Glutathione S-transferase Gene Expression Research Articles

Role of glutathione S-transferases in the mode of action of herbicides that inhibit amino acid synthesis in Amaranthus palmeri

Acetolactate synthase inhibitors (ALS inhibitors) and glyphosate are two classes of herbicides that act by inhibiting an enzyme in the biosynthetic pathway of branched-chain or aromatic amino acids, respectively. Besides amino acid synthesis inhibition, both herbicides trigger similar physiological effects in plants. The main aim of this study was to evaluate the role of glutathione metabolism, with special emphasis on glutathione S-transferases (GSTs), in the mode of action of glyphosate and ALS inhibitors in Amaranthus palmeri. For that purpose, plants belonging to a glyphosate-sensitive (GLS) and a glyphosate-resistant (GLR) population were treated with different doses of glyphosate, and plants belonging to an ALS-inhibitor sensitive (AIS) and an ALS-inhibitor resistant (AIR) population were treated with different doses of the ALS inhibitor nicosulfuron. Glutathione-related contents, GST activity, and related gene expressions (glutamate-cysteine ligase, glutathione reductase, Phi GST and Tau GST) were analysed in leaves. According to the results of the analytical determinations, there were virtually no basal differences between GLS and GLR plants or between AIS and AIR plants. Glutathione synthesis and turnover did not follow a clear pattern in response to herbicides, but GST activity and gene expression (especially Phi GSTs) increased with both herbicides in treated sensitive plants, possibly related to the rocketing H2O2 accumulation. As GSTs offered the clearest results, these were further investigated with a multiple resistant (MR) population, compressing target-site resistance to both glyphosate and the ALS inhibitor pyrithiobac. As in single-resistant plants, measured parameters in the MR population were unaffected by herbicides, meaning that the increase in GST activity and expression occurs due to herbicide interactions with the target enzymes.

PM2.5-induced DNA oxidative stress in A549 cells and regulating mechanisms by GST DNA methylation and Keap1/Nrf2 pathway

Fine particulate matter (PM2.5) increases the risks of lung cancer. Epigenetics provides a new toxicology mechanism for the adverse health effects of PM2.5. However, the regulating mechanisms of PM2.5 exposure on candidate gene DNA methylation changes in the development of lung cancer remain unclear. Abnormal expression of the glutathione S transferase (GST) gene is associated with cancer. However, the relationship between PM2.5 and DNA methylation-mediated GST gene expression is not well understood. In this study, we performed GST DNA methylation analysis and GST-related gene expression in human A549 cells exposed to PM2.5 (0, 50, 100 µg/mL, from Taiyuan, China) for 24 h (n = 4). We found that PM2.5 may cause DNA oxidative damage to cells and the elevation of GSTP1 promotes cell resistance to reactive oxygen species (ROS). The Kelch-1ike ECH-associated protein l (Keap1)/nuclear factor NF-E2-related factor 2 (Nrf2) pathway activates the GSTP1. The decrease in the DNA methylation level of the GSTP1 gene enhances GSTP1 expression. GST DNA methylation is associated with reduced levels of 5-methylcytosine (5mC), DNA methyltransferase 1 (DNMT1), and histone deacetylases 3 (HDAC3). The GSTM1 was not sensitive to PM2.5 stimulation. Our findings suggest that PM2.5 activates GSTP1 to defend PM2.5-induced ROS and 8-hydroxy-deoxyguanosine (8-OHdG) formation through the Keap1/Nrf2 signaling pathway and GSTP1 DNA methylation.

Distinctive physiological and molecular responses of foxtail millet and maize to nicosulfuron.

