Stress Conditions Research Articles

A Comparative Study on Growth Rates and Length-weight Relationships of Snow Trout (Schizothorax sp.) from Rasuwa, Nuwakot, and Okhaldhunga Districts of Nepal

Aims: Snow trout (Schizothorax spp.) are vital to Nepal's aquatic biodiversity and economy, yet little research has addressed their growth potential under controlled conditions. This study aimed to evaluate the growth performance of snow trout from three regions of Nepal (Okhaldhunga, Nuwakot, and Rasuwa) in captivity. Study Design: Original Research Article. Place and Duration of Study: Fisheries Research Station (FRS), Trishuli Nepal, between August 18 November 24, 2023. Methodology: Schizothorax species were collected from Okhaldhunga, Nuwakot, and Rasuwa districts and acclimated to the environment of the FRS in three separate raceways prior to the feeding trial. From each location, a population of 450 apparently healthy and uniform sized snow trout (initial weight: 20.00 + 1.2g) were then distributed into 3 raceway tanks, altogether 9 raceways for 3 groups, feeding upon the commercial feed (48% crude protein) in the form of dough at 3% of the body weight for 90 days. At the end of the feeding trial, growth parameters, including weight gain, specific growth rate (SGR), condition factor (K) and Length-weight relationship (LWR) were measured. Survival rate and water quality parameters were also measured. Statistical analysis for group’s means differences was conducted using one-way ANOVA in R Studio for Windows at a 5% level of significance. Results: Results indicated Fish from Nuwakot exhibited the highest weight gain (3.61 ± 1.82 g) and SGR (0.23 ± 0.12% per day), though these differences were not statistically significant (P >0.05). The condition factor (K) was highest for Rasuwa fish (0.98), followed by Nuwakot (0.97) and Okhaldhunga (0.97) (P >0.05), indicating that the fish were relatively thin, possibly due to poor nutrition or stressful conditions. The LWR analysis revealed high length-weight correlations for all groups, with Rasuwa fish exhibiting a positive allometric growth pattern (b=3.02), whereas Okhaldhunga (b=2.93) and Nuwakot (b=2.94) fish showed negative allometric growth patterns. This may suggest that snow trotu from Rasuwa were in relatively good physiological condition and adapting well to the rearing conditions at the FRS. Although with no statistical difference, the survival rate was highest for fish from Nuwakot (86.67%), followed by Rasuwa (80.00%) and Okhaldhunga (77.33%) (P >0.05). This may indicate the adequacy of the water quality (average temperature 11.75 ± 0.42℃, dissolved oxygen more than 7 mg/L, and pH 7.71 ± 0.16) maintained during the study. Conclusion: The findings suggest that while the snow trout demonstrated the ability to survive yet grow slowly under captivity, their growth performance may be significantly enhanced by optimizing rearing conditions, particularly slightly higher water temperature. This study underscores the need for targeted improvements in aquaculture practices to support the effective domestication and conservation of snow trout in Nepal.

FANCD2 genome binding is nonrandom and is enriched at large transcriptionally active neural genes prone to copy number variation

Fanconi anemia (FA) is a rare genetic disease characterized by congenital abnormalities and increased risk for bone marrow failure and cancer. Central nervous system defects, including acute and irreversible loss of neurological function and white matter lesions with calcifications, have become increasingly recognized among FA patients, and are collectively referred to as Fanconi Anemia Neurological Syndrome or FANS. The molecular etiology of FANS is poorly understood. In this study, we have used a functional integrative genomics approach to further define the function of the FANCD2 protein and FA pathway. Combined analysis of new and existing FANCD2 ChIP-seq datasets demonstrates that FANCD2 binds nonrandomly throughout the genome with binding enriched at transcription start sites and in broad regions spanning protein-coding gene bodies. FANCD2 demonstrates a strong preference for large neural genes involved in neuronal differentiation, synapse function, and cell adhesion, with many of these genes implicated in neurodevelopmental and neuropsychiatric disorders. Furthermore, FANCD2 binds to regions of the genome that replicate late, undergo mitotic DNA synthesis (MiDAS) under conditions of replication stress, and are hotspots for copy number variation. Our analysis describes an important targeted role for FANCD2 and the FA pathway in the maintenance of large neural gene stability.

