Effects Of 24-epibrassinolide Research Articles

Physiological and biochemical effects of 24-Epibrassinolide on drought stress adaptation in maize (Zea mays L.).

Maize production and productivity are affected by drought stress in tropical and subtropical ecologies, as the majority of the area under maize cultivation in these ecologies is rain-fed. The present investigation was conducted to study the physiological and biochemical effects of 24-Epibrassinolide (EBR) as a plant hormone on drought tolerance in maize. Two maize hybrids, Vivek hybrid 9 and Bio 9637, were grown under three different conditions: (i) irrigated, (ii) drought, and (iii) drought+EBR. A total of 2 weeks before the anthesis, irrigation was discontinued to produce a drought-like condition. In the drought+EBR treatment group, irrigation was also stopped, and in addition, EBR was applied as a foliar spray on the same day in the drought plots. It was observed that drought had a major influence on the photosynthesis rate, membrane stability index, leaf area index, relative water content, and leaf water potential; this effect was more pronounced in Bio 9637. Conversely, the activities of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) increased in both hybrids under drought conditions. Specifically, Vivek hybrid 9 showed 74% higher CAT activity under drought conditions as compared to the control. Additionally, EBR application further enhanced the activity of this enzyme by 23% compared to plants under drought conditions. Both hybrids experienced a significant reduction in plant girth due to drought stress. However, it was found that exogenously applying EBR reduced the detrimental effects of drought stress on the plant, and this effect was more pronounced in Bio 9637. In fact, Bio 9637 treated with EBR showed an 86% increase in proline content and a 70% increase in glycine betaine content compared to untreated plants under drought conditions. Taken together, our results suggested EBR enhanced tolerance to drought in maize hybrids. Hence, pre-anthesis foliar application of EBR might partly overcome the adverse effects of flowering stage drought in maize.

24-Epibrassinolide alleviates diazinon oxidative damage by escalating activities of antioxidant defense systems in maize plants

Excessive use of pesticides against pests has contaminated agricultural crops and raised global concerns about food safety. This research investigates the alleviation effects of 24-epibrassinolide (EBL) seed priming on diazinon (DZ) pesticide toxicity. The experiment was conducted with eight groups including control, DZ, EBL (10 µM), EBL (0.1 µM), EBL (0.01 µM), EBL (10 µM) + DZ, EBL (0.1 µM) + DZ, and EBL (0.01 µM) + DZ. Plants grown with the lowest concentration of EBL (0.01 µM) exhibited an upward increase in the activity of SOD, CAT, POD, APX, GR, and GST enzymes under DZ toxicity stress. In contrast, higher concentrations of EBL showed some inhibitory effects on the activity of antioxidant enzymes. In addition, low concentrations of EBL elevated the free radical scavenging capacity (DPPH), iron-reducing antioxidant power (FRAP), photosynthesis rate (Pn), stomatal conductance (Gs) and proline, and protein contents. EBL also reduced lipid peroxidation (MDA levels) in the DZ-exposed plants, leading to membrane integrity. The favorable effects of EBL were more evident when plants were exposed to pesticides than normal growth conditions. The results indicated that EBL seed priming intensifies the antioxidant enzymes system activity, and helps maize plants against toxic effects of DZ under proper concentration.

24-Epibrassinolide regulates volatile metabolic pathways to improve tomato flavor quality during postharvest storage

The effects of 24-epibrassinolide (EBL) on flavor quality and regulation networks of volatile metabolism genes were investigated in tomato fruit. The results showed that EBL treatment affected the accumulation of carotenoid-derived volatiles via the regulation on carotenoid contents and expression levels of lycopene metabolic genes. Meanwhile, EBL treatment uplifted the level of salicylaldehyde, while decreased that of methyl salicylate (MeSA) by regulating MeSA metabolic genes. WGCNA was performed based on 2473 differential expressed genes and 27 volatiles to obtain 11 volatile connected modules and hub genes in these modules. Modules MEpurple and MEred had significant connections with the biosynthesis of β-ionone and MeSA. BAM1, the hub gene of MEred, was involved in β-ionone metabolic pathway. PIF3, the hub gene of MEpurple, had a direct connection with MeSA metabolic pathway. Taken together, the EBL application has the potential to improve the quality characteristics of tomato during postharvest storage via the volatile regulation network.

