Se Uptake Research Articles

Overlapping Transcriptome Alterations Reveal the Mechanism of Interaction between Selenium and Zinc and Their Common Effect on Essential Nutrient Metabolism in Mung Bean (Vigna radiata L.).

Selenium (Se) and zinc (Zn) deficiencies have become serious global food security and public health problems. Biofortification through foliar fertilizer is a nonspecific, low-tech, and cost-effective strategy. Se and Zn have overlapping physiological roles and interacting relationships in plants. Mung bean is superior for Se enrichment and an excellent Zn carrier. However, the molecular mechanism underlying the interaction between Se and Zn in the mung bean remains unclear. Herein, Se and Zn accumulation, antioxidant activities, physiological determination, and transcriptomic analysis were performed under both Se and Zn treatments. Common essential roles of Se and Zn in mung bean were reflected by the comprehensively altered ten physiological indexes under both Se2 (24 g·ha-1) and Zn1 (1.2 kg·ha-1) treatments. Overlapping transcriptome changes and common DEGs in two compared groups revealed that the upregulated expression of sulfate transporters (SULTRs), phosphate transporters (PHTs), and Zinc-regulated/Iron-regulated-like protein (ZIP) family genes under Se and Zn treatments directly promoted both Se and Zn intakes. Furthermore, the altered Se/Sulfur, nitrogen, and carbohydrate metabolisms are closely interlinked with the uptake and assimilation of Se and Zn via the 20 key genes that we filtered through the protein-protein interaction (PPI) network analysis. Further analysis indicated that l-methionine γ-lyase (E 4.4.1.11) genes may play an important role in the transamination of selenomethionine and its derivatives; glutamine synthetase (GS), nitrate reductase (NR), and starch synthase (SS) genes may regulate the nitrogen assimilation and carbohydrate metabolism, which provide more carriers for Se and Zn; glutathione peroxidase (GPx), glutamate-cysteine ligase catalytic subunit (GCLC), and serine acetyltransferase (SAT) genes may accelerate the GSH-GSSH cycle and promote Se and Zn storages. This study provides new molecular insights into the comprehensive improvement of the nutritional quality of mung beans in Se and Zn biofortification productions.

Arbuscular Mycorrhizal Fungi Ameliorate Selenium Stress and Increase Antioxidant Potential of Zea mays in Seleniferous Soil.

The indigenous arbuscular mycorrhizal fungi (AMF) spores were isolated from rhizosphere soil associated with maize plants grown in natural selenium-impacted agricultural soils present in north-eastern region of Punjab, India (32°46' N, 74°46' N), with selenium concentration ranging from 2.1 to 6.1 mg kg-1 dry weight, and their role in plant growth promotion, mitigation of selenium stress and phytochemical and antioxidant potential of host maize plants in natural seleniferous soil were examined. Soils with selenium content between 2 and 200 mg kg-1 and producing plants with 45 mg selenium kg-1 dry weight are considered seleniferous soils. AMF inoculum consisting of indigenous AMF spores multiplied in pot cultures were inoculated to maize seeds at the time of sowing alongside control maize seeds in a total of 12 plots (6 replicates) made in seleniferous agricultural fields and sampled at maturity, i.e. 3 months. Asignificant difference was observed in plant growth parameters between control and AMF-inoculated maize plants. AMF-inoculated plants had 24.0 cm and 101.1 cm higher root and shoot length along with 27.2 g, 119.4 g and 28.1 g higher root, shoot and maize cob biomass in comparison to control plants. Se uptake studies through measurement of the emission spectrum of piazselenol complex by fluorescence spectrometry revealed that AMF inoculation led to 6.3 µg g-1 more selenium accumulation in mycorrhizal maize roots in comparison to control roots but lesser translocation to shoots and seeds, i.e. 17.17 µg g-1 and 19.58 µg g-1 lesser. AMF increased total phenolic content by 13 µg GAE mg-1 and total flavonoid content by 13.4 µg QE mg-1 in inoculated maize plants when compared to control plants. Antioxidant studies revealed that AMF inoculation also led to significant rise in enzyme activities by a difference of 115 and 193 EU g-1 in catalase, 140 and 93 EU g-1 in superoxide dismutase, 15 and 37 EU g-1 in ascorbate peroxidase and 19.8 and 23.6% higher DPPH radical scavenging activities, respectively, in shoots and roots of plants with AMF inoculation. The findingsof this study imply that AMF inoculated to maize plants in seleniferous field boost their plant growth and phytochemical and antioxidant properties, as well as minimize Se bioaccumulation in shoots and seeds of plants inoculated with AMF in comparison to control plants.

