Proline Accumulation Research Articles

An ecotype-specific effect of osmopriming and melatonin during salt stress in Arabidopsis thaliana

BackgroundNatural populations of Arabidopsis thaliana exhibit phenotypic variations in specific environments and growth conditions. However, this variation has not been explored after seed osmopriming treatments. The natural variation in biomass production and root system architecture (RSA) was investigated across the Arabidopsis thaliana core collection in response to the pre-sawing seed treatments by osmopriming, with and without melatonin (Mel). The goal was to identify and characterize physiologically contrasting ecotypes.ResultsVariability in RSA parameters in response to PEG-6000 seed osmopriming with and without Mel was observed across Arabidopsis thaliana ecotypes with especially positive impact of Mel addition under both control and 100 mM NaCl stress conditions. Two ecotypes, Can-0 and Kn-0, exhibited contrasted root phenotypes: seed osmopriming with and without Mel reduced the root growth of Can-0 plants while enhancing it in Kn-0 ones under both control and salt stress conditions. To understand the stress responses in these two ecotypes, main stress markers as well as physiological analyses were assessed in shoots and roots. Although the effect of Mel addition was evident in both ecotypes, its protective effect was more pronounced in Kn-0. Antioxidant enzymes were induced by osmopriming with Mel in both ecotypes, but Kn-0 was characterized by a higher responsiveness, especially in the activities of peroxidases in roots. Kn-0 plants experienced lower oxidative stress, and salt-induced ROS accumulation was reduced by osmopriming with Mel. In contrast, Can-0 exhibited lower enzyme activities but the accumulation of proline in its organs was particularly high. In both ecotypes, a greater response of antioxidant enzymes and proline accumulation was observed compared to mechanisms involving the reduction of Na+ content and prevention of K+ efflux.ConclusionsIn contrast to Can-0, Kn-0 plants grown from seeds osmoprimed with and without Mel displayed a lower root sensitivity to NaCl-induced oxidative stress. The opposite root growth patterns, enhanced by osmopriming treatments might result from different protective mechanisms employed by these two ecotypes which in turn result from adaptive strategies proper to specific habitats from which Can-0 and Kn-0 originate. The isolation of contrasting phenotypes paves the way for the identification of genetic factors affecting osmopriming efficiency.

Revitalizing maize growth and yield in water-limited environments through silicon and zinc foliar applications

Maize is an economically vital cereal crop. However, water deficiency can severely impact its productivity. Thus, it is necessary to implement an essential approach to increase maize yield while navigating the limitations imposed by scarce water supplies. The present study aimed to investigate whether foliar applications of silicon (Si) and zinc (Zn) could mitigate the adverse effects of water deficiency and improve maize growth and yield. Field experiments were conducted in Egypt during two growing seasons (2021–2022) under three irrigation regimes: full irrigation (ET0), moderate stress (ET1), and severe stress (ET2). The treatments comprised foliar sprays of Si, Zn, Si + Zn, and water control. Phenological, growth, physiological, chemical, and yield-related traits were assessed. Results showed that adequate irrigation (ET0) enhanced most parameters compared to water stress treatments. Under ET0, the combined silicon and zinc treatment resulted in the highest values for plant height, leaf area, chlorophyll content, grains per ear, kernel weight, ear size, and yield compared to other foliar treatments. Under drought stress (ET1, ET2), Si + Zn applications maintained superiority in mitigating yield losses. Proline accumulation was highest under severe stress (ET2) in the absence of foliar sprays, indicating greater drought impacts. Correlation analysis revealed positive associations of grain yield with ear size, leaf area, kernel weight, and biological yield. Cluster analysis separated irrigation regimes and visualized the consistently beneficial effects of Si + Zn across all water levels. Overall, the results demonstrate the synergistic potential of Si and Zn supplementation to sustain maize performance and yields under varying water availability.

