Stresses, Volume 3, Issue 4 (December 2023) – 13 articles

The purpose of this study was to assess the stress responses associated with vaquejada simulating tests (VSTs). Ten clinically healthy 8.9 ± 4.3-year-old Quarter horses, weighing 441.3 ± 25.0 kg, performed two VSTs five days apart. In the first VST (M1), animals ran three times with a 5-min rest between races; and in the second (M2), they ran with a 15-min rest between races. Horses were examined before (T0) and immediately after the third run (T1) and at 4 h (T2) of recovery. Stress biomarkers included heart rate (HR), heart rate variability (HRV), cortisol, and white blood cell count. All variables were analyzed by ANOVA and Tukey tests, considering p < 0.05. A significant reduction in cortisol was observed for pull (p = 0.0463) and helper (p = 0.0349) horses when they had a 15-min rest between races. The rMSSD and mean R-R values for helper horses were also significantly lower in M2. In conclusion, the 15-min rest interval proved to be better than the 5-min period for both categories of equine athletes used in vaquejada mainly for helper horses. A longer rest time between races allowed the organic recovery necessary for these animals to impose a greater applied physical effort load, which is a fact that guarantees good performance and well-being. Full article

Drought conditions have made it difficult for farmers to ensure the productivity of their crops. The objective of this study was to evaluate the potential of bioinputs in stress mitigation after a drought event in common beans. Two experiments were set up in a greenhouse. Firstly, two types of soils (clayey and sandy loam) were used. After seedling emergence, treatments were set: no bacteria inoculation (NB) and inoculation with Herbaspirillum frisingense AP21. Then, a differentiation on the irrigation (15 days) was performed with no water restriction (NWR) and with water restriction (WWR). Transpiration, stomatal conductance, leaf dry matter and proline were measured. Secondly, in the clayey soil, the bacteria treatments were NB, Herbaspirillum frisingense AP21, Rhizobium leguminosarum T88 and co-inoculation (AP21 + T88). A differentiation on the irrigation (15 days) was performed: NWR and WWR. Then, Fv/Fm, photosynthetic rate, proline and sugars were assessed, and the harvest occurred 97 days after emergence. For sandy loam soil bioinputs, they did not have an effect on the parameters evaluated. For clayey soil, H. frisingense AP21 increased the transpiration rate and stomatal conductance and hence improved the leaf dry matter in comparison to NB. Under WWR, the isolated inoculations of AP21 and T88 increased grain dry matter, but the co-inoculation showed low grain production, similar to no bacteria inoculation. Full article

Phytophthora capsici incites foliar blight, root, fruit, and crown rot in squash (Cucurbita spp.) and limits production worldwide. Resistance to crown rot in C. moschata breeding line #394-1-27-12 is conferred by three dominant genes, but the molecular mechanisms underlying this resistance are poorly understood. In the current study, RNA sequencing was used to investigate transcriptional changes in #394-1-27-12 (resistant) and Butterbush (susceptible) following infection by P. capsici at 12, 24, 48, 72, and 120 h post inoculation (hpi). Overall, the number of differentially expressed genes (DEGs) in Butterbush (2648) exceeded those in #394-1-27-12 (1729), but in both genotypes, the highest number of DEGs was observed at 72 hpi and least at 24 hpi. Our gene ontology (GO) analysis revealed a downregulation of the genes involved in polysaccharide and lignin metabolism in Butterbush but as an upregulation of those associated with regulation of peptidase activity. However, in #394-1-27-12, the downregulated genes were primarily associated with response to stimuli, whereas those upregulated were involved in oxidation–reduction and response to stress. The upregulated genes in #394-1-27-12 included defensin-like proteins, respiratory-burst oxidases, ethylene-responsive transcription factors, cytochrome P450 proteins, and peroxidases. These findings provide a framework for the functional validation of the molecular mechanisms underlying resistance to P. capsici in cucurbits. Full article

High-gravity fermentation, used for ethanol production from sugarcane, corn, and mixed substrates, offers several benefits. Yeast, a rapidly multiplying unicellular microorganism, can be adapted for high sugar and ethanol tolerance on a lab scale. However, different substrates can enhance fermentation efficiency. Our study consisted of two experiments. In the first, we compared simple batch feeding with a fed-batch system for yeast selection in high-gravity fermentation. We ran eight cycles with increasing initial sugar contents (50 to 300 g L⁻¹). No significant differences were observed in the first seven cycles, but in the eighth, the fed-batch system showed lower glycerol and fructose contents and higher cell viability than the simple batch system. In the second experiment, we used the fed-batch system with 300 g L⁻¹ from sugarcane, corn, and mixed wort. The results showed that mixed wort produced higher ethanol contents and greater fermentation efficiency compared to corn and sugarcane as substrates. In conclusion, our findings indicate that the fed-batch system is more suitable for high-gravity fermentation on a lab scale, and the combination of sugarcane juice and corn can enhance fermentation efficiency, paving the way for integrating these substrates in industrial ethanol production. Full article

