Selenium-mediated Cr(VI) reduction and SeNPs synthesis accelerated Bacillus cereus SES to remediate Cr contamination.

Microbial biotransformation of Cr(VI) is a sustainable approach to reduce Cr(VI) toxicity and remediate Cr(VI) contamination. In this study, Bacillus cereus SES with the capability of reducing both Cr(VI) and Se(IV) was isolated, and the effect of Se supplementation on Cr(VI) reduction by Bacillus cereus SES was investigated. Se(IV) addition enabled 2.6-fold faster Cr(VI) reduction, while B. cereus SES reduced 96.96% Se(IV) and produced more selenium nanoparticles (SeNPs) in the presence of Cr(VI). Co-reduction products of B. cereus SES on Cr(VI) and Se(IV) were SeNPs adsorbed with Cr(III). The relevant mechanisms were further revealed by proteomics. Se(IV) supplementation mediated the synthesis of Cr(VI) reductants and stress-resistant substances, thus enhancing Cr(VI) resistance and promoting Cr(VI) reduction. Meanwhile, high Se(IV) reduction rate was associated with Cr(VI)-induced electron transport processes, and Cr(VI) mediated the up-regulation of flagellar assembly, protein export and ABC transporters pathways to synthesis and export more SeNPs. Furthermore, Se combined with B. cereus SES had the potential to reduce the toxicity of Cr(VI) via reducing the bioavailability of Cr and improving the bioavailability of Se in soil. Results suggested that Se could be an efficient strategy to enhance the remediation of B. cereus SES on Cr contamination.

Selenium and molybdenum synergistically alleviate chromium toxicity by modulating Cr uptake and subcellular distribution in Nicotiana tabacum L.

Chromium (Cr) is a harmful heavy metal that poses a serious threat to plants and animals. Selenium (Se) and molybdenum (Mo) are two beneficial elements for plant growth and resistance. However, their interactive effects on Cr uptake and distribution are poorly understood. Therefore, a hydroponics experiment was conducted to explore the effects of the use of Se and Mo alone and simultaneously on mitigating Cr toxicity. In this study, Nicotiana tabacum L. seedlings were exposed to control, 50 µM Cr, 50 µM Cr + 2 µM Se, 50 µM Cr + 1 µM Mo, or 50 µM Cr + 2 µM Se + 1 µM Mo in Hoagland solution. After 2 weeks, the plant biomass, Cr, Se and Mo contents, photosynthesis, leaf ultrastructure, antioxidant system, subcellular distribution and associated gene expression in Nicotiana tabacum L. were determined. The results showed that simultaneous use of Se and Mo promoted tobacco growth under Cr stress, as evidenced by reducing reactive oxygen species (ROS) content and reducing Cr translocation factor (TF) and inducing a 51.3% reduction in Cr content in shoots. Additionally, Se-Mo interactions increased the levels of glutathione (GSH) and phytochelatin (PC) and the distribution of Cr in the cell walls and organelles. Furthermore, the relative expression of PCS1 was upregulated, while those of NtST1 and MSN1 were downregulated. The results concluded that the simultaneous use of Se and Mo effectively alleviated Cr toxicity in Nicotiana tabacum L., which not only offers an efficient way for crops to resist Cr toxicity but also provides evidence for the benefit of Se combined with Mo.

Antiviral Activities of Officinaloside C against Herpes Simplex Virus-1.

