Class Glutathione S-transferase Research Articles

An Epsilon Class Glutathione S-Transferase Gene Contributes to the Phytochemical Susceptibility of Tribolium castaneum (Coleoptera: Tenebrionidae)1

Abstract Evidence is accumulating that insect epsilon class glutathione S-transferases (GSTs) play an important role in the resistance to xenobiotics such as insecticides. A Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) epsilon class GST gene, TcGSTe17, was previously found to be significantly induced following exposure to the plant derivative eucalyptol. However, whether TcGSTe17 is involved in resistance to eucalyptol remains unclear. In this study, TcGSTe17 was cloned from the T. castaneum. Development stage expression profiling revealed that TcGSTe17 was expressed at all development stages of T. castaneum but was highly expressed in late-stage larvae. Subsequent expression profiling of tissues showed that TcGSTe17 was highly expressed in the gut of larvae and the fat body of adults, and also revealed gender-specific expression patterns. In addition, the transcripts of TcGSTe17 were significantly increased following exposure to eucalyptol, and RNAi increased the susceptibility of the beetles to eucalyptol. Collectively, these results suggest that TcGSTe17 contributes to the susceptibility of T. castaneum to eucalyptol. These findings provide new data for the prevention of pest resistance.

Architecture and potential roles of a delta-class glutathione S-transferase in protecting honey bee from agrochemicals

The European honey bee, Apis mellifera, serves as the principle managed pollinator species globally. In recent decades, honey bee populations have been facing serious health threats from combined biotic and abiotic stressors, including diseases, limited nutrition, and agrochemical exposure. Understanding the molecular mechanisms underlying xenobiotic adaptation of A. mellifera is critical, considering its extensive exposure to phytochemicals and agrochemicals present in the environment. In this study, we conducted a comprehensive structural and functional characterization of AmGSTD1, a delta class glutathione S-transferase (GST), to unravel its roles in agrochemical detoxification and antioxidative stress responses. We determined the 3-dimensional (3D) structure of a honey bee GST using protein crystallography for the first time, providing new insights into its molecular structure. Our investigations revealed that AmGSTD1 metabolizes model substrates, including 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrophenyl acetate (PNA), phenylethyl isothiocyanate (PEITC), propyl isothiocyanate (PITC), and the oxidation byproduct 4-hydroxynonenal (HNE). Moreover, we discovered that AmGSTD1 exhibits binding affinity with the fluorophore 8-Anilinonaphthalene-1-sulfonic acid (ANS), which can be inhibited with various herbicides, fungicides, insecticides, and their metabolites. These findings highlight the potential contribution of AmGSTD1 in safeguarding honey bee health against various agrochemicals, while also mitigating oxidative stress resulting from exposure to these substances.

Identification of putative promoter elements for epsilon glutathione s-transferases genes associated with resistance to DDT in the malaria vector mosquito anopheles arabiensis

The purpose of this study was to identify the putative regulatory elements in the promoter region of An. arabiensis strains which differed in susceptibility to DDT and compare with those identified in its sibling An. gambaie. Basal expression level of Epsilon class GSTs (Glutathione S – transferases) GSTe1 gene was 0.512 – 0.658 (95% CI) and GSTe2 0.672 – 1.204 (95% CI) in adults of DDT resistant KGB compared to 0.031 – 0.04 (95% CI) and 0.148 – 0.199 (95% CI) respectively in susceptible MAT strains of An. arabiensis. Induced mean expression of GSTe2 in larvae exposed to DDT for one hour was 0.901 – 1.172 (95% CI) in KGB and 0.475 – 0.724 (95% CI) in MAT strain. In present work, strain specific primers were used to amplify and sequenced the promoter regions of GSTe1 and GSTe2 in the KGB, MAT and field specimens. Computational analysis revealed presence of classical arthropod initiator sequence TCAGT and putative core promoter elements, GC, CAAT, TATA boxes. A typical TATA box was identified at 35 bp upstream Transcription Start Site (TSS) in GSTe1 but was absent in GSTe2. Several binding sites for regulatory elements downstream and multiple polymorphic sites were identified between strains. The role of these regulatory elements in transcription of these genes has not been determined. However, on comparison the 2 bp adenosine indel (insertion/deletion) which was essential in driving the promoter activity in An. gambiae was identified only DDT resistant KGB strain.

