Non-targeted GC-MS metabolomics-based differences in Indica rice seeds of different varieties.

Rice seeds of different varieties exhibited distinct metabolic profiles in our study. We analyzed the metabolites in seeds of six rice varieties (CH, HM, NX, YX, HY, and MX) using non-targeted GC-MS. Our findings revealed that amino acids, sugars, and organic acids were predominant in all varieties, with significant differences observed in CH compared to the others. Specifically phenylalanine and glycine content differed notably in NX and YX, respectively. Additionally, 1,5-anhydroglucitol content in NX, and glutamate, aspartate, and lactulose in NX, YX, HM, HY, and MX were up-regulated. Due to the biological functions of these amino acids and sugars, these indicated that compared to CH, rice of NX were more conducive to metabolism of carbohydrate and fat, and healthy growth maintenance in the human body, but mightThese variations suggest that NX rice may be more beneficial for carbohydrate and fat metabolism and overall health maintenance compared to CH. However, it may not be suitable for diabetic patients. YX rice may not be an ideal glycine supplement, rice ofwhile HM, HY, and MX rice could serve as potential lactulose sources. Furthermore, NX and YX rice exhibited higher levels of main storage proteins compared to CH. This study offers valuable insights into the metabolic differences among various rice varieties.

Alternative polyadenylation profiles of susceptible and resistant rice (Oryza sativa L.) in response to bacterial leaf blight using RNA-seq.

BACKGROUND: Alternative polyadenylation (APA) is an important pattern of post-transcriptional regulation of genes widely existing in eukaryotes, involving plant physiological and pathological processes. However, there is a dearth of studies investigating the role of APA profile in rice leaf blight. RESULTS: In this study, we compared the APA profile of leaf blight-susceptible varieties (CT 9737-613P-M) and resistant varieties (NSIC RC154) following bacterial blight infection. Through gene enrichment analysis, we found that the genes of two varieties typically exhibited distal poly(A) (PA) sites that play different roles in two kinds of rice, indicating differential APA regulatory mechanisms. In this process, many disease-resistance genes displayed multiple transcripts via APA. Moreover, we also found five polyadenylation factors of similar expression patterns of rice, highlighting the critical roles of these five factors in rice response to leaf blight about PA locus diversity. CONCLUSION: Notably, the present study provides the first dynamic changes of APA in rice in early response to biotic stresses and proposes a possible functional conjecture of APA in plant immune response, which lays the theoretical foundation for in-depth determination of the role of APA events in plant stress response and other life processes.

Genome-wide identification and comprehensive analysis of NAC family genes involved in fruit development in kiwifruit (Actinidia).

BACKGROUND: NAC transcription factors (TFs) are plant-specific proteins encoded by a large gene family. They play important roles in diverse biological processes, such as plant growth and development, leaf senescence, and responses to biotic or abiotic stresses. Functions of a number of NAC TFs have been identified mainly in model plants. However, very few studies on NAC TFs have been conducted in the fruit tree of kiwifruit. RESULTS: Genome-wide NAC genes were identified and their phylogeny, genomic structure, chromosomal location, synteny relationships, protein properties and conserved motifs were analyzed. In addition, the fruit developmental process was evaluated in a new kiwifruit cultivar of Actinidia eriantha 'Ganlu 1'. And expressions for all those NAC genes were analyzed by quantitative real-time PCR method in fruits of 'Ganlu 1' during its developmental process. Our research identified 142 NAC TFs which could be phylogenetically divided into 23 protein subfamilies. The genomic structures of those NAC genes indicated that their exons were between one and ten. Analysis of chromosomal locations suggested that 116 out of 142 NACs distributed on all the 29 kiwifruit chromosomes. In addition, genome-wide gene expression analysis showed that expressions of 125 out of 142 NAC genes could be detected in fruit samples. CONCLUSION: Our comprehensive study provides novel information on NAC genes and expression patterns in kiwifruit fruit. This research would be helpful for future functional identification of NAC genes involved in kiwifruit fruit development.

qTGW12a, a naturally varying QTL, regulates grain weight in rice.