The Impact of Exogenous Sodium Selenite Treatment on the Nutritional Value and Active Constituents of Pueraria lobata

Moderate amounts of Se can promote crop growth, enhance stress resistance, increase yield, and improve nutritional quality. In the present study, kudzu seedlings were used as experimental materials, and their physiological indicators, antioxidant activity, nutritional components, and flavonoid content were measured after being treated with Na2SeO3 hydroponics. Transcriptome sequencing analysis was used to reveal the relevant genes involved in regulating the effects of exogenous Se on the content of Se-compounds and flavonoids in kudzu. The results indicated that treatment with 20 mg/L Na2SeO3 significantly increased stem and root lengths, dry and fresh weight, lateral root development, and chlorophyll b content. However, at higher concentrations (30–40 mg/L), lateral root abundance and chlorophyll levels decreased. Na2SeO3 treatment also augmented the antioxidant capacity and enhanced the content of major nutrients in kudzu seedlings. The total Se content in kudzu escalated with increasing Na2SeO3 concentration, with selenomethionine emerging as the primary organic-Se species. After treatment with Na2SeO3, the content of puerarin in both aboveground and underground parts decreased, while the content of total flavonoids increased. Daidzin increased in the roots. Differential expression gene analysis revealed that genes such as TRXB2, SYM, MMT1, and METE were involved in Se uptake and transformation in kudzu, while bZIP43 and WRKY47 played a role in flavonoid biosynthesis.

Sorption of Se(VI) and Se(IV) on AFm phases

Selenate and selenite can sorb on AFm phases such as monosulfate, monocarbonate or hemicarbonate. Sorption and co-precipitation experiments were performed to determine their potential for the immobilization of two of the main aqueous species of selenium: SeVIO42− and SeIVO32−. A preferential uptake by hemicarbonate over monosulfate, and a much weaker sorption on monocarbonate was observed for both Se(IV) and Se(VI). Increased sulfate and carbonate concentrations as present at higher pH lowered the uptake of Se(VI) and Se(IV).Experimentally obtained sorption isotherms on hemicarbonate and monosulfate were reproduced with thermodynamic solid solution models, considering both surface sorption and interlayer bonding. For monocarbonate interlayer sorption was suppressed by the rigid structure and narrow interlayer distance. The observed limited uptake could be described by an anion exchange model on the outer surfaces only. This study shows that both anion exchange in the interlayer as well as sorption on outer surface sites can determine Se uptake by AFm phases.

Foliar application of microbial nano-selenium enhances selenium uptake and alleviates oxidative stress

Selenium (Se) is an essential micronutrient to humans and animals in diet primarily from edible crops. However, limited studies have been conducted on applying microbially synthesized Se nanoparticles (BioSeNPs) to affect plant Se uptake and toxicity. The bacterium Bacillus wiedmannii ES2–45 was able to efficiently produce BioSeNPs by completely reducing 5 mM selenite [Se(IV)] within 24 h. Then, fermented BioSeNPs were sprayed on the leaf surface of Brassica rapa L to investigate their effects on growth and Se accumulation. Total Se and leaf biomass increased significantly by 124 % and 14.3 % respectively in the BioSeNP treatment compared to the Se(IV) treatment. The Se(VI) treatment was found to be toxic to the leaves although Se(VI) had similar effects to BioSeNP treatments. Notably, BioSeNP treatment significantly increased the plant’s ability to alleviate oxidative stress including levels of chlorophyll, malonaldehyde (MDA), and catalase (CAT) (P<0.05). In conclusion, the foliar application of BioSeNPs is a promising strategy to improve the Se content of vegetables and alleviate Se-induced oxidative stress.

