticum aestivum L. (wheat) growth, photosynthetic pigments, oxidative stress parameters, roots' lignin content, and Cd ions accumulation in plants were analyzed. The results showed that the tested Cd-tolerant BS improved the ability of wheat seeds to germinate in the presence of different Cd concentrations (0, 0.1, 0.5, and 1 mM). In addition, the bacterial treatment significantly decreased the damaging effects of Cd stress (1 mM) on seedlings' linear dimensions (lengths of roots and shoots), biomass, as well as on the integrity and permeability of the cell walls (i.e., lipid peroxidation and electrolyte leakage) and resulted in reduced H2O2 generation. The pretreatment with BS prevented the Cd-induced degradation of the leaf photosynthetic pigments chlorophyll (Chl) a, Chl b, and carotenoids. Moreover, the bacterial treatment intensified the lignin deposition in the roots under normal and, especially, Cd stress conditions, thereby enhancing the barrier properties of the cell wall. This manifested in a reduced Cd ions accumulation in the roots and in the restriction of its translocation to the aboveground parts (shoots) of the bacterized plants under Cd stress in comparison with non-bacterized controls. Thus, the pre-sowing seed treatment with the endophyte BS may serve as an eco-friendly approach to improve wheat production in Cd-contaminated areas.

The Effects of Seed Pretreatment with Endophytic Bacteria Bacillus subtilis on the Water Balance of Spring and Winter Wheat Seedlings under Short-Time Water Deficit.

We investigated the effect of pre-sowing seed treatment with endophytic Bacillus subtilis 10-4 (B. subtilis) on spring and winter wheat (Triticum aestivum L.; cultivars Ekada-70 (Ek) and Scepter (Sc), respectively) growth and tolerance under 1-24 h of drought stress, modulated by 12% polyethylene glycol 6000 (PEG). The results showed that drought decreased transpiration intensity (TI), root relative water content (RWC), osmotic potential (Ψπ) of cell sap, and induced proline accumulation and electrolyte leakage (EL) in both wheat cultivars. It was revealed that Sc was more responsive to PEG and B. subtilis treatments than Ek. Under drought, Ek did not significantly change root length, shoot height, or dry biomass. The pretreatment of wheat plants with B. subtilis performed significantly better under drought conditions through the enhanced TI, RWC, and Ψπ of the cell sap in comparison with the plants treated with 12% PEG alone. B. subtilis also reduced stress-caused EL, especially in the Sc cultivar. Under water deficit wheat seedlings, pretreated with B. subtilis, have a higher proline accumulation in comparison to untreated stressed plants. Taken together, our results demonstrate the crucial role of endophytic B. subtilis in ameliorating the adverse effects of water stress on the water balance of both winter and spring wheat cultivars.

Components of the Phenylpropanoid Pathway in the Implementation of the Protective Effect of Sodium Nitroprusside on Wheat under Salinity.

Nitric oxide (NO) is a multifunctional, gaseous signaling molecule implicated in both physiological and protective responses to biotic and abiotic stresses, including salinity. In this work, we studied the effects of 200 µM exogenous sodium nitroprusside (SNP, a donor of NO) on the components of the phenylpropanoid pathway, such as lignin and salicylic acid (SA), and its relationship with wheat seedling growth under normal and salinity (2% NaCl) conditions. It was established that exogenous SNP contributed to the accumulation of endogenous SA and increased the level of transcription of the pathogenesis-related protein 1 (PR1) gene. It was found that endogenous SA played an important role in the growth-stimulating effect of SNP, as evidenced by the growth parameters. In addition, under the influence of SNP, the activation of phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL), and peroxidase (POD), an increase in the level of transcription of the TaPAL and TaPRX genes, and the acceleration of lignin accumulation in the cell walls of roots were revealed. Such an increase in the barrier properties of the cell walls during the period of preadaptation played an important role in protection against salinity stress. Salinity led to significant SA accumulation and lignin deposition in the roots, strong activation of TAL, PAL, and POD, and suppression of seedling growth. Pretreatment with SNP under salinity conditions resulted in additional lignification of the root cell walls, decreased stress-induced endogenous SA generation, and lower PAL, TAL, and POD activities in comparison to untreated stressed plants. Thus, the obtained data suggested that during pretreatment with SNP, phenylpropanoid metabolism was activated (i.e., lignin and SA), which contributed to reducing the negative effects of salinity stress, as evidenced by the improved plant growth parameters.

