Simultaneous extraction and determination of mono-/polyglutamyl folates using high-performance liquid chromatography-tandem mass spectrometry and its applications in starchy crops

Nanoparticles mediated folic acid enrichment

Folate is an essential component of many metabolic processes, and folate deficiency is known to cause various disorders. Folate and folic acid, a synthetic and chemically stable form of folate, enriched diet are typically used to overcome this deficiency. Folic acid and folate however, are susceptible to harsh environment and folates enrichment using nanoparticles is an intensively studied strategy in food industry. This review highlights the current methods and types of matrices utilized to develop folic acid/folate carrying nanoparticles. The folic acid/folate loaded nanoparticles prevent cargo degradation during gut absorption and under harsh food processing conditions including, high temperatures, UV light, and autoclaving. The data demonstrates that nanofortifcation of folates using proteins and biopolymers effectively enhances the bioavailability of the cargo. The encapsulation of folic acid in biopolymers by emulsion, spray drying and ionic gelation represent simplistic methods that can be easily scaled up with applications in food industry.

Folate shapes plant root architecture by affecting auxin distribution

Folate (vitamin B9) is important for plant root development, but the mechanism is largely unknown. Here we characterized a root defective mutant, folb2, in Arabidopsis, which has severe developmental defects in the primary root. The root apical meristem of the folb2 mutant is impaired, and adventitious roots are frequently found at the root-hypocotyl junction. Positional cloning revealed that a 61-bp deletion is present in the predicted junction region of the promoter and the 5' untranslated region of AtFolB2, a gene encoding a dihydroneopterin aldolase that functions in folate biosynthesis. This mutation leads to a significant reduction in the transcript level of AtFolB2. Liquid chromatography-mass spectrometry analysis showed that the contents of the selected folate compounds were decreased in folb2. Arabidopsis AtFolB2 knockdown lines phenocopy the folb2 mutant. On the other hand, the application of exogenous 5-formyltetrahydrofolic acid could rescue the root phenotype of folb2, indicating that the root phenotype is indeed related to the folate level. Further analysis revealed that folate could promote rootward auxin transport through auxin transporters and that folate may affect particular auxin/indole-3-acetic acid proteins and auxin response factors. Our findings provide new insights into the important role of folic acid in shaping root structure.

Role of miRNAs in regulation of SA-mediated upregulation of genes involved in folate and methionine metabolism in foxtail millet

The effect of exogenous salicylic acid (SA) on folate metabolism and the related gene regulatory mechanisms is still unclear. In this study, the panicle of foxtail millet treated with different SA concentrations showed that 6 mM SA doubled the 5-methyltetrahydrofolate content compared to that of the control. An untargeted metabolomic analysis revealed that 275 metabolites were enriched in amino acid metabolic pathways. Significantly, the relative content of methionine (Met) after 6 mM SA treatment was 3.14 times higher than the control. Transcriptome analysis revealed that differentially expressed genes were mainly enriched in the folate and amino acid biosynthesis pathways (including Met, Cys, Pro, Ser et al.). The miRNA-mRNA interactions related to the folate and Met metabolic pathways were analyzed and several likely structural gene targets for miRNAs were identified, miRNA-seq analysis revealed that 33 and 51 miRNAs targeted 11 and 15 genes related to the folate and Met pathways, respectively. Eight key genes in the folate metabolism pathway were likely to be up-regulated by 14 new miRNAs and 20 new miRNAs up-regulated the 9 key genes in the Met metabolism pathway. The 6 miRNA-mRNA interactions related to the folate and Met metabolism pathways were verified by qRT-PCR, and consistent with the prediction. The results showed that DHFR1 gene expression level related to folate synthesis was directly up-regulated by Nov-m0139-3p with 3.8 times, but DHFR2 was down-regulated by Nov-m0731-5p with 0.62 times. The expression level of CYSC1 and APIP related to Met synthesis were up-regulated by Nov-m0461-5p and Nov-m0664-3p with 4.27 and 1.32 times, respectively. Our results suggested that exogenous SA could induce the folate and Met accumulated in the panicle of foxtail millet. The higher expression level of DHFR1, FTHFD, CYSC1 and APIP in the folate and Met metabolism pathway and their regulators, including Nov-m0139-3p, Nov-m0717-5p, Nov-m0461-5p and Nov-m0664-3p, could be responsible for these metabolites accumulation. This study lays the theoretical foundation for elucidating the post-transcription regulatory mechanisms of folate and Met metabolism.

Heterologous Expression of SiFBP, a Folate-Binding Protein from Foxtail Millet, Confers Increased Folate Content and Altered Amino Acid Profiles with Nutritional Potential to Arabidopsis

The mechanism underlying folate degradation in foxtail millet grains remains unclear. Here, we identified SiFBP (Setaria italica folate-binding protein) from foxtail millet. A phylogenetic tree revealed that FBPs have close genetic relationships among cereal crop species. Docking analysis and heterologous expression of SiFBP in yeast showed that it could bind folic acid (FA). The SiFBP localized to the plasma membrane in tobacco mesophyll cells by transient expression. In Arabidopsis, it was expressed specifically in the roots and germinating seeds. Overexpressing SiFBP in yeast and Arabidopsis significantly increased folate contents. Untargeted metabolome analysis revealed differentially accumulated metabolites between the transgenic lines (TLs) and wild type (WT); these metabolites were mainly enriched in the amino acid metabolism pathway. The relative contents of lysine and leucine, threonine, and l-methionine were significantly higher in the TLs than in WT. Genes related to the folate and lysine synthesis pathways were upregulated in the TLs. Thus, SiFBP can be used for biofortification of folate and important amino acids in crops via genetic engineering.

