Cytokinin and indole-3-acetic acid crosstalk is indispensable for silicon mediated chromium stress tolerance in roots of wheat seedlings

The rising heavy metal contamination of soils imposes toxic impacts on plants as well as other life forms. One such highly toxic and carcinogenic heavy metal is hexavalent chromium [Cr(VI)] that has been reported to prominently retard the plant growth. The present study investigated the potential of silicon (Si, 10 µM) to alleviate the toxicity of Cr(VI) (25 µM) on roots of wheat (Triticum aestivum L.) seedlings. Application of Si to Cr(VI)-stressed wheat seedlings improved their overall growth parameters. This study also reveals the involvement of two phytohormones, namely auxin and cytokinin and their crosstalk in Si-mediated mitigation of the toxic impacts of Cr(VI) in wheat seedlings. The application of cytokinin alone to wheat seedlings under Cr(VI) stress reduced the intensity of toxic effects of Cr(VI). In combination with Si, cytokinin application to Cr(VI)-stressed wheat seedlings significantly minimized the decrease induced by Cr(VI) in different parameters such as root-shoot length (10.8% and 13%, respectively), root-shoot fresh mass (11.3% and 10.1%, respectively), and total chlorophyll and carotenoids content (13.4% and 6.8%, respectively) with respect to the control. This treatment also maintained the regulation of proline metabolism (proline content, and P5CS and PDH activities), ascorbate-glutathione (AsA-GSH) cycle and nutrient homeostasis. The protective effect of Si and cytokinin against Cr(VI) stress was minimized upon supplementation of an inhibitor of polar auxin transport- 2,3,5-triiodobenzoic acid (TIBA) which suggested a potential involvement of auxin in Si and cytokinin-mediated mitigation of Cr(VI) toxicity. The exogenous addition of a natural auxin - indole-3-acetic acid (IAA) confirmed auxin is an active member of a signaling cascade along with cytokinin that aids in Si-mediated Cr(VI) toxicity alleviation as IAA application reversed the negative impacts of TIBA on wheat roots treated with Cr(VI), cytokinin and Si. The results of this research are also confirmed by the gene expression analysis conducted for nutrient transporters (Lsi1, CCaMK, MHX, SULT1 and ZIP1) and enzymes involved in the AsA-GSH cycle (APX, GR, DHAR and MDHAR). The overall results of this research indicate towards possible induction of a crosstalk between cytokinin and IAA upon Si supplementation which in turn stimulates physiological, biochemical and molecular changes to exhibit protective effects against Cr(VI) stress. Further, the information obtained suggests probable employment of Si, cytokinin and IAA alone or combined in agriculture to maintain plant productivity under Cr(VI) stress and data regarding expression of key genes can be used to develop new crop varieties with enhanced resistance against Cr(VI) stress together with its reduced load in seedlings.

Microplate-Based Cryopreservation of Adherent-Cultured Human Cell Lines Using Amino Acids and Proteins

With the progression of regenerative medicine and cell therapy, the importance of cryopreservation techniques for cultured cells continues to rise. Traditional cryoprotectants, such as dimethyl sulfoxide and glycerol, are effective in cryopreserving suspended cells, but they do not demonstrate sufficient efficacy for two-dimensional (2D)-cultured cells. In the past decade, small molecules and polymers have been studied as cryoprotectants. Some L-amino acids have been reported to be natural and biocompatible cryoprotectants. However, the cryoprotective effects of D-amino acids have not been investigated for such organized cells. In the present study, the cryoprotective effects of D- and L-amino acids and previously reported cryoprotectants were assessed using HepG2 cells cultured on a microplate without suspending the cells. d-Proline had the highest cryoprotective effect on 2D-cultured cells. The composition of the cell-freezing solution and freezing conditions were then optimized. The d-proline-containing cell-freezing solution also effectively worked for other cell lines. To minimize the amount of animal-derived components, fetal bovine serum in the cell freezing solution was substituted with bovine serum albumin and StemFit (a commercial supplement for stem cell induction). Further investigations on the mechanism of cryopreservation suggested that d-proline protected enzymes essential for cell survival from freeze-induced damage. In conclusion, an effective and xeno-free cell-freezing solution was produced using d-proline combined with dimethyl sulfoxide and StemFit for 2D-cultured cells.

L-Proline: A Promising Tool for Boosting Cryotolerance and Fertilizing Ability of Cryopreserved Sperm in Animals

Sperm cryopreservation technology significantly contributes to the safeguarding of genetic resources, particularly for endangered species, and supports the use of artificial insemination in domestic animals. Therefore, cryopreservation can negatively affect sperm health and function leading to reduce the freezing ability and fertility potential. Therefore, it is essential to prioritize the improvement of cryotolerance in cryopreserved sperm to enhance reproductive efficiency and ensure sustainability in livestock herds. The main reason for sperm dysfunction after thawing may be related to the excessive amount of oxidative stress (OS) produced during cryopreservation. Scientists have different ways for counteracting this OS including the use of plant extracts, enzymes, minerals, anti-freezing proteins, and amino acids. Recently, one such amino acid is L-proline (LP), which has multiple roles such as osmotic and OS defense, nitrogen, and carbon metabolism, as well as cell survival and signaling. LP has been found in seminal plasma and has recently been added to the freezing extender to improve the various post-thaw parameters of sperm. This improvement is related to the ability of LP to reduce the OS, sustain the plasma membrane and to act as an osmoregulatory agent. Moreover, LP can suppress cell apoptosis by modulating intracellular redox in sperm. This review addresses the ongoing research on the addition of L-proline as an osmoregulatory agent in freezing extenders to increase the cryotolerance of animal spermatozoa to freeze-thaw.

Impact of seed priming with Selenium nanoparticles on germination and seedlings growth of tomato

Poor germination and seedlings growth can lead to significant economic losses for farmers, therefore, sustainable agricultural strategies to improve germination and early growth of crops are urgently needed. The objective of this work was to evaluate selenium nanoparticles (Se NPs) as nanopriming agents for tomato (Solanum lycopersicum) seeds germinated without stress conditions in both trays and Petri dishes. Germination quality, seedlings growth, synergism-antagonism of Se with other elements, and fate of Se NPs, were determined as function of different Se NPs concentrations (1, 10 and 50 ppm). Results indicated that the germination rate in Petri dishes improved with 10 ppm, while germination trays presented the best results at 1 ppm, increasing by 10 and 32.5%, respectively. Therefore, seedlings growth was measured only in germination trays. Proline content decreased up to 22.19% with 10 ppm, while for same treatment, the total antioxidant capacity (TAC) and total chlorophyll content increased up to 38.97% and 21.28%, respectively. Antagonisms between Se with Mg, K, Mn, Zn, Fe, Cu and Mo in the seed were confirmed. In the case of seedlings, the N content decreased as the Se content increased. Transmission Electron Microscopy (TEM) imaging confirmed that Se NPs surrounded the plastids of the seed cells. By this finding, it can be inferred that Se NPs can reach the embryo, which is supported by the antagonism of Se with important nutrients involved in embryogenesis, such as K, Mg and Fe, and resulted in a better germination quality. Moreover, the positive effect of Se NPs on total chlorophyll and TAC, and the negative correlation with proline content with Se content in the seed, can be explained by Se NPs interactions with proplastids and other organelles within the cells, resulting with the highest length and fresh weight when seeds were exposed to 1 ppm.

Proline restores mitochondrial function and reverses aging hallmarks in senescent cells

Mitochondrial dysfunction is a hallmark of cellular senescence, with the loss of mitochondrial function identified as a potential causal factor contributing to senescence-associated decline in cellular functions. Our recent findings revealed that ectopic expression of the pluripotency transcription factor NANOG rejuvenates dysfunctional mitochondria of senescent cells by rewiring metabolic pathways. In this study, we report that NANOG restores the expression of key enzymes, PYCR1 and PYCR2, in the proline biosynthesis pathway. Additionally, senescent mesenchymal stem cells manifest severe mitochondrial respiratory impairment, which is alleviated through proline supplementation. Proline induces mitophagy by activating AMP-activated protein kinase α and upregulating Parkin expression, enhancing mitochondrial clearance and ultimately restoring cell metabolism. Notably, proline treatment also mitigates several aging hallmarks, including DNA damage, senescence-associated β-galactosidase, inflammatory cytokine expressions, and impaired myogenic differentiation capacity. Overall, this study highlights the role of proline in mitophagy and its potential in reversing senescence-associated mitochondrial dysfunction and aging hallmarks.

Effect of glutathione-transport-related gene gsiD on desiccation tolerance of Cronobacter sakazakii and its related regulatory mechanism

The outstanding desiccation tolerance of Cronobacter sakazakii (C. sakazakii) enables long-term persistence in food products with low-water activity to increase the infection risk, especially in low-birth-weight, immuno-compromised neonates, and infants less than 4 weeks of age. In our previous study, the disruption of glutathione transport-related gene gsiD by transposon was found to significantly increase its inactivation rate under drying stress challenges. However, the mechanism underlying the association between glutathione transport and desiccation tolerance of C. sakazakii remains to be clarified. In this study, the mechanism underlying their association was investigated in detail by constructing the gsiD gene deletion mutant. gsiD gene deletion was found to cause the dysfunction of the glutathione transport system GsiABCD and the limitation of glutathione import. The resulting decrease in intracellular glutathione caused the decreased potassium ions uptake and increased potassium ions efflux, inhibited the proline synthesis process, limited extracellular glutathione utilization, increased oxidant stress, reduced biofilm formation, and increased outer membrane permeability, which may be the main reasons for the significant reduction of the desiccation tolerance of C. sakazakii.IMPORTANCEContributing to its superior environmental adaptability, Cronobacter sakazakii can survive under many abiotic stress conditions. The outstanding desiccation tolerance makes this species persist in low-water activity foods, which increases harm to humans. For decades, many studies have focused on the desiccation tolerance of C. sakazakii, but the existing research is still insufficient. Our study found that gsiD gene deletion inhibited glutathione uptake and further decreased intracellular glutathione content, causing a decrease in desiccation tolerance and biofilm formation and an increase in outer membrane permeability. Moreover, the expression level of relative genes verified that gsiD gene deletion made the mutant not conducive to surviving in dry conditions due to restricting potassium ions uptake and efflux, inhibiting the conversion of glutamate to compatible solute proline, and increasing the oxidative stress of C. sakazakii. The above results enrich our knowledge of the desiccation tolerance mechanism of C. sakazakii.