The iridoid compounds in traditional Chinese medicine play a prominent role in their antiviral effects. We previously reported the anti-inflammatory effect of new iridoids from the aerial parts of Morinda officinalis. Nevertheless, several open questions remain to explore the other biological functions of these new iridoid compounds. Herpes simplex virus-1 (HSV-1) is one of the most prevalent pathogens in human beings worldwide and due to limited therapies, mainly with the guanosine analog aciclovir (ACV) and other analogs, the search for new drugs with different modes of action and low toxicity becomes particularly urgent for public health. This study aimed to explore the anti-HSV-1 effects of iridoids from the aerial parts of Morinda officinalis. The dried aerial parts of Morinda officinalis were extracted with 95% ethanol and systematic separation and purification were then carried out by modern column chromatography methods such as silica gel column, RP-ODS column, Sephadex LH-20 gel column, and semi-preparative liquid phase, and the structure of these compounds were identified through the physical and chemical properties and a variety of spectral techniques. The obtained seven new iridoid compounds were screened for antiviral activity on HSV-1 through CCK8 and the cytopathic effect, and then the plaque reduction assay, the anti-fluorescence reporter virus strain replication, and RT-qPCR experiments were carried out to further evaluate the antiviral effect. Seven new iridoid compounds (officinaloside A-G) were identified from the aerial parts of Morinda officinalis, and officinaloside C showed anti-HSV-1 activity. Further functional experiments confirmed that officinaloside C has a significant inhibiting effect on HSV-1 virus plaque formation, viral gene, and protein expression, and fluorescent virus replication. Our findings suggest that officinaloside C has significant inhibitory effects on viral plaque formation, genome replication, and viral protein expression of HSV-1 which implies that officinaloside C exhibits viral activity and may be a promising treatment for HSV-1 infection.

Selenium restores mitochondrial dysfunction to reduce Cr-induced cell apoptosis in Chinese cabbage (Brassica campestris L. ssp. Pekinensis) root tips.

Chromium (Cr) disrupts the growth and physiology of plants. Selenium (Se) is considered as a promising option to help plants ameliorate Cr toxicity. To investigate the effects of exogenous Se on reactive oxygen species (ROS) burst and programmed cell death (PCD) in root tip cells under Cr stress, hydroponic experiments were carried out with Chinese cabbage seedlings grown in Hoagland solution containing 1 mg L-1 Cr and 0.1 mg L-1 Se. Results showed that Se scavenged the overproduction of H2O2 and O2－·, and alleviated the level of lipid peroxidation in root tips stressed by Cr. Moreover, Se effectively prevented DNA degradation and reduced the number of apoptotic cells in root tips. Compared with Cr treatment, Se supplementation reduced the content of ROS and malondialdehyde in mitochondria by 38.23% and 17.52%, respectively. Se application decreased the opening degree of mitochondrial permeability transition pores by 32.30%, increased mitochondrial membrane potential by 40.91%, alleviated the release of cyt c from mitochondria into cytosol by 18.42% and caused 57.40% decrease of caspase 3-like protease activity, and thus restored mitochondrial dysfunction caused by Cr stress. In addition, the alteration of Se on mitochondrial physiological properties maintained calcium homeostasis between mitochondria and cytosol, which further contributed to reducing the appearance of Cr-induced PCD. Findings suggested that Se restored mitochondrial dysfunction, which further rescued root tip cells from PCD, consequently activating defense strategies to protect plants from Cr toxicity and maintaining plant growth.

Iridoids with anti-inflammatory effect from the aerial parts of Morinda officinalis How.

Morinda officinalis How was widely applied to alleviate symptom like impotence, menstrual disorders, osteoporosis, and rheumatoid arthritis. To expand resources usage, phytochemistry of the aerial parts was studied and the structures of compounds were elucidated based on NMR, HRESIMS, IR and UV. Moreover, the anti-inflammatory effect and possible mechanism were investigated by Griess kit, RT-qPCR, ELISA, western blot and molecular docking on LPS-induced inflammation in RAW 264.7 cells. Herein, we isolated and identified 16 iridoid derivatives, including seven new iridoids officinaloside A-G (1-7) and nine known iridoids. All the compounds were safe to RAW 264.7 cells. Luckily, compounds 5 and 6 showed inhibitory effect on production of NO, and decreased the expression of inflammatory cytokines at mRNA and protein levels in a dose-dependent way. The possible mechanism of their anti-inflammation may be the affinity interaction between 5 with COX-2 protein, and 6 with iNOS protein. Overall, compounds 5 and 6 exert promising effects in inhibiting inflammatory cytokines, indicating that they could be used as lead compounds for developing health products or clinical practice for inflammation, which provides a scientific basis for further sustainable development and usage of the aerial parts of Morinda officinalis How.