Folate metabolic profiling and expression of folate metabolism-related genes during panicle development in foxtail millet (Setaria italica (L.) P. Beauv)

BACKGROUND

Foxtail millet grain has higher folate content than other cereal crops. However, the folate metabolite content and the expression patterns of folate metabolite-related genes are unknown.

RESULTS

Liquid chromatography-mass spectrometry was used to investigate 12 folate metabolites in a foxtail millet panicle. The content of total folate and derivatives gradually decreased during panicle development. Polyglutamate 5-formyl-tetrahydrofolate was the major form. Twenty-eight genes involved in the folate metabolic pathway were identified through bioinformatic analysis. These genes in Setaria italica, S. viridis and Zea mays showed genomic collinearity. Phylogenetic analysis revealed that the folate-related genes were closely related among the C4 plants compared to C3 plants. The gene expressions were then studied at three panicle development stages. The gene expression patterns were classified into two groups, namely SiADCL1 and SiGGH as two key enzymes, which are responsible for folate synthesis and degradation; their expression levels were highest at the early panicle development stage, up to 179.11- and 163.88-fold, respectively. Their expression levels had a similar downward trend during panicle development and were significantly positively correlated with the concentration of total folate and folate derivatives. However, SiSHMT3 expression levels were significantly negatively correlated with total folate concentration.

CONCLUSION

Besides being the major determinants of folate and folate derivatives accumulation, SiADCL1 and SiGGH expression levels are key limiting factors in the foxtail millet panicle. Therefore, SiADCL1 and SiGGH expression levels can be targeted in genetic modification studies to improve folate content in foxtail millet seeds in the future. © 2021 Society of Chemical Industry.

Agronomic Biofortification of Cayenne Pepper Cultivars with Plant Growth-Promoting Rhizobacteria and Chili Residue in a Chinese Solar Greenhouse

Agronomic biofortification of horticultural crops using plant growth-promoting rhizobacteria (PGPR) under crop residue incorporation systems remains largely underexploited. Bacillus subtilis (B1), Bacillus laterosporus (B2), or Bacillus amyloliquefaciens (B3) was inoculated on soil containing chili residue, while chili residue without PGPR (NP) served as the control. Two hybrid long cayenne peppers, succeeding a leaf mustard crop were used in the intensive cultivation study. Net photosynthesis, leaf stomatal conductance, transpiration rate, photosynthetic water use efficiency, shoot and root biomass, and fruit yield were evaluated. Derivatives of folate, minerals, and nitrate contents in the pepper fruits were also assessed. B1 elicited higher net photosynthesis and photosynthetic water use efficiency, while B2 and B3 had higher transpiration rates than B1 and NP. B1 and B3 resulted in 27–36% increase in pepper fruit yield compared to other treatments, whereas B3 produced 24–27.5% and 21.9–27.2% higher 5-methyltetrahydrofolate and total folate contents, respectively, compared to B1 and NP. However, chili residue without PGPR inoculation improved fruit calcium, magnesium, and potassium contents than the inoculated treatments. ‘Xin Xian La 8 F1’ cultivar had higher yield and plant biomass, fruit potassium, total soluble solids, and total folate contents compared to ‘La Gao F1.’ Agronomic biofortification through the synergy of Bacillus amyloliquefaciens and chili residue produced better yield and folate contents with a trade-off in the mineral contents of the greenhouse-grown long cayenne pepper.

Identification of the prepared foods promising for dietary folate intake in Beijing, China

The aim of the present study was to analyze folate content and composition in foods consumed daily by Chinese people. The concentration of seven folate derivatives in sixty-four selected foods was determined by a liquid-chromatography tandem-mass spectrometry method. The total folate levels ranged from 0.28 to 129 µg/100 g fresh weight, with an average of 21.18 μg/100 g. The highest folate content was found in boiled egg yolk and waxy corn (>120 µg/100 g), abundant folate levels in cooked vegetables such as hot pepper, spinach, soybean sprout, stem lettuce, coriander, and broccoli (44-72 µg/100 g), and lowest in Coca Cola (0.28 µg/100 g). 5-Methyl-tetrahydrofolate was the major folate derivative in various foods, accounting for 72% of the total folates on average, with the highest being 90% in egg yolk. These data will enable estimation of the daily folate intake and allow dietary recommendations to improve folate status in humans.

Modified EMR-lipid method combined with HPLC-MS/MS to determine folates in egg yolks from laying hens supplemented with different amounts of folic acid

Egg yolks are a good source of folates. However, the method for analyzing the naturally occurring folates in egg yolks is complicated and time-consuming. In this study, a simplified pre-treatment method followed by validated HPLC-MS/MS was developed to determine native folates in eggs from laying hens treated with different amounts of folic acid. The modified enhanced matrix removal -lipid method to purify samples showed good performance in lipid elimination, reduction of steps and time savings. According to experimental analysis, yolks contained total folate amounts ranging from 147 to 760 μg/100 g when laying hens' diet was supplemented with folic acid from 0 to 10 mg/kg. Four folate vitamers were detected in egg yolks: 5-methyltetrahydrofolate accounted for 91-98% of total folates, whereas folic acid, 5-formyltetrahydrofolate and 10-formylfolic acid together accounted for 2-9%. Therefore, laying hens efficiently converted folic acid in feed into 5-methyltetrahydrofolate in eggs with little folic acid deposition.