Corrosion resistance and wear behavior of CoCrFeNiMn@Gr high entropy alloy-based composite coatings prepared by laser cladding

In this study, we utilize laser cladding to apply a CoCrFeNiMn HEA with 2 wt.% few-layer graphene (Gr) coating onto the surface of Q235B mild steel. Alcohol stirring method was used for HEA and Gr preparation of composite powder. Raman spectroscopy and energy dispersion spectroscope (EDS) indicate the successful mixing of HEA and Gr powders, with Gr adhering to the surface of the HEA powder in a lamellar structure. The X-ray diffraction (XRD), scanning electron microscope (SEM), EDS, and Electron backscatter diffraction (EBSD) analyses revealed that grain refinement and the formation of fine carbide-hard phases in the HEA/Gr coating improve microhardness and wear resistance. The average Schmidt factors of the coating decreased from 0.47 to 0.45 with the addition of Gr, indicating enhanced resistance to plastic deformation and anisotropy. Nanoindentation experiments demonstrated that the HEA/Gr coatings exhibit superior resistance to plastic deformation, effectively enhancing the coating’s durability against spalling under stress and wear conditions. The microhardness of the HEA/Gr coating increased by 99.25%, and the wear rate decreased by 86.31% compared to the HEA coating alone. The open circuit potential (OCP), linear polarization curve, Tafel curves, electrochemical impedance spectroscopy (EIS), and Mott-Schottky tests all indicated that the HEA/Gr coating possesses superior corrosion resistance. X-ray Photoelectron Spectroscopy (XPS) results suggest that the passivation film of the HEA/Gr coating, which contains more oxides and less hydroxide, is more protective and denser, thereby slowing the corrosion rate.

Genome-wide association mapping and genomic prediction of water deficit stress tolerance indices in spring bread wheat

Genome-wide association mapping (GWAM) is crucial for identifying the genetic architecture of quantitative traits, such as drought tolerance indices in bread wheat. This study aims to identify Marker-Trait Associations (MTAs) and genes related to drought tolerance indices in wheat. Seven drought tolerance indices were calculated based on grain weight per spike under field drought stress (FDS) and field non-stress (FNS) conditions. These indices included mean productivity (MP), geometric mean productivity (GMP), relative drought index (RDI), stress tolerance index (STI), tolerance index (TOL), stress susceptibility index (SSI), and yield stability index (YSI). Genotyping of the samples was performed using single nucleotide polymorphism (SNP) markers. A total of 96 MTAs were identified for the studied indices and conditions FNS and FDS in this experiment, with a threshold of -log10p ≥ 3.0. These included FNS, FDS, GMP, MP, STI, SSI, RDI, and YSI, with 15, 11, 16, 16, 20, 6, 6, and 6 MTAs, respectively. The MTAs identified for the drought tolerance indices GMP, MP, and STI were located on chromosomes 2 A, 3B, and 6 A, respectively. Moreover, this study identified four genes related to the indices, namely “TraesCS2B02G000100,” “TraesCS3A02G000100,” “TraesCS2B02G000200,” and “TraesCS4B02G000100”. These genes play a crucial role in drought tolerance and can be utilized for marker-assisted selection to enhance drought tolerance wheat genotypes.

The antibacterial and antioxidant activities of combined Equisetum arvense extract with TiO2 nanoparticles in PMAA films

Studies on the antibacterial effects of natural compounds, particularly those derived from medicinal plants, have garnered a lot of attention because of the enhanced resistance of germs to antibiotics. The resistance of bacteria to plant-derived chemicals may develop much slower if not at all, which enhances the potential for future research in this area. This study investigates the antibacterial effect of Equisetum arvense extract combined with TiO2 nanoparticles and embedded in Polymethacrylic acid films on the growth of Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. The prepared material was characterized via X-ray Diffraction, Scanning Electron Microscopy, and Atomic Force Microscopy to understand the physicochemical merits of it, and the antibacterial properties were then examined. The results indicate that Equisetum arvense exhibits antibacterial properties against Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. At modest dosages, this plant may offer a novel treatment option for disorders associated with oxidative stress, apoptosis, or hypertonic conditions.