Epsilon Class Glutathione S-Transferase Confers Phoxim Tolerance in the Black Cutworm Agrotis ipsilon (Lepidoptera: Noctuidae).

The black cutworm Agrotis ipsilon is a serious crop pest. Phoxim, an organophosphorus insecticide, has been widely used to control A. ipsilon. When phoxim is extensively applied, the susceptibility of A. ipsilon to insecticide is reduced. However, the mechanisms of tolerance of A. ipsilon to phoxim remain unclear. Herein, we report that an epsilon class glutathione S-transferase, AiGSTE1, confers phoxim tolerance in A. ipsilon. Exposure to a sublethal concentration (LC50) of phoxim caused oxidative stress and activated the transcription of AiGSTe1 genes in A. ipsilon larvae. Recombinant AiGSTE1 expressed in Escherichia coli could metabolize phoxim. Furthermore, E. coli cells overexpressing AiGSTE1 displayed significant tolerance to oxidative stress. Knockdown of AiGSTe1 by RNA interference significantly increased the mortality of A. ipsilon larvae to phoxim. These results demonstrate that AiGSTE1 confers phoxim tolerance in A. ipsilon by metabolizing the insecticide and preventing phoxim-induced oxidative stress.

Identification and Functional Analysis of an Epsilon Class Glutathione S-Transferase Gene Associated with α-Pinene Adaptation in Monochamus alternatus.

Alpha-pinene is one of the main defensive components in conifers. Monochamus alternatus (Coleoptera: Cerambycidae), a wood borer feeding on Pinaceae plants, relies on its detoxifying enzymes to resist the defensive terpenoids. Here, we assayed the peroxide level and GST activity of M. alternatus larvae treated with different concentrations of α-pinene. Meanwhile, a gst gene (MaGSTe3) was isolated and analyzed. We determined its expression level and verified its function. The results showed that α-pinene treatment led to membrane lipid peroxidation and thus increased the GST activity. Expression of MaGSTe3 was significantly upregulated in guts following exposure to α-pinene, which has a similar pattern with the malonaldehyde level. In vitro expression and disk diffusion assay showed that the MaGSTe3 protein had high antioxidant capacity. However, RNAi treatment of MaGSTe3 did not reduce the hydrogen peroxide and malonaldehyde levels, while GST activity was significantly reduced. These results suggested MaGSTe3 takes part in α-pinene adaptation, but it does not play a great role in the resistance of M. alternatus larvae to α-pinene.

A tau class glutathione S-transferase in tea plant, CsGSTU45, facilitates tea plant susceptibility to Colletotrichum camelliae infection mediated by jasmonate signaling pathway.

Tea plant [Camellia sinensis (L.) O. Kuntze], as one of the most important commercial crops, frequently suffers from anthracnose caused by Colletotrichum camelliae. The plant-specific tau (U) class of glutathione S-transferases (GSTU) participates in ROS homeostasis. Here, we identified a plant-specific GST tau class gene from tea plant, CsGSTU45, which is induced by various stresses, including C. camelliae infection, by analyzing multiple transcriptomes. CsGSTU45 plays a negative role in disease resistance against C. camelliae by accumulating H2 O2 . JA negatively regulates the resistance of tea plants against C. camelliae, which depends on CsGSTU45. CsMYC2.2, which is the key regulator in the JA signaling pathway, directly binds to and activates the promoter of CsGSTU45. Furthermore, silencing CsMYC2.2 increased disease resistance associated with reduced transcript and protein levels of CsGSTU45, and decreased contents of H2 O2 . Therefore, CsMYC2.2 suppresses disease resistance against C. camelliae by binding to the promoter of the CsGSTU45 gene and activating CsGSTU45. CsJAZ1 interacts with CsMYC2.2. Silencing CsJAZ1 attenuates disease resistance, upregulates the expression of CsMYC2.2 elevates the level of the CsGSTU45 protein, and promotes the accumulation of H2 O2 . As a result, CsJAZ1 interacts with CsMYC2.2 and acts as its repressor to suppress the level of CsGSTU45 protein, eventually enhancing disease resistance in tea plants. Taken together, the results show that the JA signaling pathway mediated by CsJAZ1-CsMYC2.2 modulates tea plant susceptibility to C. camelliae by regulating CsGSTU45 to accumulate H2 O2 .