Metal Sulfates and Microbial Food Treatment Alleviate the Oxidative Damage Caused by PEG-Induced Osmotic Stress in Cotton Plants

Background: Drought stress restricts cotton production, which causes a considerable loss of cotton yields worldwide. Plant activators improve crop production and ameliorate abiotic stresses. Thus, the effects of plant activators on the genotype of cotton (Gossypium hirsutum L.) Candia, which is resistant to drought, were investigated.Methods: Plants were treated with the plant activators, and then osmotic stress was initiated by 30% PEG 6000 treatment for 13 days. Antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POX) were measured along with growth, relative water content (RWC), osmotic potential, photosynthetic pigments, ion leakage, proline accumulation, malondialdehyde (MDA) content, and reactive oxygen species (ROS).Results: Osmotic stress reduced shoot fresh weight (FW) and osmotic potential but increased root length of Candia. Activator treatment alleviated these effects. Photosynthetic pigment contents and cell membrane permeability were not affected by osmotic stress and activator treatments; proline accumulation and lipid peroxidation levels were enhanced by osmotic stress, but activators alleviated these increments. Activity bands for the isozymes Mn-SOD1, SOD2, and SOD3, as well as the isozyme Fe-SOD, were found in Candia. Osmotic stress elevated APX activity in Candia leaves, while activator treatment decreased it. POX activity was not affected by osmotic stress, but activator treatment decreased POX activity. Osmotic stress-induced accumulation of ROS was lessened by activator treatment.Conclusion: Plant activator treatment reduced the amount of oxidative damage (ROS buildup and lipid peroxidation) caused by drought stress in the Candia genotype.Keywords: Antioxidant system; Cotton; Gossypium hirsutum L.; Osmotic stress; PEG 6000; Plant activators

Tetragonal crystalline MnO nanoparticles alleviate Pb stress in wheat by modulating antioxidant enzymes in leaves.

Agriculture ecosystems are seriously threatened by lead (Pb) contamination, which impacts plant growth and productivity. In this study, green synthesized manganese oxide nanoparticles (MnO NPs) using citrus peel were used for priming of wheat seeds. For the synthesis of MnO nanoparticles, peel extract of Citrus paradisi and 1mM solution of manganese acetate were stirred and calcinated at 500°C. Successful synthesis of MnO NPs was determined using advanced techniques. In Fourier-transform infrared spectroscopy (FTIR), the presence of amines, alkanes, aldehydes, and alcohol molecules, on the surface of MnO NPs, confirmed their stability. X-ray diffraction analysis described their average size (22nm), while scanning electron microscopy showed tetragonal crystalline shape and nano-flowers structure of MnO NPs. Sharp peaks of energy dispersive x-ray analysis described the presence of oxygen (28.81%) and manganese (71.19%) on MnO NPs. Priming of wheat seeds with synthesized MnO NPs significantly improved the growth attributes of wheat seedlings including the size of leaf, root length, size of shoots, chlorophyll and carotenoid contents, relative water content, decreased relative electrolyte leakage, high proline accumulation and decreased concentration of malondialdehyde. Application of MnO NPs also helped plants to accumulate antioxidant enzymes in their leaves. These results proved that the priming of MnO NPs can greatly reduce lead-induced stress in wheat seedlings and these NPs can alsobe used for the priming of other crops.

ZmDST44 Gene Is a Positive Regulator in Plant Drought Stress Tolerance.

Improving drought tolerance in plants is essential for increasing crop yields under water-limited conditions. In this study, we investigated the functional role of the maize gene ZmDST44, which is targeted by the miRNA ZmmiR139. Our results indicate that ZmmiR139 regulates ZmDST44 by cleaving its mRNA, as confirmed by inverse expression patterns and 5'-RACE analysis. Overexpression of ZmDST44 in Arabidopsis, rice, and maize resulted in significant enhancements in drought tolerance. Transgenic plants exhibited reduced malondialdehyde (MDA) levels, increased proline accumulation, and upregulation of drought-responsive genes compared to wild-type plants. Transgenic Arabidopsis and rice showed improved drought resistance and higher post-drought recovery rates, and transgenic maize displayed lower sensitivity to drought stress. These findings suggest that ZmDST44 acts as a positive regulator of drought tolerance across different plant species and holds promise for developing drought-resistant crops through genetic engineering.

