Effects of foliar selenium, biochar, and pig manure on cadmium accumulation in rice grains and assessment of health risk.

Addressing cadmium (Cd) contamination in agricultural lands is crucial, given its health implications and accumulation in crops. This study used pot experiments to evaluate the impact of foliar selenium spray (Se) (0.40 mM), corn straw biochar (1%), and pig manure (1%) on the growth of rice plants, the accumulation of Cd in rice grain, and to examine their influence on health risk indices associated with Cd exposure. The treatments were designated as follows: a control group without any amendment (CK), biochar (T1), pig manure (T2), Se (T3), Se and biochar (T4), Se and pig manure (T5), and Se along with biochar and pig manure (T6). Our results indicated that the treatments affected soil pH and redox potential and improved growth and the nitrogen and phosphorus content in rice plants. The soil-plant analysis development (SPAD) meter readings of leaves during the tillering stage indicated a 5.27%-15.86% increase in treatments T2 to T6 compared to CK. The flag leaves of T2 exhibited increases of 12.06%-38.94% for electrolyte leakage and an 82.61%-91.60% decline in SOD compared to treatments T3 to T6. Treatments T1 to T6 increased protein content; however, amylose content was significantly reduced in T6. Treatment T6 recorded the lowest Cd concentration in rice grains (0.018 mg/kg), while T2 recorded the highest (0.051 mg/kg). The CK treatment group showed a grain Cd content reduction of 29.30% compared to T2. The assessment of acceptable daily intake, hazard quotient, and carcinogenic risk revealed an ascending order as follows: T6 < T3 < T5 < T4 < T1 < CK < T2. In conclusion, the application of treatment T6 demonstrates the potential to lower oxidative stress, enhance production, reduce cancer risk, and ensure the safe cultivation of rice in environments affected by Cd contamination.

Comprehensive evaluation of factors influencing selenium fertilization biofortification.

BACKGROUND: Dietary selenium (Se) deficiency, stemming from low Se concentrations in agricultural products, threatens human health. While Se-containing fertilizers can enhance the Se content in crops, the key factors governing Se biofortification with Se fertilization remain unclear. RESULTS: This study constructed a global meta-analysis dataset based on field experiments comprising 364 entries on Se content in agricultural products and 271 entries on their yield. Random forest models and mixed effects meta-analyses revealed that plant types (i.e., cereals, vegetables, legumes, and forages) primarily influenced Se biofortification, with Se fertilization rates being the next significant factor. The random forest model, which included variables like plant types, Se fertilization rates, methods and types of Se application, initial soil conditions (including Se content, organic carbon content, and pH), soil types, mean annual precipitation, and temperature, explained 82.14% of the variation in Se content and 48.42% of the yield variation in agricultural products. For the same agricultural products, the increase in Se content decreased with higher rates of Se fertilization. The increase in Se content in their edible parts will be negligible for cereals, forages, legumes, and vegetable crops, when Se fertilization rates were 164, 103, 144, and 147 g Se ha-1, respectively. Conversely, while low Se fertilization rates enhanced yields, high rates led to a yield reduction, particularly in cereals. CONCLUSION: Our findings highlight the need for balanced and precise Se fertilization strategies to optimize Se biofortification benefits and minimize the risk of yield reduction. © 2024 Society of Chemical Industry.

Soil Selenium Concentration and Residents Daily Dietary Intake in a Selenosis Area: A Preliminary Study in Yutangba Village, Enshi City, China.

In 1963, selenosis occurred in Yutangba Village, Enshi City, China. Subsequently, local residents migrated to a new area of Yutangba to avoid high selenium (Se) exposure. In this study, 19 soil samples, 43 food samples, 60 hair samples and 58 plasma samples from local residents were randomly collected in New Yutangba Village. The mean total Se concentrations in cultivated soil samples were 1753.6 ± 742.8 µg/kg (n = 14). The estimated daily Se intake in New Yutangba Village decreased to 63.2 ± 39.8 µg/day, slightly higher than the recommended dietary Se intake for adults in China (60 µg/day). The mean Se concentrations in hair and plasma samples were 549.7 ± 165.2 µg/kg (n = 60) and 98.4 ± 32.1 µg/L (n = 58), respectively. The result indicated that appropriate activities, such as relocation, consuming a mixture of local foods and market foods containing low Se concentration, could effectively reduce the risk of high Se exposure.