KEY MESSAGE: A stable QTL associated with rice grain type with a large effect value was found in multiple environments, and its candidate genes were verified by genetic transformation. Rice (Oryza sativa L.) grain size is critical to both yield and appearance quality. Therefore, the discovery and identification of rice grain size genes can provide pathways for the cultivation of high-yielding varieties. In the present work, 45,607 SNP markers were used to construct a high-density genetic map of rice recombinant inbred lines, and hence a total of 14 quantitative trait loci (QTLs) were detected based on the phenotypic data of grain weight, grain length and grain width under four different environments. qTGW12a and qGL12 are newly detected QTLs related to grain weight, and are located between 22.43 Mb and 22.45 Mb on chromosome 12. Gene annotation shows that the QTL region contains the LOC_Os12g36660 annotated gene, which encodes the multidrug and toxic compound extrusion (MATE) transporter. Mutations in exons and the splice site were responsible for the changes in grain type and weight. Gene knockout experiments were used to verify these results. Hence, these results provide a basis for the cloning of qTGW12a. This discovery provides new insights for studying the genetic mechanism of rice grain morphology, and reveals a promising gene to ultimately increase rice yield.

Research on Hazardous Waste Removal Management: Identification of the Hazardous Characteristics of Fluid Catalytic Cracking Spent Catalysts.

Fluid catalytic cracking (FCC) spent catalysts are the most common catalysts produced by the petroleum refining industry in China. The National Hazardous Waste List (2016 edition) lists FCC spent catalysts as hazardous waste, but this listing is very controversial in the petroleum refining industry. This study collects samples of waste catalysts from seven domestic catalytic cracking units without antimony-based passivation agents and identifies their hazardous characteristics. FCC spent catalysts do not have the characteristics of flammability, corrosiveness, reactivity, or infectivity. Based on our analysis of the components and production process of the FCC spent catalysts, we focused on the hazardous characteristic of toxicity. Our results show that the leaching toxicity of the heavy metal pollutants nickel, copper, lead, and zinc in the FCC spent catalyst samples did not exceed the hazardous waste identification standards. Assuming that the standards for antimony and vanadium leachate are 100 times higher than that of the surface water and groundwater environmental quality standards, the leaching concentration of antimony and vanadium in the FCC spent catalyst of the G set of installations exceeds the standard, which may affect the environmental quality of surface water or groundwater. The quantities of toxic substances in all spent FCC catalysts, except those from G2, does not exceed the standard. The acute toxicity of FCC spent catalysts in all installations does not exceed the standard. Therefore, we exclude "waste catalysts from catalytic cracking units without antimony-based passivating agent passivation nickel agent" from the "National Hazardous Waste List."

Distinct genome-wide alternative polyadenylation during the response to silicon availability in the marine diatom Thalassiosira pseudonana.

The post-transcriptional regulation involved in the responses of diatoms to silicon is poorly understood. Using a poly(A)-tag sequencing (PAT-seq) technique that interrogates only the junctions of 3'-untranslated region (UTR) and the poly(A) tails at the transcriptome level, a comprehensive comparison of alternative polyadenylation (APA) was performed to understand the role of post-transcriptional regulation in various silicon-related cellular responses for the marine diatom Thalassiosira pseudonana. In total, 23 701 poly(A) clusters and 6894 APA genes, treated with silicon starvation and replenishment, were identified at nine time points. Significant APA was found in numerous genes (e.g. five cingulin genes) closely associated with the silicon-starvation response, girdle bands and valve synthesis, suggesting that many genes participated in the responses to silicon availability and biosilica formation through changes in transcript isoforms. The poly(A) site usage profiles were distinct during various stages of silicon biomineralization responses. Moreover, a correlation between APA and expression levels of APA switching genes was also discovered. This is an interesting study that presents a genome-wide profile of transcript ends in diatoms, which is distinct from that of higher plants, animals and other microalgae. This work provides an important resource to understand a different aspect of cell-wall synthesis.

Differential alternative polyadenylation contributes to the developmental divergence between two rice subspecies, japonica and indica.