Effects of 24-epibrassinolide on photosynthetic parameters in response to different light intensities and CO<sub>2</sub> concentrations in maize seedlings under NaCl stress

Effects of 24-epibrassinolide on photosynthetic parameters in response to different light intensities and CO<sub>2</sub> concentrations in maize seedlings under NaCl stress

Effects of 24-Epibrassinolide, melatonin and their combined effect on cadmium tolerance in Primula forbesii Franch

This study aimed to investigate the interaction between 24-Epibrassinolide (EBR) and melatonin (MT) and their effects on cadmium (Cd)-stressed Primula forbesii Franch. P. forbesii seedlings were hydroponically acclimatized at 6–7 weeks, then treated with Cd (200 μmol L–1), 24-EBR (0.1 μmol L–1), and MT (100 μmol L–1) after two weeks. Cd stress significantly reduced crown width, shoot, root length, shoot fresh weight, and fresh and dry root weights. Herein, 24-EBR, MT, and 24-EBR+MT treatments attenuated the growth inhibition caused by Cd stress and improved the morphology, growth indexes, and ornamental characteristics of P. forbesii under Cd stress. 24-EBR had the best effect by effectively alleviating Cd stress and promoting plant growth and development. 24-EBR significantly increased all growth parameters compared to Cd treatment. In addition, 24-EBR significantly improved the gas exchange parameters, activities of antioxidant enzymes, and the cycle efficiency of AsA-GSH. Furthermore, 24-EBR increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) by 127.29%, 61.31%, 61.22%, and 51.04%, respectively, compared with the Cd treatment. Therefore, 24-EBR removed the reactive oxygen species produced by stress, thus protecting plants against stress damage. These results indicate that 24-EBR can effectively enhance the tolerance of P. forbesii to Cd stress.

Exogenous 24-epibrassinolide ameliorates tolerance to high-temperature by adjusting the biosynthesis of pigments, enzymatic, non-enzymatic antioxidants, and diosgenin content in fenugreek

High-temperature stress is widely considered a main plant-growth-limiting factor. The positive effects of 24-epibrassinolide (EBR) as analogs of brassinosteroids (BRs) in modulating abiotic stresses have led this hormone to be referred to as a growth regulator in plants. The current study highlights the influence of EBR on enhancing tolerance to high-temperature and altering the diosgenin content in fenugreek. Different amounts of EBR (4, 8, and 16 μM), harvesting times (6, and 24 h), as well as temperature regimes (23 °C, and 42 °C) were, used as treatments. EBR application under normal temperature and high-temperature stress resulted in decreased malondialdehyde content and electrolyte leakage percentage, while the activity of antioxidant enzymes improved significantly. Exogenous EBR application possibly contributes to activating the nitric oxide, H2O2, and ABA-dependent pathways, enhancing the biosynthesis of abscisic acid and auxin, and regulating the signal transduction pathways, which raises fenugreek tolerance to high-temperature. The SQS (eightfold), SEP (2.8-fold), CAS (11-fold), SMT (17-fold), and SQS (sixfold) expression, considerably increased following EBR application (8 μM) compared to the control. Compared to the control, when the short-term (6 h) high-temperature stress was accompanied by EBR (8 μM), a sixfold increase in diosgenin content was achieved. Our findings highlight the potential role of exogenous 24-epibrassinolide in mitigating the high-temperature stress in fenugreek by stimulating the biosynthesis processes of enzymatic and non-enzymatic antioxidants, chlorophylls, and diosgenin. In conclusion, the current results could be of utmost importance in breeding or biotechnology-based programs of fenugreek and also in the researches related to the engineering of the biosynthesis pathway of diosgenin in this valuable plant.