OsGSTU17, a Tau Class Glutathione S-Transferase Gene, Positively Regulates Drought Stress Tolerance in Oryza sativa.

As a great threat to the normal growth of rice, drought not only restricts the growth of rice, but also affects its yield. Glutathione S-transferases (GSTs) have antioxidant and detoxification functions. In rice, GSTs can not only effectively cope with biological stress, but also play a defense role against abiotic stress. In this study, we selected OsGSTU17, a member gene that was induced by drought, to explore the role of GSTs and analyze their physiological mechanisms that are involved in rice drought tolerance. With the CRISPR/Cas9 knockout system techniques, we obtained two independent mutant lines of osgstu17. After 14 days of drought stress treatment, and then re-supply of the water for 10 days, the survival rate of the osgstu17 mutant lines was significantly reduced compared to the wild-type (WT). Similarly, with the 10% (w/v) PEG6000 hydroponics experiment at the seedling stage, we also found that compared with the WT, the shoot and root biomass of osgstu17 mutant lines decreased significantly. In addition, both the content of the MDA and H2O2, which are toxic to plants, increased in the osgtu17 mutant lines. On the other hand, chlorophyll and proline decreased by about 20%. The activity of catalase and superoxide dismutase, which react with peroxides, also decreased by about 20%. Under drought conditions, compared with the WT, the expressions of the drought stress-related genes OsNAC10, OsDREB2A, OsAP37, OsP5CS1, OsRAB16C, OsPOX1, OsCATA, and OsCATB in the osgtu17 mutant lines were significantly decreased. Finally, we concluded that knocking out OsGSTU17 significantly reduced the drought tolerance of rice; OsGSTU17 could be used as a candidate gene for rice drought-tolerant cultivation. However, the molecular mechanism of OsGSTU17 involved in rice drought resistance needs to be further studied.

Functional characterization of SlGSTD3 and SlGSTD4 associated with phoxim and chlorpyrifos resistance in Spodoptera litura

Glutathione S-transferases (GSTs) is one of the main detoxification enzyme systems in insects and play important roles in insecticide resistance by direct metabolism, sequestration and antioxidant activity. Several GSTs genes in Spodoptera litura, a polyphagous agricultural pest, have been demonstrated to be overexpressed and involved in organophosphates and pyrethroids resistance. Previous studies have indicated the significant overexpression of two delta class GSTs genes (SlGSTd3 and SlGSTd4) in organophosphates and pyrethroids resistant populations. Here, they were heterologous expressed, and their metabolism activity and antioxidant activity were determined. Results indicated that the recombinant protein SlGSTD3 and SlGSTD4 both showed metabolism activity to phoxim and chlorpyrifos, but not to fenvalerate, cyhalothrin or beta cypermethrin. The metabolism activity of SlGSTD3 to phoxim and chlorpyrifos is higher than that of SlGSTD4. The recombinant vector of SlGSTD3 and SlGSTD4 both showed antioxidant activity after exposure to cumene hydroperoxide. Further modeling and docking analysis indicated that the 3D structure of SlGSTD3 and SlGSTD4 were well shaped for phoxim and chlorpyrifos, and the binding affinity for phoxim was stronger than that of chlorpyrifos. Our work provides evidence that SlGSTd3 and SlGSTd4 both play roles in phoxim and chlorpyrifos resistance in S. litura.