Effect of Seed Priming with Endophytic Bacillus subtilis on Some Physio-Biochemical Parameters of Two Wheat Varieties Exposed to Drought after Selective Herbicide Application.

Wheat plants are frequently exposed to combined herbicide and drought stress (HDS) which induces complex responses negatively, affects productivity, and is becoming more exacerbated with current climate change. In this work, we studied the influence of seed priming with endophytic bacteria Bacillus subtilis (strains 104 and 26D) on growth and tolerance of two wheat (Triticum aestivum L.) varieties (E70-drought tolerant; SY-drought susceptible) exposed to soil drought after application of selective herbicide Sekator® Turbo in pot experiments under controlled conditions; 17-day-old plants sprayed with herbicide and after 3 days were subjected to soil drought by stopping irrigating the plants for 7 days with subsequent resumption of normal irrigation (recovery). Additionally, the growth of tested strains (104, 26D) in the presence of different concentrations of herbicide Sekator® Turbo and drought (PEG-6000) were evaluated. It was established that both strains are herbicide and drought tolerant and capable to improve seed germination and early seedlings' growth under different herbicide and drought stress degrees. The results of pot experiments showed that HDS exposure declined growth (plant length, biomass), photosynthetic pigments (chlorophyll a and b), leaf area, and increased lipid peroxidation (LPO) and proline accumulation in plants, demonstrating higher damaging effects for SY variety. Strains 104 and 26D mitigated (in different levels) such negative impacts of HDS on growth of both varieties by increasing length of roots and shoots, biomass, photosynthetic pigments (chlorophyll a and b), and leaf area, reducing stress-caused LPO (i.e., malondialdehyde), and regulating proline biosynthesis, as well as contributing to a faster recovery of growth, photosynthetic pigments, and redox-status of plants in post-stress period in comparison with non-primed plants. These ultimately manifested in forming a better grain yield of both varieties primed with 104, 26D, and exposed to HDS. Thus, both strains 104 and 26D (which are herbicide and drought tolerant) may be used as seed priming agents to improve wheat HDS tolerance and grain yield; however, strain 104 more effectively protected plants of E70, while strain 26D-plants of SY. Further research should be focused on understanding the mechanisms that determine the strain and variety-specificity of endophytic symbiosis and the role of bacteria in the modulation of physiological states of primed plants under stress conditions, including HDS.

Role of Endogenous Salicylic Acid as a Hormonal Intermediate in the Bacterial Endophyte Bacillus subtilis-Induced Protection of Wheat Genotypes Contrasting in Drought Susceptibility under Dehydration.

Endophytic Bacillus subtilis is a non-pathogenic beneficial bacterium which promotes plant growth and tolerance to abiotic stresses, including drought. However, the underlying physiological mechanisms are not well understood. In this study, the potential role that endogenous salicylic acid (SA) plays in regulating endophytic B. subtilis-mediated drought tolerance in wheat (Triticum aestivum L.) was examined. The study was conducted on genotypes with contrasting levels of intrinsic drought tolerance (drought-tolerant (DT) cv. Ekada70; drought-susceptible (DS) cv. Salavat Yulaev). It was revealed that B. subtilis 10-4 promoted endogenous SA accumulation and increased the relative level of transcripts of the PR-1 gene, a marker of the SA-dependent defense pathway, but two wheat cultivars responded differently, with the highest levels exhibited in DT wheat seedlings. These had a positive correlation with the ability of strain 10-4 to effectively protect DT wheat seedlings against drought injury by decreasing osmotic and oxidative damages (i.e., proline, water holding capacity (WHC), and malondialdehyde (MDA)). However, the use of the SA biosynthesis inhibitor 1-aminobenzotriazole prevented endogenous SA accumulation under normal conditions and the maintenance of its increased level under stress as well as abolished the effects of B. subtilis treatment. Particularly, the suppression of strain 10-4-induced effects on proline and WHC, which are both contributing factors to dehydration tolerance, was found. Moreover, the prevention of strain 10-4-induced wheat tolerance to the adverse impacts of drought, as judged by the degree of membrane lipid peroxidation (MDA) and plant growth (length, biomass), was revealed. Thus, these data provide an argument in favor of a key role of endogenous SA as a hormone intermediate in triggering the defense responses by B. subtilis 10-4, which also afford the foundation for the development of the bacterial-induced tolerance of these two different wheat genotypes under dehydration.