Proline-Hinged α-Helical Peptides Sensitize Gram-Positive Antibiotics, Expanding Their Physicochemical Properties to Be Used as Gram-Negative Antibiotics

The outer membrane (OM) of Gram-negative bacteria is the most difficult obstacle for small-molecule antibiotics to reach their targets in the cytosol. The molecular features of Gram-negative antibiotics required for passing through the OM are that they should be positively charged rather than neutral, flat rather than globular, less flexible, or more increased amphiphilic moment. Because of these specific molecular characteristics, developing Gram-negative antibiotics is difficult. We focused on sensitizer peptides to facilitate the passage of hydrophobic Gram-positive antibiotics through the OM. We explored ways of improving the sensitizing ability of proline-hinged α-helical peptides by adjusting their length, hydrophobicity, and N-terminal groups. A novel peptide, 1403, improves the potentiation of rifampicin in vitro and in vivo and potentiates most Gram-positive antibiotics. The "sensitizer" approach is more plausible than those that rely on conventional drug discovery methods concerning drug development costs and the development of drug resistance.

Synergistic effect of nitrate exposure and heatwaves on the growth, and metabolic activity of microalgae, Chlamydomonas reinhardtii, and Pseudokirchneriella subcapitata

Aquatic biota are threatened by climate warming as well as other anthropogenic stressors such as eutrophication by phosphates and nitrate. However, it remains unclear how nitrate exposure can alter the resilience of microalgae to climate warming, particularly heatwaves. To get a better understanding of these processes, we investigated the effect of elevated temperature and nitrate pollution on growth, metabolites (sugar and protein), oxidative damage (lipid peroxidation), and antioxidant accumulation (polyphenols, proline) in Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata. The experiment involved a 3 × 3 factorial design, where microalgae were exposed to one of three nitrate levels (5, 50, or 200 mg L-1 NO3-l) at 20 °C for 2 weeks. Subsequently, two heatwave scenarios were imposed: a short and moderate heatwave at 24 °C for 2 weeks, and a long and intense heatwave with an additional 2 weeks at 26 °C. A positive synergistic effect of heatwaves and nitrate on growth and metabolites was observed, but this also led to increased oxidative stress. In the short and moderate heatwave, oxidative damage was controlled by increased antioxidant levels. The high growth, metabolites, and antioxidants combined with low oxidative stress during the short and moderate heatwaves in moderate nitrate (50 mg L-1) led to a sustainable increased food availability to grazers. On the other hand, long and intense heatwaves in high nitrate conditions caused unsustainable growth due to increased oxidative stress and relatively low antioxidant (proline) levels, increasing the risk for massive algal die-offs.

The impact of inter- and intra-species spore density on germination of the food spoilage fungus Aspergillus niger

Aspergilli can be used to produce food but can spoil it as well. Both food production and spoilage are initiated by germination of the conidia of these fungi that have been introduced by inoculation and contamination, respectively. Germination of these spores includes activation, swelling, establishment of cell polarity, and formation of a germ tube. So far, only quantitative single-species germination studies of fungal spores have been performed. Here, spore germination of the food spoilage fungus Aspergillus niger was studied quantitatively in mono-culture or when mixed with other food-relevant aspergilli (Aspergillus nidulans, Aspergillus terreus, Aspergillus clavatus, and Aspergillus oryzae). In the presence of the germination inducing amino acids proline or alanine, but not in the case of the lowly inducing amino acid arginine, the incidence of swelling and germ tube formation was reduced when 35,000 extra conidia of Aspergillus niger were added to wells containing 5000 of these spores. Adding 35,000 spores of one of the other aspergilli also did not have an effect on germination in the presence of arginine, but the germination inhibition was stronger when compared to the extra A. niger spores in the case of alanine. A similar effect was obtained with proline. Together, results show that the germination of A. niger conidia is impacted by the density of its own spores and that of other aspergilli under favorable nutritional conditions. These results increase our understanding of food spoilage by fungi and can be used to optimize food production with fungi.

Effects of X-ray cranial irradiation on metabolomics and intestinal flora in mice

Cranial radiotherapy is an important treatment for intracranial and head and neck tumors. To investigate the effects of cranial irradiation (C-irradiation) on gut microbiota and metabolomic profile, the feces, plasma and cerebral cortex were isolated after exposing mice to cranial X-ray irradiation at a dose rate of 2.33 Gy/min (5 Gy/d for 4 d consecutively). The gut microorganisms and metabolites were detected by 16 S rRNA gene sequencing method and LC-MS method, respectively. We found that compared with sham group, the gut microbiota composition changed at 2 W and 4 W after C-irradiation at the genus level. The fecal metabolomics showed that compared with Sham group, 44 and 66 differential metabolites were found to be annotated into metabolism pathways at 2 W and 4 W after C-irradiation, which were significantly enriched in the arginine and proline metabolism. Metabolome analysis of serum and cerebral cortex showed that, at 4 W after C-irradiation, the expression pattern of metabolites in serum samples of mice was similar to that of sham group, and the cerebral cortex metabolites of the two groups were completely separated. KEGG functional analysis showed that serum and brain tissue differential metabolites were respectively enriched in tryptophan metabolism, and arginine proline metabolism. The correlation analysis showed that the changes of gut microbiota genera were significantly correlated with the changes of metabolism, especially Helicobacter, which was significantly correlated with many different metabolites at 4 W after C-irradiation. These data suggested that C-irradiation could affect the gut microbiota and metabolism profile, even at relatively long times after C-irradiation.

Mitigating chromium toxicity in rice (Oryza sativa L.) via ABA and 6-BAP: Unveiling synergistic benefits on morphophysiological traits and ASA-GSH cycle

In recent years, the use of plant hormones, such as abscisic acid (ABA) and 6-benzylaminopurine (6-BAP), has gained significant attention for their role in mitigating abiotic stresses across various plant species. These hormones have been shown to play a vital role in enhancing the ascorbate-glutathione cycle and eliciting a wide range of plant growth and biomass, photosynthetic efficiency, oxidative stress and response of antioxidants and other physiological responses. While previous research has been conducted on the individual impact of ABA and 6-BAP in metal stress resistance among various crop species, their combined effects in the context of heavy metal-stressed conditions remain underexplored. The current investigation is to assess the beneficial effects of single and combined ABA (5 and 10 μM L-1) and 6-BAP (5 and 10 μM L-1) applications in rice (Oryza sativa L.) cultivated in chromium (Cr)-contaminated soil (100 μM). Our results showed that the Cr toxicity in the soil showed a significant declined in the growth, gas exchange attributes, sugars, AsA-GSH cycle, cellular fractionation, proline metabolism in O. sativa. However, Cr toxicity significantly increased oxidative stress biomarkers, organic acids, enzymatic and non-enzymatic antioxidants including their gene expression in O. sativa seedlings. Although, the application of ABA and 6-BAP showed a significant increase in the plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress, And Cr uptake. In addition, individual or combined application of ABA and 6-BAP enhanced the cellular fractionation and decreases the proline metabolism and AsA-GSH cycle in rice plants. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

Proline and Proline Analogues Improve Development of Mouse Preimplantation Embryos by Protecting Them against Oxidative Stress

The culture of embryos in the non-essential amino acid L-proline (Pro) or its analogues pipecolic acid (PA) and L-4-thiazolidine carboxylic acid (L4T) improves embryo development, increasing the percentage that develop to the blastocyst stage and hatch. Staining of 2-cell and 4-cell embryos with tetramethylrhodamine methyl ester and 2',7'-dichlorofluorescein diacetate showed that the culture of embryos in the presence of Pro, or either of these analogues, reduced mitochondrial activity and reactive oxygen species (ROS), respectively, indicating potential mechanisms by which embryo development is improved. Inhibition of the Pro metabolism enzyme, proline oxidase, by tetrahydro-2-furoic-acid prevented these reductions and concomitantly prevented the improved development. The ways in which Pro, PA and L4T reduce mitochondrial activity and ROS appear to differ, despite their structural similarity. Specifically, the results are consistent with Pro reducing ROS by reducing mitochondrial activity while PA and L4T may be acting as ROS scavengers. All three may work to reduce ROS by contributing to the GSH pool. Overall, our results indicate that reduction in mitochondrial activity and oxidative stress are potential mechanisms by which Pro and its analogues act to improve pre-implantation embryo development.

Synthesis, characterization and anti-breast cancer activities of stachydrine derivatives

Stachydrine is a hydrophilic quaternary amine salt with good antitumor effect, but its application is limited due to its rapid metabolism and low bioavailability. We synthesized and evaluated nine prodrugs of stachydrine, which showed suitable hydrophobicity (CLogP: -2.58-4.78, vs SS-0: -3.32) and better in vitro anticancer activity (IC50: 0.34 μM-14.03 mM, vs SS-0: 38.97 mM-147.19 mM) in comparison with stachydrine. Among them, SS-12, SS-16 and SS-18 are the most effective compounds against 4T1 cells, and the IC50 is 2.15-24.14 μM. Especially, compared with stachydrine, SS-12 significantly blocked the cell cycle in the G0/G1 phase, reduced the mitochondrial membrane potential, and induced the apoptosis of 4T1 cells through mitochondria pathway, which increased the expressions of Bax and cleaved caspase-3 protein, decrease the expression of Bcl-2. The pharmacokinetics of SS-12 showed a rational bioavailability (79.6%), and a longer retention time (T1/2 = 7.62 h) than that of stachydrine (T1/2 ≈ 1.16 h) in rats. Compared with stachydrine, SS-12 significantly enhanced the anticancer efficacy (56.32% of tumor-inhibition rates, vs SS-0: 3.89%), meanwhile, ameliorated the tumor-induced organ damage in mice. Therefore, SS-12 may be a promising prodrug of stachydrine against breast cancer.