Se changed the component of organic chemicals and Cr bioavailability in pak choi rhizosphere soil.

Rhizosphere organic chemicals response and its role on Cr/Se adsorption are of great importance to understand Cr/Se bioavailability in Cr-contaminated soil with the application of Se. In the current work, the processes were carried out using rhizobox experiment (Brassica campestris L. ssp. chinensis Makino). The results showed that in soil contaminated by 200 mg kg-1 Cr(III), Se(IV) complexed with Cr(III) and carboxylic acid (cis-9,10-Epoxystearic acid, hexadecanedioic acid) reduced Cr(VI) to Cr(III), thus increasing of Cr adsorption, furtherly decreasing Cr bioavailability. While in soil contaminated by 120 mg kg-1 Cr(VI), Se(VI) competed for adsorption sites with Cr(VI) and salicylic acid activated insoluble Cr(III), thus decreasing Cr adsorption, finally increasing Cr bioavailability. Moreover, with Cr contamination, Se bioavailability in soil was enhanced by the secretion of carboxylic acid, which can reduce Se to lower valent state and compete the adsorption sites and complex with Se oxyanion. These results yielded a better understanding of rhizosphere dynamics regulating by Se application in Cr-contaminated soil. Moreover, the current study supplemented the theoretical basis for beneficial elements application as an environment-friendly resource to facilitate cleaner production in heavy metal contaminated soil.

Selenium improved the combined remediation efficiency of Pseudomonas aeruginosa and ryegrass on cadmium-nonylphenol co-contaminated soil.

Most chemical plant wastewater contains both organic and inorganic pollutants, which are easy to diffuse along with surface runoff. The combined pollution of nonylphenol (NP) and cadmium (Cd) in soil is a serious problem that has not attracted enough attention. Based on the effects of selenium (Se) and Pseudomonas aeruginosa (P. aeruginosa) on plant and soil microbial communities, we speculated that the application of Se and P. aeruginosa in soil could improve the phytoremediation efficiency of ryegrass on contaminated soil. In this study, pot experiments with Cd and NP co-contaminated soil were conducted, and the results showed that application of P. aeruinosa alone could improve the removal rates of NP and Cd by ryegrass, and the supplementary of Se further enhanced the effect of micro-phyto remediation, with the highest removal rates of NP and Cd were 79.6% and 49.4%, respectively. The application of P. aeruginosa plus Se reduced the adsorption of Cd and NP through C-O and Si-O-Fe of the soil, changed the enzyme activity, and also affected the changing trend of the microbial community in soil. Pseudomonas, Sphingomonadales, Nitrospira, and other beneficial bacteria were enriched after a 60-day period with P. aeruginosa and Se treatment, thus promoting the removal of NP and Cd. In light of the above results, we suggest that P. aeruginosa application can efficiently facilitate the phytoremediation of ryegrass on Cd-NP co-contaminated soil, and Se supplementation in soil showed the synergistic effect on the remediation.

Oligosaccharides from Traditional Chinese Herbal Medicines: A Review of Chemical Diversity and Biological Activities.