Effects of Rhizobium leguminosarum Thy2 on the Growth and Tolerance to Cadmium Stress of Wheat Plants.

Cadmium (Cd) stress is an obstacle for crop production, quality crops, and sustainable agriculture. An important role is played by the application of eco-friendly approaches to improve plant growth and stress tolerance. In the current study, a pre-sowing seed treatment with Rhizobium leguminosarum strains, isolated from the leguminous plants Phaseolus vulgaris (strain Pvu5), Vicia sylvatica (strain VSy12), Trifolium hybridium (strain Thy2), and T. pratense (strain TPr4), demonstrated different effects on wheat (Triticum aestivum L.) plant growth under normal conditions. Among all tested strains, Thy2 significantly increased seed germination, seedling length, fresh and dry biomass, and leaf chlorophyll (Chl) content. Further analysis showed that Thy2 was capable of producing indole-3-acetic acid and siderophores and fixing nitrogen. Under Cd stress, Thy2 reduced the negative effect of Cd on wheat growth and photosynthesis and had a protective effect on the antioxidant system. This was expressed in the additional accumulation of glutathione and proline and the activation of glutathione reductase. In addition, Thy2 led to a significant reduction in oxidative stress, which was evidenced by the data on the stabilization of the ascorbate content and the activity of ascorbate peroxidase. In addition, Thy2 markedly reduced Cd-induced membrane lipid peroxidation and electrolyte leakage in the plants. Thus, the findings demonstrated the ability of the R. leguminosarum strain Thy2, isolated from T. hybridium nodules, to exert a growth-promoting and anti-stress effect on wheat plants. These results suggest that the Thy2 strain may enhance wheat plant growth by mitigating Cd stress, particularly through improving photosynthesis and antioxidant capacity and reducing the severity of oxidative damage. This may provide a basic and biological approach to use the Thy2 strain as a promising, eco-friendly candidate to combat Cd stress in wheat production.

Regulatory Role of Circadian Clocks on ABA Production and Signaling, Stomatal Responses, and Water-Use Efficiency under Water-Deficit Conditions.

Plants deploy molecular, physiological, and anatomical adaptations to cope with long-term water-deficit exposure, and some of these processes are controlled by circadian clocks. Circadian clocks are endogenous timekeepers that autonomously modulate biological systems over the course of the day-night cycle. Plants' responses to water deficiency vary with the time of the day. Opening and closing of stomata, which control water loss from plants, have diurnal responses based on the humidity level in the rhizosphere and the air surrounding the leaves. Abscisic acid (ABA), the main phytohormone modulating the stomatal response to water availability, is regulated by circadian clocks. The molecular mechanism of the plant's circadian clock for regulating stress responses is composed not only of transcriptional but also posttranscriptional regulatory networks. Despite the importance of regulatory impact of circadian clock systems on ABA production and signaling, which is reflected in stomatal responses and as a consequence influences the drought tolerance response of the plants, the interrelationship between circadian clock, ABA homeostasis, and signaling and water-deficit responses has to date not been clearly described. In this review, we hypothesized that the circadian clock through ABA directs plants to modulate their responses and feedback mechanisms to ensure survival and to enhance their fitness under drought conditions. Different regulatory pathways and challenges in circadian-based rhythms and the possible adaptive advantage through them are also discussed.

