Endophytic fungus Serendipita indica reduces arsenic mobilization from root to fruit in colonized tomato plant.

The accumulation of arsenic in crop plants has become a worldwide concern that affects millions of people. The major source of arsenic in crop plants is irrigation water and soil. In this study, Serendipita indica, an endophytic fungus, was used to investigate the protection against arsenic and its accumulation in the tomato plant. We found that inoculation of S. indica recovers seed germination, plant growth and improves overall plant health under arsenic stress. A hyper-colonization of fungus in the plant root was observed under arsenic stress, which results in reduced oxidative stress via modulation of antioxidative enzymes, glutathione, and proline levels. Furthermore, fungal colonization restricts arsenic mobilization from root to shoot and fruit by accumulating it exclusively in the root. We observed that fungal colonization enhances the arsenic bioaccumulation factor 1.48 times in root and reduces the arsenic translocation factor by 2.96 times from root to shoot and 13.6 times from root to fruit compared to non colonized plants. Further, investigation suggests that S. indica can tolerate arsenic by immobilizing it on the cell wall and accumulating it in the vacuole. This study shows that S. indica may be helpful for the reduction of arsenic accumulation in crops grown in arsenic-contaminated agriculture fields.

Synthesis of an Alginate-Based Fe3O4-MnO2 Xerogel and Its Application for the Concurrent Elimination of Cr(VI) and Cd(II) from Aqueous Solution.

In this study, magnetite-manganese oxide (Fe3O4-MnO2) nanoparticles were synthesized and immobilized on alginate, producing a magnetite-manganese oxide xerogel (mMOX). This eco-friendly xerogel was used as an adsorbent of Cr(VI) and Cd(II). It was mesoporous and thermally stable, as determined by Brunauer-Emmett-Teller and thermogravimetric analysis. A scanning electron microscope coupled with an energy-dispersive X-ray system, Zetasizer, and attenuated total reflectance-Fourier transform infrared were used for characterization of adsorbents. The performance of the mMOX was investigated for the simultaneous adsorption of Cr(VI) and Cd(II) at different temperatures, pH values, contact times, initial concentrations of the adsorbate, and adsorbent doses. The developed xerogel (mMOX) showed high adsorption capacities of 3.86 mg/g for Cr(VI) and 3.95 mg/g for Cd(II) on 120 min of contact time with 5 ppm Cr(VI) and Cd(II) solution. The kinetic data fitted well with the pseudo-second order, while the Freundlich isotherm model was found to be fit for adsorption data. Thermodynamic study revealed the adsorption to be spontaneous and exothermic. The adsorbent showed useful application for real water samples by more than 75% uptake of Cr and Cd with low adsorption of Na, K, and Mg. The regeneration study indicated that the mMOX could be reused up to six cycles with more than 50% removal of Cr(VI) and Cd(II) ions from aqueous solution with minimal leaching of metal ions (Fe, Ca, Na, K, and Mn) into the solution.

Endophytic Fungi Piriformospora indica Mediated Protection of Host from Arsenic Toxicity.

Complex intercellular interaction is a common theme in plant-pathogen/symbiont relationship. Cellular physiology of both the partners is affected by abiotic stress. However, little is known about the degree of protection each offers to the other from different types of environmental stress. Our current study focused on the changes in response to toxic arsenic in the presence of an endophytic fungus Piriformospora indica that colonizes the paddy roots. The primary impact of arsenic was observed in the form of hyper-colonization of fungus in the host root and resulted in the recovery of its overall biomass, root damage, and chlorophyll due to arsenic toxicity. Further, fungal colonization leads to balance the redox status of the cell by adjusting the antioxidative enzyme system which in turn protects photosynthetic machinery of the plant from arsenic stress. We observed that fungus has ability to immobilize soluble arsenic and interestingly, it was also observed that fungal colonization restricts most of arsenic in the colonized root while a small fraction of it translocated to shoot of colonized plants. Our study suggests that P. indica protects the paddy (Oryza sativa) from arsenic toxicity by three different mechanisms viz. reducing the availability of free arsenic in the plant environment, bio-transformation of the toxic arsenic salts into insoluble particulate matter and modulating the antioxidative system of the host cell.