Most of traditional Chinese herbal medicine (TCHM) substances come from medicinal plants, among which oligosaccharides have gradually attracted widespread attention at home and abroad due to their important biological activities and great medicinal potential. Numerous in vitro and in vivo experiments exhibited that oligosaccharides possess various activities, such as antitumor, anti-oxidation, modulate the gut microflora, anti-inflammatory, anti-infection, and immune-regulatory activities. Generally, biological activities are closely related to chemical structures, including molecular weight, monosaccharide composition, glycosidic bond connection, etc. The structural analysis of oligosaccharides is an important basis for studying their structure-activity relationship, but the structural diversity and complexity of carbohydrate compounds limit the study of oligosaccharides activities. Understanding the structures and biological functions of oligosaccharides is important for the development of new bioactive substances with natural oligosaccharides. This review provides a systematic introduction of the current knowledge of the chemical structures and biological activities of oligosaccharides. Most importantly, the reported chemical characteristics and biological activities of the famous TCHM oligosaccharides were briefly summarized, including Morinda officinalis, Rehmannia glutinosa, Arctium lappa, Polygala tenuifolia, Panax ginseng, Lycium barbarum and Astragalus membranaceus. TCHM oligosaccharides play an important role in nutrition, health care, disease diagnosis and prevention as well as have broad application prospects in the field of medicine.

Enhancement and improvement of selenium in soil to the resistance of rape stem against Sclerotinia sclerotiorum and the inhibition of dissolved organic matter derived from rape straw on mycelium.

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (S. sclerotiorum), one of the most destructive diseases in many crops including Brassica napus L. The extensive use of fungicides to control S. sclerotiorum caused severe damage to the environment in the long term. Increasing study reported that selenium (Se) is a beneficial element for plant by promoting growth and enhancing disease resistance. In this study, it was found that Se in soil shortened lesion length by 19.14% on rape stem infected with S. sclerotiorum. While resistance mechanism of rape stem against S. sclerotiorum remains unknown. Transcriptomic analysis of rape stem was performed and the results indicated that genes related to antifungal pathways were up-regulated. Moreover, metabonomic analysis was carried out to study the inhibitive effect of the dissolved organic matter derived from rape straw with Se pretreatment in soil (RSDOMSe) on S. sclerotiorum mycelium, results showed that RSDOMSe caused severe damage to energy metabolism of mycelium. Further study indicated that RSDOMSe decreased the pathogenicity of mycelium on rape leaves significantly, and enhanced content of chlorophyII, carotenoids, OD phenol and activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) in rape leaves, which suggested that RSDOMSe plays a positive role in regulating oxidative stress responses of plant when infected with S. sclerotiorum. In addition, when compared with dimcthachlon (DIM) treatment alone, DIM combined with RSDOMSe resulted in higher inhibition on mycelial growth of S. sclerotiorum (the inhibition ratio of nearly 60%). Results in this study suggested that Se enhanced the resistance of rape stem against S. sclerotiorum because of the up-regulated genes related to antifungal pathways, and RSDOMSe improved the mycelial growth inhibition and decreased the pathogenicity of mycelium on rape leaves. Overall, Se as well as Se-enrich byproducts, possessed great potential to be developed as ecological fungicides for controlling S. sclerotiorum.

Selenium as a potential fungicide could protect oilseed rape leaves from Sclerotinia sclerotiorum infection.

Sclerotinia sclerotiorum (S. sclerotiorum) is a soil-borne pathogen causing serious damage to the yield of oilseed rape. Selenium (Se) acted as a beneficial element for plants, and also proved to inhibit the growth of plant pathogens. However, whether Se could reduce S. sclerotiorum infection in oilseed rape, the related mechanism is still unclear. In this study, proper Se levels (0.1 mg/kg and 0.5 mg/kg) applied in soil decreased the lesion diameter and incidence of S. sclerotiorum in rape leaves. Se enfeebled the decrease of net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr), and maintained leaf cell structure. Se enhanced the antioxidant system of leaves, as evidenced by the maintenance of mitochondrial function, reduction of reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) content, and the improvement of antioxidant enzyme activities including catalase (CAT), polyphenol oxidase (PPO) and peroxidase (POD). The upregulated defense gene expressions (CHI, ESD1, NPR1 and PDF1.2) of leaves were also observed under Se treatments. Furthermore, metabolome analysis revealed that Se promoted the metabolism of energy and amino acids in leaves infected with S. sclerotiorum. These findings inferred that Se could act as a potential eco-fungicide to protect oilseed rape leaves from S. sclerotiorum attack. The result arising from this study not only introduces an ecological method to control S. sclerotiorum, but also provides a deep insight into microelement for plant protection.