Oxidative stress is caused by an imbalance between the production and subsequent accumulation of reactive oxygen species (ROS) in cells and tissues and the capacity of a biological system to eliminate these reactive substances. Systemic oxidative stress biomarkers in plasma, serum, urine, or red blood cells have been found to be elevated in many diseases, including skin cancer. UV radiation (UVR) induces damage to biomolecules that enter the bloodstream, reinforcing systemic oxidative stress. On the other hand, pre-existing systemic oxidative stress does not supply the skin with the adequate micronutrients and antioxidant resources to ameliorate the skin’s antioxidant defense against UVR. In both scenarios, skin cancer patients are exposed to oxidative conditions. In the case of warts, oxidation is linked to chronic inflammation, while impaired cutaneous antioxidant defense could ineffectively deal with possible oxidative stimuli from viral agents, such as HPV. Therefore, the aim of our study is to evaluate the existing data on systemic oxidative stress in skin diseases such as non-melanoma skin cancer (NMSC), basal-cell carcinoma (BCC), squamous-cell carcinoma (SCC), and melanoma as well as benign lesions such as actinic keratosis (AK), sebaceous keratosis (SK), and warts. Previous studies have demonstrated that patients with NMSC, melanoma, AK, and warts (both genital and non-genital) are subjected to severe oxidative stress, indicated by disturbed antioxidant enzyme levels, accumulated oxidized proteins and lipid products, and, to a lesser extent, lower concentrations of micronutrients. Interestingly, medical history of NMSC or melanoma as well as stage of skin cancer and treatment approach were found to affect systemic oxidative stress parameters. In the case of warts (both genital and non-genital), high oxidative stress levels were also detected, and they were found to be aligned with their recalcitrant character. Full article

Wild edible plants have attracted increasing interest from researchers because of their richness in biologically active phytochemicals. These are found to be a potential remedy for oxidative-stress-mediated diseases such as diabetes mellitus. In this study, total phenol, total terpene, and total flavonoid content as well as antioxidant and antidiabetic activities of Scorzonera phaeopappa Boiss from Lebanon were determined. Using dichloromethane, dichloromethane ammonia, methanol, acetone, and ethanol, extracts were prepared from the edible leaves. The antioxidant activity and the antidiabetic activity were determined by 2,2-diphenyl-1-picrylhydrazyl scavenging, Fe²⁺-chelating and α-amylase/α-glucosidase inhibitory assays, respectively. Dichloromethane ammonia was found to have the highest extraction capacity on phenols (2.73 mg GAE /100 mg extract) and terpenes (232.42 mg LE/100 mg extract). Methanol was found to have the highest extraction capacity on total flavonoids (63.05 mg QE/100 mg extract). The methanol extract exhibited the highest DPPH scavenging activity (IC₅₀ 0.07 mg/mL) and the highest chelating activity as compared to other extracts (0.08 mg/mL, chelating activity 50%). The acetone extract was two times more active than acarbose against α-amylase enzyme and was the most active against α-glucosidase (6.3 mg/mL). Significant positive correlations were observed between total phenol content and α-glucosidase inhibitory assay and total terpene content and α-glucosidase inhibitory assay. Full article

The reasons initiating insulin resistance are not identified. Various metabolic derailments have been characterized. These are the outcome and not the initiation of insulin resistance. In animal models of type 2 diabetes and hypertension, a decreased hormonal stimulation of the synthesis of the cyclic AMP antagonist prostaglandylinositol cyclic phosphate (cyclic PIP) was determined. The resultant imbalance of the action of cyclic AMP and cyclic PIP shifts metabolic regulation to the dominance of catabolism and a decrease in imperative anabolism. This dominance develops gradually since the more cyclic AMP dominates, the more the synthesis of cyclic PIP will be inhibited. Vanishing actions of cyclic PIP are its 10-fold activation of glucose uptake in adipocytes, its inhibition of insulin release from pancreatic β-cells, its inhibition of PKA and its 7-fold activation of protein ser/thr phosphatase. Reduced synthesis of cyclic PIP results from (a) decreased substrate availability, (b) long-time elevated cyclic AMP levels resulting from stress overloads and (c) aging and the gradual decrease in the synthesis of hormones which likely maintain mechanisms that stimulate cyclic PIP synthesis. The need is to discover which hormones, such as growth hormone, insulin-like growth factor-1, dehydroepiandrosterone, and testosterone, are involved in maintaining the stimulation of cyclic PIP synthesis. Full article