Impact of a biostimulant enriched in betalain degradation products on ROS signaling, proline accumulation, and phytohormone homeostasis

This study investigates the potential of a biostimulant derived from Selenicereus undatus peel waste and enriched in betalain degradation products (BDP), to influence Arabidopsis thaliana seedling development. Notably, lower BDP concentrations enhanced seedling development, while higher dosages exhibited adverse effects. Assessment of mitochondrial activity in both seeds and purified organelles showed that the tested biostimulant did not affect mitochondrial activity or integrity, highlighting its independence from mitochondrial performance. Mechanistically, BDP-enriched biostimulant modulated ROS-signaling, diminishing H2O2 by regulating the enzymatic activity and gene expression of SOD, CAT, GPX, and GR. Particularly, analyzing their different isoform via qRT-PCR, the primary cellular compartment where detoxification occurred were identified. Furthermore, biostimulant was able to influence proline-accumulation, altering both the expression of metabolism (PC5S, P5CR and OAT) and catabolism (PDH and P5CDH) related genes. Finally, the BDP-enriched biostimulant altered phytohormone levels, mainly affecting ABA/ABA-glu, tZea/tZea-rib, and tZea/IAA. Concerning GAs, the increase in GA4 and GA7 suggested an involvement of GA13ox, a hypothesis encouraged by qRT-PCR analysis. In summary, this study underscores the potential of BDP-based biostimulant as sustainable promoters of plant growth, influencing critical regulatory pathways during germination. Further research is necessary to explore their extensive applications in agricultural practices.

Jasmonic Acid and Salicylic Acid improved resistance against Spodoptera frugiperda Infestation in maize by modulating growth and regulating redox homeostasis

Exploring host plant resistance and elevating plant defense mechanisms through the application of exogenous elicitors stands as a promising strategy for integrated pest management. The fall armyworm, a pernicious menace to grain crops in tropical and subtropical regions, stands as a formidable threat due to its capacity for devastation and a wide-ranging spectrum of host plants. There is no literature regarding artificially induced resistance in maize against fall armyworm (Spodoptera frugiperda) by exogenous application of phytohormones. The present investigation was performed to evaluate the role of jasmonic acid (JA) and salicylic acid (SA) on two maize hybrids namely FH-1046 and YH-1898 against fall armyworm. Results showed that plant height, biomass and lengths, fresh and dry weight of root shoot which decreased with armyworm infestation improved with phytohormonal application. JA treatment resulted in a higher increase in all attributes as compared to SA treatment. Improvement in relative water contents, photosynthetic pigments and pronounced levels of phenol and proline accumulation were observed in infested plants after JA treatment. Infested plants recovered from oxidative stress as JA application activated and increased the antioxidant enzyme activity of superoxide dismutase, peroxidase and polyphenol oxidase activity in both FH-1046 and YH-1898 . The oxidative stress reduction in infested plants after JA treatment was also evident from a fair decrease in MDA and H2O2 in both varieties. The SA and JA mediated genes expression was studied and it was found that in FH1046 maize cultivar, JA dependent genes, particularly marker genes PR1 and Lox5 were highly expressed along with TPS10 and BBT12. Whereas SPI, WRKY28, ICS and PAL were shown to be activated upon SA application. Evidently, both JA and SA elicited a robust defensive response within the maize plants against the voracious S. frugiperda, which in consequence exerted a discernible influence over the pest's developmental trajectory and physiological dynamics. A decrease in detoxification enzyme activity of the insects was observed after feeding on treated plants. Moreover, it was recorded that the survival and weight gain of FAW feeding on phytohormone treated maize plants also decelerated. In conclusion, FH-1046 was found to be more tolerant than YH-1898 against fall armyworm infestation and 1 mM JA was more effective than 1 mM SA for alleviation of fall armyworm stress. Therefore, it was inferred that phytohormones regulated redox homeostasis to circumvent oxidative damage and mediate essential metabolic events in maize under stress. To our current understanding, this study is the very first presentation of induced resistance in maize against S. frugiperda with the phytohormonal application (JA and SA).

Enhancing tomato plants' tolerance to combined heat and salt stress – The role of arbuscular mycorrhizae and biochar