The Combined Analysis of Transcriptome and Antioxidant Enzymes Revealed the Mechanism of EBL and ZnO NPs Enhancing Styrax tonkinensis Seed Abiotic Stress Resistance.

As global climate change worsens, trees will have difficulties adapting to abiotic pressures, particularly in the field, where environmental characteristics are difficult to control. A prospective commercial and ornamental tree species, Styrax tonkinensis, has its seed oil output and quality reduced as a result, which lowers the economic benefits. This necessitates growers to implement efficient strategies to increase the seeds of woody biofuel species' tolerance to abiotic stress. Numerous studies have shown that ZnO nanoparticles (NPs), a new material, and BRs assist plants to increase their resilience to abiotic stress and subsequently adapt to it. However, there have not been many investigations into S. tonkinensis seed resistance. In this study, we examined the changes in antioxidant enzyme activities and transcriptomic results of S. tonkinensis seeds throughout the seed development period to investigate the effects of 24-epibrassinolide (EBL), one of the BRs, and ZnO NPs treatments alone or together on the stress resistance of S. tonkinensis seeds. On 70, 100, and 130 days after flowering (DAF), spraying EBL or ZnO NPs increased the activity of antioxidant enzymes (POD, SOD, and CAT) in S. tonkinensis seeds. Moreover, when the EBL and ZnO NPs were sprayed together, the activities of antioxidant enzymes were the strongest, which suggests that the positive effects of the two can be superimposed. On 70 and 100 DAF, the EBL and ZnO NPs treatments improved seed stress resistance, mostly through complex plant hormone crosstalk signaling, which includes IAA, JA, BR, and ABA signaling. Additionally, ABA played an essential role in hormone crosstalk, while, on 130 DAF, due to the physiological characteristics of seeds themselves in the late stage of maturity, the improvement in seed stress resistance by EBL and ZnO NPs was related to protein synthesis, especially late embryogenesis-abundant protein (LEA), and other nutrient storage in seeds. Spraying EBL and ZnO NPs during the seed growth of S. tonkinensis could significantly increase seed stress resistance. Our findings provide fresh perspectives on how cultural practices can increase abiotic stress tolerance in woody seedlings.

Effects of 24-epibrassinolide on the postharvest quality and antioxidant activities of blueberry fruits

ABSTRACT In this study, blueberry fruits (Vaccinium corymbosum cv. ‘Bluerain’) were sprayed with different concentrations (0.25, 0.5, 0.75, and 1 mg/L) of exogenous 24-epibrassionolide (EBR) after harvest and kept at 18°C and relative humidity of 90∼95% for 8 d. By observing the decay incidence and firmness changes, the optimal treatment concentration (0.75 mg/L) was screened, and then the effects of 0.75 mg/L EBR treatment on fruit quality and antioxidant activities were further explored. The results showed that EBR treatment could delay the decrease in firmness, total soluble solids, and acidity; maintain the contents of nutritional components, such as ascorbic acid, total phenol, and the total anthocyanin; and promote the activities of antioxidant enzymes, especially SOD and PAL, thereby helping to maintain the balance of reactive oxygen species and reduce the degree of membrane lipid peroxidation, as reflected by the content of MDA, and delaying the senescence process of blueberry fruit. Taken together, EBR treatment could help maintain the nutritional components of blueberry fruit and could be used as a new alternative reagent for blueberry preservation.

Epibrassinolide improves the growth performance of Sedum lineare upon Zn stress through boosting antioxidative capacities.