Contribution of Serendipita indica on growth improvement, antioxidative capacity of Dracocephalum kotschyi, and its resistance against cadmium stress

Cadmium pollution is a severe issue worldwide which causes an elevated concern in agriculture. The utilization of plant-microbial interactions offers a promising approach for the remediation of cadmium-polluted soils. To elucidate the mechanism of Serendipita indica-mediated cadmium stress tolerance, a potting experiment was conducted to study the impact of S. indica on Dracocephalum kotschyi plants grown under different cadmium concentrations (0, 5, 10, and 20 mg/kg). The effects of cadmium and S. indica on plant growth, antioxidant enzyme activities, and accumulation of cadmium were investigated. The results showed that cadmium stress significantly decreases biomass, photosynthetic pigments, and carbohydrate content concomitantly with increasing antioxidant activities, electrolyte leakage, and hydrogen peroxide, proline, and cadmium content. Inoculation with S. indica alleviated the adverse effect of cadmium stress by enhancing shoot and root dry weight, photosynthetic pigments, and carbohydrate, proline, and catalase activity. Unlike cadmium stress, the presence of fungus led to a reduction in electrolyte leakage and hydrogen peroxide content as well as the content of cadmium in D. kotschyi leaf which mitigates cadmium-induced oxidative stress. Our findings demonstrated S. indica inoculation alleviates the adverse effects of cadmium stress in D. kotschyi plants which could prolong their survival under stressful conditions. Due to the importance of D. kotschyi and the effect of biomass increase on the amount of its medicinal substances, exploiting S. indica not only promotes plant growth, but also may be used as a potential eco-friendly method for relieving the phytotoxicity of Cd and remediating Cd-contaminated soil.

Pentachlorophenol exposure induced neurotoxicity by disrupting citrulline metabolism in larvae and adult zebrafish

Pentachlorophenol (PCP) is a ubiquitous environmental toxicant with various adverse effects. Although its neurotoxicity has been reported, the underlying mechanism and subsequent detoxification remain unclear. In this study, embryos and adult zebrafish were exposed to PCP to determine its potential neurotoxic mechanism and protective indicators. The survival rate, heart rate, mobility time, active status and moving distance were significantly decreased in larvae after 30 μg/L PCP exposure. Likewise, the mobile time, latency to the first movement, velocity and moving distance of adult zebrafish were significantly reduced by PCP exposure. Untargeted metabolomics analysis of larvae revealed that arginine and proline metabolism was the primary pathway affected by PCP exposure, reflected by increased proline and decreased citrulline (CIT) contents, which were confirmed by quantitative data. PCP exposure suppressed the conversion from arginine to CIT in larvae by downregulating the expression of nos1 and nos2a. Ornithine content was increased in the brains and intestines of adult zebrafish after PCP exposure, which inhibited ornithine catabolism to CIT by downregulating otc, resulting in reduced CIT. Intriguingly, CIT supplementation significantly restored the neurobehavioral defects induced by PCP in larvae and adult zebrafish. CIT supplementation upregulated the expression of ef1α and tuba1 in larvae and inhibited the downregulation of ef1α in the brains of adult zebrafish. Taken together, these results indicated that CIT supplementation could protect against PCP-induced neurotoxicity by upregulating the expression of genes involved in neuronal development and function.

DNA fragmentation, chromosomal aberrations, and multi-toxic effects induced by nickel and the modulation of Ni-induced damage by pomegranate seed extract in Allium cepa L

This study was designed to assess the recovery effect of pomegranate seed extract (PSEx) against nickel (Ni)-induced damage in Allium cepa. Except for the control group treated with tap water, five experimental groups were exposed to 265 mg L-1 PSEx, 530 mg L-1 PSEx, 1 mg L-1 NiCI2, 265 mg L-1 PSEx + 1 mg L-1 NiCI2, and 530 mg L-1 PSEx + 1 mg L-1 NiCI2, respectively. The toxicity of Ni was examined through the analysis of physiological (germination percentage, weight gain, and root length), cytotoxicity (mitotic index), genotoxicity (micronucleus, chromosomal anomalies, and Comet test), and biochemical (malondialdehyde, proline, chlorophyll a and chlorophyll b contents, the activities of superoxide dismutase and catalase) parameters. Meristematic cell defects were also investigated. The NiCl2-DNA interaction was evaluated through spectral shift analysis. Values of all physiological parameters, mitotic index scores, and chlorophyll contents decreased while micronucleus frequency, DNA tail percentage, chromosomal anomalies, proline, MDA, and enzyme activities increased following Ni administration. According to the tail DNA percentage scale, Ni application caused "high damage" to DNA. Ni-induced chromosomal anomalies were fragment, sticky chromosome, vagrant chromosome, bridge, unbalanced chromatin distribution, reverse polarization, and nucleus with bud. NiCl2-DNA interaction caused a hyperchromic shift in the UV/Vis spectrum of DNA by spectral profile analysis. Ni exposure impaired root meristems as evidenced by the formation of epidermis cell damage, flattened cell nucleus, thickened cortex cell wall, and blurry vascular tissue. Substantial recovery was seen in all parameters with the co-administration of PSEx and Ni. Recovery effects in the parameters were 18-51% and 41-84% in the 265 mg L-1 PSEx + 1 mg L-1 NiCI2 and 530 mg L-1 PSEx + 1 mg L-1 NiCI2 groups, respectively. The Comet scale showed that PSEx applied with Ni reduced DNA damage from "high" to "moderate." Ni-induced thickened cortex cell wall and blurry vascular tissue damage disappeared completely when 530 mg L-1 PSEx was mixed with Ni. PSEx successfully reduced the negative effects of Ni, which can be attributed to its content of antioxidants and bioactive ingredients.

Integrative application of silicon and/or proline improves Sweet corn (Zea mays L. saccharata) production and antioxidant defense system under salt stress condition

Silicon (Si) and/or proline (Pro) are natural supplements that are considered to induce plants' stress tolerance against various abiotic stresses. Sweet corn (Zea mays L. saccharata) production is severely afflicted by salinity stress. Therefore, two field tests were conducted to evaluate the potential effects of Si and/or Pro (6mM) used as seed soaking (SS) and/or foliar spray (FS) on Sweet corn plant growth and yield, physio-biochemical attributes, and antioxidant defense systems grown in a saline (EC = 7.14dS m-1) soil. The Si and/or Pro significantly increased growth and yield, photosynthetic pigments, free proline, total soluble sugars (TSS), K+/Na+ratios, relative water content (RWC), membrane stability index (MSI), α-Tocopherol (α-TOC), Ascorbate (AsA), glutathione (GSH), enzymatic antioxidants activities and other anatomical features as compared to controls. In contrast, electrolytes, such as SS and/or FS under salt stress compared to controls (SS and FS using tap water) were significantly decreased. The best results were obtained when SS was combined with FS via Si or Pro. These alterations are brought about by the exogenous application of Si and/or Pro rendering these elements potentially useful in aiding sweet corn plants to acclimate successfully to saline soil.

Salicylic acid alleviates Zn-induced inhibition of growth via enhancing antioxidant system and glutathione metabolism in alfalfa

Zinc (Zn) is considered as one of the heavy metal pollutants in soil affecting agriculture. Salicylic acid (SA) is an important phytohormone that can mitigate effects against various abiotic stresses in plants, however, its exploration to improve Zn stress tolerance in alfalfa plants is still elusive. Thus, in the present study, exogenous SA treatment was conducted on alfalfa plants under Zn stress. The effects of exogenous SA on the physiological effects of alfalfa plants and the expression levels related genes were studied. This study tested the biomass, relative water content, chlorophyll levels, photosynthetic capacity, proline and soluble sugar contents, detected the activity of antioxidant enzymes (such as peroxidase and superoxide dismutase), glutathione biosynthesis, and endogenous SA levels, and quantified the genes associated with the antioxidant system and glutathione metabolism-mediated Zn stress. The results showed that exogenous SA could elevate the physiological adaptability of alfalfa plants through enhancing photosynthesis, proline and soluble sugar levels, stimulating antioxidant system and glutathione metabolism, and inducing the transcription level of related genes, thereby diminishing oxidative stress, inhibiting excessive Zn accumulation of alfalfa plants, increasing tolerance to Zn stress, and reducing the toxicity of Zn. Collectively, the application of SA alleviates Zn toxicity in alfalfa plants. The findings gave first insights into the regulatory mechanism of the Zn stress tolerance of alfalfa by exogenous SA and this might have positive implications for managing other plants which are suffering Zn stress.