Sublethal effects of halofenozide on larval development and detoxification in Phaedon brassicae (Coleoptera: Chrysomelidae).

The brassica leaf beetle, Phaedon brassicae, is a serious defoliator of cruciferous crops. Halofenozide (Hal), an ecdysone agonist, is a new class of insect growth-regulating insecticide. Our preliminary experiment revealed the outstanding larval toxicity of Hal against P. brassicae. However, the metabolic degradation of this compound in insects remains unclear. In this study, oral administration of Hal at LC10 and LC25 caused severe separation of the cuticle and epidermis, leading to larval molting failure. Sublethal dose exposure also significantly reduced the larval respiration rate as well as their pupation rates and pupal weights. Conversely, the activities of the multifunctional oxidase, carboxylesterase (CarE), and glutathione S-transferase (GST) were significantly enhanced in Hal-treated larvae. Further analysis using RNA sequencing identified 64 differentially expressed detoxifying enzyme genes, including 31 P450s, 13 GSTs, and 20 CarEs. Among the 25 upregulated P450s, 22 genes were clustered into the CYP3 clan, and the other 3 genes belonged to the CYP4 clan. Meanwhile, 3 sigma class GSTs and 7 epsilon class GSTs were dramatically increased, accounting for the majority of the upregulated GSTs. Moreover, 16 of the 18 overexpressed CarEs were clustered into the coleopteran xenobiotic-metabolizing group. These results showed the augmented expression of detoxification genes in P. brassicae after exposed to sublethal dose of Hal, and helped to better understand the potential metabolic pathways that could contribute to the reduced sensitivity to Hal in this pest. Overall, a deep insight into the detoxification mechanisms would provide practical guidance for the field management of P. brassicae.

Functional analysis of an overexpressed glutathione S-transferase BdGSTd5 involved in malathion and malaoxon detoxification in Bactrocera dorsalis

Glutathione S-transferases (GSTs) are one of the three detoxification enzyme families. The constitutive and inducible overexpression of GSTs genes plays an important role in insecticide resistance. Previous study showed that malathion resistance was polygenic, and elevated GSTs activity was one of the important factor participating in malathion resistance of Bactrocera dorsalis (Hendel), a serious economic pest worldwide. BdGSTd5 overexpression was inducible upon exposure to malathion. However, the involvement of BdGSTd5 in malathion resistance has not been clarified. In this study, we found that BdGSTd5 sequence harbored the conserved region of delta class GSTs, which were overexpressed in malathion resistant strain of B. dorsalis compared to malathion susceptible strain. The highest mRNA expression level of BdGSTd5 was found in 1-day-old adult, and the levels decreased with aging. The dsBdGSTd5 injection effectively silenced (73.4% reduction) the expression of BdGSTd5 and caused significant increase in susceptibility to malathion with a cumulative mortality increasing of 13.5% at 72 h post malathion treatment (p < 0.05). Cytotoxicity assay demonstrated that BdGSTd5 was capable of malathion detoxification. Molecular docking analysis further indicated the interactive potential of BdGSTd5 with malathion and its toxic oxide malaoxon. The recombinant BdGSTd5 exhibited glutathione-conjugating activity toward 1-chloro-2, 4-dinitrobenzene and malathion and malaoxon metabolic capacity with significant reduction (p < 0.05) of the peak areas by 90.0% and 73.1%, respectively. Taken together, the overexpressed BdGSTd5 contributes to malathion metabolism and resistance, which detoxify the malathion in B. dorsalis via directly depleting malathion and malaoxon.

Molecular identification and biochemical characteristics of a delta class glutathione S-transferase gene (FcδGST) from Chinese shrimp Fenneropenaeus chinensis

Molecular identification and biochemical characteristics of a delta class glutathione S-transferase gene (FcδGST) from Chinese shrimp Fenneropenaeus chinensis

Genome-wide identification and characterization of glutathione S-transferase gene family in quinoa (Chenopodium quinoa Willd.).