Contribution of Ascorbate and Glutathione in Endobacteria Bacillus subtilis-Mediated Drought Tolerance in Two Triticum aestivum L. Genotypes Contrasting in Drought Sensitivity.

We evaluated the effect of endobacteria Bacillus subtilis (strain 10-4) as a co-inoculant for promoting plant growth and redox metabolism in two contrasting genotypes of Triticum aestivum L. (wheat): Ekada70 (drought tolerant (DT)) and Salavat Yulaev (drought susceptible (DS)) in early stages of adaptation to drought (12% PEG-6000). Results revealed that drought reduced growth and dramatically augmented oxidative stress markers, i.e., hydrogen peroxide (H2O2) and lipid peroxidation (MDA). Furthermore, the depletion of ascorbate (AsA) and glutathione (GSH), accompanied by a significant activation of ascorbate peroxidase (APX) and glutathione reductase (GR), in both stressed wheat cultivars (which was more pronounced in DS genotype) was found. B. subtilis had a protective effect on growth and antioxidant status, wherein the stabilization of AsA and GSH levels was revealed. This was accompanied by a decrease of drought-caused APX and GR activation in DS plants, while in DT plants additional antioxidant accumulation and GR activation were observed. H2O2 and MDA were considerably reduced in both drought-stressed wheat genotypes because of the application of B. subtilis. Thus, the findings suggest the key roles in B. subtilis-mediated drought tolerance in DS cv. Salavat Yulaev and DT cv. Ekada70 played are AsA and GSH, respectively; which, in both cases, resulted in reduced cell oxidative damage and improved growth in seedlings under drought.

Seed priming with endophytic Bacillus subtilis strain-specifically improves growth of Phaseolus vulgaris plants under normal and salinity conditions and exerts anti-stress effect through induced lignin deposition in roots and decreased oxidative and osmotic damages.

Bacillus subtilis is one of the non-pathogenic beneficial bacteria that promote plant growth and stress tolerance. In the present study, we revealed that seed priming with endophytic B. subtilis (strains 10-4, 26D) improved Phaseolus vulgaris L. (common bean) seed germination and plant growth under both saline and non-saline conditions. 10-4 and 26D decreased oxidative and osmotic damage to the plant cells since bacterial inoculations reduced lipid peroxidation and proline accumulation in plants under salinity. 26D and especially 10-4 preserved different elevated levels of chlorophyll (Chl) a and Chl b in bean leaves under salinity, while carotenoids (Car) increased only by 10-4 and slightly decreased by 26D. Under normal conditions, 10-4 and 26D did not affect Chl a and Car concentrations, while Chl b decreased in the same plants. Under non-saline and especially saline conditions, 10-4 and 26D significantly increased lignin accumulation in plant roots and the highest lignin content along with better growth and oxidative damages reduction was observed after 10-4 inoculation under salinity, indicating a major role of B. subtilis-induced strengthening the root cell walls in the implementation protective effect of studied bacteria on plants. Therefore, B. subtilis 10-4 and 26D exerts protective effects on the growth of common bean plants under salinity by regulating plant defense mechanisms and the major role in tolerance development may contribute through the activation by B. subtilis lignin deposition in roots. The obtained data also indicates a strain-dependent efficiency of endophytic B. subtilis since strains 10-4 and 26D differently improved growth attributes and modulates cellular response reactions of the same common bean plants both under normal and salinity conditions, that generates interest for further investigations in this direction.

Seed Priming with Endophytic Bacillus subtilis Modulates Physiological Responses of Two Different Triticum aestivum L. Cultivars under Drought Stress.