As an essential element, zinc (Zn) can improve or inhibit the growth of plants depending on its concentrations. In this study, the effects of 24-Epibrassinolide (EBR), one well-known steroid phytohormone regulating plant growth and alleviating abiotic stress damage, on morphological parameters and antioxidant capacities of Sedum lineare were investigated under different Zn doses. Compared to plants only exposed to Zn, simultaneously foliar application of 0.75 μM EBR significantly improved multiple morphological characteristics and such growth-improving effects were more significant at high Zn concentrations. At a detrimental 800 μM Zn, EBR benefitted plant growth most prominently, as shown by that the stem length, fresh weight and internode length were increased by 111%, 85% and 157%, respectively; than Zn solely treated plants. EBR spray also enhanced both the activities of antioxidant enzymes such as peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and the contents of antioxidative agents including ascorbic acid (AsA) and glutathione (GSH), which in turn decreased the accumulation of reactive oxygen species (ROS) and alleviated the lipid peroxidation in plants. Thus, by demonstrating that EBR could help S. lineare resist high-zinc stress through strengthening the antioxidant system, this work provided a new idea for expanding the planting range of Crassulaceae plants in heavy metal contaminated soil for phytoremediation purpose in the future.

Effects of brassinosteroids and gibberellin on water uptake and performance of soya bean seeds under different temperatures

Low temperature has negative effects on seed performance and seedling growth in soya bean, reducing stand establishment. It was hypothesised, that seed treatment with plant hormones could improve seed imbibition and performance at low temperature. Therefore, the effects of 24-epibrassinolide (EBL) and gibberellic acid (GA3) on soya bean seed germination were studied. Seeds of 'CM60' and 'CM0701-24' were imbibed with 0.25 or 0.50 ppm EBL, 50 or 100 ppm GA3, or distilled water at 10, 15, 20 and 25°C. The seed imbibition patterns of the two soya bean varieties followed a similar trend. Low temperature delayed seed imbibition resulting in longer time to reach the end of phases 1 and 2 of seed germination as compared with high temperature. Soya bean seeds treated with 50 or 100 ppm GA3 showed increased germination index, shoot and root length and reduced mean germination time. Thus, 50-100 ppm GA3 could be used as a pre-soaking seed treatment to improve soya bean seed and seedling performance under low temperature.

Exogenous EBR Ameliorates Endogenous Hormone Contents in Tomato Species under Low-Temperature Stress

Low-temperature stress is a type of abiotic stress that limits plant growth and production in both subtropical and tropical climate conditions. In the current study, the effects of 24-epi-brassinolide (EBR) as analogs of brassinosteroids (BRs) were investigated, in terms of hormone content, antioxidant enzyme activity, and transcription of several cold-responsive genes, under low-temperature stress (9 °C) in two different tomato species (cold-sensitive and cold-tolerant species). Results indicated that the treatment with exogenous EBR increases the content of gibberellic acid (GA3) and indole-3-acetic acid (IAA), whose accumulation is reduced by low temperatures in cold-sensitive species. Furthermore, the combination or contribution of BR and abscisic acid (ABA) as a synergetic interaction was recognized between BR and ABA in response to low temperatures. The content of malondialdehyde (MDA) and proline was significantly increased in both species, in response to low-temperature stress; however, EBR treatment did not affect the MDA and proline content. Moreover, in the present study, the effect of EBR application was different in the tomato species under low-temperature stress, which increased the catalase (CAT) activity in the cold-tolerant species and increased the glutathione peroxidase (GPX) activity in the cold-sensitive species. Furthermore, expression levels of cold-responsive genes were influenced by low-temperature stress and EBR treatment. Overall, our findings revealed that a low temperature causes oxidative stress while EBR treatment may decrease the reactive oxygen species (ROS) damage into increasing antioxidant enzymes, and improve the growth rate of the tomato by affecting auxin and gibberellin content. This study provides insight into the mechanism by which BRs regulate stress-dependent processes in tomatoes, and provides a theoretical basis for promoting cold resistance of the tomato.