Non-senescent species are not immortal: Stress and decline in two planaria species.

Potential immortality is observed in several species (e.g. prickly pear cactus, hydra and flatworms) and is indicative of their negligible or even negative senescence rates. Unlike in senescent species, which experience reduced individual performance with age due to physiological degradation, species with negligible or negative senescence display mortality rates that remain constant or decline with age, respectively. These rates vary across taxa and are correlated with life history traits. Yet, the extent to which variable resource availability, a key driver of variation in life history traits, impacts species that show negligible or negative senescence is currently unknown. Here, we examine whether and how variation in the quantity, quality and feeding interval of resources impact population structure, population performance and life history trait trade-offs in two long-lived planaria that do not senesce: Schmidtea mediterranea and Dugesia tahitiensis. In a full factorial design, different combinations of resource quantity (reduced intake, standard intake and high intake) and quality (high and low quality) were provided in two different feeding intervals (7-day and 14-day intervals) for 19 weeks. We show that variability in resource availability, via decreases in quantity, quality and frequency of resources, does not diminish population viability in either species but does result in suboptimal conditions of stress in S. mediterranea. The high population viability we report can be attributed to two different mechanisms: increased reproduction or increased investment into maintenance at the expense of reproduction. Moreover, which mechanism was responsible for said high population viability was context-dependent and modulated by the specific life history strategy of the two planaria species. We show that suboptimal conditions can cause stress responses that have significant impacts on non-senescent species. The context-dependent response we observe suggests that species that do not senesce but are subject to suboptimal conditions of stress may ultimately exhibit declines in performance and ultimately die. A clearer understanding of the impact of suboptimal conditions of resource availability on non-senescent species is needed to determine the extent of stress experienced and ultimately whether a species can truly be immortal.

Genome-Wide Identification, Phylogenetic, and Expression Analysis of Jasmonate ZIM-Domain Gene Family in Medicago Sativa L.

JASMONATE ZIM domain (JAZ) proteins, inhibitors of the jasmonic acid (JA) signaling pathway, are identified in different plants, such as rice and Arabidopsis. These proteins are crucial for growth, development, and abiotic stress responses. However, limited information is available regarding the JAZ family in alfalfa. This study identified 11 JAZ genes (MsJAZs) in the “Zhongmu No.1” reference genome of alfalfa. The physical and chemical properties, chromosome localization, phylogenetic relationships, gene structure, cis-acting elements, and collinearity of the 11 MsJAZ genes were subsequently analyzed. Tissue-specific analysis revealed distinct functions of different MsJAZ genes in growth and development. The expression patterns of MsJAZ genes under salt stress conditions were validated using qRT-PCR. All MsJAZ genes responded to salt stress, with varying levels of upregulation over time, highlighting their role in stress responses. Furthermore, heterogeneous expression of MsJAZ1 in Arabidopsis resulted in significantly lower seed germination and survival rates in OE-2 and OE-4 compared to the WT under 150 mM NaCl treatment. This study establishes a foundation for further exploration of the function of the JAZ family and provides significant insights into the genetic improvement of alfalfa.

High light and nitrogen deficiency synergistically lead to biofuel and biomass accumulation in diatoms

As a clean energy source, the lipids from microalgae serve as alternatives to fossil oils. There are significant differences in the biofuel and biomass accumulation of microalgae under different environmental conditions. This study investigated the response of biofuel accumulation, photosynthetic capacity, and growth of diatom Thalassiosira pseudonana under stress conditions of high light and nitrogen deficiency, aiming to explore the features of biofuel and biomass accumulation in microalgae under special environmental conditions. The results indicated that the synthesis of chlorophyll was inhibited, leading to reduced light absorption and less damage to the photosynthetic system, with an improvement in electron transport efficiency. Lipid metabolism was more active during the dark cycle, with a 2.89-fold accumulation of fatty acids and a significant increase in the content of neutral lipids (2.39 times). The cell cycle progressed faster, resulting in a marked increase in biomass (1.41 times). These processes consumed a considerable amount of energy, affecting the synthesis of ribosomes. These findings suggest that increasing light exposure and reducing nitrogen supply can achieve the co-accumulation of biofuel and biomass in T. pseudonana.