β-Turn editing in Gramicidin S: Activity impact on replacing proline α-carbon with stereodynamic nitrogen

Gramicidin S, natural antimicrobial peptide is used commercially in medicinal lozenges for sore throat and Gram-negative and Gram-positive bacterial infections. However, its clinical potential is limited to topical applications because of its high red blood cells (RBC) cytotoxicity. Given the importance of developing potential antibiotics and inspired by the cyclic structure and druggable features of Gramicidin S, we edited proline α-carbon with stereodynamic nitrogen to examine the direct impact on biological activity and cytotoxicity with respect to prolyl counterpart. Natural Gramicidin S (12), proline-edited peptides 13-16 and wild-type d-Phe-d-Pro β-turn mimetics (17 and 18) were synthesized using solid phase peptide synthesis and investigated their activity against clinically relevant bacterial pathogens. Interestingly, mono-proline edited analogous peptide 13 showed moderate improvement in antimicrobial activity against E. coli ATCC 25922 and K.pneumoniae BAA 1705 as compared to Gramicidin S. Furthermore, proline edited peptide 13 exhibited equipotent antimicrobial effect against MDR S. aureus and Enterococcus spp. Analysis of cytotoxicity against VERO cells and RBC, reveals that proline edited peptides showed two-fivefold lesser cytotoxicity than the counterpart Gramicidin S. Our study suggests that introducing single azPro/Pro mutation in Gramicidin S marginally improved the activity and lessens the cytotoxicity as compared with the parent peptide.

Proline is increased in allergic asthma and promotes airway remodeling

Proline and its synthesis enzyme pyrroline-5-carboxylate reductase 1 (PYCR1) are implicated in epithelial-mesenchymal transition (EMT), yet how proline and PYCR1 function in allergic asthmatic airway remodeling via EMT has not yet been addressed to our knowledge. In the present study, increased levels of plasma proline and PYCR1 were observed in patients with asthma. Similarly, proline and PYCR1 in lung tissues were high in a murine allergic asthma model induced by house dust mites (HDMs). Pycr1 knockout decreased proline in lung tissues, with reduced airway remodeling and EMT. Mechanistically, loss of Pycr1 restrained HDM-induced EMT by modulating mitochondrial fission, metabolic reprogramming, and the AKT/mTORC1 and WNT3a/β-catenin signaling pathways in airway epithelial cells. Therapeutic inhibition of PYCR1 in wild-type mice disrupted HDM-induced airway inflammation and remodeling. Deprivation of exogenous proline relieved HDM-induced airway remodeling to some extent. Collectively, this study illuminates that proline and PYCR1 involved with airway remodeling in allergic asthma could be viable targets for asthma treatment.

SLC25A51 promotes tumor growth through sustaining mitochondria acetylation homeostasis and proline biogenesis

Solute carrier family 25 member 51 (SLC25A51) was recently identified as the mammalian mitochondrial NAD+ transporter essential for mitochondria functions. However, the role of SLC25A51 in human disease, such as cancer, remains undefined. Here, we report that SLC25A51 is upregulated in multiple cancers, which promotes cancer cells proliferation. Loss of SLC25A51 elevates the mitochondrial proteins acetylation levels due to SIRT3 dysfunctions, leading to the impairment of P5CS enzymatic activity, which is the key enzyme in proline biogenesis, and the reduction in proline contents. Notably, we find fludarabine phosphate, an FDA-approved drug, is able to bind with and inhibit SLC25A51 functions, causing mitochondrial NAD+ decrease and proteins hyperacetylation, which could further synergize with aspirin to reinforce the anti-tumor efficacy. Our study reveals that SLC25A51 is an attractive anti-cancer target, and provides a novel drug combination of fludarabine phosphate with aspirin as a potential cancer therapy strategy.

Assessing the benefits of antioxidant and antibiotics treatments for cryopreservation of the model alga Ectocarpus siliculosus and the endemic alga Acinetospora asiatica

BACKGROUND

Cryopreservation in liquid nitrogen is a suitable technique for preserving seaweeds, a group of photosynthetic organisms with many applications. Although there are some standard protocols for seaweed cryopreservation, most rely on expensive controlled-rate coolers. Moreover, several factors, such as the use of antioxidants or antibiotics, remain unexplored.

OBJECTIVE

To test the effect of 2-mercapthoethanol (antioxidant) and antibiotic mixtures on the cryopreservation of the model alga Ectocarpus siliculosus and the endemic brown seaweed Acinetospora asiatica using a low-tech passive rate cooler.

MATERIALS AND METHODS

2-mercaptoethanol was added to the cryoprotectant (CPA) solution, while antibiotic mixtures were included in the culture medium during the recovery process. In addition, two CPA solutions were tested on E. siliculosus.

RESULTS

After two weeks of recovery, the treatment comprising PSC antibiotic mixture (Penicillin G, streptomycin, and chloramphenicol) showed a significant increase in post-thaw viability. Antioxidant treatment did not improve viability. The highest viabilities for E. siliculosus and A. asiatica were 64-83%, and 83-87%, respectively, using 10% glycerol + 10% proline as CPA solution.

CONCLUSION

E. siliculosus and A. asiatica were successfully cryopreserved using a low-tech passive rate cooler, 10% glycerol + 10% proline solution, and antibiotic treatment. The highest post-thaw viabilities (64-87%) reported for PSC antibiotic mixture suggest the potential benefits of using antibiotics during post-thaw recovery of marine macroalgae. This study is the first report on the cryopreservation of A. asiatica. DOI: 10.54680/fr23310110212.

Glutamine, proline, and isoleucine support maturation and fertilisation of bovine oocytes

Successful in-vitro production of bovine embryos relies on meiotic maturation of oocytes in vitro (IVM) before they can be fertilised. High levels of IVM are currently achieved using a complex medium that contains all 20 common amino acids, namely TCM199, but can also be achieved using a simple inorganic salt solution containing non-essential amino acids, proline, and glutamine. Further simplification of the amino acid content of medium used for IVM could lead to a more defined medium that provides reproducible IVM. The aim of this study was, therefore, to determine the minimal amino acid requirements for bovine oocyte nuclear maturation, as measured by progression to metaphase II (MII) of meiosis. Supplementation of a simple medium composed of inorganic salts (M1 medium) with multiple amino-acid combinations showed that M1 containing glutamine, proline, and isoleucine resulted in nuclear maturation comparable to that of TCM199 (57.4 ± 3.4% vs 67% ± 1.7%, respectively) but was reduced when cystine (Cys2) to that seen with M1 alone (38.0 ± 2.2%). Viability of oocytes matured in this simplified medium was equal to those matured in TCM199 since the same proportion of zygotes with 2 pronuclei were observed following fertilisation in medium containing no amino acids (33.9 ± 6.5% vs 33.3 ± 3.6%, respectively). Addition of glutamine, proline and isoleucine to fertilisation medium also increased the proportion of zygotes but did not increase blastocyst development rates. Thus, a defined medium containing only glutamine, proline and isoleucine is sufficient for oocyte maturation and successful fertilisation.

Silicon modulate the non-enzymatic antioxidant defence system and oxidative stress in a similar way as boron in boron-deficient cotton flowers

Silicon (Si) application, especially via foliar application, may be promising to attenuate oxidative damage, as Si can improve the non-enzymatic antioxidant system of cotton flowers. However, studies that address the relationship between boron (B) and Si in cotton flowers are still scarce. Therefore, this paper aimed to evaluate the effect of silicon alone and added to the borate solution applied via foliar spray on the oxidative stress; proline, carotenoid, and phenol contents; and biomass production of cotton flowers grown under moderate B deficiency. The experiment was arranged in a completely randomized design with ten replicates and the following five treatments: control (cotton plants under boron deficiency); water application (without B and Si); boron application; silicon application; and B + Si. The application of B, Si, and B + Si reduced the malondialdehyde content in cotton petals by 45%, 48%, and 59%, respectively, and in cotton anthers by57%, 64%, and 67%, respectively. The dry matter of cotton petals in the respective treatments increased by 20%, 16%, 35%, and 44%, while the dry matter of cotton anthers increased by 40%, 24%, 48%, and 53%, respectively, compared to the treatment with water only. There was a strong relationship between B content and dry matter; Si content and the contents of phenols and proline; and carotenoid content and the contents of MDA and H₂O₂. B deficiency can induce oxidative stress specifically in the petals and anthers of cotton, with carotenoids being the main defense mechanism in flowers, while Si is capable of strongly activating defense mechanisms from phenol and proline. In conclusion, the development of organs related to reproduction is impaired by B deficiency. In addition, the foliar application of Si and B attenuates the effects of oxidative stress on the sepals and anthers of cotton, mainly favoring the development of cotton anthers.

Exogenous proline activated an integrated response of NER and HR pathways to reduce DNA damage in rice seedlings under chromium stress

The DNA damage induced by hexavalent chromium [Cr(VI)] pollutant causes a genotoxic effect on rice seedlings. Hereby, we examined the effects of exogenous proline (Pro) on the alleviation of DNA damage in rice seedlings under different effective concentrations of Cr(VI). Our results revealed that Cr(VI) stress induced reactive oxygen species (ROS), i.e., H₂O₂ and O₂^·- accumulation in rice seedlings, repressed genes expression activated in the homologous recombination (HR) and nucleotide excision repair (NER) pathways, and caused DNA damage. Exogenous application of Pro increased Cr accumulation in rice roots, but decreased Cr accumulation in rice shoots, wherein Pro application decreased ROS accumulation in both tissues of rice seedlings. The comet assays suggested that exogenous application of Pro significantly alleviated the DNA damage in rice seedlings during Cr(VI) treatments, judged by the Olive tail moment and tail DNA. Transcriptional assays revealed that exogenous Pro upregulated the expression level of genes associated with the HR and NER pathways and triggered coordinated actions of both repairing pathways to modulate DNA lesion in rice plants during exposure to Cr(VI). Calculations from gene expression variation factors showed that regulative effect of exogenous application of Pro on DNA repair pathways was highly activated at 2.0 mg Cr/L. The current study revealed that Cr(VI) affect rice plants and exogenous Pro rescue these effects by the activation of HR and NER pathways.

