Effects of selenate on Se, flavonoid, and glucosinolate in broccoli florets by combined transcriptome and metabolome analyses

Multifaceted role of selenium in plant physiology and stress resilience: A review

Selenium (Se) is a naturally occurring element in both seleniferous and non-seleniferous soils. Plants absorb Se in a variety of ways, mainly as selenate (SeO42-), selenite (SeO32-), and organic compounds such as selenomethionine (SeMet). Selenium significantly impacts plant growth, development, and stress responses. It is a trace element that regulates many physiological and biochemical functions in plants, acts as an antioxidant, and increases plant resistance to abiotic stresses such as heavy metal toxicity, salinity, drought, and severe temperatures. Its beneficial effects depend on the dose and vary depending on the plant species and the environmental conditions. Several functions of Se have been thoroughly discussed in this review, with special attention given to the mechanisms of Se uptake, transport, accumulation, and metabolism. Plants use Se through its assimilation into amino acids (mostly selenocysteine and selenomethionine) and integration into proteins. These processes might have different effects depending on the Se concentration. Furthermore, Se has the potential to be a useful tool in sustainable agriculture, especially in regions where environmental stress is common. This is demonstrated by its ability to increase plant tolerance to various environmental stressors. Recent research shows that Se supplementation not only boosts plant resistance but also enhances secondary metabolite accumulation. Overall, this review concludes that Se plays a dual role in plant systems, acting as both a nutrient and a stress mitigator, and provides opportunities to optimize its use in sustainable agriculture by tailoring Se supplementation to maximize plant tolerance and productivity.

β-Ionone Treatment Enhances the Antioxidant Capacity in Postharvest Broccoli (Brassica oleracea L. var. Italica) by Maintaining the Levels of Bioactive Substances

Broccoli is prone to nutrient loss during postharvest storage due to its high respiratory metabolism. In this study, we investigated the effects of 0.1 mm β-ionone on bioactive substances and antioxidant capacity during postharvest storage of broccoli. We found that the decline in the scavenging rates of 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) radicals was delayed in the treated florets. This delay is attributed to β-ionone treatment, which upregulated the expression of biosynthetic genes related to glucosinolates and riboflavin in broccoli, thereby slowing the loss of these nutrients. Additionally, β-ionone treatment increased the transcript levels of anabolic genes while reducing the expression of genes encoding enzymes involved in the catabolism of ascorbic acid (AsA) and glutathione (GSH), resulting in higher levels of AsA and GSH in treated broccoli compared to the control. Overall, β-ionone treatment enhanced antioxidant capacity by delaying the loss of bioactive substances in postharvest broccoli. These findings provide the first evidence that exogenous β-ionone helps preserve antioxidant capacity in postharvest horticultural products.

Physiological and Transcriptome Analysis Provide Insights into the Effects of Low and High Selenium on Methionine and Starch Metabolism in Rice Seedlings

Selenium (Se) is an essential micronutrient for the human body and is closely linked to health. Rice (Oryza sativa L.), as a major staple food globally, is the primary source of Se intake for humans. To better achieve Se biofortification in rice, it is crucial to understand the molecular mechanisms behind rice's response to different Se concentrations. This study investigates the morphological and transcriptomic responses of rice seedlings to low (1 µM, LSe) and high (10 µM, HSe) Se concentrations compared to a control (CK). Morphological analyses revealed that LSe promoted growth, enhancing shoot and root length and biomass, whereas HSe treatment inhibited these parameters, indicating Se's dual role in rice growth. Notably, the most significant promotion of rice growth was observed at the Se concentration of 1 µM. The organic Se content and antioxidant enzyme activities (SOD, POD and CAT) in rice seedlings also reached their maximum values simultaneously. Total RNA was extracted for transcriptome sequencing, and differential gene expression analysis was conducted using DESeq2. Transcriptomic sequencing highlighted distinct responses under LSe and HSe conditions. Gene ontology (GO) enrichment analysis revealed significant involvement in processes related to oxidoreductase activity and cellular structures. KEGG pathway analysis emphasized that Se treatments notably enhanced the glutathione metabolism pathway, which is crucial for antioxidant defense. Additionally, significant changes were observed in starch and sucrose metabolism and cysteine (Cys) and methionine (Met) metabolism pathways, showing upregulation under LSe treatment and downregulation under HSe. Six key genes were validated using qRT-PCR, confirming their differential expression under varied Se treatments. The Cys, Met and starch content assays as well as qRT-PCR data demonstrated that LSe promoted the synthesis and accumulation of Cys, Met and starch, supporting enhanced growth and antioxidant capacity. Conversely, HSe inhibited the synthesis and accumulation of Cys, Met and starch in rice seedlings, and these data were also consistent with the physiological phenotype. These findings provide insights into the molecular mechanisms by which rice seedlings adapt to varying Se levels, with implications for Se biofortification and stress management strategies in crops.