Effects of 24-Epibrassinolide on DNA Methylation Variation in Soybean (Glycine max) Leaf and Root Under Saline-Alkali Stress

Saline-alkali stress is major stress that severely reduces plant growth and productivity, it is necessary to make clear whether exogenous 24-epibrassinolide (EBR) can improve the salt-alkali resistance of soybean (Glycine max) by affecting its DNA methylation. In this study, the effects of EBR on soybean adaptation to saline-alkali stress, genomic DNA methylation level and pattern changes in saline-alkali-stressed leaf and root with or without EBR treatment were compared using methylation-sensitive amplified polymorphism (MSAP). In the results, saline-alkali stress increased DNA methylation levels in leaf and root, with higher respective hemi-methylation and global methylation rates observed in leaf (6.22, 22.24%) than root (5.72, 21.76%). EBR application reduced leaf and root DNA methylation levels, with leaf hemi-methylation rate (6.15%) exceeding that of root (4.25%) and leaf global methylation rate (21.79%) below that of root (22.51%). There were distinct DNA remethylation and demethylation variations across different tissues and treatments, demethylation in leaves was dominant. Meanwhile, untreated saline-alkali-stressed roots exhibited major demethylation-based variations, while remethylation variations predominated post-treatment. Under saline-alkali stress, root remethylation and demethylation rates (6.17, 7.55%, respectively) both exceeded respective leaf rates (5.18 and 7.46%); however, post-EBR treatment, root methylation rate (6.45%) exceeded leaf rate (5.38%), while root demethylation rate (6.13%) fell below leaf rate (6.94%). In conclusion, exogenous EBR application to saline-alkali-stressed soybean can influence leaf and root genomic DNA methylation levels and patterns via distinct tissue-specific methylation mechanisms.

Effects of 24-Epibrassinolide, Bikinin, and Brassinazole on Barley Growth under Salinity Stress Are Genotype- and Dose-Dependent

Brassinosteroids (BRs) are involved in the regulation of many plant developmental processes and stress responses. In the presented study, we found a link between plant growth under salinity stress and sensitivity to 24-epibrassinolide (24-EBL, the most active phytohormone belonging to BRs), brassinazole (Brz) and bikinin (inhibitors of BR biosynthesis and signaling pathways, respectively). Plant sensitivity to treatment with active substances and salinity stress was genotype-dependent. Cv. Haruna Nijo was more responsive during the lamina joint inclination test, and improved shoot and root growth at lower concentrations of 24-EBL and bikinin under salinity stress, while cv. Golden Promise responded only to treatments of higher concentration. The use of Brz resulted in significant dose-dependent growth inhibition, greater for cv. Haruna Nijo. The results indicated that BR biosynthesis and/or signaling pathways take part in acclimation mechanisms, however, the regulation is complex and depends on internal (genotypic and tissue/organ sensitivity) and external factors (stress). Our results also confirmed that the lamina joint inclination test is a useful tool to define plant sensitivity to BRs, and to BR-dependent salinity stress. The test can be applied to manipulate the growth and stress responses of crops in agricultural practice or to select plants that are sensitive/tolerant to salinity stress in the plant breeding projects.

Effects of 24-Epibrassinolide on the Chlorophyll Fluorescence Transient in Leaves of Pepper under Drought Stress

Effects of 24-Epibrassinolide on the Chlorophyll Fluorescence Transient in Leaves of Pepper under Drought Stress

The Effect of 24-Epibrassinolide Treatments at Different Concentrations on Some Growth Parameters and Crocin Level in Saffron (Crocus sativus L.)

Brassinosteroids (BRs) are steroid phyotohormones that play roles in plant growth, secondary metabolite accumulation, stress response, and adaptation. Saffron (Crocus sativus L.) is an important plant with significant pharmacological effects due to its rich phytochemical content. Crocin, the main pigment of the saffron stigma, is a natural food colorant and has anti-cancer activity. In this study, the effects of 24-Epibrassinolide (EBL) at different concentrations (10-6, 10-7, 10-8 and 10-9 M) on corm (mother corm) and aerial part related parameters as well as the level of crocin in saffron were investigated. The experiment was conducted in a plant growth cabinet as randomized plots design with 3 replications. 24-Epibrassinolide treatments did not affect the rates of shoot emergence from saffron corms, while 10-8 and 10-9 M EBL treatments increased the number of active nodium and cormlet (daughter corm) as compared to control. All the applied EBL concentrations significantly increased the root and shoot lengths of saffron plants. The maximum number of flowers per plant was observed as a result of the 10-8 M EBL treatment. Exogenous treatment of 10-9 M EBL enhanced the crocin level by 96.0% compared to the control. This is the first study to evaluate the effects of BRs in saffron.