The Mediterranean basin is highly susceptible to climate change, with soil salinization and the increase in average temperatures being two of the main factors affecting crop productivity in this region. Following our previous studies on describing the detrimental effects of heat and salt stress co-exposure on tomato plants, this study aimed to understand if substrate supplementation with a combination of arbuscular mycorrhizal fungi (AMF) and biochar could mitigate the negative consequences of these stresses. Upon 21 days of exposure, stressed tomato plants grown under supplemented substrates showed increased tolerance to heat (42 °C for 4 h/day), salt (100 mM NaCl), and their combination, presenting increased biomass and flowering rate. The beneficial effects of AMF and biochar were associated with a better ionic balance (i.e. lower sodium accumulation and higher uptake of calcium and magnesium) and increased photosynthetic efficiency. Indeed, these plants presented higher chlorophyll content and improved CO2 assimilation rates. Biochemical data further supported that tomato plants grown with AMF and biochar were capable of efficiently modulating their defence pathways, evidenced by the accumulation of proline, ascorbate, and glutathione, coupled with a lower dependency on energy-costly enzymatic antioxidant players. In summary, the obtained data strongly point towards a beneficial role of combined AMF and biochar as sustainable tools to improve plant growth and development under a climate change scenario, where soil salinization and heat peaks often occur together.

Effects of High Salinity and Water Stress on Wetland Grasses from the Spanish Mediterranean Coast.

The impacts of climate change are reaching unprecedented levels, heightening the risk of species loss and ecosystem service degradation. Wetlands, highly threatened ecosystems, serve vital ecological functions by capturing carbon, filtering water, and harbouring diverse wildlife. Coastal wetlands encounter many challenges, such as increased drought periods and escalating salinity levels, severely impacting plant biodiversity. Assessing how plants respond to various environmental stress factors is imperative for devising successful conservation strategies. In the present study, we examined three representative grass species found in various habitats within the Albufera Natural Park, close to the city of Valencia on the Spanish Mediterranean coast: Imperata cylindrica, Phragmites australis, and Saccharum ravennae. High salinity and water stress conditions were induced by subjecting the plants to irrigation with solutions containing 200, 400, 600, and 800 mM NaCl or withholding irrigation altogether to mimic coastal flooding and drought scenarios. The treatments were maintained until noticeable wilting of the plants occurred, at which point a range of stress biomarkers were determined, including photosynthetic pigments, ions, osmolytes, oxidative stress markers, and antioxidant metabolites, as well as antioxidant enzyme activities. Saccharum ravennae displayed the highest sensitivity to salt stress, whereas I. cylindrica appeared to be the most tolerant. The primary salinity tolerance mechanism observed in I. cylindrica and P. australis was a blockage of ion transport from the root zone to the aerial part, together with the salt-induced accumulation of proline and soluble sugars to high concentrations in the former. No significant effects of the water deficit treatment on the growth or biochemical parameters were observed for any of the analysed species. These findings offer valuable information for the effective management and conservation of coastal wetlands facing the challenges posed by climate change.

Regulation of Proline Accumulation and Protein Secretion in Sorghum under Combined Osmotic and Heat Stress.

Plants reprogramme their proteome to alter cellular metabolism for effective stress adaptation. Intracellular proteomic responses have been extensively studied, and the extracellular matrix stands as a key hub where peptide signals are generated/processed to trigger critical adaptive signal transduction cascades inaugurated at the cell surface. Therefore, it is important to study the plant extracellular proteome to understand its role in plant development and stress response. This study examined changes in the soluble extracellular sub-proteome of sorghum cell cultures exposed to a combination of sorbitol-induced osmotic stress and heat at 40 °C. The combined stress significantly reduced metabolic activity and altered protein secretion. While cells treated with osmotic stress alone had elevated proline content, the osmoprotectant in the combined treatment remained unchanged, confirming that sorghum cells exposed to combined stress utilise adaptive processes distinct from those invoked by the single stresses applied separately. Reactive oxygen species (ROS)-metabolising proteins and proteases dominated differentially expressed proteins identified in cells subjected to combined stress. ROS-generating peroxidases were suppressed, while ROS-degrading proteins were upregulated for protection from oxidative damage. Overall, our study provides protein candidates that could be used to develop crops better suited for an increasingly hot and dry climate.

Genome-wide and functional analysis of late embryogenesis abundant (LEA) genes during dormancy and sprouting periods of kernel consumption apricots (P. armeniaca L. × P. sibirica L.)