The present investigation was envisaged for large scale in-silico genome wide identification and characterization of glutathione S-transferases (GSTs) in Chenopodium quinoa. In this study, a total of 120 GST genes (CqGSTs) were identified and divided into 11 classes of which tau and phi were highest in numbers. The average protein length of protein was found to be 279.06 with their corresponding average molecular weight of 31,819.4kDa. The subcellular localization analysis results showed that proteins were centrally localized in the cytoplasm followed by chloroplast, mitochondria and plastids. Structural analysis revealed the presence of 2 -14 exons in CqGST genes. Most of the proteins possessed two exon one intron organization. MEME analysis identified 15 significantly conserved motifs with a width of 6-50 amino acids. Motifs 1, 3, 2, 5, 6, 8, 9 and 13 were found specifically in tau class family; motifs 3, 4, 5, 6, 7 and 9 were found in phi class gene family, while motifs 3, 4, 13 and 14 were found in metaxin class. Multiple sequence alignment revealed highly conserved N-terminus with active site serine (Ser; S) or cysteine (Cys; C) residue for the activation of GSH binding and GST catalytic activity. The gene loci were found to be unevenly distributed across 18 different chromosomes with a maximum of 17 genes located on chromosome number 7. Dominance of alpha helix was followed by coil, extended strand and beta turns. Gene duplication analysis revealed that segmental duplication and purifying type selection were highest in number and found to be main source of expansion of GST gene family. Cis acting regulatory elements analysis showed the presence of 21 different elements involved in stress, hormone and light response and cellular development. The evolutionary relationship of CqGST proteins carried out using maximum likelihood method revealed that all the tau and phi class GSTs were closely associated with those of G. max, O. sativa and A. thaliana. Molecular docking of GST molecules with the fungicide metalaxyl showed that the CqGSTF1 had the lowest binding energy. The comprehensive study of CqGST gene family in quinoa provides groundwork for further functional analysis of CqGST genes in the species at molecular level and has potential applications in plant breeding.

PeGSTU58, a Glutathione S-Transferase from Populus euphratica, Enhances Salt and Drought Stress Tolerance in Transgenic Arabidopsis.

Glutathione S-transferases (GSTs) play a crucial role in responding to abiotic stress and are an important target for research on plant stress tolerance mechanisms. Populus euphratica is a promising candidate species for investigating the abiotic tolerance mechanisms in woody plants. In our previous study, PeGSTU58 was identified as being associated with seed salinity tolerance. In the present study, PeGSTU58 was cloned from P. euphratica and functionally characterized. PeGSTU58 encodes a Tau class GST and is located in both the cytoplasm and nucleus. Transgenic Arabidopsis overexpressing PeGSTU58 displayed enhanced tolerance to salt and drought stress. Under salt and drought stress, the transgenic plants exhibited significantly higher activities of antioxidant enzymes, including SOD, POD, CAT, and GST, compared to the wild-type (WT) plants. Additionally, the expression levels of several stress-responsive genes, including DREB2A, COR47, RD22, CYP8D11, and SOD1 were upregulated in PeGSTU58 overexpression lines compared to those in WT Arabidopsis under salt and drought stress conditions. Furthermore, yeast one-hybrid assays and luciferase analysis showed that PebHLH35 can directly bind to the promoter region of PeGSTU58 and activate its expression. These results indicated that PeGSTU58 was involved in salt and drought stress tolerances by maintaining ROS homeostasis, and its expression was positively regulated by PebHLH35.