Metabolomics combined with physiology and transcriptomics reveal the regulation of key nitrogen metabolic pathways in alfalfa by foliar spraying with nano-selenium

Selenium promotes plant growth and improves nutritional quality, and the role of nano-selenium in alfalfa in regulating nutritional quality is unknown. In this study, using the 15N labeling method, it was found that nano-selenium could promote plant nitrogen metabolism and photosynthesis by increasing the light energy capture capacity and the activities of key enzymes of the nitrogen metabolism process, leading to an increase in alfalfa nitrogen accumulation and dry matter content. The transcriptome and metabolome revealed that nano-selenium mainly affected the pathways of 'biosynthesis of amino acids', 'starch and sucrose metabolism', 'pentose and glucuronate interconversions', 'pentose phosphate pathway', and 'flavonoid biosynthesis'. At the early stage of nano-selenium treatment, the nitrogen metabolism, sugar metabolism, and flavonoid metabolism pathways were regulated by modulating the expression of genes such as NR, Nir, GS, GOGAT, E3.1.1.11, adh, CHS, FLS, etc., which increased the amount of L-glutamic, L-histidine, glycerone-P, coniferin, naringenin chalcone, and other beneficial substances, thus promoting the acceleration of nitrogen accumulation by plants. In summary, this study provides a better understanding of the mechanisms by which nano-selenium regulates key nitrogen metabolic pathways in alfalfa.

Characterization of selenium-containing broccoli (Brassica oleracea L. var. italica planch) proteins and evaluation of antioxidant activity by electron spin resonance

Selenoproteins found in selenium (Se)-enriched vegetables play a vital role in maintaining human health. In this study, four Se-containing broccoli proteins (Se-BP: albumin, globulin, prolamin, and glutelin) were continuous extracted by Osborne method. Three ultrafiltered fractions were subsequently obtained from the glutelin hydrolysate, composed of Se-contained broccoli peptides (Se-Bp) with different molecular weights (MW), namely, < 1 kDa, 1-3 kDa, and 3-10 kDa. Glutelin exhibited the highest protein yield (65.60 ± 1.07%), purity (78.39 ± 0.95%), nutritional value, organic Se content (88.05 ± 0.32% of total Se content), and Se speciation distribution (selenocystine, selenomethionine, methylselenocysteine, and selenoethionine). Additionally, the antioxidant activity of different MW of Se-Bp was assessed using electron spin resonance spectroscopy. The results revealed that antioxidant activity of the candidate peptide is dependent upon its Se content, amino acid composition, and MW, especially Se-Bp with MW of 1-3 kDa displayed the strongest free radical scavenging ability.

Effects of Different LED Spectra on the Antioxidant Capacity and Nitrogen Metabolism of Chinese Cabbage (Brassica rapa L. ssp. Pekinensis)

Light quality optimization is a cost-effective method for increasing leafy vegetable quality in plant factories. Light-emitting diodes (LEDs) that enable the precise modulation of light quality were used in this study to examine the effects of red-blue (RB), red-blue-green (RBG), red-blue-purple (RBP), and red-blue-far-red (RBF) lights on the growth, antioxidant capacity, and nitrogen metabolism of Chinese cabbage leaves, while white light served as the control (CK). Results showed that the chlorophyll, carotenoid, vitamin C, amino acid, total flavonoid, and antioxidant levels of Chinese cabbage were all significantly increased under RBP combined light treatment. Meanwhile, RBG combined light treatment significantly increased the levels of amino acids but decreased the nitrite content of Chinese cabbage. In addition, RBF combined light treatment remarkably increased the amino acid levels but decreased the antioxidant capacity of Chinese cabbage. In conclusion, the addition of purple light to red-blue light was effective in improving the nutritional value and antioxidant capacity of Chinese cabbage. This light condition can be used as a model for a supplemental lighting strategy for leafy vegetables in plant factory production.

Preharvest sodium selenite treatments affect the growth and enhance nutritional quality of purple leaf mustard with abundant anthocyanin

Both selenium (Se) and anthocyanins are crucial for maintaining human health. Preharvest Se treatments could promote anthocyanin biosynthesis and augment Se levels in vegetables, helping to combat Se deficiencies in dietary intake. However, it remains unknown whether preharvest Se treatment could balance growth and anthocyanin biosynthesis in plants and what the appropriate treatment concentration is. In this study, preharvest treatments with sodium selenite at varying concentrations (0, 5, 10, and 30 mg/kg) affect the growth and nutritional quality of purple leaf mustard (Brassica juncea) with abundant anthocyanins. Lower Se concentrations (≤10 mg/kg) of preharvest treatments enhanced photosynthesis, facilitated root system development, consequently elevated the biomass. Conversely, higher Se levels (≥30 mg/kg) reduced photosynthesis and biomass. The dosage-dependent effects of Se treatments were corroborated through seedlings cultivated in hydroponic conditions. Moreover, nearly all Se treatments elevated the contents of various nutrients in leaf mustard, particularly anthocyanin and organic se. These results suggest an overall enhancement in nutritional quality of leaf mustard plants. Furthermore, the application of 10 mg/kg Se significantly enhanced the activity of phenylalanine ammonia-lyase and upregulated the expression of 12 genes pivotal for anthocyanin biosynthesis, further demonstrating the fortified effects of Se enrichment on anthocyanins in leaf mustard. Low-level Se treatments resulted in heightened antioxidant activity (APX, CAT, and POD), mitigating reactive oxygen species induced by increasing Se content in tissues. The enhanced antioxidant activities may be beneficial for the normal growth of leaf mustard under Se stress conditions. In conclusion, our study demonstrated preharvest Se treatment at 10 mg/kg could balance the growth and anthocyanin biosynthesis in purple leaf mustard. This study offers valuable insights into anthocyanin fortification through Se enrichment methods in agricultural practices, ensuring that such fortification does not compromise leafy vegetable yield.