Alternative polyadenylation (APA) is a widespread post-transcriptional mechanism that regulates gene expression through mRNA metabolism, playing a pivotal role in modulating phenotypic traits in rice (Oryza sativa L.). However, little is known about the APA-mediated regulation underlying the distinct characteristics between two major rice subspecies, indica and japonica. Using a poly(A)-tag sequencing approach, polyadenylation (poly(A)) site profiles were investigated and compared pairwise from germination to the mature stage between indica and japonica, and extensive differentiation in APA profiles was detected genome-wide. Genes with subspecies-specific poly(A) sites were found to contribute to subspecies characteristics, particularly in disease resistance of indica and cold-stress tolerance of japonica. In most tissues, differential usage of APA sites exhibited an apparent impact on the gene expression profiles between subspecies, and genes with those APA sites were significantly enriched in quantitative trait loci (QTL) related to yield traits, such as spikelet number and 1000-seed weight. In leaves of the booting stage, APA site-switching genes displayed global shortening of 3' untranslated regions with increased expression in indica compared with japonica, and they were overrepresented in the porphyrin and chlorophyll metabolism pathways. This phenomenon may lead to a higher chlorophyll content and photosynthesis in indica than in japonica, being associated with their differential growth rates and yield potentials. We further constructed an online resource for querying and visualizing the poly(A) atlas in these two rice subspecies. Our results suggest that APA may be largely involved in developmental differentiations between two rice subspecies, especially in leaf characteristics and the stress response, broadening our knowledge of the post-transcriptional genetic basis underlying the divergence of rice traits.

Tempo-spatial alternative polyadenylation analysis reveals that 3' UTR lengthening of Mdm2 regulates p53 expression and cellular senescence in aged rat testis.

Although tissue aging is accompanied with cellular senescence, it is much complicated than senescence given both types and number of cells change with age. Alternative polyadenylation (APA) had shown tissue specificity and APA-mediated 3' untranslated region (3' UTR) lengthening could regulate senescence-associated phenotypes. However, whether tissue aging shows similar trends remains unknown. Here, we performed a comprehensive analysis on RNA-seq datasets derived from multiple cells and rat tissues of young and old age. Although APA-mediated 3' UTR lengthening in various senescent cells reinforced the previous discovery, tissue aging showed much more complexity in APA. Interestingly, testis was the only tissue displaying dramatic 3' UTR lengthening and decreased expression trend of corresponding genes in aged rat. Genes with longer 3' UTR in aged testis were enriched in senescence-associated pathways, among which, Mdm2, encoding an E3 ligase of p53, favored distal poly(A) site resulting in lengthened 3' UTR and decreased expression. Longer 3' UTR of Mdm2 generated less protein, and decreased Mdm2 expression led to senescence-associated phenotypes along with increased p53 and p21 protein abundance, which could all be reversed by Mdm2 overexpression. Our work revealed complicated APA changes during tissue aging and discovered APA-mediated 3' UTR lengthening of Mdm2 is a hidden layer in regulating the well-known senescence-related p53-p21 signal axis during testis aging, and also has potential implications regarding declined male fertility along aging.

Alternative polyadenylation is involved in auxin-based plant growth and development.

Auxin is widely involved in plant growth and development. However, the molecular mechanism on how auxin carries out this work is unclear. In particular, the effect of auxin on pre-mRNA post-transcriptional regulation is mostly unknown. By using a poly(A) tag (PAT) sequencing approach, mRNA alternative polyadenylation (APA) profiles after auxin treatment were revealed. We showed that hundreds of poly(A) site clusters (PACs) are affected by auxin at the transcriptome level, where auxin reduces PAC distribution in 5'-untranslated region (UTR), but increases in the 3'UTR. APA site usage frequencies of 42 genes were switched by auxin, suggesting that auxin affects the choice of poly(A) sites. Furthermore, poly(A) signal selection was altered after auxin treatment. For example, a mutant of poly(A) signal binding protein CPSF30 showed altered sensitivity to auxin treatment, indicating interactions between auxin and the poly(A) signal recognition machinery. We also found that auxin activity on lateral root development is likely mediated by altered expression of ARF7, ARF19 and IAA14 through poly(A) site switches. Our results shed light on the molecular mechanisms of auxin responses relative to its interactions with mRNA polyadenylation.

