Silicon nutrition potentiates the antioxidant metabolism of rice plants under iron toxicity

Iron toxicity reduces growth of rice plants in acidic lowlands. Silicon nutrition may alleviate many stresses including heavy metal toxicity in plants. In the present study, the ameliorating effects of silicon nutrition on rice (Oryza sativa L.) plants under toxic Fe levels were investigated. Plants were cultivated in greenhouse in hydroponics under different Fe treatments including 10, 50, 100, and 250 mg L^?1 as Fe-EDTA and silicon nutrition including 0 and 1.5 mM sodium silicate. Iron toxicity imposed significant reduction in plant fresh weight, tiller, and leaf number. The activity of catalase, cell wall, and soluble peroxidases, and polyphenol oxidase in shoots decreased due to moderate Fe toxicity (50 and 100 mg L^?1), but increased at greater Fe concentration. Ascorbate peroxidase activity increased in both roots and shoots of Fe-stressed plants. Iron toxicity led to increased tissue hydrogen peroxide and lipid peroxidation. Silicon nutrition improved plant growth under all Fe treatments and alleviated Fe toxicity symptoms, probably due to lower Fe concentration of Si-treated plants. Silicon application could improve the activity of antioxidant enzymes such as catalase, ascorbate peroxidase, and soluble peroxidase under moderate Fe toxicity, which resulted in greater hydrogen peroxide detoxification and declined lipid peroxidation. Thus, silicon nutrition could ameliorate harmful effects of Fe toxicity possibly through reduction of plant Fe concentration and improvement of antioxidant enzyme activity.     

An ice nucleation protein from Fusarium acuminatum: cloning,expression, biochemical characterization and computational modeling

Ice nucleation proteins (INP) are a major cause of frost damage in plants and crops. Here, an INP gene from Fusarium acuminatum was optimized, synthesized, expressed in E.coli and subsequently purified and characterized. The protein belongs to the second class of ice nucleation proteins with an optimum pH 5.5, relative activity and stability between pH 5 and 9.5 and up to 45 °C. The protein was fully active and stable in the presence of dimethyl sulfoxide (DMSO), dioxane, acetone and ethyl acetate. Moreover, it retained over 50 % of its original activity in the presence of polyvinyl alcohol. The 3D structure model of the INP-F indicated the protein had three distinct domains as exist in other ice nucleation proteins with some variations. Considering these promising results, INP-F could be a novel candidate for industrial applications.     

A survey of aflatoxins in sesame seeds imported into Khorasan Province, Iran

Sesame seed is one of the main nutrient substances which is used in the food industries of Khorasan Razavi, Iran. Because it is likely that stored sesame seeds are contaminated with mycotoxins, the levels of aflatoxins (AF) in five lots of imported sesame seeds before their distribution to the market were studied during one year. A total of 269 sub-samples were obtained from a total of 9,321 tons of sesame seeds from five importing companies. Aflatoxins at >1 μg/kg were found in 50 % of all samples, but at low levels in most cases, which is illustrated by mean AFB₁ and total AF levels of 1.25?±?3.70 and 1.43?±?4.38 μg/kg, respectively. A few (1.9 %) samples exceeded the National Iranian Standard maximum accepted level for AFB₁ (5 μg/kg) or total AF (15 μg/kg); the maximum total AF level found in one sample was 48 μg/kg. The results indicate that the risk of a violative AF contamination in imported sesame seeds is not negligible but is currently relatively low.     

Protein modeling of cathepsin C mutations found in Papillon–Lefèvre syndrome

Background

Papillon–Lefèvre syndrome (PLS) is a rare autosomal recessive disorder characterized by hyperkeratosis involving the palms, soles, elbows, and knees followed by periodontitis, destruction of alveolar bone, and loss of primary and permanent teeth. Mutations of the lysosomal protease cathepsin C gene (CTSC) have been shown to be the genetic cause of PLS. This study analyzed CTSC mutations in five Iranian families with PLS and modeled the protein for mutations found in two of them.