Brassinosteroid application affects the growth and gravitropic response of maize by regulating gene expression in the roots, shoots and leaves

Brassinosteroids (BRs) are a class of plant-specific steroid hormones that play key roles in plant physiology and that actively participate in the regulation of plant responses to stress. Thus, these compounds are also considered biostimulants that could be applied to crops to improve plant performance and induce abiotic stress tolerance. In this study, with a combined physiological and molecular approach, new insights into the effects of 24-epibrassinolide (EBL), a synthetic BR, on hydroponically grown maize seedlings were gained. To this aim, a preliminary assessment of the effect of different EBL concentrations and treatment times on root elongation was evaluated to determine the concentration to use in subsequent experiments. Treatment with 1 nM EBL and an exposure time of 48 h were selected to better assess the effects of this molecule on shoot growth and the root gravitropic response. Subsequently, an untargeted RNA-Seq-based approach was applied to obtain an overview of the transcriptomic regulation occurring in the roots, shoots and leaves upon exogenous brassinosteroid application. Our outcomes highlight the substantial influence exerted by this molecule on the growth and root gravitropic response of maize seedlings. Moreover, new insights into the BR response and BR signalling in plants were gained by performing the functional characterization of differentially expressed genes via Gene Ontology (GO) and pathway analyses. Overall, this study provides useful information that could help future agricultural applications of these substances.

Effects of 24-epibrassinolide and 28-homobrassinolide on iron plaque formation and the uptake of As and Cd by rice seedlings (Oryza sativa L.) in solution culture

Abstract The effects of 24-epibrassinolide (Br24) or 28-homobrassinolide (Br28) on the formation of iron plaque (IP) and the uptake of As and Cd by rice plant are poorly understood. Thus, the current work was performed to examine the impacts of Br24/Br28 (10−8 M) application on IP formation (50 mg Fe2＋ L−1 supply) and their interactions on As and Cd accumulation in rice seedlings exposed to As (III) (0.5 mg L−1) and/or Cd (0.5 mg L−1) stresses by a hydroponic experiment. The results showed that the combination of Br24/Br28 and IP induction decreased rice biomass, but markedly promoted IP formation and Fe concentrations in rice plant in comparison with single IP induction. Under Cd stress, IP induction significantly reduced Cd concentrations in shoots by 31% and root tissues by 51%, but the combinations of IP induction and Br24/Br28 promoted Cd concentrations in shoots, root tissues and root surface under Cd or As+Cd treatments. Under As stress, Br24 or IP induction did not affect As concentrations in root tissues and root surface, but markedly decreased that by 27% and 48% in shoots. Under As or As+Cd treatments, the interactions between IP induction and Br24/Br28 significantly enhanced As concentrations on the root surface and decreased that by 14%–50% in shoot. Our results demonstrate that Br24/Br28 application plays vital roles in promoting iron plaque formation and regulating As and Cd accumulation in rice plant.

24-Epibrassinolide delays senescence in harvested kiwifruit through effects on mitochondrial membrane and antioxidant activity

To explore the effects of 24-epibrassinolide (EBR) on senescence, kiwifruit were treated with 5 μmol L−1 EBR and then stored at 20 °C for 20 days. Results showed that EBR delayed changes in quality characteristics including respiration rate, pulp color and ascorbic acid content and inhibited accumulation of superoxide anion and hydrogen peroxide in kiwifruit. EBR-treated kiwifruit had higher levels of mitochondrial membrane fluidity and cytochrome c/a and lower levels of mitochondrial permeability transition pore opening, succinic dehydrogenase and cytochrome c oxidase, which were responsible for better mitochondrial membrane integrity and function. EBR also promoted the activity of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase leading to an enhancement of antioxidant activity in kiwifruit to counteract oxidative stress. We suggest that EBR treatment is an applicable strategy for kiwifruit to delay senescence and maintain storage quality.