Cellular Resiliency and Survival of a Neuro-2a Cell Line Under Extreme Stress

The study investigates the survival and recovery of Neuro-2a (N2a) cells following a cryogenic storage failure that exposed them to extreme stress conditions, such as hypoxia, hypothermia, and acute toxicity. Remarkably, a small fraction of the cells survived and eventually recovered. To understand the underlying resilience mechanisms, we created a model to replicate the dewar failure event and examined changes in phenotype, transcriptomics, proteomics, and mitochondrial activity of the surviving cells during recovery. The results revealed that the surviving cells initially displayed a stressed morphology, with irregular membranes and clustering. They showed increased expression of proteins related to DNA repair and chromatin modification pathways, as well as heightened mitochondrial function, shortly after the stress event. As recovery progressed, these stress-responsive pathways and mitochondrial activity normalized, indicating a return to a stable state. These findings suggest that an initial robust energetic state supports key stress-responsive pathways, facilitating cell survival and recovery after extreme stress. This work provides valuable insights into cellular resilience mechanisms, with potential implications for improving cell preservation and recovery in biomedical applications and developing therapeutic strategies for conditions involving cell damage and stress.

Expansion of a hole in a thin plate considering arbitrary smooth pressure-independent yield criterion and work-hardening law

A solution for arbitrary smooth pressure-independent yield criterion and work-hardening law is obtained for the expansion of a hole in an initially uniform infinite plate under plane stress conditions. It is then specialized to widely used yield criteria and work-hardening laws. It is shown that both yield criterion and work-hardening law affect the qualitative behavior of the solution, especially near the hole's surface. In particular, local thickening or thinning may occur there. It is due to the fact that the thickness and yield stress contribute to sustaining the pressure applied to the hole's surface. Therefore, the higher hardening rate requires a smaller thickness. A criterion for the solution's validity applies, and a procedure for using this criterion is developed. Numerical examples illustrate the solution for von Mises and Hosford's yield criteria and Swift's and Voce's hardening laws.

Mercury removal by Aquarius palifolius (Nees & Mart.) Christenh. & Byng: Isotherms model, superoxide dismutase activity, and chlorophyll content

Mercury is one of the heavy metals that became a global threat in this industrialization era. Artisanal and Small-Scale Gold Mining activities are the leading cause of this mercury pollution. Sustainable and environmentally friendly methods can be a solution to overcome this problem. Bioremediation methods use plants with defense mechanisms against mercury, namely Mexican sword plants or Aquarius palifolius, which is a promising solution. This research aimed to analyze the isotherm model of mercury content in A. palifolius in the Free Water Surface-Constructed Wetland (FWS-CW) reactor using the Langmuir and Freundlich isotherm equations; analyzed the activity of antioxidant enzymes in A. palifolius such as Superoxide dismutase (SOD); and also analyzed the effect of mercury stress on chlorophyll levels in A. palifolius. This research shows that the mercury phytoremediation process by A. palifolius is more suitable with the Langmuir isotherm model. There are no significant differences in SOD activity and chlorophyll levels between A. palifolius with and without mercury concentration. This indicates that A. palifolius is a hyperaccumulator plant that can survive in mercury stress conditions and even remove mercury from contaminated water.

Electric fields to support microalgae growth with a differentiated biochemical composition

Microalgae are a group of microorganisms well-known for their high metabolic plasticity and biomass with commercial interest for several industries. In the present work, the influence of in-situ electric field application (INEF) on the growth and biochemical composition of Pavlova gyrans was, for the first time, assessed. Electrical protocols were tested, namely by applying INEF in different growth stages, in varying treatment times and even by combining it with dark phase of cells' photoperiod. INEF did not promote a stimulatory effect on growth but influenced the biochemical composition of P. gyrans – maximum increases of 74.9 and 66.2 % in the chlorophyll a and carotenoid content and of 4.72, 18.7 and 5.41 % in the lipid, carbohydrate and protein content were observed in independent experiments. Hence, with this study, the potential of INEF application as a strategy to modulate growth and to promote biochemical composition alterations was proven. Industrial relevanceMicroalgae, with their unique ability to efficiently convert sunlight and carbon dioxide into biomass, offer a sustainable platform for the synthesis of diverse bioactive compounds. By subjecting microalgae to controlled electric stress conditions, their metabolic pathways can be redirected towards the production of specific target compounds. This strategy has the potential to enhance the yield of high-value molecules, including biofuels, pharmaceuticals, nutraceuticals, and pigments, whilst minimizing resource inputs. Additionally, metabolic stress responses in microalgae often trigger the accumulation of secondary metabolites with bioactive properties. Harnessing the metabolic plasticity of microalgae through controlled stress manipulation represents a cutting-edge strategy for sustainable and economically viable bioproduction systems that align with the goals of green chemistry and circular economy principles.