Genome-wide dynamics of alternative polyadenylation in rice.

Alternative polyadenylation (APA), in which a transcript uses one of the poly(A) sites to define its 3'-end, is a common regulatory mechanism in eukaryotic gene expression. However, the potential of APA in determining crop agronomic traits remains elusive. This study systematically tallied poly(A) sites of 14 different rice tissues and developmental stages using the poly(A) tag sequencing (PAT-seq) approach. The results indicate significant involvement of APA in developmental and quantitative trait loci (QTL) gene expression. About 48% of all expressed genes use APA to generate transcriptomic and proteomic diversity. Some genes switch APA sites, allowing differentially expressed genes to use alternate 3' UTRs. Interestingly, APA in mature pollen is distinct where differential expression levels of a set of poly(A) factors and different distributions of APA sites are found, indicating a unique mRNA 3'-end formation regulation during gametophyte development. Equally interesting, statistical analyses showed that QTL tends to use APA for regulation of gene expression of many agronomic traits, suggesting a potential important role of APA in rice production. These results provide thus far the most comprehensive and high-resolution resource for advanced analysis of APA in crops and shed light on how APA is associated with trait formation in eukaryotes.

Position-specific intron retention is mediated by the histone methyltransferase SDG725.

BACKGROUND: Intron retention (IR), the most prevalent alternative splicing form in plants, plays a critical role in gene expression during plant development and stress response. However, the molecular mechanisms underlying IR regulation remain largely unknown. RESULTS: Knockdown of SDG725, a histone H3 lysine 36 (H3K36)-specific methyltransferase in rice, leads to alterations of IR in more than 4700 genes. Surprisingly, IR events are globally increased at the 5' region but decreased at the 3' region of the gene body in the SDG725-knockdown mutant. Chromatin immunoprecipitation sequencing analyses reveal that SDG725 depletion results in a genome-wide increase of the H3K36 mono-methylation (H3K36me1) but, unexpectedly, promoter-proximal shifts of H3K36 di- and tri-methylation (H3K36me2 and H3K36me3). Consistent with the results in animals, the levels of H3K36me1/me2/me3 in rice positively correlate with gene expression levels, whereas shifts of H3K36me2/me3 coincide with position-specific alterations of IR. We find that either H3K36me2 or H3K36me3 alone contributes to the positional change of IR caused by SDG725 knockdown, although IR shift is more significant when both H3K36me2 and H3K36me3 modifications are simultaneously shifted. CONCLUSIONS: Our results revealed that SDG725 modulates IR in a position-specific manner, indicating that H3K36 methylation plays a role in RNA splicing, probably by marking the retained introns in plants.

Down-regulation of cancer-associated gene CDC73 contributes to cellular senescence.

Dysregulated gene expression is another important contributor in explaining cancer-related phenotypes in addition to mutations. Cellular senescence is a mechanism for the prevention of cancer and thus it is important to understand the regulation of gene expression in senescence due to its potential in anti-cancer therapy. Here, we found that CDC73, which encodes the cell division cycle 73 and acts as a tumor suppressor, was unexpectedly up-regulated in several cancer types but down-regulated in a variety of senescent cells. Importantly, depletion of CDC73 could induce senescence-associated phenotypes in both normal and cancer cells, with an increase in p21 expression. In terms of molecular mechanism, alternative polyadenylation (APA)-mediated 3' untranslated region (3' UTR) lengthening explained, at least in part, the decreased CDC73 expression in senescent cells because longer 3' UTR had a higher rate of RNA degradation compared to the shorter one. Our work discovered that post-transcriptional down-regulation of CDC73 contributed to cellular senescence.

Mercury in soil, vegetable and human hair in a typical mining area in China: Implication for human exposure.