The protective effects against drought stress of the endophytic bacterium Bacillus subtilis 10-4 were measured by studying the priming response in two wheat (Triticum aestivum L.)-Ekada70 (E70) and Salavat Yulaev (SY)-lines, tolerant and susceptible to drought, respectively. B. subtilis 10-4 improved germination and growth parameters under normal conditions in both cultivars with the most pronounced effect observed in cv. E70. Under drought conditions, B. subtilis 10-4 significantly ameliorated the negative impact of stress on germination and growth of cv. E70, but had no protective effect on cv. SY. B. subtilis 10-4 induced an increase in the levels of photosynthetic chlorophyll (Chl) a, Chl b, and carotenoids (Car) in the leaves of cv. E70, both under normal and drought conditions. In cv. SY plants, bacterial inoculation decreased the contents of Chl a, Chl b, and Car under normal conditions, but pigment content were almost recovered under drought stress. B. subtilis 10-4 increased water holding capacity (WHC) of cv. E70 (but did not affect this parameter in cv. SY) and prevented the stress-induced decline in WHC in both cultivars. Notably, B. subtilis 10-4 increased endogenous salicylic acid (SA) concentration in both cultivars, especially in cv. E70. Moreover, B. subtilis 10-4 reduced drought-induced endogenous SA accumulation, which was correlated with the influence of endophyte on growth, indicating a possible involvement of endogenous SA in the implementation of B. subtilis-mediated effects in both cultivars. Overall, B. subtilis 10-4 inoculation was found to increase drought tolerance in seedlings of both cultivars, as evidenced by decreased lipid peroxidation, proline content, and electrolyte leakage from tissues of wheat seedlings primed with B. subtilis 10-4 under drought conditions.

The Effect of Endophytic Bacteria Bacillus subtilis and Salicylic Acid on Some Resistance and Quality Traits of Stored Solanum tuberosum L. Tubers Infected with Fusarium Dry Rot.

The effect of endophytic Bacillus subtilis (strains 10-4, 26D) and their compositions withsalicylic acid (SA) on some resistance and quality traits of stored potatoes infected with Fusariumdry rot were studied. The experiments were carried out on hydroponically grown Solanumtuberosum L. tubers that were infected before storage with Fusarium oxysporum and coated with B.subtilis 10-4, 26D with and without exogenous SA, and then stored for six months. It has been shownthat 10-4, 26D, 10-4 + SA, and 26D + SA reduced in different levels (up to 30-50%) the incidence ofF. oxysporum-caused dry rot (with the highest effect for 10-4 + SA). SA notably enhanced the positiveeffect of 10-4, while for 26D, such an effect was not observed. All of the tested treatments increasedamylase (AMY) and AMY inhibitors activity in infected tubers, while decreased Fusarium-inducedprotease activity (except in the case of 10-4 + SA, which promoted a slight increase) was revealed.10-4, 26D, and their compositions with SA decreased (in different degrees) the pathogen-causedlipid peroxidation, proline, and reducing sugars accumulation in potatoes after long-term storage.It was also discovered 10-4 and 26D, regardless of SA presence, decrease pathogen-inducedglycoalkaloids α-Solanine and α-Chaconine accumulation and preserved increased levels of starchand total dry matter in infected stored potatoes. The findings indicate endophytic B. subtilis and itscompositions with SA is a promising eco-friendly and bio-safe approach to cope with postharvestdecays of potato during long-term storage; however, when developing preparations-compositionsit should take into account the strain-dependent manner of B. subtilis action together with SA.

Effects of Endophytic Bacillus Subtilis and Salicylic Acid on Postharvest Diseases (Phytophthora infestans, Fusarium oxysporum) Development in Stored Potato Tubers.