Methods

DNA analysis was performed by direct automated sequencing of genomic DNA amplified from exonic regions and associated splice intron site junctions of CTSC. RFLP analyses were performed to investigate the presence of previously unidentified mutation(s) in control groups. Protein homology modeling of the deduced novel mutations (P35 delL and R272P) was performed using the online Swiss-Prot server for automated modeling and analyzed and tested with special bioinformatics tools to better understand the structural effects caused by mutations in cathepsin C protein (CTSC).

Results

Six Iranian patients with PLS experienced premature tooth loss and palm plantar hyperkeratosis. Sequence analysis of CTSC revealed a novel mutation (P35delL) in exon 1 of Patient 1, and four previously reported mutations; R210X in Patient 2, R272P in Patient 3, Q312R in two siblings of family 4 (Patients 4 and 5), and CS043636 in Patient 6. RFLP analyses revealed different restriction fragment patterns between 50 healthy controls and patients for the P35delL mutation. Modeling of the mutations found in CTSC, P35delL in Patient 1 and R272P in Patient 3 revealed structural effects, which caused the functional abnormalities of the mutated proteins.

Conclusions

The presence of this mutation in these patients provides evidence for founder CTSC mutations in PLS. This newly identified P35delL mutation leads to the loss of a leucine residue in the protein. The result of this study indicates that the phenotypes observed in these two patients are likely due to CTSC mutations. Also, structural analyses of the altered proteins identified changes in energy and stereochemistry that likely alter protein function.     

Application of Maltodextrin as Chiral Selector in Capillary Electrophoresis for Quantification of Amlodipine Enantiomers in Commercial Tablets

Maltodextrin was investigated as a chiral selector in capillary electrophoresis (CE) analysis of amlodipine (AM) enantiomers. For development of a stereoselective CE method, various effective parameters on the enantioseparation were optimized. The best results were achieved on an uncoated fused silica capillary at 20 °C using phosphate buffer (100 mM, pH 4) containing 10% w/v maltodextrin (dextrose equivalent value 4–7). The UV detector was set at 214 nm and a constant voltage of 20 kV was applied. The range of quantitation was 2.5–250 µg/mL (R² > 0.999) for both enantiomers. Intra‐ (n = 5) and interday (n = 3) relative standard deviation (RSD) values were less than 7%. The limits of quantitation and detection were 1.7 µg/mL and 0.52 µg/mL, respectively. Recoveries of R(+) and S(?) enantiomers from tablet matrix were 97.2% and 97.8%, respectively. The method was applied for the quantification of AM enantiomers in commercial tablets. Also, the enantioseparation capability of heparin was evaluated and the results showed that heparin did not have any chiral selector activity in this study. Chirality 26:394–399, 2014. © 2014 Wiley Periodicals, Inc.     

Effect of TiO2 nanoparticles on oxidative damage and antioxidant defense systems in chickpea seedlings during cold stress

The effects of TiO₂ nanoparticles (NPs) on physiologo-biochemical responses were studied in two chickpea (Cicer arietimun L.) genotypes differing in cold sensitivity (tolerant Sel11439 and sensitive ILC533) during cold stress (CS). The results showed that hydrogen peroxide and MDA contents and electrolyte leakage index (ELI) increased under CS conditions in both genotypes and that these damage indices were higher in ILC533 than in Sel11439 plants. In plants treated with TiO₂ NPs, a decreased H₂O₂ level was accompanied by a decrease in the MDA content and ELI compared to control plants, and these changes occurred more effectively in Sel11439 than in ILC533 plants. The antioxidant enzymes were more effective in cell protection against CS in Sel11439 plants compared to ILC533 plants, as well as in plants treated with TiO₂ NPs compared to control plants. The lipoxygenase activity was induced efficiently only in Sel11439 plants treated with TiO₂ NPs during CS, probably indicating its role in stress response (which was confirmed by measuring allen oxide synthase activity). TiO₂ NPs caused stability of chlorophyll and carotenoid contents during CS. Results suggest that TiO₂ NPs confer an increased tolerance of chickpea plants to CS, decreasing the level of injuries and increasing the capacity of defense systems.