Regulation of chromium translocation to shoot and physiological, metabolomic, and ionomic adjustments confer chromium stress tolerance in the halophyte Suaeda maritima

Chromium (Cr) is a highly toxic element adversely affecting the environment, cultivable lands, and human populations. The present study investigated the effects of Cr (VI) (100-400 μM) on plant morphology and growth, photosynthetic pigments, organic osmolytes, ionomics, and metabolomic dynamics of the halophyte Suaeda maritima to decipher the Cr tolerance mechanisms. Cr exposure reduced the growth and biomass in S. maritima. The photosynthetic pigments content significantly declined at higher Cr concentrations (400 μM). However, at lower Cr concentrations (100-300 μM), the photosynthetic pigments remained unaffected or increased. The results suggest that a high concentration of Cr exposure might have adverse effects on PS II in S. maritima. The enhanced uptake of Na⁺ in S. maritima imposed to Cr stress indicates that Na⁺ might have a pivotal role in osmotic adjustment, thereby maintaining water status under Cr stress. The proline content was significantly upregulated in Cr-treated plants suggesting its role in maintaining osmotic balance and scavenging ROS. The metabolomic analysis of control and 400 μM Cr treated plants led to the identification of 62 metabolites. The fold chain analysis indicated the upregulation of several metabolites, including phytohormones (SA and GA₃), polyphenols (cinnamic acid, sinapic acid, coumaric acid, vanillic acid, and syringic acid), and amino acids (alanine, leucine, proline, methionine, and cysteine) under Cr stress. The upregulation of these metabolites suggests the enhanced metal chelation and sequestration in vacuoles, reducing oxidative stress by scavenging ROS and promoting photosynthesis by maintaining the chloroplast membrane structure and photosynthetic pigments. Furthermore, in S. maritima, Cr tolerance index (T_i) was more than 60% in all the treatments, and Cr bio-concentration factor (BCF) and translocation factor (T_f) values were all greater than 1.0, which clearly indicates the Cr-hyperaccumulator characteristics of this halophyte.

Nitric oxide overcomes copper and copper oxide nanoparticle-induced toxicity in Sorghum vulgare seedlings through regulation of ROS and proline metabolism

This study aimed to investigate the phytotoxic effect of copper (Cu) and copper nanoparticles (CuONPs) and ameliorative potential of nitric oxide (NO) against these toxic materials in Sorghum vulgare Pers. seedlings. Data suggested that exposure of Cu and CuONPs significantly reduced growth, chlorophyll, carotenoids and protein in root and shoot, which coincided with increased Cu accumulation. However, addition of sodium nitroprusside (SNP, a donor of NO) lowered Cu and CuONPs mediated toxicity through restricting Cu accumulation and improving photosynthetic pigments and total soluble protein contents. Data further suggested that exposure of Cu and CuONPs significantly increased hydrogen peroxide (H2 O2 ), superoxide radicals (O2 •- ), and malondialdehyde (MDA) contents. Enhanced level of oxidative stress severely inhibited the enzymatic activities of glutathione reductase (GR), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) but enhanced superoxide dismutase (SOD) and catalase (CAT) activity. However, addition of SNP positively regulated antioxidants enzymes activity, particularly the enzymes involved in the ascorbate-glutathione cycle to overcome Cu- and CuONPs-induced stress in Sorghum seedlings. Further, Cu and CuONPs enhanced accumulation of free proline through inducing Δ1 -pyrroline-5-carboxylate synthetase (P5CS) activity while lowering the proline dehydrogenase (PDH) activity. However, addition of SNP reversed these responses. Therefore, overall results revealed that SNP has enough potential of reducing the toxicity of Cu and CuONPs in Sorghum seedlings through regulation of proline metabolism and activity of enzymes of the ascorbate-glutathione cycle. These findings can be employed in developing new resistant varieties of Sorghum having enhanced tolerance against Cu or CuONP stress and improved productivity.

Structural and Functional Characteristics of the Proline-Rich Antimicrobial Peptide Minibactenecin from Leukocytes of Domestic Goat Capra hircus

We performed structural and functional studies of minibactenecin mini-ChBac7.5Nα, a natural proline-rich cathelicidin from domestic goat Capra hircus. To identify the key residues important for the biological action of the peptide, a panel of its alanine-substituted analogues was produced. The development of E. coli resistance to the natural minibactenecin, as well as to its analogues carrying substitutions for hydrophobic amino acids in the C-terminal residues was studied. The data obtained indicate the possibility of rapid development of the resistance to this class of peptides. The main factors in the formation of the antibiotic resistance are various mutations leading to inactivation of the SbmA transporter.

Effective Reduction of Tau Amyloid Aggregates in the Presence of Cyclophilin from Platanus orientalis Pollens; An Alternative Mechanism of Action of the Allergen

BACKGROUND

A hallmark pathology of Alzheimer's disease (AD) is the construction of neurofibrillary tangles, which are made of hyperphosphorylated Tau. The cis-proline isomer of the pThr/Ser-Pro sequence has been suggested to act as an aggregation precursor according to the 'Cistauosis' hypothesis; however, this aggregation scheme is not yet completely approved. Various peptidyl-prolyl isomerases (PPIases) may specifically isomerize cis/trans-proline bonds and restitute Tau's ability to attach microtubules and may control Tau amyloid aggregation in AD.

METHODS

In this study, we provided experimental evidence for indicating the effects of the plant Cyclophilin (P-Cyp) from Platanus orientalis pollens on the Tau aggregation by various spectroscopic techniques.

RESULTS

Our findings disclosed that the rate/extent of amyloid formation in the Tau sample which is incubated with P-Cyp decreased and these observations do not seem to be due to the macromolecular crowding effect. Also, as proven that 80% of the prolines in the unfolded protein are in the trans conformation, urea-induced unfolding analyses confirmed this conclusion and showed that the aggregation rate/extent of urea-treated Tau samples decreased compared with those of the native protein. Also, XRD analysis indicated the reduction of scattering intensities and beta structures of amyloid fibrils in the presence of P-Cyp. Therefore, the ability of P-Cyp to suppress Tau aggregation probably depends on cis to trans isomerization of proline peptide bonds (X-Pro) and decreasing cis isomers in vitro.

CONCLUSION

The findings of the current study may inspire possible protective/detrimental effects of various types of cyclophilins on AD onset/progression through direct regulation of intracellular Tau molecules and provides evidence that a protein from a plant source is able to enter the cell cytoplasm and may affect the behavior of cytoplasmic proteins.

Antibacterial activity and immunomodulatory role of a proline-rich antimicrobial peptide SpPR-AMP1 against Vibrio campbellii infection in shrimp Litopenaeus vannamei

Antimicrobial peptides (AMPs) constitute one of the most promising sources of natural molecules used for the design of effective antimicrobial agents alternative to antibiotics. Previously, we have showed that a crab proline-rich AMP designated as SpPR-AMP1 is a potent AMP that exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria. Here, we demonstrated the importance of SpPR-AMP1 peptide in treating a virulent acute hepatopancreatic necrosis disease (AHPND) Vibrio campbellii VH-639 isolate and eliciting the innate immune response to counter the AHPND infection in shrimp Litopenaeus vannamei. SpPR-AMP1 exhibited a strong antimicrobial activity against V. campbellii VH-639 at MIC value of 0.195-0.39 μM. Scanning electron microscopy (SEM) revealed the membrane disruption potential of SpPR-AMP1 against the V. campbellii VH-639 cells. The in vivo effect of SpPR-AMP1 in shrimp L.vannamei was investigated and the results showed that SpPR-AMP1 was capable of modulating the innate immune response by stimulating the expression levels of AMP transcripts in shrimp hemocytes. Moreover, treatments with SpPR-AMP1 could promote the resistance of shrimp against V. campbellii VH-639 infection as demonstrated by a significant increase in shrimp survival rate and decrease in both the bacterial load and the expression levels of bacterial PirA and PirB toxin gene transcripts in the infected shrimp. These results suggest the potential of SpPR-AMP1 peptide with the combined antimicrobial and immunoenhancing capabilities as promising antimicrobial agent to treat V. campbellii VH-639 causing AHPND infection in shrimp aquaculture.

Associations of forest negative air ions exposure with cardiac autonomic nervous function and the related metabolic linkages: A repeated-measure panel study

Forest environment has many health benefits, and negative air ions (NAI) is one of the major forest environmental factors. Many studies have explored the effect of forest environment on cardiac autonomic nervous function, while forest NAI in the among function and the underlying mechanism still remain unclear. To explore the associations and molecular linkages between short-term exposure to forest NAI and heart rate variability (HRV), a repeated-measure panel study was conducted among 31 healthy adults. Participants were randomly selected to stay in a forest park for 3 days and 2 nights. Individual exposures including NAI were monitored simultaneously and HRV indices were measured repeatedly at the follow-up period. Urine samples were collected for non-targeted metabolomics analysis. Mixed-effect models were adopted to evaluate associations among NAI, HRV indices and metabolites. The median of NAI concentration was 68.11 (138.20) cm^-3 during the study period. Short-term exposure to forest NAI was associated with the ameliorative HRV indices, especially the excitatory parasympathetic nerve. For instance, per interquartile range increase of 5-min moving average of NAI was associated with 9.99 % (95%CI: 8.95 %, 11.03 %) increase of power in high frequency. Eight metabolites were associated with NAI exposure. The down-regulated tyrosine metabolism was firstly observed, followed by other amino acid metabolic alterations. The NAI-related metabolic changes reflect the reduction of inflammation and oxidative stress. HRV indices were associated with 25 metabolites, mainly including arginine, proline and histidine metabolism. Short-term exposure to forest NAI is beneficial to HRV, especially to the parasympathetic nerve activity, by successively disturbing different metabolic pathways which mainly reflect the increased anti-inflammation and the reduced inflammation. The results will provide epidemiological evidences for developing forest therapy and improving cardiac autonomic nervous function.