Effect of sodium selenite on the synthesis of glucosinolates and antioxidant capacity in Chinese cabbage (Brassica rapa L.ssp.pekinensis)

Chinese cabbage (Brassica rapa ssp. pekinensis) is a globally cultivated and consumed leafy vegetable due to its abundant plant secondary metabolites and antioxidant compounds, including flavonoids, ascorbic acids, glucosinolates, and vitamins, which have been reported to confer health-promoting effects. Glucosinolates components in leaves of Chinese cabbage plantlets under different concentrations of sodium selenite (0, 30, and 50 μmol/L) were analyzed. Seven glucosinolates were identified and quantified using UHPLC-QTOF-MS. Finally, treatments with 30 and 50 μmol/L Na2SeO3 solution significantly increased the levels of total selenium content as well as total phenols, flavonoids, anthocyanins, and DPPH free radical scavenging ability in Chinese cabbage seedlings. Our results revealed that 30 μmol/L Na2SeO3 effectively enhanced aliphatic glucosinolate levels and total glucosinolate content while causing a significant reduction in indole glucosinolates. Furthermore, downregulation was observed for BrCYP79F1, BrBCAT4, and BrMAM1 genes associated with aliphatic glucosinolate synthesis. Conversely, BrMYB28 and BrCYP83A1 genes exhibited significant upregulation. Thus, the positive influence of Na2SeO3 on glucosinolate biosynthesis in Chinese cabbage can be attributed to the upregulation of key genes related to this process.

Combined transcriptome and metabolome analyses reveal the effects of selenium on the growth and quality of Lilium lancifolium

Lilium lancifolium Thunb (L. lancifolium) is an important medicinal and edible plant with outstanding functionality for selenium (Se) biofortification. However, the molecular response of L. lancifolium to exogenous Se has not been fully elucidated. In this study, the effects of different levels of Se on L. lancifolium growth and quality were explored by transcriptome, metabolome and biochemical analyses. The results showed that the total Se and organic Se content in L. lancifolium bulbs increased with increasing Se dosage (0-8.0 mmol/L). Moreover, Se stimulated the growth of L. lancifolium at low level (2.0 mmol/L) but showed an inhibitory effect at high levels (≥4.0 mmol/L). Metabolomic and biochemical analyses revealed that the bulb weight and the content of amino acid, soluble sugar, and soluble protein were significantly increased in the 2.0 mmol/L Se treatment compared with those in the control (0 mmol/L Se). Transcriptome and metabolome analyses revealed that the significant upregulation of the GPD1, GPAT and ADPRM genes promoted glycerophospholipid accumulation. Additionally, the significantly upregulated glyA and downregulated asnB, nadB, thrA and SAT genes coordinate to the regulation of amino acid biosynthesis. The significantly upregulated SUS, bgl B, BAM, and SGA1 genes were involved in soluble sugar accumulation under Se treatment. In summary, this study identified the optimal Se concentration (2.0 mmol/L), which significantly improved the growth and nutritional quality of L. lancifolium and contributed to understanding the combined effects of Se treatment on the expression of genes and the accumulation of metabolites in L. lancifolium bulbs.

Selenium in plants: A nexus of growth, antioxidants, and phytohormones

Selenium (Se) is an essential micronutrient for both human and animals. Plants serve as the primary source of Se in the food chain. Se concentration and availability in plants is influenced by soil properties and environmental conditions. Optimal Se levels promote plant growth and enhance stress tolerance, while excessive Se concentration can result in toxicity. Se enhances plants ROS scavenging ability by promoting antioxidant compound synthesis. The ability of Se to maintain redox balance depends upon ROS compounds, stress conditions and Se application rate. Furthermore, Se-dependent antioxidant compound synthesis is critically reliant on plant macro and micro nutritional status. As these nutrients are fundamental for different co-factors and amino acid synthesis. Additionally, phytohormones also interact with Se to promote plant growth. Hence, utilization of phytohormones and modified crop nutrition can improve Se-dependent crop growth and plant stress tolerance. This review aims to explore the assimilation of Se into plant proteins, its intricate effect on plant redox status, and the specific interactions between Se and phytohormones. Furthermore, we highlight the proposed physiological and genetic mechanisms underlying Se-mediated phytohormone-dependent plant growth modulation and identified research opportunities that could contribute to sustainable agricultural production in the future.