The role of ruminant urine and faeces in the recycling of nutrients by forages

This study addresses the effect of using animal excreta on the nutritional content of forages, focusing on macro- and micro-element concentrations (nitrogen; N, phosphorus; P, sulphur; S, copper; Cu, zinc; Zn, manganese; Mn, selenium; Se) from animal feed to excreta, soil, and plants. Data were collected from pot and field trials using separate applications of sheep or cattle urine and faeces. Key findings indicate that soil organic carbon (SOC) and the type of excreta significantly influences nutrient uptake by forages, with varied responses among the seven elements defined above. Although urine contributes fewer micronutrients compared to faeces (as applied at a natural volume/mass basis, respectively), it notably improves forage yield and micronutrient accumulation, thus potentially delivering positive consequences at the farm level regarding economic performance and soil fertility when swards upon clayey soil types receive said urine in temperate agro-climatic regions (i.e., South West England in the current context). In contrast, faeces application in isolation hinders Se and Mn uptake, once again potentially delivering unintended consequences such as micronutrient deficiencies in areas of high faeces deposition. As it is unlikely that (b)ovine grazing fields will receive either urine or faeces in isolation, we also explored combined applications of both excreta types which demonstrates synergistic effects on N, Cu, and Zn uptake, with either synergistic or dilution effects being observed for P and S, depending largely on SOC levels. Additionally, interactions between excreta types can result in dilution or antagonistic effects on Mn and Se uptake. Notably, high SOC combined with faeces reduces Mn and Se in forages, raising concerns for grazed ruminant systems under certain biotic situations, e.g., due to insufficient soil Se levels typically observed in UK pastures for livestock growth. These findings underscore the importance of considering SOC and excreta nutritional composition when designing forage management to optimize nutrient uptake. It should be noted that these findings have potential ramifications for broader studies of sustainable agriculture through system-scale analyses, as the granularity of results reported herein elucidate gaps in knowledge which could affect, both positively and negatively, the interpretation of model-based environmental impact assessments of cattle and sheep production (e.g., in the case of increased yields [beneficial] or the requirement of additional synthetic supplementation [detrimental]).

Effects of tea infusion on selenium uptake in grapevine

Increased selenium (Se) content in fruits can supply Se in human body, but the effects of teas on the Se uptake in fruit trees are unknown. The effects of infusions of four teas (green, black, dark, and white) on the Se uptake of grapevine were studied to promote the Se uptake in fruit trees in this study. However, only black tea infusion increased the biomass, photosynthetic pigment content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, and soluble protein content of grapevine. Except for white tea infusion, other tea infusions also increased the catalase (CAT) activity of grapevine. Furthermore, the tea infusions increased the activities of adenosine triphosphate sulfurase (ATPS) and adenosine 5’-phosphosulfate reductase (APR), and decreased the activities of serine acetyltransferase (SAT) and selenocysteine methyltransferase (SMT). Only the dark and white tea infusions increased the shoot total Se content by 86.53% and 23.32%, respectively (compared with the control), and also increased the shoot inorganic Se content and shoot organic Se content. Notably, four tea infusions decreased the organic Se proportion and increased the inorganic Se proportion in grapevine. Correlation and grey relational analyses showed that the root total Se content, ATPS activity, and ARP activity were closely associated with the shoot total Se content. The principal component and cluster analyses also showed that the ATPS activity, APR activity, root total Se content, and shoot total Se content were classified into one category. These findings show that black tea infusion can promote grapevine growth, while dark and white tea infusions can promote the Se uptake in grapevine.