Response of broilers to supplementation of Salvia officinalis L. essential oil in hot ambient conditions.

Heat stress has various detrimental effects on poultry production. The aim of the study was to alleviate the effects of heat stress in broiler production. For this purpose, 288 one-day-old broiler chicks (Ross 308) were obtained from a commercial hatchery and randomly allocated to one of three treatment groups; CON: corn-soybean meal based commercial diet, SEO100: CON with 100mg/kg Sage essential oil (SEO) and SEO200: CON with 200mg/kg SEO with 96 birds in each group (4 replicates each) in a completely randomized design under hot ambient temperatures for 42 days. No differences were observed in the body weight, feed intake, and feed conversion ratio at 42 days of age among groups. However, there was a significant increase in 21-day body weight in SEO200 chicks compared to CON. Furthermore, the addition of SEO significantly decreased the mortality rate under heat stress conditions. The total oxidant status value was lower in broiler chickens in which SEO was added to their diets. While the total antioxidant status value was higher in SEO100 chicks, it did not show a linear increase. Additionally, the results demonstrated that the addition of SEO to broiler diets under heat stress did not have a significant effect on inspected meat quality traits, with the exception of the b*(yellowness) value of breast muscle. In conclusion, the results of this study indicate that 200mg/kg SEO can be added to diets for the welfare of broiler chickens under heat stress conditions for struggling with oxidants and increasing viability. Further research is needed to investigate the antioxidant activity and meat quality of different levels of SEO in hot ambient conditions.

Serine and threonine activate Ser/Thr kinase gene to increase the density of Lactobacillus bulgaricus sp1.1 under salt stress

Salt stress significantly impedes high cell-density culture by suppressing the reproductive capacity of lactic acid bacteria. This study examined the effects of salt stress conditions (2% w/v NaCl) on Lactobacillus bulgaricus sp1.1. Although DNA replication and division ring localization remained unaffected, the down-regulation of the ftsZ and dnaA genes inhibited division ring assembly. Consequently, bacteria exhibited filamentation, increased cell length, and accumulated chromosomes and division rings, which obstructed cell division. Under salt stress, sp1.1 experienced several transcriptional changes. The serine/threonine kinase gene was identified as a significant regulator of bacterial division under salt stress. Exogenous addition of serine and threonine could stimulate the expression of Ser/Thr kinase gene, promote the assembly of division ring, and enhance the dividing ability of the bacterium, which led to a density of 7.93 log CFU/mL under the salt stress, which was 6.92 times higher than that of the untreated group. This study provides a new perspective for high-density cultivation of lactic acid bacteria.

Maintaining mitochondrial DNA copy number mitigates ROS-induced oocyte decline and female reproductive aging

Oocytes play a crucial role in transmitting maternal mitochondrial DNA (mtDNA), essential for the continuation of species. However, the effects of mitochondrial reactive oxygen species (ROS) on mammalian oocyte maturation and mtDNA maintenance remain unclear. We investigated this by conditionally knocking out the Sod2 gene in primordial follicles, elevating mitochondrial matrix ROS levels from early oocyte stages. Our data indicates that reproductive aging in Sod2 conditional knockout females begins at 6 months, with oxidative stress impairing oocyte quality, particularly affecting OXPHOS complex II and mtDNA-encoded mRNA levels. Despite unchanged mtDNA mutation load, mtDNA copy numbers exhibited significant variations. Strikingly, reducing mtDNA copy numbers by reducing mtSSB protein, crucial for mtDNA replication, accelerated reproductive aging onset to three months, underscoring the critical role of mtDNA copy number maintenance under oxidative stress conditions. This research provides new insights into the relationship among mitochondrial ROS, mtDNA, and reproductive aging, offering potential strategies for delaying aging-related fertility decline.