Concentrations of total mercury (T-Hg) and methylmercury (MeHg) in soil, vegetables, and human hair were measured in a mercury mining area in central China. T-Hg and MeHg concentrations in soil ranged from 1.53 to 1054.97mg/kg and 0.88 to 46.52µg/kg, respectively. T-Hg concentrations was correlated with total organic carbon (TOC) content (R2=0.50, p<0.01) and pH values (R2=0.21, p<0.05). A significant linear relationship was observed between MeHg concentrations and the abundance of sulfate-reducing bacteria (SRB) (R2=0.39, p<0.05) in soil. Soil incubation experiments amended with specific microbial stimulants and inhibitors showed that Hg methylation was derived from SRB activity. T-Hg and MeHg concentrations in vegetables were 24.79-781.02µg/kg and 0.01-0.18µg/kg, respectively; levels in the edible parts were significantly higher than in the roots (T-Hg: p<0.05; MeHg: p<0.01). Hg species concentrations in rhizosphere soil were positively correlated to those in vegetables (p<0.01), indicating that soil was an important source of Hg in vegetables. Risk assessment indicated that the consumption of vegetables could result in higher probable daily intake (PDI) of T-Hg than the provisional tolerable daily intake (PTDI) for both adults and children. In contrast, the PDI of MeHg was lower than the reference dose. T-Hg and MeHg concentrations in hair samples ranged from 1.57 to 12.61mg/kg and 0.04 to 0.94mg/kg, respectively, and MeHg concentration in hair positively related to PDI of MeHg via vegetable consumption (R2=0.39, p<0.05), suggesting that vegetable may pose health risk to local residents.

Identification of the RRM1 gene family in rice (Oryza sativa) and its response to rice blast.

To better understand RNA-binding proteins in rice, a comprehensive investigation was conducted on the RRM1 gene family of rice. It encompassed genome-wide identification and exploration of its role in rice blast resistance. The physicochemical properties of the rice OsRRM1 gene family were analyzed. There genes were also analyzed for their conserved domains, motifs, location information, gene structure, phylogenetic trees, collinearity, and cis-acting elements. Furthermore, alterations in the expression patterns of selected OsRRM1 genes were assessed using quantitative real-time PCR (qRT-PCR). A total of 212 members of the OsRRM1 gene family were identified, which were dispersed across 12 chromosomes. These genes all exhibit multiple exons and introns, all of which encompass the conserved RRM1 domain and share analogous motifs. This observation suggests a high degree of conservation within the encoded sequence domain of these genes. Phylogenetic analysis revealed the existence of five subfamilies within the OsRRM1 gene family. Furthermore, investigation of the promoter region identified cis-regulatory elements that are involved in nucleic acid binding and interaction with multiple transcription factors. By employing GO and KEGG analyses, four RRM1 genes were tentatively identified as crucial contributors to plant immunity, while the RRM1 gene family was also found to have a significant involvement in the complex of alternative splicing. The qRT-PCR results revealed distinct temporal changes in the expression patterns of OsRRM1 genes following rice blast infection. Additionally, gene expression analysis indicates that the majority of OsRRM1 genes exhibited constitutive expressions. These findings enrich our understanding of the OsRRM1 gene family. They also provide a foundation for further research on immune mechanisms rice and the management of rice blast.

Re-rolling treatment in the fermentation process improves the taste and liquor color qualities of black tea.

Fermentation is a vital process occurred under the premise of rolling affecting black tea quality. Theoretically, re-rolling during fermentation will remodel the biochemical conditions of tea leaves, and thus influence black tea quality. Herein, we studied the effect of re-rolling on black tea taste and liquor color. Sensory evaluation showed that re-rolling significantly weakened the astringency taste and improved the redness and luminance of liquor. With re-rolling, the color attributes of a* and L* and the contents of theaflavins and thearubigins were significantly improved. Metabolomics analysis showed that the contents of 110 non-volatile compounds were significantly different among black teas with different rolling treatments. In summary, re-rolling accelerated the oxidation of polyphenols into pigments, the hydrolysis of proteins into amino acids, and the metabolism of alkaloids, organic acids, glycosidically-bound volatiles, and lipids during the fermentation period. Our study provided a novel and simple way to improve black tea quality.

Organochlorine pesticides in the lower reaches of Yangtze River: occurrence, ecological risk and temporal trends.