Toxicokinetics of selenate in earthworm sub-tissues and potential bio-accessibility assessment of earthworm-derived selenium

Selenium (Se) pollution is mainly caused by anthropogenic activities, and the resulting biosecurity concerns have garnered significant attention in recent years. Using one-compartmental toxicokinetic (TK) modelling, this study explored the kinetic absorption, sub-tissue distribution, and elimination processes of the main Se species (selenate, Se(VI)) in the cultivated aerobic soil of the earthworm Eisenia fetida. The bio-accessibility of earthworm-derived Se was assessed using an in vitro simulated gastrointestinal digestion test to evaluate its potential trophic risk. The results demonstrated that Se accumulated in the pre-clitellum (PC) and total tissues (TT) of earthworms in a time- and dose-dependent manner. The highest Se levels in the PC, post-clitellum (PoC), and TT were 70.54, 57.93, and 64.26 mg/kg during the uptake phase, respectively. The kinetic Se contents in the earthworms PC and TT were consistent with the TK model but not with PoC. The earthworm TT exhibited a faster uptake (Kus = 0.83–1.02 mg/kg/day) and elimination rate of Se (Kee = 0.044–0.049 mg/kg/day), as well as a shorter half-life time (LT1/2 = 15.88–14.22 days) than PC at low soil Se levels (≤5 mg/kg). Conversely, the opposite trend was observed with higher Se concentrations (10 and 20 mg/kg). These results are likely attributable to the tissue specificity and concentration of the toxicant. Earthworms PC and TT exhibited a higher kinetic Se accumulation factor (BAFk) than steady-state BAF (BAFss), with values ranging from 8 to 24 and 3–13, respectively. Furthermore, the bio-accessibility of earthworm-derived Se to poultry ranged from 66.25 % to 84.35 %. As earthworms are at the bottom of the terrestrial food chain, the high bio-accessibility of earthworm-derived Se poses a potential risk to predators. This study offers data support and a theoretical foundation for understanding the biological footprint of soil Se and its toxicological impacts and ecological hazards.

Guidance on assessing the potential impacts of selenium in freshwater ecosystems.

Despite decades of fate and effects studies, environmental selenium (Se) contamination and management remain an issue for many freshwater systems in North America. Several regulatory bodies have promulgated updated targets or management levels for Se; however, additional guidance on best practices for monitoring Se to protect freshwater aquatic life is warranted. In this article, we describe current approaches to assessing the ecological risks of Se in impaired freshwater systems and outline recommended methods for collecting and analyzing biological and abiotic samples and interpreting data. Because reproductive impairment of fish populations is most commonly used to determine the potential impacts of Se, several biological factors that could affect Se toxicity are explored, including diet, trophic positions, reproductive biology, body size and maturity, migratory movements, and use of seasonal habitats. Measuring Se concentrations in mature eggs is the most reliable metric for estimating potential reproductive impairment in fish populations because the range of toxicity thresholds is relatively narrow for all but a few tolerant fish species. In situations where collecting mature eggs is not feasible, we review the use of alternative fish tissue for estimating potential effects. Factors affecting Se uptake from freshwater are also considered with guidance on collecting abiotic (e.g., water and sediment) and biotic components of aquatic food webs (e.g., macroinvertebrates, biofilm). Integr Environ Assess Manag 2024;00:1-16. © 2024 SETAC.

Screening and Identification of Soil Selenium-Enriched Strains and Application in Auricularia auricula.