Response of soybean (Glycine max L.) seedlings to polystyrene nanoplastics: Physiological, biochemical, and molecular perspectives

Micro and nanoplastics are new generation contaminants of global concern. It is important to evaluate the effects on edible products due to the presence of micro- and nano-sized plastics in the treated wastewater. A hydroponic experiment was carried out to explore the effect of polsytrene nanoplastics (PS-NPs; 20 nm) at different concentrations (0, 12.5, 25, and 50 mg L^-1) on Glycine max L. (soybean) seedlings for 7-days. In the current study, firstly the uptake of PS-NPs by Glycine max L. (soybean) roots were confirmed by laser confocal scanning microscope. Exposure to PS-NPs, negatively affected growth parameters and increased Fe, Zn and Mn contents in roots and leaves of soybean seedlings. PS-NPs treatments caused oxidative stress in soybean seedlings. The hydrogen peroxide and malondialdehyde contents, showed similar increase pattern in seedlings exposed to PS-NPs. Response to PS-NPs, the level of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase) and proline content were generally enhanced in roots and leaves of soybean. The expression level of stress-related genes examined in the study included CSD5, FSD3, APX1, and POD up-regulated in PS-NPs treated-soybean seedlings in a tissue specific manner. The results of the present study showed the adverse effects of PS-NPs on soybean seedlings, which may have important implications for the risk assessment of NPs on crop production and environmental safety.

Toxicity of dibutyl phthalate to pakchoi (Brassica campestris L.): Evaluation through different levels of biological organization

Dibutyl phthalate (DBP) is a typical persistent organic pollutant with a high load in the agricultural soils of vegetable crops. Currently, studies on the toxicity of DBP in vegetable crops are limited. Therefore, in this study, pakchoi (Brassica campestris L.), a typical vegetable crop, was used to evaluate the toxic effects of DBP. Pakchoi was exposed to DBP for 24 d at three doses (2, 20, and 200 mg/kg), and the phenotypic, biochemical, and molecular indicators were determined. The results revealed that DBP could reduce the emergence of pakchoi and inhibit plant height, root length, fresh weight, and leaf area. At the biochemical level, DBP exposure could reduce the content of three typical photosynthetic pigments (chlorophyll a and b and carotenoids). The effects of DBP exposure on the quality of pakchoi were primarily through reduced soluble sugar and increased proline contents. In addition, O₂·^- and H₂O₂ levels increased after DBP stress, and the corresponding antioxidant enzymes (SOD, POD, and CAT) were activated to resist oxidative damage. The dose- and time-dependent toxicities of DBP to pakchoi were demonstrated using an integrated biological response index. Finally, the molecular-level results on Day 24 showed that the three antioxidant enzyme genes (sod, pod, and cat) were significantly downregulated, and the antioxidant enzyme genes were more sensitive biomarkers than the enzyme activities. However, the expression level of enzyme genes was opposite to that of enzyme activity (SOD and POD); thus, DBP might directly interact with these enzymes. Molecular docking showed that DBP could stably bind near the SOD/POD active center through intermolecular interaction forces. This study provides essential information on the risk of DBP toxicity to vegetable crops.

The participation of nitric oxide in hydrogen sulphide-mediated chromium tolerance in pepper (Capsicum annuum L) plants by modulating subcellular distribution of chromium and the ascorbate-glutathione cycle

The promising response of chromium-stressed (Cr(VI)-S) plants to hydrogen sulphide (H₂S) has been observed, but the participation of nitric oxide (NO) synthesis in H₂S-induced Cr(VI)-S tolerance in plants remains to be elucidated. It was aimed to assess the participation of NO in H₂S-mediated Cr(VI)-S tolerance by modulating subcellular distribution of Cr and the ascorbate-glutathione (AsA-GSH) cycle in the pepper seedlings. Two weeks following germination, plants were exposed to control (no Cr) or Cr(VI)-S (50 μM K₂Cr₂O₇) for further two weeks. The Cr(VI)-S-plants grown in nutrient solution were supplied with 200 μM sodium hydrosulphide (NaHS, donor of H₂S), or NaHS plus 100 μM sodium nitroprusside (SNP, a donor of NO). Chromium stress suppressed plant growth and leaf water status, while elevated proline content, oxidative stress, and the activities of AsA-GSH related enzymes, as well as endogenous H₂S and NO contents. The supplementation of NaHS increased Cr accumulation at root cell walls and vacuoles of leaves as soluble fraction to reduce its toxicity. Furthermore it limited oxidative stress, improved plant growth, modulated leaf water status, and the AsA-GSH cycle-associated enzymes' activities, as well as it further improved H₂S and NO contents. The positive effect of NaHS was found to be augmented on those parameters in the CrS-plants by the SNP supplementation. However, 0.1 mM cPTIO, the scavenger of NO, inverted the prominent effect of NaHS by decreasing NO content. The supplementation of SNP along with NaHS + cPTIO reinstalled the positive effect of NaHS by restoring NO content, which suggested that NO might have a potential role in H₂S-induced tolerance to Cr(VI)-S in pepper plants by stepping up the AsA-GSH cycle.

Foliar-applied selenium nanoparticles alleviate cadmium stress through changes in physio-biochemical status and essential oil profile of coriander (Coriandrum sativum L.) leaves

Since large areas of agricultural soils around the world are contaminated by Cd, a cost-effective and practical method is needed for the safe production of edible plants. The effective role of many nanomaterials to improve plant yield by mitigating environmental pollutions is addressed; however, the impacts of selenium nanoparticles (Se-NPs) have not been well-known yet. The aim of this work was to investigate foliar application of Se-NPs on yield, water content, proline concentration, phenolic content, lipid peroxidation, and essential oil (EO) attributes of coriander (Coriandrum sativum L.) under Cd stress. The plants were exposed to Cd contamination (0, 4, and 8 mg L^-1) and foliar application of Se-NPs (0, 20, 40, and 60 mg L^-1). The results showed increased Cd accumulation in roots and shoots of coriander plants upon Cd stress; however, Se-NPs alleviated the uptake of Cd. Cd toxicity, particularly 8 mg L^-1, decreased shoot and root weight, chlorophyll (Chl), and relative water content (RWC), while Se-NPs improved these attributes. The Cd concentration at 4 mg L^-1 and Se-NPs at 40 or 60 mg L^-1 increased phenolic and flavonoid contents as well as EO yield. Proline concentration and malondialdehyde (MDA) increased by enhancing Cd stress, but Se-NPs decreased MDA. The GC/MS analysis showed that the main EO constitutes were n-decanal (18.80-29.70%), 2E-dodecanal (14.23-19.87%), 2E-decanal (12.60-19.40%), and n-nonane (7.23-12.87%), representing different amounts under Cd pollution and Se-NPs. To sum up, Se-NPs at 40-60 mg L^-1 are effective in alleviating Cd stress.

Chromium in plant growth and development: Toxicity, tolerance and hormesis

Research over the last three decades showed that chromium, particularly the oxyanion chromate Cr(VI) behaves as a toxic environmental pollutant that strongly damages plants due to oxidative stress, disruption of nutrient uptake, photosynthesis and metabolism, and ultimately, represses growth and development. However, mild Cr(VI) concentrations promote growth, induce adventitious root formation, reinforce the root cap, and produce twin roots from single root meristems under conditions that compromise cell viability, indicating its important role as a driver for root organogenesis. In recent years, considerable advance has been made towards deciphering the molecular mechanisms for root sensing of chromate, including the identification of regulatory proteins such as SOLITARY ROOT and MEDIATOR 18 that orchestrate the multilevel dynamics of the oxyanion. Cr(VI) decreases the expression of several glutamate receptors, whereas amino acids such as glutamate, cysteine and proline confer protection to plants from hexavalent chromium stress. The crosstalk between plant hormones, including auxin, ethylene, and jasmonic acid enables tissues to balance growth and defense under Cr(VI)-induced oxidative damage, which may be useful to better adapt crops to biotic and abiotic challenges. The highly contrasting responses of plants manifested at the transcriptional and translational levels depend on the concentration of chromate in the media, and fit well with the concept of hormesis, an adaptive mechanism that primes plants for resistance to environmental challenges, toxins or pollutants. Here, we review the contrasting facets of Cr(VI) in plants including the cellular, hormonal and molecular aspects that mechanistically separate its toxic effects from biostimulant outputs.

Using Exogenous Melatonin, Glutathione, Proline, and Glycine Betaine Treatments to Combat Abiotic Stresses in Crops

Abiotic stresses, such as drought, salinity, heat, cold, and heavy metals, are associated with global climate change and hamper plant growth and development, affecting crop yields and quality. However, the negative effects of abiotic stresses can be mitigated through exogenous treatments using small biomolecules. For example, the foliar application of melatonin provides the following: it protects the photosynthetic apparatus; it increases the antioxidant defenses, osmoprotectant, and soluble sugar levels; it prevents tissue damage and reduces electrolyte leakage; it improves reactive oxygen species (ROS) scavenging; and it increases biomass, maintains the redox and ion homeostasis, and improves gaseous exchange. Glutathione spray upregulates the glyoxalase system, reduces methylglyoxal (MG) toxicity and oxidative stress, decreases hydrogen peroxide and malondialdehyde accumulation, improves the defense mechanisms, tissue repairs, and nitrogen fixation, and upregulates the phytochelatins. The exogenous application of proline enhances growth and other physiological characteristics, upregulates osmoprotection, protects the integrity of the plasma lemma, reduces lipid peroxidation, increases photosynthetic pigments, phenolic acids, flavonoids, and amino acids, and enhances stress tolerance, carbon fixation, and leaf nitrogen content. The foliar application of glycine betaine improves growth, upregulates osmoprotection and osmoregulation, increases relative water content, net photosynthetic rate, and catalase activity, decreases photorespiration, ion leakage, and lipid peroxidation, protects the oxygen-evolving complex, and prevents chlorosis. Chemical priming has various important advantages over transgenic technology as it is typically more affordable for farmers and safe for plants, people, and animals, while being considered environmentally acceptable. Chemical priming helps to improve the quality and quantity of the yield. This review summarizes and discusses how exogenous melatonin, glutathione, proline, and glycine betaine can help crops combat abiotic stresses.

