Expression Of Thioredoxin Peroxidase Research Articles

Identification and characterization of the catalase gene involved in resistance to thermal stress in Heortia vitessoides using RNA interference

To elucidate the role of catalase (CAT) in Heortia vitessoides Moore, which is one of the most destructive defoliating pests in Aquilaria sinensis (Loureiro) Sprenger forests, a CAT gene (HvCAT) was identified in the transcriptome of adult H. vitessoides. Sequence analyses indicated that HvCAT encodes a protein containing 507 amino acids, including a proximal active site sequence (FXRERIPERVVHAKGXGA), heme-ligand sequence (RLFSYNDTX), heme-binding residues (H73, S112, N146, F151, F159, R352, and Y356), and NADPH-binding residues (P149, H192, Y196, G199, R201, N211, H233, K235, I300, W301, P302, H303, Q442, and L445). A phylogenetic analysis indicated that CAT from lepidopteran species could be assigned to one well-supported cluster. Regarding its stage- and tissue-specific expression profiles, HvCAT was expressed at high levels in fifth-instar larvae, fat body of larvae, and abdomen of adults. Furthermore, when fifth-instar larvae were exposed to thermal stress at 35, 37, and 39 °C, hydrogen peroxide and malondialdehyde content significantly increased. HvCAT mRNA was upregulated when the larvae were exposed to temperatures of 31, 33, 35, 37, and 39 °C. The enzymatic activity of HvCAT was significantly elevated following thermal stress (35 and 37 °C). After the knockdown of HvCAT by double-stranded RNA interference, the expression of thioredoxin peroxidase (Tpx) increased, whereas that of copper zinc superoxide dismutase (Cu/ZnSOD) decreased. Additionally, knocking down HvCAT transcripts in fifth-instar larvae resulted in accelerated death following thermal stress at 35 °C. In summary, the results suggest that HvCAT plays a major role in the thermotolerance of H. vitessoides.

Azadirachtin ingestion is lethal and inhibits expression of ferritin and thioredoxin peroxidase genes of the sweetpotato whitefly Bemisia tabaci

Azadirachtin is a plant-derived triterpenoid compound, which has adverse effects on growth, feeding, and reproduction of insects. However, its action is not well understood at the molecular level. The effects of oral ingestion of azadirachtin in whiteflies, Bemisia tabaci, a serious pest of various agriculturally important plants, were determined by assessing their mortality and changes in gene expression. Whiteflies (0-day-old) were allowed to ingest 20% sugar solution containing 0, 1, 5, or 10ppm azadirachtin using a two-layered parafilm feeding chamber. Mortality gradually increased with time and increased dosage, with all individuals dead at 72 and 48h at 5 and 10ppm, respectively. Furthermore, the mRNA levels of 15 genes, which are associated with development, metabolism, defenses, and stresses, were compared between whiteflies which ingest either 0 or 5ppm azadirachtin for 12h by quantitative real-time RT-PCR. Most genes changed mRNA levels at less than 2 folds. However, the expression of thioredoxin peroxidase 1 and two ferritin genes which have protective roles against oxidative stress was inhibited up to 3–6 folds more than that in untreated whiteflies. These results suggest that lethal toxicity of azadirachtin may be due to increased cellular oxidative stress of B. tabaci.

Characterization of the thioredoxin peroxidase from Cryptosporidium parvum

Cryptosporidium parvum can survive exposure to harsh environmental conditions, various disinfectants, and high doses of γ-radiation. Recently, it was found that the expression of thioredoxin peroxidase (CpTPx) in C. parvum increased after a high dose of γ-irradiation to the parasite. CpTPx is a two-cysteine peroxiredoxin that contains cysteines at positions 49 and 170. Recombinant CpTPx fused to an N-terminal hexahistidine sequence, (His)6-CpTPx, exhibited substantial thiol-dependent peroxidase activity that protected plasmid DNA from damage by metal-catalyzed oxidation in vitro. (His)6-CpTPx was used to screen sera from C. parvum-infected mice and humans for antibodies against CpTPx. In Western blots, 10% of the mouse sera and 20% of the human sera reacted with (His)6-CpTPx, suggesting that after infection by C. parvum CpTPx can induce a host-immune reaction but is not a major antigen. Immunolocalization studies revealed that CpTPx is expressed mainly in the cytoplasm of C. parvum at various developmental stages.

Antioxidant Gene Expression in Preeclamptic Placentae: A Preliminary Investigation

Oxidative stress has been implicated in the pathogenesis of preeclampsia. This study measured the relative mRNA expression of antioxidant proteins glutathione peroxidase 1 and 4, glutathione reductase, thioredoxin 1 and 2, thioredoxin reductase 1, thioredoxin peroxidase 3 and superoxide dismutase 1 and 2 in preeclamptic and non-preeclamptic placentae. Quantitative real-time PCR was conducted on placental mRNA isolated from preeclamptic and control patients. Cycle threshold numbers and fold differences were calculated as a measure of linear product amplification and used for comparison. The mRNA expression of glutathione reductase was significantly reduced (fold difference 0.41, p < 0.05) in preeclamptic placenta when compared to controls while the expression of thioredoxin peroxidase 3 was significantly increased (fold difference 3.25, p < 0.001) in the preeclamptic placentae. No significant difference in expression was observed for glutathione peroxidase 1 and 4, thioredoxin 1 and 2, thioredoxin reductase 1 and superoxide dismutase 1 and 2. These results suggest that it is the abnormal oxidative insult associated with preeclampsia not mRNA expression of antioxidant proteins that may be responsible for reduced antioxidant enzyme activity in preeclamptic placentae.