Recombinant expression and characterization of GSTd3 from a resistant population of Anopheles arabiensis and comparison of DDTase activity with GSTe2

The development of insecticide resistance in malaria vectors is a challenge for the global effort to control and eradicate malaria. Glutathione S-transferases (GSTs) are multifunctional enzymes involved in the detoxification of many classes of insecticides. For mosquitoes, it is known that overexpression of an epsilon GST, GSTe2, confers resistance towards DDT and pyrethroids. In addition to GSTe2, consistent overexpression of a delta class GST, GSTd3, has been observed in insecticide resistant populations of different malaria vector species. However, the functional role of GSTd3 towards DDT resistance has not yet been investigated. Here, we recombinantly expressed both GSTe2 and GSTd3 from Anopheles arabiensis and compared their metabolic activities against DDT. Both AaGSTd3 and AaGSTe2 exhibited CDNB-conjugating and glutathione peroxidase activity and DDT metabolism was observed for both GSTs. However, the DDT dehydrochlorinase activity exhibited by AaGSTe2 was much higher than for AaGSTd3, and AaGSTe2 was also able to eliminate DDE although the metabolite could not be identified. Molecular modeling revealed subtle differences in the binding pocket of both enzymes and a better fit of DDT within the H-site of AaGSTe2. The overexpression but much lower DDT metabolic activity of AaGSTd3, might suggest that AaGSTd3 sequesters DDT. These findings highlight the complexity of insecticide resistance in the major malaria vectors and the difficulties associated with control of the vectors using DDT, which is still used for indoor residual spraying.

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.

A sigma class glutathione S-transferase gene regulated by the CncC pathway is required for phytochemical tolerance in the red flour beetle, Tribolium castaneum

Insect glutathione S-transferases (GSTs) play a crucial role in the detoxification of exogenous compounds, especially insecticides and plant allelochemicals. A sigma class GST gene, TcGSTS7, mediates the response to eugenol in Tribolium castaneum. However, the mechanism underlying this effect remains largely unknown. In this study, TcGSTS7, which exhibits a structural motif and domain organization characteristic of GSTs, was cloned from the T. castaneum genome. Spatiotemporal expression analysis revealed that TcGSTS7 was most highly expressed at the late larva stage and was mainly expressed in the fat body and epidermis of larvae and adults, suggesting that TcGSTS7 may play a potential role in the protection against toxic xenobiotics in T. castaneum. Furthermore, the expression of TcGSTS7 was significantly induced after exposure to eugenol, while RNA interference (RNAi) targeting TcGSTS7 enhanced the sensitivity of the beetle to eugenol, indicating that TcGSTS7 is involved in the tolerance of T. castaneum to this insecticide. Interestingly, the depletion of TcCncC, which encodes a transcription factor of the CncC pathway that has been associated with the regulation of detoxification-related genes in insects, led to a reduction in the TcGSTS7 transcript level following exposure to eugenol, which suggests that TcGSTS7 acts downstream of the CncC pathway. Combined, these results indicated that TcGSTS7 participates in the tolerance of T. castaneum to phytochemicals in a CncC pathway-dependent manner. These findings have implications for the development of novel drugs for use in pest control.

In Vivo Glutathione S-Transferases Superfamily Proteome Analysis: An Insight into Aedes albopictus Mosquitoes upon Acute Xenobiotic Challenges.

In this study, the induction of glutathione S-transferase (GST) enzymatic activities in Aedes albopictus under 24 h of xenobiotic challenges was investigated. From LCMS analysis, 23 GST isoforms were identified under Delta, Epsilon, Sigma, Zeta, Omega, and Iota classes, together with one GSTX1-1 isoform, in both treated and untreated samples. Using STRING 11.5, the functional enrichment network of Gene Ontology (GO) analysis, the identified peptides were found to be involved in the glutathione metabolic biological process (GO:0006749, p-value: 1.93 × 10-29), and the molecular functions involved are due to glutathione transferase (GO:0016848, p-value: 2.92 × 10-8) aside from carbon-halide lyase activity (GO:004364, p-value: 1.21 × 10-31). The Protein-Protein Interaction (PPI) network (STRING 11.5) showed significant interactions within the GST superfamily and some of the GST classes interacted with other proteins among the input domain of the identified peptides (p-value &lt; 1.0 × 10-16). In TMT labeling for the quantification of peptide abundance, isoforms from Delta (GSTD1-2, GSTD1-3, GSTD1-4) and Epsilon (GSTE3-1, GSTE4-2) were found to be overexpressed (between 1.5-fold and 2-fold changes). In the PPI analysis, 12 common enriched pathways of Kyoto Encyclopedia of Genes and Genomes (KEGG) were found to be intercorrelated with the identified GSTs at PPI enrichment p-value &lt; 1.0 × 10-16. Overall, this study indicates that distinct GST enzymes, which were identified up to their specific protein isoforms, are involved in the metabolic mechanisms underlying xenobiotic stress.