Nicosulfuron is the leading acetolactate synthase inhibitor herbicide product, and widely used to control gramineous weeds. Here, we investigated the metabolic process of nicosulfuron into foxtail millet and maize, in order to clarify the mechanism of the difference in sensitivity of foxtail millet and maize to nicosulfuron from the perspective of physiological metabolism and provide a theoretical basis for the breeding of nicosulfuron-resistant foxtail millet varieties. We treated foxtail millet (Zhangzagu 10, Jingu 21) and maize (Nongda 108, Ditian 8) with various doses of nicosulfuron in both pot and field experiments. The malonaldehyde (MDA) content, target enzymes, detoxification enzymes, and antioxidant enzymes, as well as related gene expression levels in the leaf tissues of foxtail millet and maize were measured, and the yield was determined after maturity. The results showed that the recommended dose of nicosulfuron caused Zhangzagu 10 and Jingu 21 to fail to harvest; the yield of the sensitive maize variety (Ditian 8) decreased by 37.09%, whereas that of the resistant maize variety (Nongda 108) did not decrease. Nicosulfuron stress increased the CYP450 enzyme activity, MDA content, and antioxidant enzyme activity of foxtail millet and maize, reduced the acetolactate synthase (ALS) activity and ALS gene expression of foxtail millet and Ditian 8, and reduced the glutathione S-transferase (GST) activity and GST gene expression of foxtail millet. In conclusion, target enzymes, detoxification enzymes, and antioxidant enzymes were involved in the detoxification metabolism of nicosulfuron in plants. ALS and GST are the main factors responsible for the metabolic differences among foxtail millet, sensitive maize varieties, and resistant maize varieties. These findings offer valuable insights for exploring the target resistance (TSR) and non-target resistance (NTSR) mechanisms in foxtail millet under herbicide stress and provides theoretical basis for future research of develop foxtail millet germplasm with diverse herbicide resistance traits.

Validation of biomarkers for neonicotinoid exposure in Folsomia candida under mutual exposure to diethyl maleate.

Neonicotinoid insecticides are harmful to non-target soil invertebrates, which are crucial for sustainable agriculture. Gene expression biomarkers could provide economic and high-throughput metrics of neonicotinoid exposure and toxicity to non-target invertebrates. Thereby, biomarkers can help guide remediation efforts or policy enforcement. Gene expression of Glutathione S-Transferase 3 (GST3) has previously been proposed as a biomarker for the neonicotinoid imidacloprid in the soil ecotoxicological model species Folsomia candida (Collembola). However, it remains unclear how reliably gene expression of neonicotinoid biomarkers, such as GST3, can indicate the exposure to the broader neonicotinoid family under putative GST enzymatic inhibition. In this work, we exposed springtails to two neonicotinoids, thiacloprid and imidacloprid, alongside diethyl maleate (DEM), a known GST metabolic inhibitor that imposes oxidative stress. First, we determined the influence of DEM on neonicotinoid toxicity to springtail fecundity. Second, we surveyed the gene expression of four biomarkers, including GST3, under mutual exposure to neonicotinoids and DEM. We observed no effect of DEM on springtail fecundity. Moreover, the expression of GST3 was only influenced by DEM under mutual exposure with thiacloprid but not with imidacloprid. The results indicate that GST3 is not a robust indicator of neonicotinoid exposure and that probable GST enzymatic inhibition mediates the toxicity of imidacloprid and thiacloprid differentially. Future research should investigate biomarker reliability under shifting metabolic conditions such as provided by DEM exposure.

Differential effects of arsenite and arsenate on rice (Oryza sativa) plants differing in glutathione S-transferase gene expression

Contamination of paddy soils with arsenic (As) can cause phytotoxicity in rice and increase the accumulation of arsenic in grains. The uptake and accumulation of As in rice depends on the different As species present in the soil. Plants detoxify As by conjugating and sequestering xenobiotic compounds into vacuoles using various enzymes. However, the severity of damage induced by arsenite (As(III)) and arsenate (As(V)), as well as the roles of glutathione S-transferase in detoxifying these As species in rice, are not fully understood. In this study, we developed plant materials overexpressing a glutathione S-transferase gene OsGSTU40 under the control of the maize UBIL promoter. Through systematic investigations of both wild-type Nipponbare (Oryza sativa L., ssp. japonica) and OsGSTU40 overexpression lines under chronic or acute stress of As, we aimed to understand the toxic effects of both As(III) and As(V) on rice plants at the vegetative growth stage. We hypothesized that (i) As(III) and As(V) have different toxic effects on rice plants and (ii) OsGSTU40 played positive roles in As toxicity tolerance. Our results showed that As(III) was more detrimental to plant growth than As(V) in terms of plant growth, biomass, and lipid peroxidation in both chronic and acute exposure. Furthermore, overexpression of OsGSTU40 led to better plant growth even though uptake of As(V), but not As(III), into shoots was enhanced in transgenic plants. In acute As(III) stress, transgenic plants exhibited a lower level of lipid peroxidation than wild-type plants. The element composition of plants was dominated by the different As stress treatments rather than by the genotype, while the As concentration was negatively correlated with phosphorus and silicon. Overall, our findings suggest that As(III) is more toxic to plants than As(V) and that glutathione S-transferase OsGSTU40 differentially affects plant reactions and tolerance to different species of arsenic.