Selenium (Se) is an essential trace element for human physiological metabolism. The application of organic Se as a source to cultivate Se-rich plants for micronutrient supplementation has been receiving increasing attention. In our study, a bacterial strain named H1 was isolated from the soil in Heilongjiang Province, China, and under optimal culture conditions, the unit Se content could reach 3000 μg·g-1 and its 16S ribosomal DNA sequence seemed to be a new molecular record of an Enterobacter species. After the domestication of Se tolerance and Se-rich experiments, H1 can be used as a Se source for cultivation of Se-rich Auricularia auricula. The results showed that soluble protein, soluble sugar, free amino acid and vitamin C contents in Auricularia auricula were notably increased by 28.7%, 21.8%, 32.5% and 39.2% under the treatment of Se concentration of 0.24 mg·kg-1, respectively. These findings enhance our understanding that H1 is more conducive to Se uptake and nutrient accumulation.

Effects of different rootstocks grafting on selenium accumulation in Cyphomandra betacea Sendt. seedlings under selenium-contaminated soil

The effects of rootstocks tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.), and nightshade (Solanum nigrum L.) grafting on the growth and selenium (Se) accumulation of Cyphomandra betacea Sendt. seedlings were studied to identify the most suitable rootstock for increasing Se uptake of fruit trees grown in Se-contaminated soil. The rootstocks of tomato, eggplant, and nightshade grafting increased the scion biomass of C. betacea seedlings by 146.1%, 23.2%, and 94.5%, respectively, compared with the un-grafted seedlings. Moreover, tomato, eggplant, and nightshade rootstocks grafting increased the photosynthesis, superoxide dismutase activity, and peroxidase activity, while reducing the catalase activity and soluble protein content of C. betacea seedlings. Although all three rootstocks grafting decreased Se contents in rootstock roots and stems, only nightshade rootstock grafting increased Se content in the scions of C. betacea seedlings. Notably, root biomass, catalase activity, soluble protein content, rootstock root Se content, and rootstock stem Se content were closely related to the scion Se content. These findings suggest that only grafting onto nightshade rootstock significantly enhances Se uptake in C. betacea, whereas tomato and eggplant rootstocks grafting have no effect on Se uptake.

Acidovorax bellezanensis sp. nov., a novel bacterium from uranium mill tailings repository sites with selenium bioremediation capabilities

A Gram-stain-negative bacterial strain designated Be4T, belonging to the genus Acidovorax, was isolated from mining porewaters sampled in uranium mill tailings repository sites, located in Bellezane, near Bessines-sur-Gartempe (Limousin, France). Cells were facultative anaerobic, rod-shaped, non-endospore-forming and motile with flagella. The mean cell size was 1.25–1.31 μm long and 0.70–0.73 μm wide. Colonies were light yellow, opaque, circular, convex with smooth margins, and 1–2 mm in diameter. Growth occurs at 4–37 °C and between pH 5.5–9.0. It differed from its phylogenetically related strains by phenotypic and physiological characteristics such as growth at 4 °C, presence of acid phosphatase, naphthol-AS-BI-phosphohydrolase and β-glucosidase enzymatic activities, and fermentation of l-xylose and esculin. The major fatty acids were C16:0, C16:1 ω7c/C16:1 ω6c, C17:0 cyclo and C18:1 ω7c. Phylogenetic analysis based on 16S rRNA and 938 core genes, confirmed its placement within the genus Acidovorax as a novel species. Strain Be4T showed highest 16S rRNA sequence similarity to Acidovorax antarcticus (98.2 %), Acidovorax radicis (97.9 %), Acidovorax temperans (97.8 %) and Acidovorax facilis (97.7 %). The genome of strain Be4T is 5,041,667 bp size with a DNA G + C content of 65.15 %. By automatic annotation numerous sequences involved in the interaction with metals/metalloids including some genes related to Se uptake and selenite resistance were detected in its genome. The average nucleotide identity (ANI) values calculated from whole genome sequences between strain Be4T and the most closely related strains A. radicis and A. facilis were below the threshold value of 95 %. Thus, the data from the phylogenetic, physiological, biochemical, and genomic analyses clearly indicates that strain Be4T represents a novel species with the suggested name Acidovorax bellezanensis sp. nov. The type strain is Acidovorax bellezanensis Be4T (=DSM116209T = CECT30865T). This novel species, due to its unique isolation source, genomic analysis, and preliminary laboratory tests where it was able to reduce toxic Se(IV) to less harmful Se(0) in the form of nanoparticles, holds great potential for further investigation in bioremediation, particularly concerning Se.