In the present study, different Pseudomonas strains were isolated from the rhizospheric soil of Curcuma longa (turmeric) and further identified and characterized based on morphological, biochemical, and molecular characteristics through the 16S rRNA gene sequencing analysis. The identified bacterial strains belong to the Pseudomonas genus viz. Pseudomonas sp. CL10, Pseudomonas sp. CL11, and P. fluorescence CLI4. However, the isolated strains tested positive for IAA production, siderophore production, and the solubilization of tricalcium phosphate during plant growth promoting traits analysis. Further phenotype microArray (PM) technology was used to evaluate the antibiotic and chemical sensitivity of the isolated bacterial strains. The antibiotics phleomycin, oxacillin, vancomycin, novobiocin, spiramycin, and rifampicin, as well as chemicals like, 5-7 dichloro-8-hydroxy quanaldine, 5-7 dichloro-8-hydroxyquinoline, domophenbrobide, and 3-5 dimethoxy benzyl alcohol, showed resistance in all the rhizobacterial strains. However, upon further detailed study, Pseudomonas sp. CL10 exhibited resistance to thirteen antibiotics, CL11 to fourteen, and CL14 showed resistance against seventeen antibiotics and chemical classes. The results of the study indicate that some of these strains can be used as bioinoculum to enhance the plant growth and health. Full article

Catalase can decompose hydrogen peroxide in plants under controlled and stressed conditions. In a stressed environment, an increase in hydrogen peroxide production makes catalase activity a major defense system for plant growth. The current study was conducted to evaluate the catalase activity of the pre-isolated and identified bacterial strains Bacillus aryabhattai (AN30), Bacillus megaterium (AN24), Bacillus megaterium (AN31) and Bacillus megaterium (AN35) and their potential for rice seedling growth promotion. These strains were characterized for quantitative catalase, urease, siderophore and exopolysaccharide production using LB media. Subsequently, the effectiveness of these strains was checked by quantifying the catalase activity in the rhizosphere, roots and shoots of rice seedlings. The secretion of organic and phenolic compounds produced by the tested strains in liquid culture was also investigated. Plant growth parameters were also studied in a growth room trial. Our results showed that the strain AN24 showed the maximum catalase activity (1.36 mol cm⁻¹), urease activity (1.35 mol cm⁻¹) and exopolysaccharide (4.20 µg mL⁻¹) and siderophore (2.32%) production in LB media. All tested strains showed significantly higher catalase activity in soil compared to the control. Among sole applications, strain AN24 showed better results; however, the consortium application of strains AN24 + AN30 + AN35 + AN31 showed the maximum improvement in dry biomass, shoot and root length, and increase in catalase activity of rice seedlings. The results showed that a consortium of these Bacillus strains with catalase activity has greater potential to enhance the antioxidant defense system and growth promotion of rice seedlings. However, further experimentation under natural conditions is required before using these strains as potential bioinoculants for improving rice growth and yield. Full article

Rice (Oryza sativa L.) is a primary energy food for the Asian population. One of the greatest constraints in rice production is soil salinity because rice is very susceptible to salt. Meanwhile, many agricultural lands in Asia are in saline areas. It is important to identify and develop salt-tolerant rice varieties that highly adapt to Asian climates. By combining morphological, physiological, and biochemical assessments for screening the salt tolerance of 116 Asian rice cultivars, we were able to classify them into tolerant, moderate, and sensitive rice cultivars under salinity stress conditions and also understand salt tolerance mechanisms. The rice cultivars that are salt-tolerant include Pokkali from India, TCCP 266 and IR 45427 from the Philippines, and Namyang 7 from Republic of Korea. However, salt-sensitive rice varieties like IR29 and IR58 are from the Philippines, and Daegudo and Guweoldo are from Korea. The salt-tolerant varieties showed signs of tolerance, including a lower percent reduction in germination percentage, root length, root fresh weight, shoot length, plant biomass, and chlorophyll content. In order to maintain the cellular osmotic balance under saline conditions, the salt-tolerant varieties exhibited less membrane damage, a lower Na/K ratio, high proline and sugar accumulation, and lower levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂). Pokkali from India, TCCP 266 and IR 45427 from the Philippines, and Namyang 7 from Republic of Korea are recommended as valuable germplasm resources for Asian rice breeding programs in saline agricultural areas. Full article