Nomilin and its analogue obacunone alleviate NASH and hepatic fibrosis in mice via enhancing antioxidant and anti-inflammation capacity.

Nonalcoholic steatohepatitis (NASH) and hepatic fibrosis are leading causes of cirrhosis with rising morbidity and mortality worldwide. Currently, there is no appropriate treatment for NASH and hepatic fibrosis. Many studies have shown that oxidative stress is a main factor inducing NASH. Nomilin (NML) and obacunone (OBA) are limonoid compounds naturally occurring in citrus fruits with various biological properties. However, whether OBA and NML have beneficial effects on NASH remains unclear. Here, we demonstrated that OBA and NML inhibited hepatic tissue necrosis, inflammatory infiltration and liver fibrosis progression in methionine and choline-deficient (MCD) diet, carbon tetrachloride (CCl4 )-treated and bile duct ligation (BDL) NASH and hepatic fibrosis mouse models. Mechanistic studies showed that NML and OBA enhanced anti-oxidative effects, including reduction of malondialdehyde (MDA) level, increase of catalase (CAT) activity and the gene expression of glutathione S-transferases (GSTs) and Nrf2-keap1 signaling. Additional, NML and OBA inhibited the expression of inflammatory gene interleukin 6 (Il-6), and regulated the bile acid metabolism genes Cyp3a11, Cyp7a1, multidrug resistance-associated protein 3 (Mrp3). Overall, these findings indicate that NML and OBA may alleviate NASH and liver fibrosis in mice via enhancing antioxidant and anti-inflammation capacity. Our study proposed that NML and OBA may be potential strategies for NASH treatment.

Receptor-Like Cytoplasmic Kinase STK Confers Salt Tolerance in Rice

BackgroundSoil salinization is a major abiotic environmental stress factor threatening crop production throughout the world. Salt stress drastically affects the growth, development, and grain yield of rice (Oryza sativa L.), and the improvement of rice tolerance to salt stress is a desirable approach for meeting increasing food demand. Receptor-like cytoplasmic kinases (RLCKs) play essential roles in plant growth, development and responses to environmental stresses. However, little is known about their functions in salt stress. Previous reports have demonstrated that overexpression of an RLCK gene SALT TOLERANCE KINASE (STK) enhances salt tolerance in rice, and that STK may regulate the expression of GST (Glutathione S-transferase) genes.ResultsThe expression of STK was rapidly induced by ABA. STK was highest expressed in the stem at the heading stage. STK was localized at the plasma membrane. Overexpression of STK in rice increased tolerance to salt stress and oxidative stress by increasing ROS scavenging ability and ABA sensitivity. In contrast, CRISPR/Cas9-mediated knockout of STK increased the sensitivity of rice to salt stress and oxidative stress. Transcriptome sequencing analysis suggested that STK increased the expression of GST genes (LOC_Os03g17480, LOC_Os10g38140 and LOC_Os10g38710) under salt stress. Reverse transcription quantitative PCR (RT-qPCR) suggested that four stress-related genes may be regulated by STK including OsABAR1, Os3BGlu6, OSBZ8 and OsSIK1.ConclusionsThese findings suggest that STK plays a positive regulatory role in salt stress tolerance by inducing antioxidant defense and associated with the ABA signaling pathway in rice.