Genetic Incorporation of N(ε)-Formyllysine, a New Histone Post-translational Modification.

Lysine formylation is a newly discovered post-translational modification (PTM) in histones and other nuclear proteins; it has a well-recognized but poorly defined role in chromatin conformation modulation and gene expression. To date, there is no general method to site-specifically incorporate N(ε)-formyllysine at a defined site of a protein. Here we report the highly efficient genetic incorporation of the unnatural amino acid N(ε)-formyllysine into proteins produced in Escherichia coli and mammalian cells, by using an orthogonal N(ε)-formyllysine tRNAsynthetase/tRNACUA pair. This technique can be applied to study the role of lysine formylation in epigenetic regulation.

Inhibitory effect of selenium against Penicillium expansum and its possible mechanisms of action.

Some organic and inorganic salts could inhibit the growth of many pathogens. Selenium (Se), as an essential micronutrient, was effective in improving the plant resistance and antioxidant capacity at a low concentration. Penicillium expansum is one of the most important postharvest fungal pathogens, which can cause blue mold rot in various fruits and vegetables. In this study, the inhibitory effect of Se against P. expansum was evaluated. The result showed that Se strongly inhibited spore germination, germ tube elongation, and mycelial spread of P. expansum in the culture medium. The inhibitory effect was positively related to the concentration of Se used. Fluorescence microscopy observation of P. expansum conidia stained with propidium iodide (PI) indicated that the membrane integrity decreased to 37 % after the conidia were treated with Se (20 mg/l) for 9 h. With the use of an oxidant-sensitive probe 2,7-dichlorofluorescin (DCHF-DA), we found that Se at 15 mg/l could induce the generation of intracellular reactive oxygen species (ROS). Furthermore, methane dicarboxylic aldehyde (MDA) content, hydrogen peroxide (H2O2), and superoxide anion (O2 (-)) production rate in P. expansum spores exposed to Se increased markedly. Compared with the control, the activities of superoxide dismutase (SOD) and the content of glutathione (GSH) were reduced, confirming that damage of Se to cellular oxygen-eliminating system is the main reason. These results suggest that Se might serve as a potential alternative to synthetic fungicides for the control of the postharvest disease of fruit and vegetables caused by P. expansum.

Characterization of a selenium-tolerant rhizosphere strain from a novel Se-hyperaccumulating plant Cardamine hupingshanesis.

A novel selenium- (Se-) hyperaccumulating plant, Cardamine hupingshanesis, accumulating Se as a form of SeCys2, was discovered in Enshi, Hubei, China, which could not be explained by present selenocysteine methyltransferase (SMT) theory. However, it is interesting to investigate if rhizosphere bacteria play some roles during SeCys2 accumulation. Here, one Se-tolerant rhizosphere strain, Microbacterium oxydans, was isolated from C. hupingshanesis. Phylogenetic analysis and 16S rRNA gene sequences determined the strain as a kind of Gram positive bacillus and belonged to the family Brevibacterium frigoritolerans. Furthermore, Se tolerance test indicated the strain could grow in extreme high Se level of 15.0 mg Se L(-1). When exposed to 1.5 mg Se L(-1), SeCys2 was the predominant Se species in the bacteria, consistent with the Se species in C. hupingshanesis. This coincidence might reveal that this strain played some positive effect in SeCys2 accumulation of C. hupingshanesis. Moreover, when exposed to 1.5 mg Se L(-1) or 15.0 mg Se L(-1), As absorption diminished in the logarithmic phase. In contrast, As absorption increased when exposed to 7.5 mg Se L(-1), indicating As metabolism processes could be affected by Se on this strain. The present study provided a sight on the role of rhizosphere bacteria during Se accumulation for Se-hyperaccumulating plant.

Characterization of Selenium Speciation in Se-Enriched Crops: Crop Selection Approach.

Accurately quantifying selenium (Se) speciation and transformation in Se-enriched crops is highly significant for human health. The investigation of Se species in Se-enriched crops involves assessing the enrichment of both organic and inorganic Se species, considering their plant families and edible parts. The staple crops of rice, corn, and wheat showed no or less inorganic Se with the increase of total Se; however, potatoes expressed a proportion of selenate [Se(VI)]. In addition, the organic Se proportions in Se-enriched crops of Cruciferous, Brassicaceae, and Umbelliferae plant families were relatively lower than the proportion of inorganic Se. Concurrently, the edible parts of the Se-enriched gramineous or cereal crops enriched with organic Se and crops with fruit, stem, leaf, and root as edible parts contain the maximum percentage of organic Se with a certain proportion of inorganic Se. This study contributes to a sparse body of literature by meticulously discerning appropriate Se-enriched crop selection through a comprehensive evaluation of Se speciation and its organic and inorganic accumulation potential.