Late embryogenesis abundant (LEA) proteins play a crucial role in protecting cells from stress, making them potential contributors to abiotic stress tolerance. This study focuses on apricot (P. armeniaca L. × P. sibirica L.), where a comprehensive genome-wide analysis identified 54 LEA genes, categorized into eight subgroups based on phylogenetic relationships. Synteny analysis revealed 14 collinear blocks containing LEA genes between P. armeniaca × P. sibirica and Arabidopsis thaliana, with an additional 9 collinear blocks identified between P. armeniaca × P. sibirica and poplar. Examination of gene structure and conserved motifs indicated that these subgroups exhibit consistent exon-intron patterns and shared motifs. The expansion and duplication of LEA genes in P. armeniaca × P. sibirica were driven by whole-genome duplication (WGD), segmental duplication, and tandem duplication events. Expression analysis, utilizing RNA-seq data and quantitative real-time RT-PCR (qRT-PCR), indicated induction of PasLEA2-20, PasLEA3-2, PasLEA6-1, Pasdehydrin-3, and Pasdehydrin-5 in flower buds during dormancy and sprouting phases. Coexpression network analysis linked LEA genes with 15 cold-resistance genes. Remarkably, during the four developmental stages of flower buds in P. armeniaca × P. sibirica - physiological dormancy, ecological dormancy, sprouting period, and germination stage - the expression patterns of all PasLEAs coexpressed with cold stress-related genes remained consistent. Protein-protein interaction networks, established using Arabidopsis orthologs, emphasized connections between PasLEA proteins and cold resistance pathways. Overexpression of certain LEA genes in yeast and Arabidopsis conferred advantages under cold stress, including increased pod length, reduced bolting time and flowering time, improved survival and seed setting rates, elevated proline accumulation, and enhanced antioxidative enzymatic activities. Furthermore, these overexpressed plants exhibited upregulation of genes related to flower development and cold resistance. The Y1H assay confirmed that PasGBF4 and PasDOF3.5 act as upstream regulatory factors by binding to the promoter region of PasLEA3-2. PasDOF2.4, PasDnaJ2, and PasAP2 were also found to bind to the promoter of Pasdehydrin-3, regulating the expression levels of downstream genes. This comprehensive study explores the evolutionary relationships among PasLEA genes, protein interactions, and functional analyses during various stages of dormancy and sprouting in P. armeniaca × P. sibirica. It offers potential targets for enhancing cold resistance and manipulating flower bud dormancy in this apricot hybrid.

Foliar Application of Chitosan (CTS), γ-Aminobutyric Acid (GABA), or Sodium Chloride (NaCl) Mitigates Summer Bentgrass Decline in the Subtropical Zone.

Creeping bentgrass (Agrostis stolonifera) is an excellent cool-season turfgrass that is widely used in urban gardening, landscaping, and golf turf. Triennial field experiments from 2017 to 2019 were conducted to investigate effects of the foliar application of chitosan (CTS), γ-aminobutyric acid (GABA), or sodium chloride (NaCl) on mitigating summer bentgrass decline (SBD) and exploring the CTS, GABA, or NaCl regulatory mechanism of tolerance to summer heat stress associated with changes in chlorophyll (Chl) loss and photosynthetic capacity, osmotic adjustment (OA), oxidative damage, and cell membrane stability. The findings demonstrated that persistent ambient high temperatures above 30 °C during the summer months of 2017, 2018, and 2019 significantly reduced the turf quality (TQ), Chl content, photochemical efficiency of PSII (Fv/Fm and PIABS), leaf relative water content, and osmotic potential (OP) but significantly increased electrolyte leakage (EL) and the accumulations of free proline, water-soluble carbohydrate (WSC), hydrogen peroxide (H2O2), and malondialdehyde (MDA). The foliar application of CTS, GABA, or NaCl could significantly alleviate SBD, as reflected by improved TQ and delayed Chl loss during hot summer months. Heat-induced declines in Fv/Fm, PIABS, the net photosynthetic rate (Pn), the transpiration rate (Tr), and water use efficiency (WUE) could be significantly mitigated by the exogenous application of CTS, GABA, or NaCl. In addition, the foliar application of CTS, GABA, or NaCl also significantly improved the accumulations of free proline and WSC but reduced the EL, OP, and H2O2 content and the MDA content in leaves of creeping bentgrass in favor of water and redox homeostasis in summer. Based on the comprehensive evaluation of the subordinate function value analysis (SFVA), the CTS had the best effect on the mitigation of SBD, followed by GABA and NaCl in 2017, 2018, and 2019. The current study indicates that the foliar application of an appropriate dose of GABA, CTS, or NaCl provides a cost-effective strategy for mitigating SBD.