Changes in hepatic thiol contents and regulation of glutathione S-transferase by high-fructose diet: Effects of kefir and some probiotic bacteria

In this study, thiol/disulfide homeostasis in the liver tissues of high-fructose-fed rats was investigated in conjunction with the changes in the main hepatic detoxification enzyme, glutathione S-transferase (GST). Additionally, the effects of well-known probiotics namely Kefir, Lactobacillus helveticus, and Lactobacillus plantarum supplementation on the thiol/disulfate contents and GST activity and gene expression levels were analyzed. Fructose, administered as a 20% solution in drinking water for 15 weeks, developed an animal model of metabolic syndrome in male Wistar rats. Kefir, L. helveticus, and L. plantarum supplementations were given by gastric gavage once a day during the final 6-weeks. The changes in hepatic GST were determined with kinetic-optimized spectrophotometric enzyme assays and qRT-PCR. Total thiol, native thiol, and disulfide levels were analyzed using (5,5-dithio-bis-(2-nitrobenzoic acid) as a chromogenic agent. High-fructose consumption reduced total and native thiol contents while increasing disulfide levels in the liver tissues of rats. Kefir and L. plantarum normalized the thiol levels and all probiotics reduced disulfide contents. High fructose augmented total GST activity but reduced the GST-Mu isoform. L. helveticus and L. plantarum normalized the total and GST-Mu activity, respectively. These results demonstrated a shift toward disulfide formation in the hepatic tissues of rats fed with high fructose. A possible reason would be the increase in total GST activity that uses the free glutathione, the main native thiol source in cells, as a substrate. Besides, probiotics such as Kefir, L. helveticus, and L. plantarum have an improving effect on thiol/disulfide homeostasis as well as main detoxification enzymes.

Transcription Factor AhR Regulates Glutathione S-Transferases Conferring Resistance to lambda-Cyhalothrin in Cydia pomonella.

Aryl hydrocarbon receptor (AhR) enhances insect resistance to insecticides by regulating the detoxification network. Our previous studies have confirmed that overexpressions of cytochrome P450 monooxygenases (P450s) and glutathione S-transferases (GSTs) are involved in lambda-cyhalothrin resistance in Cydia pomonella. Here, we report that CpAhR regulates the expression of GST and P450 genes, thus conferring resistance. Expression patterns indicated that the expression of CpAhR was highly induced by lambda-cyhalothrin exposure and upregulated in a lambda-cyhalothrin-resistant population. RNA interference (RNAi) of CpAhR decreases the expression of key resistance-related genes (CpGSTe3, CpCYP9A121, and CpCYP9A122) and the activity of the GST enzyme, reducing the tolerance to lambda-cyhalothrin. Furthermore, β-naphthoflavone, a novel agonist of AhR, was first proven to be effective in increasing CpAhR expression and larval tolerance to lambda-cyhalothrin. These results demonstrate that CpAhR regulates the expression of key detoxifying genes and GST activity, resulting in the development of resistance to lambda-cyhalothrin in C. pomonella.

Genes encoding cytochrome P450 monooxygenases and glutathione S-transferases associated with herbicide resistance evolved before the origin of land plants.

Cytochrome P450 (CYP) monooxygenases and glutathione S-transferases (GST) are enzymes that catalyse chemical modifications of a range of organic compounds. Herbicide resistance has been associated with higher levels of CYP and GST gene expression in some herbicide-resistant weed populations compared to sensitive populations of the same species. By comparing the protein sequences of 9 representative species of the Archaeplastida-the lineage which includes red algae, glaucophyte algae, chlorophyte algae, and streptophytes-and generating phylogenetic trees, we identified the CYP and GST proteins that existed in the common ancestor of the Archaeplastida. All CYP clans and all but one land plant GST classes present in land plants evolved before the divergence of streptophyte algae and land plants from their last common ancestor. We also demonstrate that there are more genes encoding CYP and GST proteins in land plants than in algae. The larger numbers of genes among land plants largely results from gene duplications in CYP clans 71, 72, and 85 and in the GST phi and tau classes [1,2]. Enzymes that either metabolise herbicides or confer herbicide resistance belong to CYP clans 71 and 72 and the GST phi and tau classes. Most CYP proteins that have been shown to confer herbicide resistance are members of the CYP81 family from clan 71. These results demonstrate that the clan and class diversity in extant plant CYP and GST proteins had evolved before the divergence of land plants and streptophyte algae from a last common ancestor estimated to be between 515 and 474 million years ago. Then, early in embryophyte evolution during the Palaeozoic, gene duplication in four of the twelve CYP clans, and in two of the fourteen GST classes, led to the large numbers of CYP and GST proteins found in extant land plants. It is among the genes of CYP clans 71 and 72 and GST classes phi and tau that alleles conferring herbicide resistance evolved in the last fifty years.