Anti-Phytophthora Activity of Halofuginone and the Corresponding Mode of Action

Febrifugine, a natural alkaloid, exhibits specific anti-phytophthora activity; however, its mode of action is unclear. In this study, halofuginone, a synthetic derivative of febrifugine, showed significantly higher anti-phytophthora activities than those of febrifugine and the commercial drug metalaxyl against Phytophthora sojae, Phytophthora capsici, and Phytophthora infestans with effective concentration for 50% inhibition (EC₅₀) values of 0.665, 0.673, and 0.178 μg/mL, respectively. Proline could alleviate the growth inhibition of halofuginone on P. capsici, implying that halofuginone might target prolyl-tRNA synthetase (PcPRS). The anti-phytophthora mechanism of halofuginone was then investigated by molecular docking, fluorescence titration, and enzymatic inhibition assays. The results revealed that halofuginone could bind to PcPRS and shared a similar binding site with the substrate proline. Point mutations at Glu316 and Arg345 led to 24.5 and 16.1% decreases in the enzymatic activity of PcPRS but 816.742- and 459.557-fold increases in the resistance to halofuginone, respectively. The results further confirmed that halofuginone was a competitive inhibitor of proline against PcPRS, and Glu316 and Arg345 played important roles in the binding of halofuginone and proline. Taken together, the results indicated that halofuginone is an alternative anti-phytophthora drug candidate and that PcPRS represents a potential target for the development of new pesticides.

Bioremediation of Cadmium Toxicity in Wheat (Triticum aestivum L.) Plants Primed with L-Proline, Bacillus subtilis and Aspergillus niger

Cadmium toxicity is one of the deleterious abiotic factors that reduce wheat production. Two different cultivars (Akbar and Dilkash) were compared for their cadmium (0, 40 and 80 mg/kg) tolerance and responses towards Bacillus subtilis NA2, Aspergillus niger PMI-118 and L-proline. Both microbes were tested for heavy metal tolerance and production of various plant hormones and biological active enzyme characteristics under normal and cadmium stress. A completely randomized design (two cultivars × four treatments × three cadmium levels × three replicates) was adopted using distilled water as a control. The growth promotion potential of these strains under cadmium stress was determined by N-fixation, IAA synthesis, P-solubilization, amylase and proteases production. A pot experiment under controlled conditions was conducted to evaluate the effect of bacteria, fungi, and L-proline under cadmium stress. It was indicated from the result that plant biomass (46.43%), shoot length (22.40%), root length (25.06%), chlorophyll (17.17%), total sugars (27.07%), total proteins (86.01%) and ascorbic acid (83.27%) were improved with inoculation under control and cadmium stress. The accumulation of total flavonoids (48.64%), total phenolics (24.88%), hydrogen peroxide (53.96%) and activities of antioxidant enzymes CAT (26.37%) and APX (43.71%) were reduced in the plants treated with bacteria, fungi and L-proline than those under control. With parallel aids, Bacillus subtilis NA2 showed a higher cadmium tolerance and plant growth stability as compared to Aspergillus niger PMI-118 and L-proline and may be adopted in the future.

Mechanisms of the ethanol extract of Gelidium amansii for slow aging in high-fat male Drosophila by metabolomic analysis

Gelidium amansii (GA) is a kind of red alga homologous to medicine and food and is distributed all over the world. Studies on GA are mainly focused on its polysaccharides, with little research on the ethanol extract. The ethanol extract of Gelidium amansii (GAE) was subjected to a reverse-phase column to obtain 7 components. Among them, 100% methanol solution (GAM), enriched with phytene-1,2-diol, exhibited the strongest DPPH free radical scavenging activity (IC50 = 0.17 mg mL-1). Subsequently, high-fat male flies (HMFs) were used as a model to explore the antioxidant and anti-aging effects of GAM in vivo. Studies showed that GAM can effectively prolong the lifespan of HMFs. When GAM concentrations were 0.2 and 1.0 mg mL-1, the average lifespan of HMFs was increased by 28.7 and 40.7%, respectively, while the longest lifespan of HMFs was increased by 20.55% and 32.88%, respectively. Further research revealed that GAM can significantly downregulate the levels of malondialdehyde (MDA) and protein carbonyl (PCO), and can significantly upregulate the levels of catalase (CAT) and total superoxide dismutase (T-SOD). In addition, by analyzing differential metabolites, we found that GAM relieves aging caused by oxidative stress by regulating amino acid, lipid, sugar, and energy metabolism. The GAM group significantly regulated the levels of adenine, cholic acid, glutamate, L-proline, niacin, and stachyose which tend to recover to the levels of the normal diet male fly (NMF) group. In general, our research provides ideas for the high-value utilization of GA and provides a lead compound for the research and development of anti-aging food or medicine.

Analysis of the femoral neck from rats in the periestropause treated with oxytocin and submitted to strength training

Among the interventions used to prevent osteoporosis in female organisms, strength training (ST) and oxytocin (OT) stand out, as a promising hormone with anabolic action on bone. This study aimed to verify whether the combined action of OT and ST, compared to isolated interventions, potentiates the bone remodeling process of the femoral neck of Wistar rats during periestropause. Forty Wistar rats (18 months) with irregular estrous cycle were randomly distributed into groups: 1-Vehicle (Veh; NaCl 0.15 mol/L ip); 2-Oxytocin (Ot; 134 μg/kg/ip); 3-Strength training (St); 4-Ot + St. The animals of the 1, 2 and 4 groups received two intraperitoneal injections with an interval of 12 h every 30 days, totaling 8 injections at the end of the experimental period (18 to 21 months). The animals in the St and Ot + St groups performed ST on a ladder 3 times a week, maximal voluntary carrying capacity (MVCC) test monthly. After 120 days, the animals were euthanized; the femur was collected for analysis of biomechanical testing, densitometry, bone microtomography, Raman spectroscopy, tissue PCR, and blood for analysis of bone biomarkers, liver damage, and oxidative stress. The main effects in the Ot group were observed in the maximum load and energy in the compression testing (femoral head), and stiffness and energy in the three-points bending testing (femur diaphysis). In addition, the main effects occurred on the bone mineral density (BMD), cortical thickness (Ct.Th), number of pores (Po.N), polar moment of inertia (J), trabecular thickness (Tb.Th), and connectivity density (Conn.Dn), Bone alkaline phosphatase (Alp), Tumor necrosis factor receptor superfamily member 11b (Opg), Tumor necrosis factor ligand superfamily member 11 (Rankl) and Cathepsin K (Ctsk) expression. There was an effect in the tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP). In the St group, the main effect was observed on the energy (compression and the three-points bending), stiffness, aBMD, BMD, cortical bone area (Ct.Ar), Po.N, trabecular bone volume (BV/TV), Tb.Th and in the mineralization ratio (ѵ₁PO₄/proline), Runt-related transcription factor 2 (Runx2), Bone morphogenetic protein 2 (Bmp2), Alp, Osteopontin/secreted phosphoprotein 1 (Opn/Spp1), Opg, Tumor necrosis factor receptor superfamily member 11ª (Rank), Rankl, Ctsk expression. There was an effect in the TRAP and ALP. The interaction in the combination of therapies in the Ot + St group was verified in energy to maximum load (compression and three-points bending testing), stiffness, BMD, Ct.Th, J, Tb.Th and ѵ₁PO₄/proline. In the gene analysis there was interaction in the Runx2, Osterix/Sp7 transcription factor (Osx/Sp7), Bmp2, Alp, Osteocalcin/Bone gamma-carboxyglutamate protein (Ocn/Bglap), Opg, Rankl and Acid phosphatase 5, tartrate resistant (Trap/Acp5) expression. In addition, the combination of OT and ST resulted in a higher maximum load compared to the Veh group, with higher BV/TV than the Ot group, higher Rankl and Ctsk expression than Veh and Ot groups, and lower Po.N and lower activity of TRAP than the other groups. In oxidative stress, total antioxidant capacity (TAC) was lower. These results showed that the combination of interventions is a promising anabolic strategy for the prevention of osteoporosis in the period of periestropause, standing out from the effects of isolated interventions.

Iron oxide nanoparticles impart cross tolerance to arsenate stress in rice roots through involvement of nitric oxide

The growth and development patterns of crop plants are being seriously threatened by arsenic (As) contamination in the soil, and it also acts as a major hurdle in crop productivity. This study focuses on arsenate As(V) mediated toxicity in rice plants. Further, among the different type of NPs, iron oxide nanoparticles (FeO NPs) display a dose-dependent effect but their potential role in mitigating As(V) stress is still elusive. FeO NPs (500 μM) play a role in imparting cross-tolerance against As(V) induced toxicity in rice. Growth attributes, photosynthetic performance, nutrient contents and biochemical parameters were significantly altered by As(V). But FeO NPs rescued the negative consequences of As(V) by restricting its entry with the possible involvement of NO in rice roots. Moreover, results related with gene expression of NO(OsNoA1 and OsNIA1) and proline metabolism were greatly inhibited by As(V) toxicity. But, FeO NPs reversed the toxic effect of As(V) by improving proline metabolism and stimulating NO mediated up-regulation of antioxidant enzymes particularly glutathione-S-transferase which may be possible reasons for the reduction of As(V) toxicity in rice roots. Overall, it can be stated that FeO NPs may act as an As(V) barrier to restrict the As(V) uptake by roots and have the ability to confer cross tolerance by modulating various morphological, biochemical and molecular characteristics with possible intrinsic involvement of NO.