Elicitors directed in vitro growth and production of stevioside and other secondary metabolites in Stevia rebaudiana (Bertoni) Bertoni

Stevia rebaudiana (stevia) is a plant in the Asteraceae that contains several biologically active compounds including the antidiabetic diterpene glycosides (e.g. stevioside, rebaudioside and dulcoside) that can serve as zero-calorie sugar alternatives. In this study, an elicitation strategy was applied using 5% polyethylene glycol (PEG), sodium chloride (NaCl; 50 and 100 mM) and gibberellic acid (2.0 and 4.0 mg/L GA3) to investigate their effect on shoot morphogenesis, and the production of phenolics, flavonoids, total soluble sugars, proline and stevioside, as well as antioxidant activity, in shoot cultures of S. rebaudiana. Herewith, the media supplemented with 2 mg/L and 4 mg/L GA3 exhibited the highest shooting response (87% and 80%). The augmentation of lower concentrations of GA3 (2 mg/L) in combination with 6-benzylaminopurine (BAP) resulted in the maximum mean shoot length (11.1 cm). The addition of 100 mM NaCl salts to the media led to the highest observed total phenolics content (TPC; 4.11 mg/g-DW compared to the control 0.52 mg/g-DW), total flavonoids content (TFC; 1.26 mg/g-DW) and polyphenolics concentration (5.39 mg/g-DW) in shoots cultured. However, the maximum antioxidant activity (81.8%) was observed in shoots raised in media treated with 50 mM NaCl. The application of 2 mg/L of GA3 resulted in the highest accumulation of proline (0.99 μg/mL) as compared to controls (0.37 μg/mL). Maximum stevioside content (71 µL/mL) was observed in cultures supplemented with 100 mM NaCl and 5% PEG, followed by the 4 mg/L GA3 treatment (70 µL/mL) as compared to control (60 µL/mL). Positive correlation was observed between GA3 and stevioside content. Notably, these two compounds are derived from a shared biochemical pathway. These results suggest that elicitation is an effective option to enhance the accumulation of steviosides and other metabolites and provides the groundwork for future industrial scale production using bioreactors.

GA3 and BAP phytohormone seed priming enhances germination and PEG induced drought stress tolerance in soybean by triggering the expression of osmolytes, antioxidant enzymes and related genes at the early seedling growth stages

Drought stress strongly affects seed germination and seedling development during the early stages of plant growth in soybean (Glycine max L.). Seed priming with phytohormone (PH) is known to regulate various physiological and biochemical processes that govern plant growth and yield under optimal and stress conditions. In the present study, the effects of seed priming with Gibberellic acid (GA3) (0.28 mM), 6-Benzyl aminopurine (BAP) (20 mM) and Methyl Jasmonate (MJ) (2.5 mM) was studied during germination and at early seedling growth stages in JS-335 (drought sensitive) and MAUS-71 (moderately drought tolerant) soybean varieties under PFG induced drought stress conditions. The seed priming effects were studied in terms of germination percentage and rate (Timson Index), accumulation of osmolytes (proline and glycine betaine), antioxidant enzymes activity (superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)), and the relative expression of genes viz., Cu/Zn-superoxide dismutase copper chaperone (SOD-CCS) , iron-superoxide dismutase (SODB2) , betaine aldehyde dehydrogenase (BADH2) and dehydration-responsive element binding protein (DREB2A). The germination percentage of non-primed soybean seeds decreased under drought stress but significantly increased upon GA3 and BAP priming. Interestingly, seed priming with MJ completely inhibited the germination in both the varieties. GA3 and BAP seed priming increased proline and glycine betaine accumulation under PEG induced drought stress in both the soybean varieties. The results showed that the activities of SOD, APX and CAT were significantly enhanced in the leaves of seedlings raised from GA3 and BAP-primed seeds, as compared to the non-primed seeds under the drought stress conditions. Isozyme profiling of SOD and APX revealed that the GA3 and BAP seed priming treatments enhanced the drought-inducible expression of SOD isozymes rather than inducing novel isoforms. In case of APX isozymes, GA3 seed priming appears to preserve APX isozyme diversity in both varieties, and BAP seed priming elevated the expression of APX isoforms in both soybean varieties under the drought conditions. In response to the drought stress, relative expression of the genes associated with superoxide dismutase and glycine betaine viz., SOD CCS, SODB2, BADH2 and DREB2A was markedly upregulated in the leaves of seedlings raised from the GA3 and BAP primed seeds in both the soybean varieties. The global correlation analysis designated that the osmolyte Proline, antioxidant enzyme APX and CAT, and SOD CCS, SODB2, BADH2 and DREB2A genes were potent regulator for drought stress tolerance mechanism in soybean. This study illuminates the intricate interplay of GA3 and BAP hormonal seed priming during the germination and early seedling stages in soybean plants under the drought stress. This finding emphasizes the critical consideration of genotype specific reactions to the hormonal seed priming under PEG induced drought stress conditions.