Salt stress improves the low-temperature tolerance in sugar beet in which carbohydrate metabolism and signal transduction are involved

Low temperatures can inhibit crop growth and yield. To investigate the physiological mechanisms by which salt stress affects low temperature tolerance, sugar beet seedlings subjected to low temperature stress after treated with 0, 200 and 400 mM NaCl were analyzed for physiome, transcriptome and metabolome profiles. Salt stress significantly alleviated the maximum quantum efficiency of PS II (Fv/Fm) and the reduction of relative leaf water content (RWC) caused by low temperature. Salt stress enhanced reactive oxygen species (ROS) metabolism and significantly increased the activities of superoxide dismutase, peroxidase (POX) and dehydroascorbate reductase, and it also increased the gene expression of glutathione S-transferase, POX and L-ascorbate peroxidase. Meanwhile, salt stress also contributed to the increase in carbohydrate enzyme activities (e.g. vacuolar invertase, hexokinase and fructokinase) and gene expression. Salt stress resulted in a decrease in sucrose concentration and an increase in proline concentration. Sucrose concentration was significantly and negatively correlated with the gene expression of the signal transduction pathway. Additionally, the expression of genes related to abscisic acid (protein phosphatase 2 C and receptor), gibberellin signaling (DELLA and F-box protein) and 3-ketoacyl-CoA synthase was significantly increased by salt stress under low temperature. These results suggest that salt stress regulated ROS metabolism, carbohydrate metabolism and hormone signaling, thereby enhancing low temperature tolerance in sugar beet.

Genome-wide screening and expression of glutathione S-transferase genes reveal that GSTe4 contributes to sensitivity against β-cypermethrin in Zeugodacus cucurbitae

Glutathione S-transferases (GSTs) are an essential multifunctional protein family with common detoxifying enzymes. In this study, 34 GST genes were identified from the melon fly, Zeugodacus cucurbitae, one of the most destructive pests worldwide. These GSTs include 32 cytosolic genes and two microsomal genes. Furthermore, these cytosolic GSTs were classified into six classes: 11 delta, 13 epsilon, three theta, one sigma, two zeta, and two omega. Most of these showed dynamic expression during the developmental stage, some of which showed stage-specific expression. The expression in various adult tissues showed that most of them were expressed in anti-stress-related tissues. The transcriptional response of the delta and epsilon families was determined when Z. cucurbitae was exposed to three insecticides, abamectin, dinotefuran, and β-cypermethrin. Seven genes were significantly up-regulated by abamectin exposure. Moreover, five and four genes were significantly up-regulated with dinotefuran and β-cypermethrin exposure, respectively, demonstrating their involvement in the detoxification of these such toxic substances in Z. cucurbitae. One example of these genes, ZcGSTe4, was randomly selected to explore its function in response to β-cypermethrin exposure. Over-expressed ZcGSTe4 in E. coli showed significant tolerance to β-cypermethrin, and RNAi-mediated suppression of ZcGSTe4 also increased the sensitivity of melon fly to this agent. This study provides a foundation for further studies on the mechanism of detoxification metabolism in the melon fly.

Effects of blueberry anthocyanins on perfluorooctane sulfonate-induced oxidative stress and mitochondrial dysfunction in dugesia japonica

The effects of blueberry anthocyanins against perfluorooctane sulfonate on antioxidant-related gene expression levels, antioxidase activities, malondialdehyde content, glutathione/oxidized glutathione ratios, mitochondrial metabolic enzyme activities, and mitochondrial permeability transition pore opening rates were examined in the planarian Dugesia japonica. Glutathione reductase, glutathione peroxidase, and glutathione S-transferase gene expression levels were up-regulated on day 1 and then down-regulated following exposure to 5 mg/L perfluorooctane sulfonate with those of the control. The activities of the three corresponding enzymes were inhibited by perfluorooctane sulfonate and activated by anthocyanins. Malondialdehyde contents and mitochondrial permeability transition pore opening rates as well as the activities of mitochondrial metabolic enzymes, also increased and the glutathione/oxidized glutathione ratio decreased. Anthocyanin treatments have an alleviating effect on the disorder caused by perfluorooctane sulfonate.