Potential Regulatory Networks and Heterosis for Flavonoid and Terpenoid Contents in Pak Choi: Metabolomic and Transcriptome Analyses

Pak choi exhibits a diverse color range and serves as a rich source of flavonoids and terpenoids. However, the mechanisms underlying the heterosis and coordinated regulation of these compounds-particularly isorhamnetin-remain unclear. This study involved three hybrid combinations and the detection of 528 metabolites from all combinations, including 26 flavonoids and 88 terpenoids, through untargeted metabolomics. Analysis of differential metabolites indicated that the heterosis for the flavonoid and terpenoid contents was parent-dependent, and positive heterosis was observed for isorhamnetin in the two hybrid combinations (SZQ, 002 and HMG, ZMG). Moreover, there was a high transcription level of flavone 3'-O-methyltransferase, which is involved in isorhamnetin biosynthesis. The third group was considered the ideal hybrid combination for investigating the heterosis of flavonoid and terpenoid contents. Transcriptome analysis identified a total of 12,652 DEGs (TPM > 1) in various groups that were used for comparison, and DEGs encoding enzymes involved in various categories, including "carotenoid bio-synthesis" and "anthocyanin biosynthesis", were enriched in the hybrid combination (SZQ, 002). Moreover, the category of anthocyanin biosynthesis also was enriched in the hybrid combination (HMG, ZMG). The flavonoid pathway demonstrated more differential metabolites than the terpenoid pathway did. The WGCNA demonstrated notable positive correlations between the dark-green modules and many flavonoids and terpenoids. Moreover, there were 23 ERF genes in the co-expression network (r ≥ 0.90 and p < 0.05). Thus, ERF genes may play a significant role in regulating flavonoid and terpenoid biosynthesis. These findings enhance our understanding of the heterosis and coordinated regulation of flavonoid and terpenoid biosynthesis in pak choi, offering insights for genomics-based breeding improvements.

Decreased cadmium content in Solanum melongena induced by grafting was related to glucosinolates synthesis

Grafting is an effective horticultural method to reduce Cd accumulation in crops. However, the mechanism of grafting inducing the decrease in Cd content in scions remains unclear. This study evaluated the effect of grafting on fruit quality, yield, and Cd content of Solanum melongena, and explored the potential mechanism of grafting reducing Cd content in scions. In the low Cd-contaminated soil, compared with un-grafted (UG) and self-grafted plants (SG), the fruit yield of inter-grafted plants (EG) increased by 38 %, and the fruit quality was not markedly affected. In EG, the decrease in total S and Cd content was not related to organic acids and thiol compounds. The decrease in total S and Cd content in EG leaves and fruits was closely related to the synthesis and transportation of glucosinolates (GSL). The genes encoding GSL synthesis in leaves, such as basic helix-loop-helix, myelocytomatosis proteins, acetyl-CoA, cytochrome P450, and glutathione S-transferases, were significantly downregulated. In EG leaves, the contents of five of the eight amino acids involved in GSL synthesis decreased significantly (P < 0.05). Notably, total GSL in EG stems, leaves, and fruits had a significant linear correlation with total S and Cd. In summary, the decrease in total S and Cd content in scions caused by grafting is closely related to GSL. Our findings provide a theoretical basis for the safe use of Cd-contaminated soil, exploring the long-distance transport of Cd in plants and cultivating crops with low Cd accumulation.

Metabolomics combined with physiology and transcriptomics reveal key metabolic pathway responses in apple plants exposure to different selenium concentrations

Selenium (Se) can be absorbed by plants, thereby affects plant physiological activity, interferes gene expression, alters metabolite content and influences plant growth. However, the molecular mechanism underlying the plant response to Se remains unclear. In this study, apple plants were exposed to Se at concentrations of 0, 3, 6, 9, 12, 24, and 48 μM. Low concentrations of Se promoted plant growth, while high Se concentrations (≥24 μM) reduced photosynthesis, disturbed carbon and nitrogen metabolism, damaged the antioxidant system, and ultimately inhibited plant growth. The transcriptome and metabolome revealed that Se mainly affected three pathways, namely the 'biosynthesis of amino acids', 'starch and sucrose metabolism', and 'phenylpropanoid biosynthesis' pathways. 9 μM Se improved the synthesis, catabolism and utilization of amino acids and sugars, ultimately promoted plant growth. However, 24 μM Se up-regulated the related genes expression of PK, GPT, P5CS, SUS, SPS and CYP98A, and accumulated a large number of osmoregulation substances, such as citric acid, L-proline, D-sucrose and chlorogenic acid in the roots, ultimately affected the balance between plant growth and defense. In conclusion, this study reveals new insights into the key metabolic pathway in apple plants responses to Se.