Postharvest diseases of potato lead to significant food and economic losses worldwide. The exogenous application of eco-friendly methods plays an important role in the control of postharvest decay. In this work the effects of endophytic bacteria B. subtilis (10-4, 26D) were studied in the context of two application parameters: concentration, with a range between 103-108 CFU/mL tested, and synergistic effects of the signal molecule salicylic acid (SA) (0.05 mM) on potato tubers' resistance to Phytophthora infestans and Fusarium oxysporum during storage. The experiments were carried out on hydroponically grown potato (Solanum tuberosum L.) mini-tubers. This study demonstrates the suppressive effect of B. subtilis (10-4, 26D) on diseases of potato during storage and reveals that this effect happens in a dose-dependent manner, both individually and in combination with SA. The most effective concentrations of B. subtilis for suppression of both Ph. infestans and F. oxysporum are 108 CFU/mL (10-4 and 26D), 107 CFU/mL (10-4 + SA) and 106 CFU/mL (26D + SA). The ability of B. subtilis (10-4, 26D) to effectively penetrate and colonize the internal tubers' tissues when applied immediately prior to storage, and the ability of SA to accelerate these processes, have been proven. B. subtilis (10-4, 26D), individually and in compositions with SA, increased ascorbic acid content and decreased pathogen-induced proline accumulation and lipid peroxidation in tubers. This indicates a protective effect conferred to cells against reactive oxygen and an extension of aging processes, manifested by a prolonged shelf life and extended preservation of fresh appearance.

Calcium signaling and salt tolerance are diversely entwined in plants.

In plants dehydration imposed by salinity can invoke physical changes at the interface of the plasma membrane and cell wall. Changes in hydrostatic pressure activate ion channels and cause depolarization of the plasma membrane due to disturbance in ion transport. During the initial phases of salinity stress, the relatively high osmotic potential of the rhizosphere enforces the plant to use a diverse spectrum of strategies to optimize water and nutrient uptake. Signals of salt stress are recognized by specific root receptors that activate an osmosensing network. Plant response to hyperosmotic tension is closely linked to the calcium (Ca2+) channels and interacting proteins such as calmodulin. A rapid rise in cytosolic Ca2+ levels occurs within seconds of exposure to salt stress. Plants employ multiple sensors and signaling components to sense and respond to salinity stress, of which most are closely related to Ca2+ sensing and signaling. Several tolerance strategies such as osmoprotectant accumulation, antioxidant boosting, polyaminses and nitric oxide (NO) machineries are also coordinated by Ca2+ signaling. Substantial research has been done to discover the salt stress pathway and tolerance mechanism in plants, resulting in new insights into the perception of salt stress and the downstream signaling that happens in response. Nevertheless, the role of multifunctional components such as Ca2+ has not been sufficiently addressed in the context of salt stress. In this review, we elaborate that the salt tolerance signaling pathway converges with Ca2+ signaling in diverse pathways. We summarize knowledge related to different dimensions of salt stress signaling pathways in the cell by emphasizing the administrative role of Ca2+ signaling on salt perception, signaling, gene expression, ion homeostasis and adaptive responses.

Bacillus Spp.: Efficient Biotic Strategy to Control Postharvest Diseases of Fruits and Vegetables.

: Postharvest diseases significantly reduce the shelf-life of harvested fruits/vegetables worldwide. Bacillus spp. are considered to be an eco-friendly and bio-safe alternative to traditional chemical fungicides/bactericides due to their intrinsic ability to induce native anti-stress pathways in plants. This review compiles information from multiple scientific databases (Scopus, ScienceDirect, GoogleScholar, ResearchGate, etc.) using the keywords "postharvest diseases", "Bacillus", "Bacillus subtilis", "biocontrol", "storage", "losses", and "fruits/vegetables". To date, numerous examples of successful Bacillus spp. application in controlling various postharvest-emerged pathogens of different fruits/vegetables during handling, transportation, and storage have been described in the literature. The mechanism/s of such action is/are still largely unknown; however, it is suggested that they include: i) competition for space/nutrients with pathogens; ii) production of various bio-active substances with antibiotic activity and cell wall-degrading compounds; and iii) induction of systemic resistance. With that, Bacillus efficiency may depend on various factors including strain characteristics (epiphytes or endophytes), application methods (before or after harvest/storage), type of pathogens/hosts, etc. Endophytic B. subtilis-based products can be more effective because they colonize internal plant tissues and are less dependent on external environmental factors while protecting cells inside. Nevertheless, the mechanism/s of Bacillus action on harvested fruits/vegetables is largely unknown and requires further detailed investigations to fully realize their potential in agricultural/food industries.

Diverse role of γ-aminobutyric acid in dynamic plant cell responses.