Selenium loss during boiling processes and its bioaccessibility in different crops: Estimated daily intake.

Food crops provide a good selenium (Se) source for Se-deficient populations. This study assessed how boiling affects Se concentration, speciation, and bioaccessibility in common food crops to determine human Se intake. Boiling rice resulted in an 11.9% decrease in minimum Se content, while sorghum experienced a maximum (34.9%) reduction. Boiled vegetables showed a 21% - 40% Se loss. Cereals showed notable decreases in selenomethionine (SeMet) and selenocysteine (SeCys2), while most vegetables exhibited a significant reduction in Se-methylselenocysteine (SeMeCys). Boiling significantly reduced the Se bioaccessibility in all food crops, except cabbage and potato. Cereal crops were more efficacious in meeting the recommended daily intake (RDI) of Se compared to vegetables. Rice exceeds other crops and provides up to 39.2% of the WHO/FAO-recommended target minimum daily intake of 60 µg/day. This study provides insight into a substantial dissonance between the estimated daily intake (EDI) of Se and the bioaccessible Se in both raw and boiled crops. Consequently, revising EDI standards is imperative.

A preliminary predictive model for selenium nutritional status in residents based on three selenium biomarkers.

BACKGROUND: Selenium (Se) is an essential nutrient and an important component of many selenoproteins that possess fundamental importance to human health. Selenium deficiency and excess will cause corresponding diseases in the human body. The nutritional health of Se in the human body mainly depends on the daily dietary Se intake of the human body, which in turn depends to a certain extent on the content of Se transmitted along the food chain. This study aims to research the transport of Se through the soil-crop-human chain in regions with different Se levels, and to establish the model between the residents' dietary Se intake and the three Se biomarkers (hair, nails, and plasma), to predict the nutritional health status of Se in residents through Se biomarkers. METHOD: Carry out field and cross-sectional surveys of populations in Loujiaba Village and Longshui Village. Samples were collected from soil, crops, drinking water, residents' hair, nails, plasma, and diet. The concentration of available Se fractions was extracted from soil samples using 0.1 mol/L K2HPO4. The concentration of total Se for all samples was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and the relative standard deviation was less than 5%. In this study, hair, nails, and blood samples were collected from volunteers according to the Declaration of Helsinki and the Ethics Committee of Soochow University. The dietary nutritional structure and dietary Se intake of the population were randomly selected by 12 volunteers using the duplicate portion method. Data were described using mean ± standard deviation. We performed saliency analysis and correlation analysis (with Pearson correlation coefficient), and fitted a regression to evaluate the associations between these variables. RESULTS: The soil total Se (5201 ± 609.2 µg/kg) and available Se (307.7 ± 83.5 µg/kg) in Luojiaba Village (LJB) were significantly higher than the soil total Se (229.2 ± 32.5 µg/kg) and available Se (21.9 ± 4.0 µg/kg) in Longshui Village (LS). The residents' dietary Se intake of LJB (150.3 ± 2.2 µg/d) was within the World Health Organization (WHO) recommended intake range, while LS (16.0 ± 0.4 µg/d) was close to the range of Keshan disease occurrence, and there was a risk of insufficient Se intake. The correlation analysis found significant positive correlations between residents' dietary Se intake and the three Se biomarkers. According to the preliminary model established in this study, if the daily dietary Se intake of residents reaches the WHO recommended value of 55-400 µg, the hair, nails, and plasma of Se concentration will be 522.1-2850.5 µg/kg, 1069.0-6147.4 µg/kg, and 128.3-661.36 µg/L, respectively. CONCLUSION: Selenium is transmitted through the soil-crop-human chain, and the Se concentration that enters the human body through the food chain in high-Se areas is significantly higher than that in low-Se areas. The nutritional health status of Se in the human body depends on the daily dietary intake of the human body, and there is a significant correlation between the daily dietary Se intake of the human body and the three biomarkers of Se levels in the human body, so the three biomarkers can be used to evaluate the Se nutritional health of the human.