Glucoraphanin Accumulation via Glucoraphanin Synthesis Promotion during Broccoli Germination

Glucoraphanin is an important glucosinolate which is widely distributed in Brassica vegetables and poses an anticancer effect to humans. Although researchers have paid a lot of attention to the changes in glucoraphanin concentration in seedlings of broccoli over 1-2 weeks, there has been little research focusing on the total whole-sprout glucoraphanin content within broccoli seedlings over 1-5 weeks. However, it is necessary to clarify the changes in total glucoraphanin content during the broccoli sprouting stage as broccoli seedlings are novel plant foods. This research explored glucoraphanin absolute accumulation and the biosynthesis mechanism in broccoli seedlings during a 5-week growth period. The results showed that glucoraphanin accumulation content was higher at week 4 than in the seeds. Moreover, the relative DL-methionine contents increased significantly after 3 weeks. Glucoraphanin synthetic gene expression levels were increased after 3 weeks, but the gene expressions of AOP3 (encoding 2-oxoglutarate-dependent dioxygenases) and MYR (encoding myrosinase) were significantly decreased. Furthermore, the 20 essential DEGs obtained can provide new insight into understanding the developmental regulation of broccoli seedlings. In addition, the results can also provide information on how to obtain higher glucoraphanin contents in broccoli sprouts.

Transcriptome and physiological determination reveal the effects of selenite on the growth and selenium metabolism in mung bean sprouts

Selenium (Se) biofortification of crops has been studied to substantially improve the Se content in human dietary food intake. In the present study, Vigna radiata (mung bean) seeds were soaked in different concentrations of sodium selenite (Na₂SeO₃). Low concentration of selenite is conducive to seed germination and growth, and can increase the fresh weight (FW) and dry weight (DW) of sprouts. The concentration of Na₂SeO₃ lower than 50 mg/kg resulted in noticeable elongation in the stem and marginal elongation in root. Mung bean seeds soaked with 80 mg/kg Na₂SeO₃ accounted for 93.77% of organic Se after growing for about 5 days. Transcriptome data revealed that Se treatment enhances starch and sugar metabolism, along with the up-regulation of ribosomal protein and DNA synthesis related genes. Further analysis indicated that the mung bean seeds absorbed Na₂SeO₃ through PHT1.1 and NIP2. Se (IV) was transformed into Se (VI) and transported to stems, leaves and roots through cotyledons during the germination of bean sprouts. SULTR3;3 may play an important role in the transit process. Se (VI) or Se (IV) transported to the leaves was catalytically transformed into SeCys through SiR and CS, and SeCys is further converted to MeSeCys through SMT. Most SeCys were transformed into SeHCys through CBL, transported to plastids, and finally transformed into SeMet through Met Synthase.

Proteome reveals the mechanism of selenium-sulfur interaction in regulating isothiocyanate biosynthesis and the physiological metabolism of broccoli sprouts

Broccoli sprouts have a strong ability to accumulate isothiocyanate and selenium. In this study, the isothiocyanate content increased significantly as a result of ZnSO₄ stress. Particularly, based on the isothiocyanate content is not affected, the combined ZnSO₄ and Na₂SeO₃ treatment alleviated the inhibition of ZnSO₄ and induced selenium content. Gene transcription and protein expression analyses revealed the changes in isothiocyanate and selenium metabolite levels in broccoli sprouts. ZnSO₄ combined with Na₂SeO₃ was proven to activate a series of isothiocyanate metabolite genes (UGT74B1, OX1, and ST5b) and selenium metabolite genes (BoSultr1;1, BoCOQ5-2, and BoHMT1). The relative abundance of the total 317 and 203 proteins, respectively, in 4-day-old broccoli sprouts varied, and the metabolic and biosynthetic pathways for secondary metabolites were significantly enriched in ZnSO₄/control and ZnSO₄ combined Na₂SeO₃/ZnSO₄ comparisons. The findings demonstrated how ZnSO₄ combined with Na₂SeO₃ treatment reduced stress inhibition and the accumulation of encouraged selenium and isothiocyanates during the growth of broccoli sprouts.

Hot-air-assisted radio frequency blanching of broccoli: heating uniformity, physicochemical parameters, bioactive compounds, and microstructure

BACKGROUND

Vegetables are often blanched before drying. The hot-water blanching (HWB) of broccoli reduces quality and is environmentally harmful. In this work, hot-air-assisted radio frequency heating blanching (HA-RFB) of broccoli was developed for use before further drying processes. Blanching sufficiency, heating uniformity, and heating rate during HA-RFB were investigated to improve the product's physicochemical properties and texture. Suitable heating conditions were achieved when HA-RFB was applied with hot air at 70 °C, with an electrode gap of 10.7 cm, using a cylindrical container for the broccoli.

RESULTS

Under these conditions, the relative peroxidase activity in broccoli decreased to 3.26% within 117 s, with 13.45% of weight loss. In comparison with HWB broccoli, the products blanched by HA-RFB preserved their texture, bioactive compounds, and microstructure better. The ascorbic acid, sulforaphane, and total glucosinolate content in HA-RFB products were 251.1%, 131.9% and 36.7% higher than those in HWB broccoli, and HA-RFB treatment led to a greater weight loss (13.45 ± 0.50%) than HWB (8.70 ± 1.70%), which is very helpful for the subsequent drying process.