UVB exposure enhanced the dermal penetration of zinc oxide nanoparticles and induced inflammatory responses through oxidative stress mediated by MAPKs and NF-κB signaling in SKH-1 hairless mouse skin.

Besides titanium dioxide (TiO2), zinc oxide (ZnO) nanoparticles (NPs) are commonly used in sunscreen formulations as protective agents against exposure to ultraviolet radiation. Although the majority of prior studies have concluded that NPs do not penetrate healthy skin, compromised skin slightly enhanced metal oxide NP penetration. However, a question arises regarding the possible toxic consequences if consumers who had applied sunscreens containing ZnO-NPs were exposed to environmentally relevant doses of UVB. Considering this, we planned a study where SKH-1 hairless mice were topically exposed to a 5% and/or 10% dose of ZnO-NPs (<50 nm and <100 nm) either alone or along with UVB (50 mJ cm-2). In two additional groups, mice were treated with either bulk ZnO-NPs (<5 µm) or with ZnO-NPs (<5 µm) and subsequently UVB (50 mJ cm-2). Animals of all groups were sacrificed after 6, 24 and 48 h and the Zn ion content in the skin was measured. In addition, estimation of ROS generation, histopathology, myeloperoxidase (MPO) activity, immunohistochemistry for COX-2 and western blot analysis for MAPKs, p-IκBα, p-NF-κB, and COX-2 were also carried out. Significant increases in the Zn ion in exposed skin were seen. Enhanced ROS generation and MPO activity were also found in ZnO-NPs followed by UVB exposed groups at all three time points. Similarly, hyperplasia and over-expression of COX-2 were also greater in ZnO-NPs and UVB exposed groups than in the ZnO-NPs and UVB only groups. The expression of MAPKs, and transcription factors NF-κB along with COX-2 were also enhanced significantly in ZnO-NPs and the UVB treated group. Collectively, our findings suggest that UVB exposure enhanced ZnO-NP penetration in mouse skin and possibly dissolution of these ZnO-NPs takes place during this process, causing significant Zn ion generation leading to oxidative stress by ROS generation which subsequently activates MAPK-NF-κB signaling and increases COX-2 and inflammation.

The comparative effects of metals on the hatching of earthworm cocoons.

To establish the use of Metaphire posthuma as a sensitive model for ecotoxicological studies, the comparative effects of five metals on the hatching profiles of the cocoons of the earthworms, Metaphire posthuma, Eisenia foetida and Perionyx excavatus, were studied. The cocoons of the three species of earthworms were exposed to copper, chromium (III), chromium (VI), lead and zinc at 1.25, 2.5, 5.0 and 10.0 ppm. Viable cocoons were incubated at 20 +/- degrees C by using the immersion method. The results indicated that the inhibition of cocoon hatching was concentration dependent. The normal hatching, delayed hatching and non-viability of cocoons were recorded. At a concentration of 1.25 ppm, there was almost no effect on the hatching of the cocoons of all three species of earthworms, except when exposed to chromium (VI), but higher concentrations (2.5 and 5.0 ppm) caused severe effects. It was concluded that M. posthuma was more sensitive than the other two species, and that it is a suitable model for use in ecotoxicity testing.

Carbaryl-induced behavioural and reproductive abnormalities in the earthworm Metaphire posthuma: a sensitive model.

Carbaryl, an N-methyl carbamate insecticide, is used in India to control foliar insects, but, due to soil contamination, it also adversely affects non-target organisms such as earthworms. This paper deals with the toxic effects of carbaryl on the behavioural and reproductive profiles of the earthworm, Metaphire posthuma. Locomotion and geotaxis were significantly affected, even after a 20-minute exposure to 0.125ppm carbaryl. The hatching of cocoons was altered at 0.5ppm, whereas cocoon production was retarded even at 0.125ppm carbaryl. No cocoon production was observed at 2.0ppm carbaryl. Sperm head abnormalities were reported even at the lowest test concentration of 0.125ppm. Wavy head abnormalities were observed at 0.125ppm carbaryl, whereas at 0.25ppm and 0.5ppm, the sperm heads became amorphous and the head nucleus was turned into granules deposited within the wavy head. It is concluded that the earthworm could be used as an ecosystem model for the initial toxicity testing of environmental pollutants.