Stress responsive ZmWRKY53 gene increases cold tolerance in rice.

Plant WRKY transcription factors are responsible for biotic and abiotic stresses and play an important role in enhancing their adaptability. The AtWRKY33 is a gene that functions in response to abiotic stresses such as low temperature, drought, salinity, etc. In this study, a recombinant vector YG8198-ZmWRKY53 carrying the ZmWRKY53, an interspecific homolog of the dicotyledonous AtWRKY33, was transferred to rice plants by Agrobacterium mediated transformation. The ectopic expression of the ZmWRKY53 in transgenic rice plants conferred cold tolerance with a higher accumulation of free proline and water-soluble sugars, an increase in chlorophyll content, a decrease in electrolyte leakage rate and MDA levels compared to control plants. This result suggests that ZmWRKY53 may confer cold tolerance in rice.

Surface modified ZnO NPs by betaine and proline build up tomato plants against drought stress and increase fruit nutritional quality

Drought stress is a serious challenge for global food production. Nanofertilizers and nanocomposites cope with such environmental stresses and also increase nutritional contents of fruits. An in vitro experiment was designed to use Zinc Oxide Nanoparticles (ZnO NPs) primed with Proline and Betaine (ZnOP and ZnOBt NPs) at 50 and 100 mg/kg soil against drought stress in Tomato (Solanum lycopersicum) plants. Plant morphological, biochemical, and fruit nutritional quality were accessed. Maximum plant height was observed under the treatment of ZnOP50 (1.09 m) and ZnO 100 (1.06 m). ZnOP and ZnOBt also improved the chlorophyll content up to 86% and 87.16%, respectively. Application of ZnOP NPs also demonstrated maximum tomato yield (204 g tomato/plant) followed by ZnO NPs and ZnOBt NPs. Nanocomposites decreased phenolics and flavonoids contents in drought stressed plants demonstrating the mitigation of oxidative stress. Nanofertilizer also increased the concentration of phenolics and flavonoids in fruits that increased the nutritional contents. Furthermore a significant accumulation of betaine, proline, and lycopene in fruits on nanocomposite treatment made it nutritional and healthy. Lycopene content increased up to 2.01% and 1.23% in presence of ZnOP50 and ZnOP100, respectively. These outcomes validate that drought stress in plant can be reduced by accumulation of different phytochemicals and quenching oxidative stress. The study deems that nano zinc carrying osmoregulators can greatly reduce the negative effects of drought stress and increase nutritional quality of tomato fruits.

Integrated metabolomics and transcriptomics reveal that HhERF9 positively regulates salt tolerance in Hibiscus hamabo Siebold & Zuccarini

Hibiscus hamabo Siebold & Zuccarini is one of the few semi-mangrove plants in the genus Hibiscus that can survive in saline-alkali soil and flooded land, but the mechanism underlying its adaptation to salt soil remains unknown. Here, to uncover this unsolved mystery, we characterized the changes in the accumulation of specific metabolites under salt stress in H. hamabo by integrating physiological, metabolic, and transcriptomic data, and found that osmotic adjustment and abscisic acid (ABA) is highly associated with the salt stress response. Further, a weighted gene co-expression network analysis was performed on the root transcriptome data, which identified three key candidate transcription factors responsive to salt stress. Among them, the expression HhERF9 was significantly upregulated under salt stress and ABA treatment and was involved in regulating the expression of genes related to the salt stress response. Further research indicated that HhERF9 enhances the accumulation of proline and soluble sugars by regulating the expression of genes such as NHX2 and P5CS. These findings provide a reference for improving H. hamabo through targeted genetic engineering and lay a theoretical foundation for its future promotion and cultivation in saline-alkali areas.