CONCLUSION

This study demonstrated that HA-RFB could be a promising substitute for HWB to blanch broccoli and other flower vegetables, especially as a pretreatment in the drying process. © 2023 Society of Chemical Industry.

Integrated transcriptome and metabolome analysis reveals the mechanism of tolerance to manganese and cadmium toxicity in the Mn/Cd hyperaccumulator Celosia argentea Linn

Understanding the molecular mechanism of tolerance to heavy metals in hyperaccumulators is important for improving the efficiency of phytoremediation and is interesting for evolutionary studies on plant adaption to abiotic stress. Celosia argentea Linn. was recently discovered to hyperaccumulate both manganese (Mn) and cadmium (Cd). However, the molecular mechanisms underlying Mn and Cd detoxification in C. argentea are poorly understood. Laboratory studies were conducted using C. argentea seedlings exposed to 360 μM Mn and 8.9 μM Cd hydroponic solutions. Plant leaves were analyzed using transcriptional and metabolomic techniques. A total of 3960 differentially expressed genes (DEGs) in plants were identified under Cd stress, among which 17 were associated with metal transport, and 10 belonged to the ATP transporter families. Exposures to Mn or Cd led to the differential expression of three metal transport genes (HMA3, ABCC15, and ATPase 4). In addition, 33 and 77 differentially expressed metabolites (DEMs) were identified under Mn and Cd stresses, respectively. Metabolic pathway analysis showed that the ABC transporter pathway was the most affected in Mn/Cd exposed seedlings. Conjoint transcriptome and metabolome analysis showed that the glutathione (GSH) metabolic pathway was over-represented in the KEGG pathway of both DEGs and DEMs. Our results confirm that the ABC transporter and GSH metabolic pathways play important roles in Mn and Cd detoxification. These findings provide new insight into the molecular mechanisms of tolerance to Mn and Cd toxicity in plants.

Effect of Nano-Selenium on Nutritional Quality of Cowpea and Response of ABCC Transporter Family

It is an important way for healthy Selenium (Se) supplement to transform exogenous Se into organic Se through crops. In the present study, Vigna unguiculata was selected as a test material and sprayed with biological nano selenium (SeNPs) and Na₂SeO₃, and its nutrient composition, antioxidant capacity, total Se and organic Se content were determined, respectively. Further, the response of ABC transporter family members in cowpea to different exogenous Se treatments was analyzed by transcriptome sequencing combined with different Se forms. The results show that the soluble protein content of cowpea increased after twice Se treatment. SeNPs treatment increased the content of cellulose in cowpea pods. Na₂SeO₃ treatment increased the content of vitamin C (Vc) in cowpea pods. Se treatments could significantly increase the activities of Peroxidase (POD), polyphenol oxidase (PPO) and catalase (CAT) in cowpea pods and effectively maintain the activity of Superoxide dismutase (SOD). SeNPs can reduce the content of malondialdehyde (MDA) in pods. After Se treatment, cowpea pods showed a dose-effect relationship on the absorption and accumulation of total Se, and Na₂SeO₃ treatment had a better effect on the increase of total Se content in cowpea pods. After treatment with SeNPs and Na₂SeO₃, the Se species detected in cowpea pods was mainly SeMet, followed by MeSeCys. Inorganic Se can only be detected in the high concentration treatment group. Analysis of transcriptome data of cowpea treated with Se showed that ABC transporters could play an active role in response to Se stress and Se absorption, among which ABCB, ABCC and ABCG subfamilies played a major role in Se absorption and transportation in cowpea. Further analysis by weighted gene co-expression network analysis (WGCNA) showed that the content of organic Se in cowpea treated with high concentration of SeNPs was significantly and positively correlated with the expression level of three transporters ABCC11, ABCC13 and ABCC10, which means that the ABCC subfamily may be more involved in the transmembrane transport of organic Se in cells.

Preharvest application of selenite enhances the quality of Chinese flowering cabbage during storage via regulating the ascorbate-glutathione cycle and phenylpropanoid metabolisms