Selenium enhancement strategy under precise fertilization in foxtail millet rhizosphere.

Enhancing selenium content in millet is a crucial strategy to address malnutrition due to selenium deficiency. Jingu 21 was used as the experimental material in this study. The effects of selenium fertilizer application amount, vertical position of fertilization, and horizontal position of fertilization on the selenium content in various millet organs were assessed using a three-factor, five-level quadratic rotation combination design. The results indicate that selenium fertilizer application amount, vertical fertilization position, and horizontal fertilization position significantly affected the selenium content in various millet organs. Analysis of the selenium accumulation for different millet organs show that the recommended optimal agronomic strategy for producing selenium-enriched millet comprises a selenium fertilizer application amount ranging from 100.65 to 120.15 kg/hm2, a vertical fertilization position of 10.28-11.76 cm, and a horizontal fertilization position of 6.74-7.29 cm. This study elucidates the patterns of selenium content accumulation under precise fertilization measures of millet and provides valuable insights for implementing selenium enhancement techniques in the production of selenium-enriched millet.

Metabolome and Transcriptome Association Analysis Reveals Mechanism of Synthesis of Nutrient Composition in Quinoa (Chenopodium quinoa Willd.) Seeds.

Quinoa (Chenopodium quinoa Willd.) seeds are rich in nutrition, superior to other grains, and have a high market value. However, the biosynthesis mechanisms of protein, starch, and lipid in quinoa grain are still unclear. The objective of this study was to ascertain the nutritional constituents of white, yellow, red, and black quinoa seeds and to employ a multi-omics approach to analyze the synthesis mechanisms of these nutrients. The findings are intended to furnish a theoretical foundation and technical support for the biological breeding of quinoa in China. In this study, the nutritional analysis of white, yellow, red, and black quinoa seeds from the same area showed that the nutritional contents of the quinoa seeds were significantly different, and the protein content increased with the deepening of color. The protein content of black quinoa was the highest (16.1 g/100 g) and the lipid content was the lowest (2.7 g/100 g), among which, linoleic acid was the main fatty acid. A combined transcriptome and metabolome analysis exhibited that differentially expressed genes were enriched in "linoleic acid metabolism", "unsaturated fatty acid biosynthesis", and "amino acid biosynthesis". We mainly identified seven genes involved in starch synthesis (LOC110716805, LOC110722789, LOC110738785, LOC110720405, LOC110730081, LOC110692055, and LOC110732328); five genes involved in lipid synthesis (LOC110701563, LOC110699636, LOC110709273, LOC110715590, and LOC110728838); and nine genes involved in protein synthesis (LOC110710842, LOC110720003, LOC110687170, LOC110716004, LOC110702086, LOC110724454 LOC110724577, LOC110704171, and LOC110686607). The data presented in this study based on nutrient, transcriptome, and metabolome analyses contribute to an enhanced understanding of the genetic regulation of seed quality traits in quinoa, and provide candidate genes for further genetic improvements to improve the nutritional value of quinoa seeds.

Effect of 3,3'-diselenodipropionic Acid on Dextran Sodium Sulfate-Induced Ulcerative Colitis in Mice.

3,3'-Diselenodipropionic acid (DSePA), a synthetic organoselenium compound, has received considerable attention because of its antioxidant properties and safety. Its protective effect against dextran sodium sulfate (DSS)-induced mouse ulcerative colitis (UC) and the role of T helper 17 (Th17) cell proliferation were investigated. Fifty C57BL/6 male mice were randomly assigned to one of five groups: control (Con), DSePA, DSS, low-dose DSePA (LSe), and high-dose DSePA (HSe). Mice in the DSS, LSe, and HSe groups drank 2% DSS to induce UC, and received normal saline, 1 and 2 mg/mL DSePA solution by intraperitoneal injection, respectively. The DSePA group only received 2 mg/mL DSePA solution. After 5 weeks, DSS challenge induced UC in the mice, which manifested as decreased body weight, shortened colon length, the loss of goblet cells, activated proliferating cells, and multiple signs of intestinal lesions by histological observation, all of which were reversed to varying degrees by DSePA administration. DSS upregulated the colonic protein expression of the macrophage marker F4/80 and proinflammatory cytokines (IL-1ß, IL-6, and TNFα), whereas DSePA administration downregulated the expression of these factors. DSS upregulated the mRNA expression of retinoic acid receptor-related orphan receptor γt (RORγt, mainly expressed in Th17 cells), IL-17A, and IL-17F and the levels of IL-17A and IL-17F in the colon, whereas DSePA administration decreased them. No difference was observed between the Con group and the DSePA group without DSS induction. Thus, DSePA administration ameliorated DSS-induced UC by regulating Th17-cell proliferation and the secretion of proinflammatory cytokines.