Tolerance of local gogo rice sprouts under salinity stress conditions

The expansion of rice planting areas in the future needs to be carried out outside Java, as fertile land in Java is shrinking due to land conversion. Most of the land outside Java consists of marginal land, such as areas with high salinity. High salinity levels in the soil cause a decrease in plant germination, growth, and production. The research aimed to examine the tolerance of each cultivar at each level of NaCl concentration, to obtain cultivars that were tolerant to salinity stress, and to determine the NaCl concentration that suppresses the germination of local upland rice. The research was structured using a completely randomized design with a two-factor factorial pattern. The first was the six upland rice cultivars, namely, dongan, jahara, Pulu Konta, pomegranate, kalendeng, and pulu tau leru, while the second factor was the NaCl concentration consisting of 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1%. Thus, there were 36 experimental units, which were repeated three times so that there were 108 experimental units. The results of the research showed that there was no interaction with all germination variables; cultivar and concentration had a significant effect on maximum growth potential, germination capacity, germination time, plumule length, radicle length and dry weight of sprouts, while cultivar affected the wet weight of sprouts. Kalendeng has a high salinity tolerance. The use of NaCl concentrations of up to 0.6% has been able to reduce the germination capacity of local upland rice. The conclusion of the research showe that there was no interaction between all germination variables.

The role of SlCHRC in carotenoid biosynthesis and plastid development in tomato fruit

Chromoplasts are specialized plastids in plants involved in carotenoid synthesis, accumulation, and stress resistance. In tomatoes (Solanum lycopersicum), the Chromoplast-associated carotenoid binding protein (CHRC) regulates chromoplast development and carotenoid accumulation, although its precise mechanisms are not yet fully understood. To investigate the role of SlCHRC in carotenoid biosynthesis, we generated transgenic tomatoes using overexpression (oe-SlCHRC) and CRISPR/Cas9-mediated gene editing (cr-SlCHRC) techniques. The results demonstrated inhibited fruit ripening and delayed onset of color break in both transgenic lines. The oe-SlCHRC lines exhibited increased carotenoid accumulation, particularly (E/Z)-phytoene, lycopene, and γ-carotene, with abundant plastoglobules and carotenoid crystals observed via TEM. In contrast, cr-SlCHRC mutants showed a greener phenotype, reduced carotenoid content, and fewer plastoglobules at the BK + 10 stage. Transcriptome analysis indicated that SlCHRC influences key genes in carotenoid biosynthesis, such as SlNCED2, as well as genes related to chloroplast development, photosynthesis, and plastoglobule formation. Additionally, SlCHRC enhances heat stress tolerance in tomato fruits by upregulating heat shock proteins (HSPs), antioxidants, and proline accumulation. These findings indicate that SlCHRC plays a crucial role in improving tomato fruit quality under heat stress conditions.

Toward understanding the surface morphology and microscopic mechanical properties of asphalt after experiencing tensile and compressive stress

Load-induced stress is a one of the major causes of asphalt pavement failure. It is, therefore, necessary to understand the changes in stress on the microscopic mechanical properties of asphalt in improving pavement design. While much research been carried out concerning effects brought about by tensile, the effects that compressive stress would have on the microscopic mechanical properties of asphalt remains less explored. In the current study, a custom-designed tension–compression device was developed and atomic force microscopy (AFM), complemented by molecular dynamics (MD) simulations, to investigate the microscopic properties of asphalt in both undeformed and deformed states. The findings reveal that asphalt exhibits significantly weaker compressive strength compared to tensile strength. Under tensile stress, the various components in asphalt align loosely in the direction of tension, while asphaltenes are affected the least. These changes in apparent morphology reflect different migration rates of the various components. Under compressive stress, the asphalt surface is more compact, and this reduces the area of the “bee” structure. Under varying stress conditions, asphalt exhibits a smoothing of the rough region with an associated loss in adhesion. Specifically, increased tensile strain leads to smoother topography and increased adhesion, while increasing compressive strain has the opposite effect. These results provide valuable theoretical insights for the design and maintenance of more durable asphalt pavements.