Evaluation of metabolic stress status in common carp (Cyprinus carpio) exposed to the fungicide folpet

Among pesticides, fungicides are the most extensively used ones in agriculture and their effects on fish health and indirectly human health are needed to evaluate. Folpet has been used for over 50 years as a fungicide across the world. The mechanism of action of folpet on non-target aquatic organisms is so poorly understood and there is no available information about potential acute toxicity of folpet and its mechanism of action in non-target aquatic organisms. With this motivation, two successive experiments were set up: first, 96 h-LC50 value of folpet for common carp (Cyprinus carpio) was determined; and second, effects of different sublethal concentrations (0, 0.025, 0.50, 0.1 and 0.15 mg/L) of folpet on hematological serum biochemical blood parameters, DNA damages, expression levels of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and cortisol receptor (HSP70) genes were evaluated in this study. It was calculated that 0.199 mg/L of folpet was the 96 h-LC50 value. After the folpet exposure for 14 days, significant decreases in red blood cells, hemoglobin, hematocrit, serum total protein, and GST gene expression levels were observed while serum glucose, liver enzymes activities, and expression levels of CAT, SOD, GPx, HSP70 genes increased. Also, folpet induced a significant genotoxic effect on the blood cells regarding to DNA damages. Consequently, the results have shown the toxic effects of folpet even at the lowest concentration on common carp.

Molecular Cloning of a TCHQD Class Glutathione S-Transferase and GST Function in Response to GABA Induction of Melon Seedlings under Root Hypoxic Stress

Glutathione-S-transferase (GST), a versatile enzyme that occurs widely in plants, plays a key role in plant resistance to environmental stresses. Previous results have demonstrated that GST proteins are involved in alleviating root hypoxic injury caused by gamma-aminobutyric acid (GABA); however, the induction mechanism of the GST gene in the melon under root hypoxic stress and its functional mechanisms remain unclear. In this study, based on gene cloning and bioinformatics analysis, GST gene expression and activity and glutathione (GSH) content were assessed under root hypoxic and normoxic conditions with or without GABA. The results showed that the CmGST locus includes an 804 bp gene sequence that encodes 267 amino acids. The sequence was highly similar to those of other plant TCHQD GSTs, and the highest value (94%) corresponded to Cucumis sativus. Real-time PCR results showed that the CmGST gene was induced by root hypoxic stress and GABA, and this induction was accompanied by increased GST activity and GSH content. Root hypoxic stress significantly upregulated CmGST expression in melon roots (0.5–6 d), stems, and leaves (0.5–4 d), and GST activity and GSH content were also significantly increased. Exogenous GABA treatment upregulated CmGST gene expression, GST activity, and GSH content, particularly under root hypoxic conditions. As a result, CmGST expression in GABA-treated roots and leaves at 0.5–4 d and stems at 0.5–6 d was significantly higher than that under root hypoxic stress alone. This study provides evidence that the TCHQD CmGST may play a vital role in how GABA increases melon hypoxia tolerance by upregulating gene expression and improving metabolism.

Cytochrome P450 and Glutathione S-Transferase Confer Metabolic Resistance to SYP-14288 and Multi-Drug Resistance in Rhizoctonia solani.