Identification of nitrate sources in Taihu Lake and its major inflow rivers in China, using δ(15)N-NO(3)(-) and δ(18)O-NO(3)(-) values.

In the present study, δ(15)N and δ(18)O-NO(3)(-) values, as well as concentrations of some major ion tracers were determined in seasonal water samples from Taihu Lake and major watersheds to investigate the temporal and spatial variations of nitrate sources and assess the underlying nitrogen (N) biogeochemistry process. The results lead to the conclusion that the nitrate concentrations in Taihu Lake are lower in summer than that in winter due to the dilution effect of wet deposition. In winter, sewage and manure were the primary nitrate sources in major inflow rivers and North Taihu Lake (NTL), while nitrate sources in East Taihu Lake (ETL) probably derived from soil organic N. In summer, atmospheric deposition and sewage/manure inputs appear to play an important role in controlling the distribution of nitrates in the whole lake. The δ(18)O-NO(3)(-) values suggest that the nitrate produced from microbial nitrification is another major nitrate source during both winter and summer months. The variations in isotopic values in nitrate suggest denitrification enriched the heavier isotopes of nitrate in NTL in winter and in ETL in summer.

[Effects of organic selenium supplement on glutathione peroxidase activities: a meta-analysis of randomized controlled trials].

OBJECTIVE: To study the effects of organic selenium supplementation on glutathione peroxidase (GPx) activities. METHODS: Randomized controlled trials (RCT) published from January 1988 to December 2010 on the relationship between organic selenium supplementation and GPx activities were collected. Meta-analysis was applied to estimate the combined standardized mean difference (SMD) and 95% confidence interval (95% CI). RESULTS: A total of 10 RCTs were included. The number of studies observing GPx activities in plasma, erythrocyte and platelet was 8, 5 and 5, respectively. Compared with the controls, the combined SMD (95% CI) of GPx activities in plasma, erythrocyte and platelet of subjects supplemented with organic selenium was 0.46 (0.09 - 0.83), 0.36 (0.02 - 0.69) and 0.56 (-0.02 - 1.15). CONCLUSION: Supplementation with organic selenium increases GPx activities in healthy adults.

Protective effects of epigallocatechin-3-o-gallate combined with organic selenium against transforming growth factor-beta 1-induced fibrosis in LX-2 cells.

In this study, we investigated the protective effects and possible mechanism of epigallocatechin-3-o-gallate (EGCG) combined with organic selenium in transforming growth factor (TGF)-ß1-activated LX-2 cells. After 12 h of starvation, LX-2 cells were treated with 10 ng/ml of recombinant TGF-ß1 and different concentrations of EGCG, L-selenomethionine (L-SeMet), or L-selenomethylcysteine (L-SeMC) for 24 h. We found that 100 and 200 µM EGCG combined with 1 mM L-SeMet or L-SeMC showed a synergistic effect in decreasing the survival rate of activated LX-2 cells. In addition, the combination of 100 mM EGCG and 1 mM L-SeMet or L-SeMC promoted the apoptosis of activated LX-2 cells. Compared with the EGCG treatment group, the combination intervention group had significantly suppressed levels of hepatic stellate cell activation markers including alpha-smooth muscle actin, collagen type I alpha 1, collagen type III alpha 1, 5-hydroxytryptophan (5-HT), and 5-HT receptors 2A and 2B. Moreover, interleukin-10 levels were decreased, while TGF-ß1 levels were increased after TGF-ß1 activation in LX-2 culture medium, whereas the combin1ation intervention reversed this phenomenon. The combination treatment had a more pronounced effect than any single treatment at the same dose. These results demonstrated that the combination of EGCG and organic selenium synergistically improves the TGF-ß1-induced fibrosis of LX-2 cells to some extent by promoting apoptosis and inhibiting cell activation. PRACTICAL APPLICATIONS: Here, we found that the effects of epigallocatechin-3-o-gallate (EGCG) + L-selenomethionine or L-selenomethylcysteine were more pronounced than those of EGCG alone. Future studies should investigate the protective effects of green tea and selenium-enriched green tea against hepatic fibrosis and explore the differences in their molecular mechanisms. The results of this study will be helpful for the development and utilization of selenium-enriched tea for food processing and health supplement production.