English

Type 2 diabetes mellitus (T2DM) is characterized by chronic hyperglycemia and associated with an increased production of reactive oxygen species (ROS) affecting beta cells in pancreas. Glutathione S- transferases (GSTs) are a family of antioxidant enzymes that include several classes of GSTs. These enzymes have important roles in decreasing ROS species and act as a kind of antioxidant defense. In a case-control study, the role of GSTMI and TI polymorphisms in predisposition for T2DM using multiplex polymerase chain reaction in 103 T2DM patients and 170 healthy controls from Turabah Province, Saudi Arabia was investigated. GSTM1 null variant was associated with higher genetic risk predisposing to T2DM in the study population. Our study revealed that individuals who are GSTM1 null genotype are associated with 1.863 times risk for predisposition to T2DM (Odds ratio = 1.863; 95% CI = 1.265 - 2.742; P-value=0.00001). While GSTT1 polymorphism has no role in genetic predisposing to T2DM in the study population (Odds ratio = 1.053; 95% CI = 0.921 - 1.203) and its contribution in susceptibility for T2DM was only detected with combined double deletions with GSTM1 null variant in the population (P-value = 0.041, Odds Ratio = 1.104; 95% CI = 0.991 - 1.230). These results indicated that individuals who have GSTM1 null variant or GSTM1 and GSTT1 double deletion are at higher risk for developing T2DM than those who are positive genotyped for GSTT1gene. Key words: T2DM, glutathione S-transferase, Genetic polymorphisms, Turabah, SA.

Tandem duplication of a genomic region encoding glutathione S-transferase epsilon-2 and -4 genes in DDT-resistant Anopheles stephensi strain from India

The glutathione S-transferases (GST) genes are a multigene family of enzymes involved in the metabolism of endogenous and xenobiotic compounds by catalysing the conjugation of the reduced form of glutathione to the substrate. The epsilon class of GST (GSTe), unique to arthropods, is known to be involved in the detoxification process of several classes of insecticides, and GSTe2 in particular is known to have DDT dehydrochlorinase activity. This communication reports a tandem duplication of a genomic region encoding GSTe2 and GSTe4 genes in a laboratory-colonized DDT-resistant Anopheles stephensi. We identified duplication breakpoints and the organization of gene duplication through Sanger sequencing performed on long-PCR products. Manual annotation of sequences revealed a tandemly-arrayed duplication of a 3.62 kb segment of GST epsilon gene clusters comprised of five genes: a partial GSTe1, GSTe2, GSTe2-pseudogene, GSTe4 and partial GSTe5, interconnected by a conserved 2.42 kb DNA insert segment major part of which is homologous to a genomic region located on a different chromosome. The tandemly duplicated array contained a total of two GSTe2 and three GSTe4 functional paralog genes. Read-depth coverage and split-read analysis of Illumina-based whole-genome sequence reads confirmed the presence of duplication in the corresponding region of the genome. The increased gene dose in mosquitoes as a result of the GSTe gene-duplication may be an adaptive process to increase levels of detoxifying enzymes to counter insecticide pressure.

Alexander Munn

An immunohistochemical study of glutathione S-transferase (GST) expression in hepatocellular carcinoma and cholangiocarcinoma is described. Unlike most animal models of hepatic malignancy pi class GST was not consistently overexpressed in...