Chinese flowering cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) is a candidate of selenium (Se) accumulator, but it is not clear whether and how preharvest Se treatment affects its quality after harvest. Here, we showed that preharvest application of 100 μmol/L selenite to roots enhanced storage quality of Chinese flowering cabbage. It increased antioxidant capacity and reduced weight loss, leaf yellowing, and protein degradation after harvest. Furthermore, it increased the activities of antioxidant enzymes such as POD, CAT, GSH-Px, and GR, as well as contents of AsA, GSH, phenolics, and flavonoids during storage. Metabolome analysis revealed that phenolic acids including p-Coumaric acid, caffeic acid, and ferulic acid; flavonoids such as naringenin, eriodictyol, apigenin, quercetin, kaempferol, and their derivatives were notably increased by preharvest selenite treatment. Consistently, the total antioxidant capacity, evaluated by DPPH, ABTS, and FRAP methods, were all markedly enhanced in selenite-treated cabbage compared to the control. Transcriptomics analysis showed that the DEGs induced by selenite were significantly enriched in AsA-GSH metabolisms and phenylpropanoids biosynthesis pathways. Moreover, preharvest selenite treatment significantly up-regulated the expressions of BrGST, BrGSH-Px, BrAPX, BrASO, BrC4H, BrCOMT, BrCHS, and BrFLS during storage. These results suggest that preharvest selenite treatment enhanced quality of cabbage not only by increasing Se biological accumulation, but also through regulating AsA-GSH cycle and increasing phenolics and flavonoids synthesis after harvest. This study provides a novel insight into the effects of preharvest Se treatment on quality of Chinese flowering cabbage during storage.

The Integral Boosting Effect of Selenium on the Secondary Metabolism of Higher Plants

Selenium is a micronutrient with a wide range of functions in animals, including humans, and in microorganisms such as microalgae. However, its role in plant metabolism remains ambiguous. Recent studies of Se supplementation showed that not only does it increase the content of the element itself, but also affects the accumulation of secondary metabolites in plants. The purpose of this review is to analyze and summarize the available data on the place of selenium in the secondary metabolism of plants and its effect on the accumulation of some plant metabolites (S- and N-containing secondary metabolites, terpenes, and phenolic compounds). In addition, possible molecular mechanisms and metabolic pathways underlying these effects are discussed. It should be noted that available data on the effect of Se on the accumulation of secondary metabolites are inconsistent and contradictory. According to some studies, selenium has a positive effect on the accumulation of certain metabolites, while other similar studies show a negative effect or no effect at all. The following aspects were identified as possible ways of regulating plant secondary metabolism by Se-supplementation: changes occurring in primary S/N metabolism, hormonal regulation, redox metabolism, as well as at the transcriptomic level of secondary metabolite biosynthesis. In all likelihood, the confusion in the results can be explained by other, more complex regulatory mechanisms in which selenium is involved and which affect the production of metabolites. Further study on the involvement of various forms of selenium in metabolic and signaling pathways is crucial for a deeper understanding of its role in growth, development, and health of plants, as well as the regulatory mechanisms behind them.

Transcriptome and Metabolome Analysis Revealed That Exogenous Spermidine-Modulated Flavone Enhances the Heat Tolerance of Lettuce

Lettuce is sensitive to high temperature, and exogenous spermidine can improve heat tolerance in lettuce, but its intrinsic mechanism is still unclear. We analyzed the effects of exogenous spermidine on the leaf physiological metabolism, transcriptome and metabolome of lettuce seedlings under high-temperature stress using the heat-sensitive lettuce variety 'Beisansheng No. 3' as the material. The results showed that exogenous spermidine increased the total fresh weight, total dry weight, root length, chlorophyll content and total flavonoid content, increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and decreased malondialdehyde (MDA) content in lettuce under high temperature stress. Transcriptome and metabolome analyses revealed 818 differentially expressed genes (DEGs) and 393 metabolites between water spray and spermidine spray treatments under high temperature stress, and 75 genes from 13 transcription factors (TF) families were included in the DEGs. The Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis of DEG contains pathways for plant-pathogen interactions, photosynthesis-antennal proteins, mitogen-activated protein kinase (MAPK) signaling pathway and flavonoid biosynthesis. A total of 19 genes related to flavonoid synthesis were detected. Most of these 19 DEGs were down-regulated under high temperature stress and up-regulated after spermidine application, which may be responsible for the increase in total flavonoid content. We provide a possible source and conjecture for exploring the mechanism of exogenous spermidine-mediated heat tolerance in lettuce.

Treatment of Ginkgo biloba with Exogenous Sodium Selenite Affects Its Physiological Growth, Changes Its Phytohormones, and Synthesizes Its Terpene Lactones

Ginkgolide is a unique terpenoid natural compound in Ginkgo biloba, and it has an important medicinal value. Proper selenium has been reported to promote plant growth and development, and improve plant quality, stress resistance, and disease resistance. In order to study the effects of exogenous selenium (Se) on the physiological growth and the content of terpene triolactones (TTLs) in G. biloba seedlings, the seedlings in this work were treated with Na2SeO3. Then, the physiological indexes, the content of the TTLs, and the expression of the related genes were determined. The results showed that a low dose of Na2SeO3 was beneficial to plant photosynthesis as it promoted the growth of ginkgo seedlings and increased the root to shoot ratio. Foliar Se application significantly increased the content of soluble sugar and protein and promoted the content of TTLs in ginkgo leaves; indeed, it reached the maximum value of 7.95 mg/g in the ninth week, whereas the application of Se to the roots inhibited the synthesis of TTLs. Transcriptome analysis showed that foliar Se application promoted the expression levels of GbMECPs, GbMECT, GbHMGR, and GbMVD genes, whereas its application to the roots promoted the expression of GbDXS and GbDXR genes. The combined analysis results of metabolome and transcriptome showed that genes such as GbDXS, GbDXR, GbHMGR, GbMECPs, and GbCYP450 were significantly positively correlated with transcription factors (TFs) GbWRKY and GbAP2/ERF, and they were also positively correlated with the contents of terpene lactones (ginkgolide A, ginkgolide B, ginkgolide M, and bilobalide). Endogenous hormones (MeJA-ILE, ETH, and GA7) were also involved in this process. The results suggested that Na2SeO3 treatment affected the transcription factors related to the regulation of endogenous hormones in G. biloba, and further regulated the expression of genes related to the terpene synthesis structure, thus promoting the synthesis of ginkgo TTLs.