Hair Se Is a Sensitive Biomarker to Monitor the Effects of Se Supplementation in Elderly.

It is rapidly increasing to have selenium (Se) supplementation for urban elderly population in China since they are facing a widespread deficiency daily Se intake. However, until now, there is no low-cost, non-invasive, rapid, and reliable method to monitor the health improvement or risk for elderly Se-supplemented population in China. The present cross-sectional study (229 participants with older than 55 years old) performed in Beijing, China, revealed that the Se concentrations of non-supplementer users (n = 27) were 55 ± 23 µg/L in urine, 139.9 ± 102.3 µg/L in serum, and 487.6 ± 158.7 µg/kg in hair. But a significant increase on hair Se concentrations (615.4 ± 238.8 µg/kg) was observed for Se supplementer users (n = 202) (p < 0.05); there were no significant statistical differences in serum and urine between the Se-supplemented (n = 202) and Se non-supplemented groups (n = 27). This indicated the hair Se levels could be a more sensitive biomarker for Se-supplemented elderly population. Participants who consumed Se supplements for 7-12 months had the highest Se status based on hair and serum Se concentrations (p < 0.05). The present study also revealed that most elderly adults in Beijing just need to supplement 50 µg Se per day to achieve Se plateau status. Furthermore, hair Se levels were positively related with triglycerides/TG levels (p < 0.05) but not body mass index/BMI, total cholesterol/TC, and low-density lipoprotein cholesterol/LDL, implicating Se supplementation for Se sufficiency baseline in elderly population in Beijing likely posed health risk, especially on TG because of excessive Se oxidation stress. An ongoing monitoring of Se status via hair is still warranted to prevent future Se deficiency or excess in China.

The influence of sea animals on selenium distribution in tundra soils and lake sediments in maritime Antarctica.

The biogeochemical behavior of selenium (Se) has been extensively studied in Se-enriched or Se contaminated soils at low and middle latitudes. However, the Se distribution patterns have not been studied in tundra ecosystems of remote Antarctica. Here, the soils/sediments were collected from penguin and seal colonies, their adjacent tundra and lakes, tundra marsh, human-activity areas, normal tundra and the periglacial in maritime Antarctica, and total Se and seven operationally defined Se fractions were analyzed. Overall the regional distribution of Se levels showed high spatial heterogeneity (coefficient of variation, CV = 114%) in tundra soils, with the highest levels in penguin (mean 6.12 ± 2.66 µg g-1) and seal (mean 2.29 ± 1.43 µg g-1) colony soils, and the lowest in normal tundra soils and periglacial sediments (<0.5 µg g-1). The contribution rates of penguins and seals to tundra soil Se levels amounted to 91.7% and 78.0%. The lake sediment Se levels (mean 2.15 ± 0.87 µg g-1) close to penguin colonies were one order of magnitude higher than those (mean 0.49 ± 0.87 µg g-1) around normal tundra. Strong positive correlations (p < 0.01) of Se concentrations between lake sediments and adjacent tundra soils, and lower Se: P (<0.001) and S: P (<1) ratios in the lake sediments close to penguin colonies, indicated the infiltration or leaching of penguin guano as the predominant Se source in lake sediment. The Se species in penguin and seal guano were dominated by SeCys2 (76.6%) and SeMet (73.5%), respectively. The evidence from the predominant proportions of total organic matter-bound Se (Seom, 67%-70% of total Se) in penguin or seal colony soils further supported penguin or seal guano had a great influence on the distribution patterns of Se fractions in the tundra. This study confirmed that sea animal activities transported substantial amount Se from ocean to land, and significantly altered the biogeochemical cycle of Se in maritime Antarctica.

Selenium Effect Threshold for Soil Nematodes Under Rice Biofortification.