Brassinosteroids enhance cold tolerance in Elymus nutans via mediating redox homeostasis and proline biosynthesis

Brassinosteroids (BRs) are a class of polyhydroxylated steroidal phytohormones that induce plant tolerance to a wide variety of stresses. Cold stress is a major environmental factor that limits plant growth. However, the mechanisms by which BRs regulate cold tolerance in alpine plants remains unclear. We analyzed the effects of 24-epibrassinolide (EBR) on growth, antioxidant defense, proline metabolism, and cold stress-related genes in Elymus nutans seedlings exposed to cold stress. Cold stress increased the transcript levels of BR-biosynthetic genes and the endogenous levels of BRs in E. nutans, which indicates the role of BRs in regulating cold tolerance. In addition, cold stress inhibited plant growth and increased malondialdehyde and reactive oxygen species (ROS) accumulation. However, application of EBR (1 μM) triggered catalase (CAT) activity and ascorbate (AsA)-reduced glutathione (GSH) cycle, thereby leading to lower ROS levels and plant growth inhibition. BR-induced cold tolerance was associated with an increase in proline levels. Pretreatment with EBR prior to cold stress improved the activities of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and Δ1-pyrroline-5-carboxylate reductase (P5CR), while slightly reduced the activities of proline dehydrogenase (PDH) and Δ1-pyrroline-5-carboxylate dehydrogenase (P5CDH). Increased transcript levels of P5CS and P5CR genes and decreased transcript level of PDH1 were detected in EBR-pretreated seedlings. Exogenous proline could alleviate the plant damage caused by cold stress in E. nutans and Arabidopsis bak1 mutant. Furthermore, bak1 mutant accumulated less proline compared with wild type plants, which indicates the close association between BR-mediated cold tolerance and proline metabolism. EBR Pretreatment also induced the expression of cold stress-related genes. These findings suggest that BRs enhance cold tolerance by inducing cold stress-related genes, which further regulates antioxidant defense and proline accumulation.

24-Epibrassinolide promotes NO3\u2212 and NH4+ ion flux rate and NRT1 gene expression in cucumber under suboptimal root zone temperature

BackgroundSuboptimal root zone temperature (RZT) causes a remarkable reduction in growth of horticultural crops during winter cultivation under greenhouse production. However, limited information is available on the effects of suboptimal RZT on nitrogen (N) metabolism in cucumber seedlings. The aim of this study is to investigate the effects of 24-Epibrassinolide (EBR) on nitrate and ammonium flux rate, N metabolism, and transcript levels of NRT1 family genes under suboptimal RZT in cucumber seedlings.ResultsSuboptimal RZT (LT) negatively affected on cucumber growth and proportionately decreased EBR contents, bleeding rate, root activity, enzyme activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT), nitrate (NO3−) influx rate, ammonium (NH4+) efflux rate, and transcript levels of nitrate transporter (NRT1) encoding genes. However, exogenous EBR reduced the harmful effects of suboptimal RZT and increased endogenous EBR contents, bleeding rate, root activity, enzyme activities of NR, NiR, GS, and GOGAT, NH4+ and NO3− flux rates and contents, and N accumulation. EBR-treated seedlings also upregulated the transcript levels of nitrate transporters CsNRT1.1, CsNRT1.2A, CsNRT1.2B, CsNRT1.2C, CsNRT1.3, CsNRT1.4A, CsNRT1.5B, CsNRT1.5C, CsNRT1.9, and CsNRT1.10, and downregulated CsNRT1.5A and CsNRT1.8. LT treatment upregulated the expression level of CsNRT1.5A, while exogenous BZR application downregulated the expression level of NRT1 genes.ConclusionThese results indicate that exogenous application of EBR alleviated the harmful effects of suboptimal RZT through changes in N metabolism, NH4+ and NO3− flux rates, and NRT1 gene expression, leading to improved cucumber seedlings growth. Our study provides the first evidence of the role of EBR in the response to suboptimal RZT in cucumber, and can be used to improve vegetable production.