Rhizosphere enrichment and crop utilization of selenium and metals in typical permian soils of Enshi

Enshi, China, is renowned as “Selenium(Se) Capital” where widely distributed soils derived from Permian parent rocks are notably rich in Se, as well as metals, particularly cadmium(Cd). However, the soil enrichment and crop uptake of Se and metals in these high-Se and high-Cd areas are not well understood. To propose the optimal crop planting plan to ensure the safety of agricultural products, we investigated the soils and corresponding typical crops (rice, tea, and maize). The results showed significant soil enrichment of elements, with average contents (mg/kg) as follows: Cr (185), Zn (126), Cu (58.8), Pb (31.1), As (15.7), Se (6.85), Cd (5.41), and Hg (0.211). All soil Se contents were above 0.4 mg/kg, indicating Se-rich soils. Se primarily existed in an organic-bound form, accounting for an average proportion of 61.3%, while Cd was mainly exchangeable, with an average of 62.5%. Cd exhibited higher activity according to the Relative Index of Activity (RIA). Nemerow single-factor index analysis confirmed significant soil contamination, with Cd showing the highest level, followed by Cr and Cu, while Pb had the lowest level. Tea exhibited a high Se rich ratio (82.0%) without exceeding the Cd standard. In contrast, corn and rice had relatively lower Se-rich ratios (42.0% and 51.5% respectively) and high rates of Cd exceeding the standard, at 49.0% and 61.0% respectively. Canonical analysis revealed that rice was more influenced by soil factors related to Se and Cd compared to maize and tea crops. Therefore, tea cultivation in the Enshi Permian soil area is recommended for safe crop production. This study provides insights into the enrichment, fractionation, and bioavailability of soil Se, Cd, and other metals in the high-Se and high-Cd areas of permian stratas in Enshi, offering a scientific basis for selecting local food crops and producing safe Se-rich agricultural products in the region.

Exogenous indole-3-acetic acid promotes the plant growth and accumulation of selenium in grapevine under selenium stress

To alleviate the selenium (Se) stress in fruit trees and improve its accumulation, the effects of exogenous indole-3-acetic acid (IAA) on the growth and Se accumulation of grapevine under Se stress were studied. The application of exogenous IAA increased the biomass of grapevine, and the concentration of exogenous IAA had a regression relationship with the biomass. The root and shoot biomass were the maximum at 60 mg L− 1 IAA, increasing by 15.61% and 23.95%, respectively, compared with the control. Exogenous IAA also increased the photosynthetic pigments and the activities of superoxide dismutase and peroxidase in grapevine. Moreover, exogenous IAA increased the contents of total Se, organic Se, and inorganic Se, and the concentration of exogenous IAA had a regression relationship with the total Se content. The highest contents of root total Se and shoot total Se were accumulated at 90 mg L− 1 IAA, increasing by 29.94% and 55.77% respectively,. In addition, the correlation and path analyses revealed that the carotenoid content and root total Se content were closely associated with the shoot total Se content. Therefore, the application of exogenous IAA can alleviate the stress of Se to grape and promote its uptake and the most effective amount for the uptake of Se is 90 mg L− 1 IAA.