Comparative physiological and metabolomic analyses reveal that Fe3O4 and ZnO nanoparticles alleviate Cd toxicity in tobacco

BACKGROUND

Heavy metals repress tobacco growth and quality, and engineered nanomaterials have been used for sustainable agriculture. However, the underlying mechanism of nanoparticle-mediated cadmium (Cd) toxicity in tobacco remains elusive.

RESULTS

Herein, we investigated the effects of Fe3O4 and ZnO nanoparticles (NPs) on Cd stress in tobacco cultivar 'Yunyan 87' (Nicotiana tabacum). Cd severely repressed tobacco growth, whereas foliar spraying with Fe3O4 and ZnO NPs promoted plant growth, as indicated by enhancing plant height, root length, shoot and root fresh weight under Cd toxicity. Moreover, Fe3O4 and ZnO NPs increased, including Zn, K and Mn contents, in the roots and/or leaves and facilitated seedling growth under Cd stress. Metabolomics analysis showed that 150 and 76 metabolites were differentially accumulated in roots and leaves under Cd stress, respectively. These metabolites were significantly enriched in the biosynthesis of amino acids, nicotinate and nicotinamide metabolism, arginine and proline metabolism, and flavone and flavonol biosynthesis. Interestingly, Fe3O4 and ZnO NPs restored 50% and 47% in the roots, while they restored 70% and 63% in the leaves to normal levels, thereby facilitating plant growth. Correlation analysis further indicated that these metabolites, including proline, 6-hydroxynicotinic acid, farrerol and quercetin-3-O-sophoroside, were significantly correlated with plant growth.

CONCLUSIONS

These results collectively indicate that metal nanoparticles can serve as plant growth regulators and provide insights into using them for improving crops in heavy metal-contaminated areas.

Hepatoprotective Effects of Ixeris chinensis on Nonalcoholic Fatty Liver Disease Induced by High-Fat Diet in Mice: An Integrated Gut Microbiota and Metabolomic Analysis

Ixeris chinensis (Thunb.) Nakai (IC) is a folk medicinal herb used in Mongolian medical clinics for the treatment of hepatitis and fatty liver diseases even though its pharmacological mechanism has not been well characterized. This study investigated the hepatoprotective mechanism of IC on mice with nonalcoholic fatty liver disease (NAFLD) by integrating gut microbiota and metabolomic analysis. A high-fat diet (HFD) was used to develop nonalcoholic fatty liver disease, after which the mice were treated with oral IC (0.5, 1.5 and 3.0 g/kg) for 10 weeks. HFD induced NAFLD and the therapeutic effects were characterized by pathological and histological evaluations, and the serum indicators were analyzed by ELISA. The gut microbial and metabolite profiles were studied by 16S rRNA sequencing and untargeted metabolomic analysis, respectively. The results showed that the administration of IC resulted in significant decreases in body weight; liver index; serum biomarkers such as ALT, TG, and LDL-C; and the liver inflammatory factors IL-1β, IL-6, and TNF-α. The 16S rRNA sequencing results showed that administration of IC extract altered both the composition and abundance of the gut microbiota. Untargeted metabolomic analysis of liver samples detected a total of 212 metabolites, of which 128 were differentially expressed between the HFD and IC group. IC was found to significantly alter the levels of metabolites such as L-glutamic acid, pyridoxal, ornithine, L-aspartic acid, D-proline, and N4-acetylaminobutanal, which are involved in the regulation of glutamine and glutamate, Vitamin B6 metabolism, and arginine and proline metabolic pathways. Correlation analysis indicated that the effects of the IC extract on metabolites were associated with alterations in the abundance of Akkermansiaceae, Lachnospiraceae, and Muribaculaceae. Our study revealed that IC has a potential hepatoprotective effect in NAFLD and that its function might be linked to improvements in the composition of gut microbiota and their metabolites.

Cold plasma can alleviate cadmium stress by optimizing growth and yield of wheat (Triticum aestivum L.) through changes in physio-biochemical properties and fatty acid profile

Cold plasma (CP) application has increasing interest due to its environmental-friendly, high efficient, and low cost aspects to mitigate deletion effects of heavy metals on plants. A pot experiment was carried out to evaluate the CP application on yield, physiological, and fatty acid profile of wheat (Triticum aestivum L.) in a completely randomized design (CRD) with five replicates. Cadmium (Cd) was applied at four levels (0, 50, 100, and 150 μM), and CP were used on germinated seeds at three levels (0, 60, and 120 s) in a hydroponic system. The results showed CP alleviated the Cd accumulation in roots, shoots, and grains. The significant reduction of grain yield (GY) and thousand grain yield (TGY) was observed in plants exposed to 100 and 150 μM compared with the control plants; however, CP improved GY and TGY particularly at severe Cd stress. The minimum chlorophyll (Chl) and relative water content (RWC) were observed in plants exposed in 100 μM Cd and non-CP treatments. Proline increased by Cd stress but decreased with CP in most treatments. Unlike proline, methionine showed significant reduction under Cd stress. The fatty acid profile of wheat represented that severe Cd stress decreased monounsaturated fatty acid (MUFA) but increased polyunsaturated fatty acid (PUFA). Heat map (HM) showed that GY and methionine were the most sensitive traits under treatments of Cd and CP. Totally, we suggest the use of 120 s of CP to mitigate Cd stress on wheat plants.

Exogenous melatonin mitigates chromium toxicity in maize seedlings by modulating antioxidant system and suppresses chromium uptake and oxidative stress

Melatonin, being an endogenous signaling molecule plays important role in plant growth and stress alleviation. The present study was conducted to evaluate the ameliorative role of melatonin against Cr toxicity in maize seedlings. The Cr toxicity (50, 100 and 200 µM) severely affected hydroponically grown seedlings growth in a dose-dependent manner; however, the melatonin (0.5 and 1.0 µM) application markedly restored toxicity-induced growth retardation. Higher dose of melatonin (1.0 µM) was more effective in case of lower Cr toxicity (50 and 100 µM). Exposure of 200 µM Cr caused 45% and 43% reduction in shoot and root lengths and more than 80% reduction in biomass. In case of 200 µM Cr toxicity, application of 1.0 µM MT effectively restored shoot and root lengths reduction (from 45 to 30%) and biomass decline (from 80 to around 60%). Biomass restoration by 1.0 µM melatonin under 50 and 100 µM Cr was even more pronounced bringing it near to control plants having no Cr exposure. Further, both melatonin levels also improved root tips, root diameter, root volume and root surface area that had been damaged by Cr exposure. The melatonin also alleviated Cr-induced chlorophyll and carotenoids inhibition, improved relative water content, and markedly lowered proline and MDA content in shoots. Lower accumulation of MDA and proline, and greater membrane stability indices indicate that the melatonin conferred better plant growth by playing the role of antioxidant and detoxifying oxidative stress creating substances. Although antioxidant enzymes viz. SOD, POD, CAT and APX activities were also elevated by MT, this increase was not significantly different in the most of cases. No significant difference in NPK contents of shoot was observed by Cr and melatonin application indicating the growth retardation being caused directly by Cr intrinsic toxicity and not by nutrients deficiency. The melatonin-based amelioration of Cr toxicity in maize seedlings seems as the result of its nature as antioxidant, and not by activation/elevation of antioxidative enzymatic system.

Expedited Approach toward the Rational Design of Noncovalent SARS-CoV-2 Main Protease Inhibitors

The main protease (Mpro) of SARS-CoV-2 is a validated antiviral drug target. Several Mpro inhibitors have been reported with potent enzymatic inhibition and cellular antiviral activity, including GC376, boceprevir, calpain inhibitors II, and XII, with each containing a reactive warhead that covalently modifies the catalytic Cys145. Coupling structure-based drug design with the one-pot Ugi four-component reaction, we discovered one of the most potent noncovalent inhibitors, 23R (Jun8-76-3A) that is structurally distinct from the canonical Mpro inhibitor GC376. Significantly, 23R is highly selective compared with covalent inhibitors such as GC376, especially toward host proteases. The cocrystal structure of SARS-CoV-2 Mpro with 23R revealed a previously unexplored binding site located in between the S2 and S4 pockets. Overall, this study discovered 23R, one of the most potent and selective noncovalent SARS-CoV-2 Mpro inhibitors reported to date, and a novel binding pocket in Mpro that can be explored for inhibitor design.

Design, synthesis and biological evaluation of P2-modified proline analogues targeting the HtrA serine protease in Chlamydia

High temperature requirement A (HtrA) serine proteases have emerged as a novel class of antibacterial target, which are crucial in protein quality control and are involved in the pathogenesis of a wide array of bacterial infections. Previously, we demonstrated that HtrA in Chlamydia is essential for bacterial survival, replication and virulence. Here, we report a new series of proline (P2)-modified inhibitors of Chlamydia trachomatis HtrA (CtHtrA) developed by proline ring expansion and Cγ-substitutions. The structure-based drug optimization process was guided by molecular modelling and in vitro pharmacological evaluation of inhibitory potency, selectivity and cytotoxicity. Compound 25 from the first-generation 4-substituted proline analogues increased antiCtHtrA potency and selectivity over human neutrophil elastase (HNE) by approximately 6- and 12-fold, respectively, relative to the peptidic lead compound 1. Based on this compound, second-generation substituted proline residues containing 1,2,3-triazole moieties were synthesized by regioselective azide-alkyne click chemistry. Compound 49 demonstrated significantly improved antichlamydial activity in whole cell assays, diminishing the bacterial infectious progeny below the detection limit at the lowest dose tested. Compound 49 resulted in approximately 9- and 22-fold improvement in the inhibitory potency and selectivity relative to 1, respectively. To date, compound 49 is the most potent HtrA inhibitor developed against Chlamydia spp.