Gamma-aminobutyric acid (GABA), a four-carbon non-protein amino acid, is found in most prokaryotic and eukaryotic organisms. Although, ample research into GABA has occurred in mammals as it is a major inhibitory neurotransmitter; in plants, a role for GABA has often been suggested as a metabolite that changes under stress rather than as a signal, as no receptor or motif for GABA binding was identified until recently and many aspects of its biological function (ranging from perception to function) remain to be answered. In this review, flexible properties of GABA in regulation of plant responses to various environmental biotic and abiotic stresses and its integration in plant growth and development either as a metabolite or a signaling molecule are discussed. We have elaborated on the role of GABA in stress adaptation (i.e., salinity, hypoxia/anoxia, drought, temperature, heavy metals, plant-insect interplay and ROS-related responses) and its contribution in non-stress-related biological pathways (i.e., involvement in plant-microbe interaction, contribution to the carbon and nitrogen metabolism and governing of signal transduction pathways). This review aims to represent the multifunctional contribution of GABA in various biological and physiological mechanisms under stress conditions; the objective is to review the current state of knowledge about GABA role beyond stress-related responses. Our effort is to place findings about GABA in an organized and broader context to highlight its shared metabolic and biologic functions in plants under variable conditions. This will provide potential modes of GABA crosstalk in dynamic plant cell responses.

Effects of growth under different light spectra on the subsequent high light tolerance in rose plants.

Photosynthesis is defined as a light-dependent process; however, it is negatively influenced by high light (HL) intensities. To investigate whether the memory of growth under monochromatic or combinational lights can influence plant responses to HL, rose plants were grown under different light spectra [including red (R), blue (B), 70:30 % red:blue (RB) and white (W)] and were exposed to HL (1500 µmol m-2 s-1) for 12 h. Polyphasic chlorophyll a fluorescence (OJIP) transients revealed that although monochromatic R- and B-grown plants performed well under control conditions, the functionality of their electron transport system was more sensitive to HL than that of the RB- and W-grown plants. Before exposure to HL, the highest anthocyanin concentration was observed in R- and B-grown plants, while exposure to HL reduced anthocyanin concentration in both R- and B-grown plants. Ascorbate peroxidase and catalase activities decreased, while superoxide dismutase activity was increased after exposure to HL. This caused an increase in H2O2 concentration and malondialdehyde content following HL exposure. Soluble carbohydrates were decreased by exposure to HL, and this decrease was more emphasized in R- and B-grown plants. In conclusion, growing plants under monochromatic light reduced the plants ability to cope with HL stress.

Effects of Bacillus subtilis on some physiological and biochemical parameters of Triticum aestivum L. (wheat) under salinity.

Endophytic strain Bacillus subtilis (B. subtilis) 10-4, producing indole-3-acetic acid (IAA) and siderofores but not active in phosphate solubilization, exerted a protective effect on Triticum aestivum L. (wheat) plant grown under salinity (2% NaCl) stress. Exposure to salt stress resulted in an essential increase of proline (Pro) and malondialdehyde (MDA) level in the seedlings. At the same time the seedlings inoculated with B. subtilis 10-4 were characterized by decreased level of stress-induced Pro and MDA accumulation. It was revealed that both B. subtilis 10-4 and salinity caused increase in the content of endogenous salicylic acid (SA) in wheat seedlings as compared to SA content in the control, while B. subtilis 10-4 suppressed stress-induced SA accumulation. Water storage capacity (WSC) in leaf tissues was increased and stress-induced hydrolysis of statolite starch in root cap cells of the germinal roots was reduced by B. subtilis 10-4. The obtained data indicated that the activation of the defense reactions induced by B. subtilis 10-4 induced defense reactions may be connected with their ability to decrease the level of stress-induced oxidative and osmotic stress in seedlings and with the increase of endogenous SA level that can make a significant contribution to the implementation of the protective effect of B. subtilis 10-4 and is manifested in the improvement of plant growth, WSC of leaves and slowing down of the process of statolite starch hydrolysis under salinity.