Effects of water extract from Nasturtium officinale R. Br. straw on growth and selenium uptake of peach seedlings

AbstractThe content of selenium (Se) in most horticultural crops is low. To improve Se uptake in fruit trees, we investigated the impact of water extract derived from Nasturtium officinale R. Br. straw on the growth and Se uptake of peach seedlings under Se‐enriched soil by a pot experiment. The water extract of N. officinale straw exhibited notable effects on various growth parameters and Se accumulation in peach seedlings, with the most significant outcomes observed at a 200‐fold dilution. Specifically, the extract led to substantial enhancements in biomass, photosynthetic pigment content, antioxidant enzyme activity, and soluble protein content in peach seedlings. Remarkably, the 200‐fold dilution of N. officinale straw extract resulted in a 60.78% increase in root biomass and a 31.26% increase in shoot biomass when compared to the control. Moreover, the water extract augmented the levels of total Se, inorganic Se, and organic Se, along with the activities of Se metabolism‐related enzymes in peach seedlings. Among various tested dilutions, the 300‐fold and 400‐fold dilutions of N. officinale straw extract exhibited the highest total Se contents in roots and shoots, respectively, indicating increments of 97.26% and 44.08% over their respective controls. Additionally, correlation and gray relational analyses unveiled significant associations between peroxidase activity, soluble protein content, chlorophyll a content, chlorophyll a/b ratio, and the total shoot Se content. In conclusion, the water extract of N. officinale straw holds substantial potential for promoting the growth and Se uptake in peach seedlings, with the best concentration of 300‐fold dilution.

Selected trace element uptake by rice grain as affected by soil arsenic, water management and cultivar -a field investigation

Accumulation of arsenic (As) in rice grain was reported in many regions of the world, including the United States, which has been a threat to human health. This field research investigated the grain As accumulation and its relationship with the uptake of selenium (Se), molybdenum (Mo), and cadmium (Cd) in soils with and without monosodium methanearsonate (MSMA) amended, as effects of selected rice cultivars and water management. Results indicated that MSMA increased the accumulation of As and Se but decreased Mo for all six cultivars under four irrigation management. MSMA also increased grain-Cd in some cultivars. In no MSMA-amended soil (Native soil), intermittent flooding decreased grain-As by 66%, grain-Se by 21%, and grain-Mo by 63%, but increased grain-Cd by 64% in Zhe 733, a straighthead resistant cultivar, while in MSMA-amended soil, intermittent flooding decreased grain-As by 63% and grain-Mo by 44% but increased grain-Se by 68% and grain-Cd by three times. For all other five cultivars, intermittent flooding generally decreased grain-As and grain-Mo but increased grain-Se and grain-Cd. Zhe 733 cultivar resulted in the lowest grain concentrations of all trace elements in all water treatments. A negative grain As-Se correlation and a positive grain As-Mo correlation were significant but not the As-Cd correlation. This research showed that the uptake of As, Se, Mo, and Cd by rice grain occurred as a complex function of multiple variables, including cultivar type and soil chemistry. As a result, accumulation of As and other trace elements in rice grain may be controlled by selecting appropriate cultivars and adopting appropriate water management practices.

Foliar spraying of chitosan promotes selenium uptake in grapevine planted in soil supplemented with sodium selenite

AbstractSelenium (Se) is an important trace element for human body, and the fruit Se source is one option for human Se supplementation. To increase grapevine uptake of Se, grape seedlings were transplanted in soils supplemented with sodium selenite, and the concentrations of 0, 1, 2, 4, and 6 g L−1 chitosan were sprayed on grapevine seedling leaves. Next, the effects of chitosan on grapevine Se uptake were studied. The chitosan‐based foliar application increased the biomass, photosynthetic pigment content, antioxidant enzyme activity, and soluble protein content of grapevine. Chitosan application also increased the total Se, inorganic Se, and organic Se contents in grapevine. However, while the root organic Se was increased, the shoot inorganic Se was decreased. Compared to the control, the concentrations of 1, 2, 4, and 6 g L−1 chitosan increased the shoot total Se content by 9.29%, 12.39%, 17.70%, and 14.16%, respectively. Chitosan application also increased the nitrogen (N), phosphorus (P), and potassium (K) contents in grapevine. Moreover, correlation, gray relational, principal component, and cluster analyses revealed that the root total Se, shoot total N, and root total K contents were the top three indicators closely associated with the shoot total Se content. Therefore, foliar‐based chitosan application on grape seedlings can promote the Se uptake in grapevine under sodium selenite supply, and 4 g L−1 is the best concentration.