SYP-14288 is a fungicide as an uncoupler of oxidative phosphorylation, which is effective in controlling fungal pathogens like Rhizoctonia solani. To determine whether R. solani can develop SYP-14288 resistance and possibly multi-drug resistance (MDR), an SYP-14288-resistant mutant of R. solani X19-7 was generated from wild-type strain X19, and the mechanism of resistance was studied through metabolic and genetic assays. From metabolites of R. solani treated with SYP-14288, three compounds including M1, M2, and M3 were identified according to UPLC-MS/MS analysis, and M1 accumulated faster than M2 and M3 in X19-7. When X19-7 was treated by glutathione-S-transferase (GST) inhibitor diethyl maleate (DEM) and SYP-14288 together, or by DEM plus one of tested fungicides that have different modes of action, a synergistic activity of resistance occurred, implying that GSTs promoted metabolic resistance against SYP-14288 and therefore led to MDR. By comparing RNA sequences between X19-7 and X19, six cytochrome P450s (P450s) and two GST genes were selected as a target, which showed a higher expression in X19-7 than X19 both before and after the exposure to SYP-14288. Furthermore, heterologous expression of P450 and GST genes in yeast was conducted to confirm genes involved in metabolic resistance. In results, the P450 gene AG1IA_05136 and GST gene AG1IA_07383 were related to fungal resistance to multiple fungicides including SYP-14288, fluazinam, chlorothalonil, and difenoconazole. It was the first report that metabolic resistance of R. solani to uncouplers was associated with P450 and GST genes.

Effects of diisononyl phthalate exposure on the oxidative stress and gut microorganisms in earthworms (Eisenia fetida)

Phthalate esters (PAEs) are widely used as plasticizers and can be ubiquitously detected in environment. However, the toxic effects and mechanisms of diisononyl phthalate (DINP) on earthworms are still poorly understood. In this study, earthworms (Eisenia fetida) were exposed to DINP at various doses (0, 300, 600, 1200, and 2400 mg/kg) to investigate their subchronic toxicity. The results demonstrated that the reactive oxygen species (ROS) levels displayed an “increase-decrease” trend with the increasing DINP doses after DINP exposure on days 7, 14, 21, and 28. The malondialdehyde (MDA) content increased with increasing DINP doses on days 7, 14, and then decreased on days 21, 28. The values of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) showed similar variation patterns and reached a maximum level on 21 d. Moreover, on day 28, the SOD and CAT gene expression levels were upregulated, while the GST gene expression levels were downregulated. Meanwhile, 16S rRNA genes of E. fetida gut bacteria and surrounding soil bacteria were measured after 28 days of exposure to DINP. The Chao index of E. fetida gut bacteria decreased when the treatment with the highest concentration (2400 mg/kg) was applied. At the phylum level, the abundance of Chloroflexi was significantly lower in the gut of E. fetida. In addition, the abundance of Proteobacteria at the phylum level and Ottowia at the genus level significantly increased in the surrounding soil. Overall, our results shed light on the toxic mechanism of DINP at biochemical, molecular, and omics levels, and contributed to a better understanding of the ecotoxicity of DINP.

The roles of GSTs in fipronil resistance in Nilaparvata lugens: Over-expression and expression induction

As one of the most important detoxification enzymes in insects, Glutathione S-transferases (GSTs) play key roles in insecticide resistance via direct metabolism and protection against oxidative stress induced by insecticide exposure. Insect GSTs are often considered as the phase II detoxification enzymes, they have potential function to metabolize fipronil as well as its fipronil's metabolites. In the fipronil-resistant Nilaparvata lugens strain G28, GSTs' inhibitor DEM (diethyl maleate) showed the optimal synergistic effects (5.73-fold), indicating the essential roles of GSTs in the resistance to fipronil in this insect species. Four GST genes, NlGSTs1, NlGSTs2, NlGSTe1 and NlGSTd1, were found over-expressed in G28 when compared to its relative susceptible counterpart strain S28. The roles of these four GSTs in fipronil resistance were confirmed via RNAi. The four GST genes were highly over-expressed in the midgut and/or fat body with detoxification action, which might provide more chances for insects to metabolize fipronil and its metabolites. Additionally, the higher induction levels in the GST gene expression by insecticides in the midgut and/or fat body compared to the whole insect also supported the significant roles of the four GSTs in the detoxification. Above all, the results provided evidences to understand the functions of GSTs in fipronil resistance in N. lugens, and gave a reference for other insects in fipronil resistance.