Selenium reduces the pathogenicity of Sclerotinia sclerotiorum by inhibiting sclerotial formation and germination.

Sclerotinia sclerotiorum (S. sclerotiorum) is a devastating fungal pathogen with worldwide distribution, and threatened the agro-ecological safety in the long term. To control the damage caused by Sclerotinia diseases, as well as consider the fungicide resistance and chemical residues, strategy of which plant nutritional regulation, as an eco-friendly approach, is gaining much significance. Selenium (Se), as a beneficial microelement for plant, has been manifested to be effective in inhibiting the mycelial growth of S.sclerotiorum in our previous study. In the present study, we observed that Se (both selenate and selenite) inhibited the formation of sclerotia, which is an important life form in the disease cycle of S. sclerotiorum. And the inhibition ratios of number of sclerotia in treatments of Se(VI)5.0 and Se(IV)5.0 were 54.55% and 43.84%, respectively; the inhibition ratios of weight of sclerotia in treatments of Se(VI)5.0 and Se(IV)5.0 were 42.29% and 25.67%, respectively. Results suggested that Se inhibited mycelial growth, severely damaged sclerotial ultrastructure, reduced the capacity of acid production, decreased superoxide dismutase (SOD) and catalase (CAT) activities, increased the content of hydrogen peroxide (H2O2) and superoxide anion (O2-) in mycelium, and all of these resulted in the reduction in sclerotial formation. Further studies revealed that Se application in medium increased Se concentration in sclerotia and thus inhibited sclerotial germination. Moreover, the pathogenicity of mycelia germinating from sclerotia that pretreated with Se, decreased significantly to rape leaves. These findings broadened our understanding of Se application in plant protection, as well as provided evidences for developing environment-friendly fungicide for S. sclerotiorum control.

Selenium (Se) reduces Sclerotinia stem rot disease incidence of oilseed rape by increasing plant Se concentration and shifting soil microbial community and functional profiles.

Sclerotinia stem rot (SSR), a soil-borne plant disease, cause the yield loss of oilseed rape. Selenium (Se), a beneficial element of plant, improves plant resistance to pathogens, and regulates microbial communities in soil. Soil microbial communities has been identified to play an important role in plant health. We studied whether the changes in soil microbiome under influence of Se associated with oilseed rape health. SSR disease incidence of oilseed rape and soil biochemical properties were investigated in Enshi district, "The World Capital of Selenium", and soil bacterial and fungal communities were analyzed by 16S rRNA and ITS sequencing, respectively. Results showed that Se had a strong effect on SSR incidence, and disease incidence inversely related with plant Se concentration. Besides, soil Se enhanced the microbiome diversities and the relative abundance of PGPR (plant growth promoting rhizobacteria), such as Bryobacter, Nitrospirae, Rhizobiales, Xanthobacteraceae, Nitrosomonadaceae and Basidiomycota. Furthermore, Soil Se decreased the relative abundance of pathogenic fungi, such as Olpidium, Armillaria, Coniosporium, Microbotryomycetes and Chytridiomycetes. Additionally, Se increased nitrogen metabolism, carbohydrate metabolism and cell processes related functional profiles in soil. The enrichment of Se in plants and improvement of soil microbial community were related to increased plant resistance to pathogen infection. These findings suggested that Se has potential to be developed as an ecological fungicide for biological control of SSR.

Selenium induces changes of rhizosphere bacterial characteristics and enzyme activities affecting chromium/selenium uptake by pak choi (Brassica campestris L. ssp. Chinensis Makino) in chromium contaminated soil.