Selenobacteria-mediated Se transformation and uptake involving the unique genetic code.

Selenium (Se) is a crucial micronutrient for human health. Plants are the primary source of Se for humans. Selenium in the soil serves as the primary source of Se for plants. The soil contains high total Se content in large areas in Guangxi, China. However, the available Se is low, hindering Se uptake by plants. Microorganisms play a pivotal role in the activation of Se in the soil, thereby enhancing its uptake by plants. In this study, selenobacteria were isolated from Se-rich soils in Guangxi. Then two selenobacteria strains, YLB1-6 and YLB2-1, representing the highest (30,000 μg/mL) and lowest (10,000 μg/mL) Se tolerance levels among the Se-tolerant bacteria, were selected for subsequent analysis. Although the two selenobacteria exhibited distinct effects, they can significantly transform Se species, resulting in a decrease in the soil residual Se (RES-Se) content while concurrently increasing the available Se (AVA-Se) content. Selenobacteria also enhance the transformation of Se valencies, with a significant increase observed in soluble Se6+ (SOL-Se6+). Additionally, selenobacteria can elevate the pH of acidic soil. Selenobacteria also promote the uptake of Se into plants. After treatment with YLB1-6 and YLB2-1, the Se content in the aboveground part of Chinese flowering cabbage increased by 1.96 times and 1.77 times, respectively, while the Se accumulation in the aboveground part of the plant significantly increased by 104.36% and 81.69%, respectively, compared to the control. Further whole-genome sequencing revealed the genetic difference between the two selenobacteria. Additionally, 46 and 38 candidate genes related to selenium utilization were identified from YLB1-6 and YLB2-1, respectively. This work accelerates our understanding of the potential molecular mechanism of Se biofortification by selenobacteria. It also provides microorganisms and gene targets for improving crop varieties or microorganisms to exploit the rich Se source in soil.

Continuous selenite biotransformation and biofuel production by marine diatom in the presence of fulvic acid

In this study, the biochemical response of Phaeodactylum tricornutum to varying concentrations of inorganic selenium (Se) was investigated. It was observed that, when combined with fulvic acid, P. tricornutum exhibited enhanced uptake and biotransformation of inorganic Se, as well as increased microalgal lipid biosynthesis. Notably, when subjected to moderate (5 and 10 mg/L) and high (20 and 40 mg/L) concentrations of selenite under fulvic acid treatment, there was a discernible redirection of carbon flux towards lipogenesis and protein biosynthesis from carbohydrates. In addition, the key parameters of microalgae-based biofuels aligned with the necessary criteria outlined in biofuel regulations. Furthermore, the Se removal capabilities of P. tricornutum, assisted by fulvic acid, were coupled with the accumulation of substantial amounts of organic Se, specifically SeCys. These findings present a viable and successful approach to establish a microalgae-based system for Se uptake and biotransformation.

Liposomes as selenium nanocarriers for foliar application to wheat plants: A biofortification strategy

In the present work, liposomes have been used as nanocarriers in the biofortification of wheat plants with selenium (Se) through foliar application. Liposomal formulations were prepared using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and Phospholipon®90H (P90H) (average size <100 nm), loaded with different concentrations of inorganic Se (selenite and selenate) and applied twice to the plants in the stage of vegetative growth. Liposomes enhanced Se uptake by wheat plants compared to direct application. The highest Se enrichment was achieved using the phospholipid DPPC and a concentration of 1000 μmol·L−1 of Se without affecting the biomass, chlorophylls, carotenoids, and the concentration of mineral nutrients of the plants. The chemical speciation of Se in the plants was further investigated by X-ray absorption spectroscopy (XAS). The results from XAS spectra revealed that most of the inorganic Se was transformed to organic Se and that the use of liposomes influenced the proportion of C-Se-C over C-Se-Se-C species.