Residues of 24 organochlorine pesticides (OCPs) including DDT metabolites were investigated in the water and surface sediments from the lower reaches of the Yangtze River to evaluate their pollution and potential risks. Concentrations of OCP residues (ΣOCP24 ranged from 3.07 to 23.70 ng/L in water and 0.67 to 58.80 ng/g dw in sediments) were generally within safe levels, while adverse biological effects are likely from DDT pollution in the lower reaches. HCH and DDT residues dominated the OCPs. High detection rates but low concentrations of some other OCPs, such as chlordane and endosulfan, were detected in both water and sediments. The HCH and DDT residues in the lower reaches primarily originated from historical use of technical HCH and DDT, although additional sources of lindane and dicofol existed in the region. Temporal trends of pesticide contamination levels indicated that HCH concentrations have decreased over the past decades. However, there was no obvious trend of declining DDT concentrations in the sediments from the Yangtze River. The DDT metabolites, DDMU (bis (chlorophenyl)-1-chloroethylene), DBP (dichlorobenzophenone) and DDM (bis (chlorophenyl) methane), were also investigated for the first time in water and sediments from the Yangtze River.

Effects of cadmium on the synthesis of active ingredients in Salvia miltiorrhiza.

Cadmium (Cd) could pose threats to human health by affecting Salvia miltiorrhiza (SM) safety. Cd enrichment trait and its effects on the active ingredient synthesis in SM remain unknown. Here we investigated the Cd concentration using ICP-MS-based method, physiologies (contents of malondialdehyde and proline, and activities of superoxide dismutase, peroxidase [POD], and catalase [CAT]), and LC-MS/MS-based metabolites of SM under 25, 50, and 100 mg kg-1 Cd stress. The results revealed that Cd concentrations, as it rose in soil, increased in roots and leaves of SM with transfer factors and bioconcentration factors below 1 in Cd-treated groups; POD and CAT activities and proline content increased and then declined. Amino acids and organic acids (especially d-glutamine [d-Gln], l-aspartic acid [l-Asp], l-phenylalanine [l-Phe], l-tyrosine [l-Tyr], geranylgeranyl-PP [GGPP], and rosmarinic acid [RA]) contributed more in discriminating SM roots of different groups. GGPP was negatively related to l-Tyr and l-Phe, and RA was positively related to d-Gln and l-Asp in SM. These results revealed that SM belonged to a non-Cd-hyperaccumulator with most Cd accumulated in roots, Cd could enhance phenolic acid synthesis via regulating amino acid metabolism and might inhibit tanshinone synthesis by declining the GGPP content, and proline, POD, and CAT played vital roles in resisting Cd stress. These provided new ideas and theoretical basis for further study on medical plants' response to heavy metals.

Re-Rolling Treatment in the Fermentation Process Improves the Aroma Quality of Black Tea.

Aroma is a vital factor influencing tea quality and value. It is a challenge to produce a kind of black tea with a floral/fruity aroma, good taste, and without a green/grassy odor simultaneously using small- and medium-leaf tea species. In this study, the effect of re-rolling treatment on the aroma quality of small-leaf Congou black tea was investigated using the methods of the equivalent quantification of aroma and gas chromatography-mass spectrometry (GC-MS). Sensory evaluation showed that re-rolling treatment improved the aroma quality of Congou black tea by conferring upon it floral and fruity scents. In total, 179 volatile compounds were identified using GC-MS, of which 97 volatiles showed statistical differences (Tukey s-b(K), p < 0.05). Re-rolling treatment significantly reduced the levels of alcoholic fatty acid-derived volatiles (FADVs) and volatile terpenoid (VTs), but increased the levels of aldehydic and ester FADVs, most amino acid-derived volatiles (AADVs), carotenoid-derived volatiles (CDVs), alkene VTs, and some other important volatile compounds. Based on the odor characteristics and fold changes of differential volatile compounds, hexanoic acid, hexyl formate, cis-3-hexenyl hexanoate, (Z)-3-hexenyl benzoate, hexyl hexanoate, phenylacetaldehyde, benzyl alcohol, ß-ionone, α-ionone, dihydroactinidiolide, ipsenone, ß-farnesene, ß-octalactone, melonal, etc., were considered as the potential key odorants responsible for the floral and fruity scents of re-rolled black tea. In summary, this study provides a novel and simple processing technology to improve the aroma quality of small-leaf Congou black tea, and the results are beneficial to enriching tea aroma chemistry.