Crop biofortification with inorganic selenium (Se) fertilizer is a feasible strategy to improve the health of residents in Se-deficient areas. For eco-friendly crop Se biofortification, a comprehensive understanding of the effects of Se on crop and soil nematodes is vital. In this study, a rice pot experiment was carried out to test how selenite supply (untreated control (0), 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, or 200 mg Se kg-1) in soil affected rice growth, rice Se accumulation, and soil nematode abundance and composition. The results showed that selenite supply (5-200 mg kg-1) generally increased the number of rice tillers, rice yield, and Se concentrations in rice grains. In soil under 10 mg kg-1 Se treatment, the genus composition of nematodes changed significantly compared with that in the control soil. With increased Se level (> 10 mg kg-1), soil nematode abundance decreased significantly. Correlation analysis also demonstrated the positive relationships between soil Se concentrations (total Se and bioavailable Se) with rice plant parameters (number of rice tillers, rice yield, and grain Se concentration) and negative relationships between soil Se concentrations (total Se and bioavailable Se) with soil nematode indexes (nematode abundance and relative abundance of Tobrilus). This study provides insight into balancing Se biofortification of rice and soil nematode community protection and suggests the effective concentrations for total Se (1.45 mg kg-1) and bioavailable Se (0.21 mg kg-1) to soil nematode abundances at 20% level (EC20) as soil Se thresholds. At Se concentrations below these thresholds, rice plant growth and Se accumulation in the grain will still be promoted, but the disturbance of the soil nematodes would be negligible.

Synergistic Effect of Melatonin and Selenium Improves Resistance to Postharvest Gray Mold Disease of Tomato Fruit.

Melatonin (MT) is a ubiquitous hormone molecule that is commonly distributed in nature. MT not only plays an important role in animals and humans but also has extensive functions in plants. Selenium (Se) is an essential micronutrient for animals and humans, and is a beneficial element in higher plants at low concentrations. Postharvest diseases caused by fungal pathogens lead to huge economic losses worldwide. In this study, tomato fruits were treated with an optimal sodium selenite (20 mg/L) and melatonin (10 µmol/L) 2 h and were stored for 7 days at room temperature simulating shelf life, and the synergistic effects of Se and MT collectively called Se-Mel on gray mold decay in tomato fruits by Botrytis cinerea was investigated. MT did not have antifungal activity against B. cinerea in vitro, while Se significantly inhibited gray mold development caused by B. cinerea in tomatoes. However, the interaction of MT and Se showed significant inhibition of the spread and growth of the disease, showing the highest control effect of 74.05%. The combination of MT with Se treatment enhanced the disease resistance of fruits by improving the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as increasing the gene expression level of pathogenesis-related (PR) proteins. Altogether, our results indicate that the combination of MT and Se would induce the activation of antioxidant enzymes and increase the expression of PR proteins genes that might directly enhance the resistance in tomato fruit against postharvest pathogenic fungus B. cinerea.

Selenium volatilization from tundra soils in maritime Antarctica.

Maritime Antarctica harbors a large number of penguins and seals that provide considerable input of selenium (Se) originating as guano into terrestrial ecosystems. Subsequent Se emissions via biomethylation and volatilization from these sources of Se have not been studied. Here, penguin colony soils (PCS) and adjacent tundra marsh soils (TMS), seal colony soils (SCS) and adjacent tundra soils (STS), and normal upland tundra soils (NTS) were collected in maritime Antarctica. For the first time, Se volatilization and speciation were investigated in these soils through incubation experiments using chemo-trapping method. The Se contents in PCS, SCS, STS and TMS were highly enriched compared with NTS, with organic matter-bound Se accounting for 70%-80%. Laboratory incubations yielded the greatest Se volatilization rates (VRSe) in PCS (0.20 ± 0.01 µg kg-1 d-1), followed by SCS (0.14 ± 0.01 µg kg-1 d-1) at low temperature (4 °C). Soil frozen-thawing induced 1-4 fold increase in VRSe, and the VRSe continuously increased until the soils fully thawed. The VRSe showed a significant positive correlation (R2 = 0.96, p < 0.01) with soil temperature. Methylated Se species were dominated by dimethylselenide (DMSe) in PCS and dimethyldiselenide (DMDSe) in SCS. Our results imply that the combination of climate warming, frozen-thawing processes, and high-Se inputs from sea animals will significantly increase tundra soil Se volatilization in maritime Antarctica. High VRSe from penguin colony soils, and significantly elevated Se levels in the mosses close to penguin colony, suggest that volatilization of Se from penguin colony soils play an important role in the mobilization and regional biogeochemical cycling of Se in maritime Antarctica.