Understanding the chemical response and characteristics of bacterial communities in soil is critical to evaluate the effects of selenium (Se) supplement on plant growth and chromium (Cr)/Se uptake in Cr contaminated soil. The rhizosphere soil characteristics of pak choi (Brassica campestris L. ssp. Chinensis Makino) were investigated in soil contaminated with different levels and forms of Cr when supplemented with Se. Although inhibition of plant growth caused by Cr stress was not completely alleviated by Se, Cr content in plant tissues decreased in Cr(VI)120Se5 treatment (Cr(VI): 120 mg kg-1 soil; Se: 5 mg kg-1 soil) and its bioavailability in soil decreased in Cr(III)200Se5 (Cr(III): 200 mg kg-1 soil; Se: 5 mg kg-1 soil) treatment. Moreover, antagonism of Cr and Se on soil enzyme activities and bacterial communities were revealed. Notably, results of Cr(VI) reduction and Se metabolism functional profiles confirmed that bacterial communities play a critical role in regulating Cr/Se bioavailability. Additionally, the increases of Se bioavailability in Cr contaminated soil were ascribed to oxidation of Cr(VI) and reduction of Se reductases proportions, as well as the enhancing of pH in soil. These findings reveal that Se has the potential capacity to sustain the stability of microdomain in Cr contaminated soil.

Dissolved organic matter derived from rape straw pretreated with selenium in soil improves the inhibition of Sclerotinia sclerotiorum growth.

Sclerotinia sclerotiorum (S. sclerotiorum) is a soil-borne pathogen with broad host range. Dissolved organic matter (DOM) plays a vital role in regulating microbial activity in soil. Exogenous selenium (Se) inhibits plant pathogen growth and enhances the capacity of plants to resist disease. DOM from rape straw with Se treated in soil (RSDOMSe) was extracted, and the inhibitory effect on S. sclerotiorum growth was investigated. RSDOMSe inhibited S. sclerotiorum growth, which not only caused severe damage to S. sclerotiorum hyphae but also enhanced soluble protein leakage, thereby improving the growth inhibition ratio by 20.9%. As the action in intercellular, RSDOMSe led to a significant increase in oxalic acid and decrease in CWDE (cell wall-degrading enzyme, which helps pathogens to invade plants) activities, downregulation of Bi1 (BAX inhibitor-1, required for S. sclerotiorum virulence), Ggt1 (γ-glutamyl transpeptidase, regulates the ROS antioxidant system), CWDE2 and CWDE10 gene expression levels, compared with non-Se treated RSDOM (RSDOMN). Eight metabolites upregulated in RSDOMSe were identified by GC-TOF-MS, and among these metabolites, fumaric acid, maleic acid, malonic acid, mucic acid, saccharic acid, succunic acid and phenylacetic acid showed significant inhibition on S. sclerotiorum growth. These findings provide valuable insight into a new approach for developing eco-friendly fungicides.

Cadmium in plants: uptake, toxicity, and its interactions with selenium fertilizers.

Cd is the third major contaminant of greatest hazard to the environment after mercury and lead and is considered as the only metal that poses health risks to both humans and animals at plant tissue concentrations that are generally not phytotoxic. Cd accumulation in plant shoots depends on Cd entry through the roots, sequestration within root vacuoles, translocation in the xylem and phloem, and Cd dilution within the plant shoot throughout its growth. Several metal transporters, processes, and channels are involved from the first step of Cd reaching the root cells and until its final accumulation in the edible parts of the plant. It is hard to demonstrate one step as the pivotal factor to decide the Cd tolerance or accumulation ability of plants since the role of a specific transporter/process varies among plant species and even cultivars. In this review, we discuss the sources of Cd pollutants, Cd toxicity to plants, and mechanisms of Cd uptake and redistribution in plant tissues. The metal transporters involved in Cd transport within plant tissues are also discussed and how their manipulation can control Cd uptake and/or translocation. Finally, we discuss the beneficial effects of Se on plants under Cd stress, and how it can minimize or mitigate Cd toxicity in plants.