Melatonin Combined with Wax Treatment Enhances Tolerance to Chilling Injury in Red Bell Pepper.

Bell peppers (Capsicum annuum L.) are prone to chilling injury (CI) when stored at temperatures below 7 °C. Melatonin, a natural plant regulator, plays a critical role in defending against different pre- and post-harvest abiotic stresses, including those associated with cold storage. This study aimed to assess the effects of applying exogenous melatonin alone and in combination with a commercial wax on the CI tolerance, postharvest life, and potential biomarker search of red bell peppers. In the initial experiment, the effective melatonin concentration to reduce CI effects was determined. Peppers were sprayed with either distilled water (control) or a melatonin aqueous solution (M100 = 100 μM or M500 = 500 μM) and then stored for 33 d at 4 °C, followed by 2 d at 20 °C. The M500 treatment proved to be more effective in reducing fruit CI incidence (superficial scalds) and metabolic rate, while weight loss, softening, and color were comparable to the control. A second experiment assessed the potential synergistic effects of a combined melatonin and commercial wax treatment on pepper CI and quality. Fruits were sprayed with distilled water (control), melatonin (M500), commercial wax (Wax), or the combined treatment (Wax + M500) and stored for 28 d at 4 °C, followed by 2 d at 20 °C. The Wax + M500 was the most effective in significantly reducing the incidence of fruit CI symptoms and calyx fungal infection. Furthermore, this combined treatment enhanced fruit weight loss prevention compared with individual melatonin or wax treatment. Also, Wax + M500-treated peppers exhibited notable proline accumulation, indicative of a metabolic response counteracting the cold effects, resulting in better fruit stress acclimation. This treatment also preserved the peppers' color and antioxidant capacity. In summary, these findings highlight the suitability of applying a combined Wax + M500 treatment as a highly effective strategy to enhance the CI tolerance of peppers and extend their postharvest life.

Effect of Phosphorus Fertilizer on Morpho-physiological, and Biochemical Traits of Bambara Groundnut (Vigna subterranea (L.) Verdc.) Plants Under Water Deficit

Aims: To evaluate the effect of water deficit (WD) and P-fertilizer on the growth and biochemical composition of Bambara groundnut. Study Design: The experimental design was a randomized complete block with three factors: landraces (L1, L2, and L3), single superphosphate doses (0, 20, 40, 60, 100 mg P2O5.kg-1), and watering regime (90% (control), 60%, and 30% of field capacity (FC)). Place and Duration of Study: Department of Plant Biology, Faculty of Science, University of Yaounde I for three months. Methodology: The seedlings (radicle at 2 mm) were sown in the polyethylene pots filled with substrate with the appropriate P-doses. The plants were grown for up to four weeks under normal watering level (90%_FC). Four weeks after sowing (WAS), the WD was applied by stopping irrigation and maintaining the desired FC. At harvest (8WAS), growth, physiological and biochemical parameters were evaluated. Results: P-fertilizer significantly improved growth and biochemical composition under WD or none. The plant height increased from 20.3% from 0 to 100 mg P2O5 at 30%_FC to L2 at the 8th week. At 90%_FC, the doses 20, 40, 60, 100 mg increased sugars content by 52.6, 59.4, 64.6, and 90.4%, respectively, compared to 0 mg at L3. Proline content at 30%_FC was twice (2.5) that of 90%_FC at L2. Increased accumulation of sugars, proline, and amino acids in leaves was recorded at the severe level of WD. Conclusion: P-fertilizer mitigated the adverse effect of WD on the growth and biochemical composition of Bambara groundnut. A sufficient P-supply (60 mg P2O5.kg-1) was recommended to help Bambara groundnut plants tolerate WD. L1 and L3 appear to be more tolerant than L2 and can be recommended to farmers. As the adaptation mechanisms of these landraces to WD are different, it would be advisable to evaluate their performance in the field to better assess their behavior.

Exogenously Applied γ-Aminobutyric Acid Improves Salt Tolerance in Alfalfa by Modulating Ion Homeostasis, Proline Accumulation and Antioxidant Defence System

Exogenously Applied γ-Aminobutyric Acid Improves Salt Tolerance in Alfalfa by Modulating Ion Homeostasis, Proline Accumulation and Antioxidant Defence System