Elevated proline and melatonin alter the methylation pattern in the promoter of their biosynthesis genes in rice

Salt stress upregulates osmoprotectants proline and melatonin in plants, and their exogenous application under salt stress can protect them from stress. While melatonin-induced plant epigenetic reprogramming is known in plants, such a mechanism is yet to be identified in the case of proline. The studies conducted so far used proline and melatonin along with one or more stress factors to look into their stress-alleviating effects. We investigated the impact of externally applied proline and melatonin on the methylation of promoter sequences of proline and melatonin biosynthesis genes in 14-day-old rice plants using a combination of biochemical, bioinformatics, and molecular techniques. Our findings demonstrate that exogenously applied proline and melatonin elevate endogenous levels of these compounds in rice, mimicking stress conditions in plants, as the biochemical assays corroborated the activation of antioxidant systems, particularly ascorbate peroxidase (APX) and catalase (CAT). Bioinformatics analysis unveiled multiple stress-responsive transcription factor binding sites on gene promoters associated with proline and melatonin biosynthesis pathways. Restriction analysis using the isoschizomer pair MspI/HpaII revealed distinct cytosine methylations at the restriction sites on the promoters analyzed in plants treated with proline and melatonin compared to the control. Differential methylation identified in the promoter sequences were matching with the biosynthesis of proline and melatonin and also the antioxidant enzyme levels. These observations are consistent with previous transcriptome data of proline and melatonin biosynthesis genes, providing insights into underlying regulatory mechanisms of proline and melatonin biosynthesis, their role in epigenome control during abiotic stress, and the evolution of various stress-tolerant varieties.

The impact of chitosan nanoparticles on seedling and germination attributes and enzymatic activity of guar (Cyamopsis tetragonoloba L.) under osmotic stress

This research was conducted to examine the effects of nano chitosan particles on seed germination and seedling growth of guar (Cyamopsis tetragonoloba L.) under osmotic stress conditions. This experiment was conducted in a factorial layout based on a completely randomized design with two factors and four replications. The experimental factors included: osmotic stress at five levels (0, -3, -6, -9 and -12 bar) and seed priming with nano chitosan particles at five concentrations (0, 50, 100, 200, and 300 ppm). The evaluated parameters in this study were alometric traits and enzymatic activities including proline, catalase, ascorbate peroxidase, superoxide dismutase, and total soluble sugar, as well as the content of chlorophyll a, b, and carotenoids. The results indicated the significant effect of most of the studied quantitative and qualitative traits. The highest values of seedling, plumule and radicle length (48.20, 17.79 and 30.15 mm, respectively), and the fresh weight of seedlings and plumule (0.9743 and 0.9192 g, respectively) were observed at a concentration of 200 ppm of chitosan nanoparticles. The highest amount of all studied parameters observed under non-stress conditions (control), and the lowest values of them obtained in -12 bar of osmotic stress. Furthermore, by increasing of osmotic stress levels, germination percentage and rate and seed vigor showed a decreasing trend about 56, 83 and 95% compared to the control. Besed on the interaction effects, the maximum values of seedling and plumule length were achieved with the application of 200 ppm chitosan nanoparticles in combination with no osmotic stress. Under non-osmotic conditions, concentrations of 300, 100, and 200 ppm chitosan led to the highest values of germination percentage and rate and seed vigor, respectively. Additionally, the highest percentage of normal seedlings (94%) and the lowest percentage of abnormal seedlings (zero) were obtained under the application of 200 ppm of nano chitosan and no osmotic stress. In relation to qualitative traits, the lowest values of soluble sugar and proline were obtained at the osmotic level of -12 bar. Moreover, the application of 200 ppm of nano chitosan and -6 bar of osmotic stress resulted in the highest levels of catalase, superoxide dismutase, ascorbate peroxidase, chlorophyll a, b, and carotenoids. As a whole, the results of the study demonstrated that seed priming with chitosan nanoparticles can reduce the negative effects of drought stress on guar seedlings. In addition, application of 200 ppm of this substance was the most suitable treatments that improve most quantitative and qualitative indices of guar. Keywords: Enzymatic activity, Nano particles, Priming, Seed structure.