Crops are constantly threatened by salinity. Nitric oxide (NO) is an attenuating agent for salt stress; however, the specific roles of NO in gas exchange and lettuce production are not well established. The objective of this study was to evaluate the application of different concentrations of sodium nitroprusside (SNP) as an agent to mitigate salt stress in lettuce plants. Lettuce seedlings in pots were subjected to irrigation without and with saline water (0.2 and 3.5 dS m⁻¹) and applications of different concentrations (0, 50, 100, 150, and 200 µM) of SNP, a NO donor. Saline stress negatively affected lettuce development with a reduction of 29.5% in leaf area, 6.3% in relative water content in the leaf, 17.2% in stem diameter, and 10.7% in dry matter mass in the control, but the application of SNP mitigated the deleterious effects of salt stress. Concentrations between 100 and 150 µM of SNP improved the photosynthetic metabolism of lettuce under salinity, with an increase of 46.7% in CO₂ assimilation and 42.3% in fresh matter mass. Pearson’s correlation showed that fresh matter correlated positively with CO₂ assimilation. Therefore, SNP can be used to mitigate salt stress in lettuce. Full article

This study examined the effects of three selected doses of kaempferol (KAE; 12.5, 25 or 50 μM) on bovine sperm motility and oxidative profile directly related to cold storage. We also elucidated the effect of KAE on the expression profiles of heat shock proteins (HSPs) 70 and 90 as well as the pro-apoptotic BCL2-associated X (BAX) protein and the anti-apoptotic B-cell lymphoma 2 (Bcl-2) protein. Frozen samples supplemented with KAE were compared with a native control (fresh spermatozoa) and a cryopreserved control, frozen in the absence of KAE. Our results demonstrate that the administration of all KAE doses led to a higher degree of sperm motility (p < 0.05) when compared with the cryopreserved control. The highest levels of protection of sperm DNA (p < 0.05), lipids (p < 0.05) and proteins (p < 0.05) were detected in samples exposed to 25 μM KAE when compared with samples frozen without KAE. Administration of 25 μM KAE led to a significant increase in HSP70 and HSP90 (p < 0.05) when compared with the unsupplemented frozen control. No significant differences were observed in the expression patterns of BAX; however, a significant up-regulation of Bcl-2 protein was observed in the frozen samples enriched with 25 μM KAE when compared with the cryopreserved control (p < 0.05). In summary, we may consider KAE as an effective agent in stabilizing the sperm membranes by preventing reactive oxygen species (ROS) overproduction in the mitochondria and subsequent oxidative damage to molecules critical for a proper sperm architecture and function. These protective properties of KAE may lead to higher post-thaw sperm activity and viability. Full article

Heavy metal (HM) stress poses a global risk to crops, ecological systems, and human health. It disrupts cellular ionic equilibrium, cell membrane integrity, metabolic balance, and the activities of enzymes and proteins, severely impacting physiological processes, plant development, and agricultural productivity. Although plants naturally activate defense mechanisms to mitigate the adverse effects of HM stress, they cannot completely prevent them. Phytohormones counter HM toxicity, aiding growth. External application and internal regulation via signaling/biosynthesis genes offer defense against HM-induced damage. A pivotal signaling molecule in plant adaptive responses to environmental stressors, including HM toxicity, is abscisic acid (ABA). Despite ABA’s role in abiotic stress responses such as drought and salinity, its function and crosstalk with other phytohormones under HM stress remain poorly understood. Nonetheless, exogenously applied ABA serves as a strategic approach to enhancing plants’ resistance to HM toxicity by promoting osmolyte accumulation and reinforcing antioxidant activity. ABA significantly regulates various plant growth and metabolic activities under diverse environmental conditions. This review highlights the effects of HM stress on plants and explores ABA involvement in production, signaling, catabolism, and transport within plant tissues. The purpose of this paper is to shed light on the complex interplay between the metabolism of ABA, its signaling, and its interactions with other phytohormones (e.g., auxins, gibberellins, and ethylene) during HM exposure. Furthermore, we delve into the function of ABA to mitigate HM stress and elucidate its interactions with other phytohormones. Full article