Seleno-Metabolites and Their Precursors: A New Dawn for Several Illnesses?

Selenium (Se) is an essential element for human health as it is involved in different physiological functions. Moreover, a great number of Se compounds can be considered potential agents in the prevention and treatment of some diseases. It is widely recognized that Se activity is related to multiple factors, such as its chemical form, dose, and its metabolism. The understanding of its complex biochemistry is necessary as it has been demonstrated that the metabolites of the Se molecules used to be the ones that exert the biological activity. Therefore, the aim of this review is to summarize the recent information about its most remarkable metabolites of acknowledged biological effects: hydrogen selenide (HSe-/H2Se) and methylselenol (CH3SeH). In addition, special attention is paid to the main seleno-containing precursors of these derivatives and their role in different pathologies.

Preharvest Methyl Jasmonate Treatment Increased Glucosinolate Biosynthesis, Sulforaphane Accumulation, and Antioxidant Activity of Broccoli

Broccoli is becoming increasingly popular among consumers owing to its nutritional value and rich bioactive compounds, such glucosinolates (GSLs) and hydrolysis products, which are secondary metabolites for plant defense, cancer prevention, and higher antioxidant activity for humans. In this study, 40 μmol/L methyl jasmonate (MeJA) was sprayed onto broccoli from budding until harvest. The harvested broccoli florets, stem, and leaves were used to measure the contents of GSLs, sulforaphane, total phenolics, and flavonoids, as well as myrosinase activity, antioxidant activity, and gene expression involved in GSL biosynthesis. The overall results revealed that GSL biosynthesis and sulforaphane accumulation were most likely induced by exogenous MeJA treatment by upregulating the expression of CYP83A1, SUR1, UGT74B1, and SOT18 genes. Exogenous MeJA treatment more remarkably contributed to the increased GSL biosynthesis in broccoli cultivars with low-level GSL content (Yanxiu) than that with high-level GSLs (Xianglv No.3). Moreover, MeJA treatment had a more remarkable increasing effect in broccoli florets than stem and leaves. Interestingly, total flavonoid content substantially increased in broccoli florets after MeJA treatment, but total phenolics did not. Similarly, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, trolox-equivalent antioxidant capacity (ABTS), and ferric-reducing antioxidant power (FRAP) were higher in broccoli floret after MeJA treatment. In conclusion, MeJA mediated bioactive compound metabolism, had positive effects on GSL biosynthesis, sulforaphane, and flavonoids accumulation, and showed positive correlation on inducing higher antioxidant activities in broccoli floret. Hence, preharvest supplementation with 40 μM MeJA could be a good way to improve the nutritional value of broccoli florets.

Effects of Plant Hormones, Metal Ions, Salinity, Sugar, and Chemicals Pollution on Glucosinolate Biosynthesis in Cruciferous Plant

Cruciferous vegetable crops are grown widely around the world, which supply a multitude of health-related micronutrients, phytochemicals, and antioxidant compounds. Glucosinolates (GSLs) are specialized metabolites found widely in cruciferous vegetables, which are not only related to flavor formation but also have anti-cancer, disease-resistance, and insect-resistance properties. The content and components of GSLs in the Cruciferae are not only related to genotypes and environmental factors but also are influenced by hormones, plant growth regulators, and mineral elements. This review discusses the effects of different exogenous substances on the GSL content and composition, and analyzes the molecular mechanism by which these substances regulate the biosynthesis of GSLs. Based on the current research status, future research directions are also proposed.

Impact of Dietary Factors on Brugada Syndrome and Long QT Syndrome

A healthy regime is fundamental for the prevention of cardiovascular diseases (CVD). In inherited channelopathies, such as Brugada syndrome (BrS) and Long QT syndrome (LQTS), unfortunately, sudden cardiac death could be the first sign for patients affected by these syndromes. Several known factors are used to stratify the risk of developing cardiac arrhythmias, although none are determinative. The risk factors can be affected by adjusting lifestyle habits, such as a particular diet, impacting the risk of arrhythmogenic events and mortality. To date, the importance of understanding the relationship between diet and inherited channelopathies has been underrated. Therefore, we describe herein the effects of dietary factors on the development of arrhythmia in patients affected by BrS and LQTS. Modifying the diet might not be enough to fully prevent arrhythmias, but it can help lower the risk.