Free radical formation via BDE-209 thermolysis in the precalciner of a cement kiln: Simulation and DFT study.

To deeply understand the formation mechanism of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in the thermal disposal process of polybrominated diphenyl ether (PBDE)-containing waste, this paper studied the formation pathways of key intermediates (free radicals, FRs) in the formation process of PBDD/Fs. BDE-209, the most common PBDE in the environment, was selected as the object of study to analyze FR formation by simulating the key conditions such as temperature (850 °C) and Fe-based materials when PBDE-containing waste entering cement kiln precalciner. Electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations were used to study the reaction. The result of simulation experiments revealed carbon-centered radicals, and DMPO-OH analysis further confirmed the generation of FRs. The findings confirmed previous calculations predicting the existence of radical intermediates during the formation of PBDD/Fs from BDE-209. DFT calculations revealed the existence of an inner ortho-position CBr bond in BDE-209. The priority order of the bond breaking of BDE-209 was ether bond, inner ortho-position CBr bond, and outside ortho-position CBr bond. BDE-209 can further form three kinds of FRs, namely, oxygen-centered radicals of single benzene rings, carbon-centered radicals of single benzene rings, and carbon-centered radicals of double benzene rings. The specific processes of FR formation were inferred: high-temperature homogeneous cleavage of chemical bonds, electron transfer, and chemisorption, where electron transfer and chemisorption may be more important pathways. The proposed inner ortho-position cleavage within BDE-209 provides new insights into the degradation of PBDEs and the formation of PBDD/Fs; the results regarding BDE-209 generation radicals further elucidate the synthesis mechanism of dioxins, which is important for controlling dioxin generation and emission during the treatment and disposal of waste containing PBDEs.

Untargeted LC-MS/MS-Based Metabolomic Profiling for the Edible and Medicinal Plant Salvia miltiorrhiza Under Different Levels of Cadmium Stress.

Salvia miltiorrhiza, a medicinal and edible plant, has been extensively applied to treat cardiovascular diseases and chronic hepatitis. Cadmium (Cd) affects the quality of S. miltiorrhiza, posing serious threats to human health. To reveal the metabolic mechanisms of S. miltiorrhiza's resistance to Cd stress, metabolite changes in S. miltiorrhiza roots treated with 0 (CK), 25 (T1), 50 (T2) and 100 (T3) mg kg-1 Cd by liquid chromatography coupled to mass spectrometry (LC-MS/MS) were investigated. A total of 305 metabolites were identified, and most of them were amino acids, organic acids and fatty acids, which contributed to the discrimination of CK from the Cd-treated groups. Among them, S. miltiorrhiza mainly upregulated o-tyrosine, chorismate and eudesmic acid in resistance to 25 mg kg-1 Cd; DL-tryptophan, L-aspartic acid, L-proline and chorismite in resistance to 50 mg kg-1 Cd; and L-proline, L-serine, L-histidine, eudesmic acid, and rosmarinic acid in resistance to 100 mg kg-1 Cd. It mainly downregulated unsaturated fatty acids (e.g., oleic acid, linoleic acid) in resistance to 25, 50, and 100 mg kg-1 Cd and upregulated saturated fatty acids (especially stearic acid) in resistance to 100 mg kg-1 Cd. Biosynthesis of unsaturated fatty acids, isoquinoline alkaloid, betalain, aminoacyl-tRNA, and tyrosine metabolism were the significantly enriched metabolic pathways and the most important pathways involved in the Cd resistance of S. miltiorrhiza. These data elucidated the crucial metabolic mechanisms involved in S. miltiorrhiza Cd resistance and the crucial metabolites that could be used to improve resistance to Cd stress in medicinal plant breeding.