Caloric restriction increases levels of taurine in the intestine and stimulates taurine uptake by conjugation to glutathione

Our previous study indicated increased levels of taurine-conjugated bile acids (BA) in the intestine content of mice submitted to caloric restriction (CR). In the current project, we found increased levels of free taurine and taurine conjugates, including glutathione (GSH)-taurine, in CR compared to ad libitum fed animals in the mucosa along the intestine but not in the liver. The levels of free GSH were decreased in the intestine of CR compared to ad libitum fed mice. However, the levels of oxidized GSH were not affected and were complemented by the lack of changes in the antioxidative parameters. Glutathione-S transferases (GST) enzymatic activity was increased as was the expression of GST genes along the gastrointestinal tract of CR mice. In the CR intestine, addition of GSH to taurine solution enhanced taurine uptake. Accordingly, the expression of taurine transporter (TauT) was increased in the ileum of CR animals and the levels of free and BA-conjugated taurine were lower in the feces of CR compared to ad libitum fed mice. Fittingly, BA- and GSH-conjugated taurine levels were increased in the plasma of CR mice, however, free taurine remained unaffected. We conclude that CR-triggered production and release of taurine-conjugated BA in the intestine results in increased levels of free taurine what stimulates GST to conjugate and enhance uptake of taurine from the intestine.

Different effects of two dietary levels of tea polyphenols on the lipid deposition, immunity and antioxidant capacity of juvenile GIFT tilapia (Oreochromis niloticus) fed a high-fat diet

Long-term feeding of fish with a high-fat diet (HFD) causes excess fat deposition and an impairment of immune function. In the present study, we aimed to determine whether dietary tea polyphenols (TPs) would ameliorate the adverse effects of HFD-feeding in GIFT tilapia. Juvenile GIFT tilapias (5.4 ± 0.9 g) were raised in twelve 200-L tanks (three tanks per diet, 20 fish per tank) and fed a control diet (6% fat, 36% protein), an HFD (12% fat, 36% protein), or an HFD supplemented with 50 mg/kg or 200 mg/kg TP for 8 weeks. The fish were hand-fed 5% of their body weight per day in three feeds, and maintained at 28 ± 1 °C under a 14-h light/10-h dark cycle. The fish in each tank were bulk weighed and counted fortnightly, and the daily feed amount was adjusted accordingly. At the end of the trial, the cumulative survival rate was calculated, and the weight gain and feed conversion ratio were calculated according to the bulk weight of fish in each tank. Tissues were collected from nine fish per diet, their organs were weighed, and biochemical and molecular indices were subsequently measured. HFD-feeding significantly increased lipid deposition, reduced cumulative survival from 96% to 75%, reduced hepatic alkaline phosphate activity (AKP) and serum total antioxidant capacity (T-AOC); and reduced the hepatic expression of immunoglobulin M (IgM), transforming growth factor-beta (TGF-β) and glutathione-S-transferase (GST) genes versus the control diet. The addition of TPs at 50 or 200 mg/kg both ameliorated the HFD-induced increase in lipid droplets in the liver (50 mg/kg TP from 40.83% to 17.27%; 200 mg/kg TP to 25.33%), and increased the cumulative survival rate of the tilapia. The addition of 50 mg/kg TP had a marked effect increasing cumulative survival to 90%, and increasing the activities of serum acid phosphatase (ACP), T-AOC; and IgM, TGF-β, nuclear factor-κB (NF-κB), superoxide dismutase (SOD), and GST gene expression to the highest level of the HFD-fed groups. The 50 mg/kg TP-containing diet also significantly increased the hepatic expression of carnitine palmitoyltransferase 1 alpha (CPT1α) versus the control diet. In contrast, the tilapia fed an HFD supplemented with 200 mg/kg TPs had the lowest expression of adipose triglyceride lipase, hormone-sensitive lipase, CPT1α, fatty acid synthase and acetyl-CoA carboxylase alpha genes of any of the groups, which implies that the lower and higher levels of TP supplementation have differing effects on lipid metabolism. The 200 mg/kg supplement had lower cumulative survival rate (82%), and smaller effects on serum ACP and hepatic AKP activities than the 50 mg/kg dose, and had no significant effect on serum T-AOC or the expression of IgM, TGF-β, GST, or NF-κB genes in the tilapia. These results indicate that the beneficial effects of TPs on the lipid metabolism and health of fish fed an HFD are dose-related. Moreover, they are likely to be largely mediated through lipid catabolism.