Accumulation, contents of protein, non-enzymatic antioxidant glutathione (GSH and GSSG), lipid peroxidation product (melondialdehyde-MDA) and organic acids (fumarate, succinate, malate and citrate), and activities of neurological (acetylcholinesterase-AChE), detoxification (glutathione S-transferase-GST) and metabolic (lactate dehydrogenase-LDH, aspartate transaminase-AST and alanine transaminase-ALT) enzymes were recorded in the hatchlings of Cyprinus carpio, Ctenopharyngodon idella, Labeo rohita and Cirrhinus mrigala after 7 and 14 days exposure and 10 days post exposure (recovery period) to sublethal concentrations (0.005, 0.01, 0.02 and 0.05 mg/L) of triclosan, a highly toxic and persistent biocide used in personal care products. Accumulation was maximum between 7-14 days at 0.01 mg/L for C. carpio and L. rohita but at 0.005 mg/L for C. idella and C. mrigala. No triclosan was observed at 0.005 mg/L in C. carpio and C. mrigala after recovery. Significant decline in protein, glutathione and acetylcholinesterase but increase in glutathione S-transferase, lactate dehydrogenase, aspartate transaminase, alanine transaminase, melondialdehyde and organic acids over control during exposure continued till the end of recovery period. Integrated biomarker response (IBR) analysis depicted higher star plot area for glutathione and glutathione S-transferase during initial 7 days of exposure, thereafter, during 7-14 days of exposure and the recovery period, higher star plot area was observed for acetylcholinesterase, aspartate transaminase, alanine transaminase and organic acids. Higher star plot area was observed for protein in all the species throughout the study. The study shows that L. rohita is most sensitive and glutathione, acetylcholinesterase, aspartate transaminase and alanine transaminase are the biomarkers for the toxicity of sublethal concentrations of TCS.
The present study focused on assessing the effects of jasmonic acid (JA) seed treatment on the physiology of Brassica juncea seedlings grown under imidacloprid (IMI) toxicity. It has been observed that IMI application declined the chlorophyll content and growth of seedlings. However, JA seed treatment resulted in the significant recovery of chlorophyll content and seedling growth. Contents of oxidative stress markers like superoxide anion, hydrogen peroxide, and malondialdehyde were enhanced with IMI application, but JA seed treatment significantly reduced their contents. Antioxidative defense system was activated with IMI application which was further triggered after JA seed treatment. Activities of antioxidative enzymes and contents of non-enzymatic antioxidants were enhanced with the application of IMI as well as JA seed treatment. JA seed treatment also regulated the gene expression of various enzymes under IMI stress. These enzymes included respiratory burst oxidase (RBO), Ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO), NADH-ubiquinone oxidoreductase (NADH), carboxylesterase (CXE), chlorophyllase (CHLASE), cytochrome P450 monooxygenase (P450). JA seed treatment up-regulated the expressions of RUBISCO, NADH, CXE, and P450 under IMI toxicity. However, expressions of RBO and CHLASE were down-regulated in seedlings germinated from JA seed treatment and grown in presence of IMI. Seed soaking with JA also resulted in a significant reduction of IMI residues in B. juncea seedlings. The present study concluded that seed soaking with JA could efficiently reduce the IMI toxicity by triggering the IMI detoxification system in intact plants.
BACKGROUND: Pesticides cause oxidative stress to plants and their residues persist in plant parts, which are a major concern for the environment as well as human health. Brassinosteroids (BRs) are known to protect plants from abiotic stress conditions including pesticide toxicity. The present study demonstrated the effects of seed-soaking with 24-epibrassinolide (EBR) on physiological responses of 10-day old Brassica juncea seedlings grown under imidacloprid (IMI) toxicity. RESULTS: In the seedlings raised from EBR-treated seeds and grown under IMI toxicity, the contents of hydrogen peroxide (H2O2) and superoxide anion (O.2-) were decreased, accompanied by enhanced activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST), guaiacol peroxidase (POD) and the content of glutathione (GSH). As compared to controls, the gene expressions of SOD, CAT, GR, POD, NADH (NADH-ubiquinone oxidoreductase), CXE (carboxylesterase), GSH-S (glutathione synthase), GSH-T (glutathione transporter-1), P450 (cytochrome P450 monooxygenase) and GST1-3,5-6 were enhanced in the seedlings raised from EBR-treated seeds and grown in IMI supplemented substratum. However, expression of RBO (respiratory burst oxidase, the gene responsible for H2O2 production) was decreased in seedlings raised from EBR treated seeds and grown under IMI toxicity. Further, the EBR seed treatment decreased IMI residues by more than 38% in B. juncea seedlings. CONCLUSIONS: The present study revealed that EBR seed soaking can efficiently reduce oxidative stress and IMI residues by modulating the gene expression of B. juncea under IMI stress. In conclusion, exogenous EBR application can protect plants from pesticide phytotoxicity.
Title: Purification and characterization of tannin acyl hydrolase from Aspergillus niger MTCC 2425 Bhardwaj R, Singh B, Bhat TK Ref: J Basic Microbiol, 43:449, 2003 : PubMed
The present investigation was carried out for increasing the yield of tannase of Aspergillus niger and the physico-chemical characterization of this enzyme. the extraction of enzyme protein. However, extraction of fungal pigments and proteins was observed to have high pH dependence, and maximum enzyme extraction was obtained at pH 5.5. The two-step purification protocol gave 51-fold purified enzyme with a yield of 20%. The total tannase activity was made up of nearly equal activity of esterase and depsidase. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of purified tannase protein indicated it to be made up of two polypeptides of molecular weight 102 and 83 kDa. Based on the Michaelis-Menten constant (Km) of tannase for three substrates tested, tannic acid was the best substrate with Km of 2.8 x 10(-4) M, followed by methyl gallate and propyl gallate. The inhibition was maximum for CaCl2 (58%) whereas EDTA had no modulatory effect on tannase activity. The inhibitor binding constant (KI) of CaCl2 was 5.9 x 10(-4) M Homogenization and detergent pretreatments did not have any remarkable effect on and the inhibition was of noncompetitive type.
