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Faizābād, India

Tripathi B.N.,Guru Ghasidas University | Tripathi B.N.,Academy of Innovative Research | Singh V.,Amity University | Ezaki B.,Okayama University | And 2 more authors.
Journal of Plant Growth Regulation

Proline hyperaccumulation, a frequently reported phenomenon in the plant kingdom, is considered an adaptive strategy of plants to cope with a variety of stresses. The present study demonstrated the mechanism of proline hyperaccumulation in Triticum aestivum exposed to excess Cu and Cd. The intracellular level of proline was increased significantly in the plants treated with test metals. Enhanced proline accumulation due to Cu and Cd was negatively correlated with the growth of the treated plants, indicating that plants divert their resources toward induction of survival strategies rather than improving growth and development. The activities of pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) were increased immediately after metal treatment and remained higher through the end of the experiment, whereas ornithine amino transferase (OAT) activity of the treated plants was lower than P5CS and P5CR enzymes. The activity of proline dehydrogenase (PDH) was decreased sharply in the early phase of metal exposure (up to 12 h) but remained unchanged thereafter until the end of the experiment. Expression analysis of the transcripts of P5CS, OAT, and PDH also supports the above findings and indicates the tissue-specific expression of these genes. Based on these results, increased proline synthesis through the glutamate pathway involving the P5CS and P5CR enzymes is a major contributor to proline hyperaccumulation followed by decreased catabolism of proline. © 2013 Springer Science+Business Media New York. Source

Bhatt I.,Banasthali University | Tripathi B.N.,Guru Ghasidas University | Tripathi B.N.,Academy of Innovative Research
Biotechnology Advances

Peroxiredoxins (Prx) are a family of thiol dependent peroxidases found in almost all kingdoms. In plants, five major classes of Prx are known. They are known to catalyze the decomposition of peroxides and as they lack a prosthetic group, the catalytic cycle results in the generation of an inactive form of Prx. In order to regain the active form, Prx rely on external electron donors such as thioredoxins, glutaredoxins, cyclophilins, NADPH-dependent thioredoxin reductase C (NTRC) etc. In addition to their well established role in antioxidative defense, Prx are also reported to play an important role in growth and development, dessication tolerance in dormant seeds, protection of photosynthesis, defense against pathogens and redox signaling. Prx are also known to establish an alternate water-water cycle for the detoxification of H 2O 2, parallel to ascorbate-dependent H 2O 2 detoxification. But the relative contribution of Prx in detoxifying H 2O 2 compared to ascorbate peroxidase is not known so far due to experimental limitations. In view of the above, the present review focuses on the recent developments on Prxs. © 2011 Elsevier Inc. Source

Aggarwal A.,Banasthali University | Ezaki B.,Okayama University | Tripathi B.N.,Banasthali University | Tripathi B.N.,Academy of Innovative Research
Environmental and Experimental Botany

Present study demonstrates an antioxidant defense system against Al-induced oxidative damage and a role of external malate detoxification in providing Al-resistance in an Al resistant genotype of wheat, Raj 3077. Al dependent growth inhibition was higher in Raj 4120 (Al-sensitive) in comparison to Raj 3077. Oxidative damage indicators such as lipid peroxidation and H2O2 content were measured in the roots of both genotypes. However, these parameters were higher in the shoots of Raj 4120 indicating presence of oxidative stress in there. Antioxidant enzymes such as SOD (EC, CAT (EC and APX (EC played important roles in providing resistance to the Raj 3077 against Al-induced oxidative stress. Inefficient activation of the antioxidant enzymes in the roots of Raj 4120 suggested that a severe oxidative damage was occurred in root and a higher amount of translocated toxic Al ions to shoot consequently caused Al stress there. Interestingly, a higher CAT activity was found higher in the shoot of Raj 4120 than Raj 3077, but it seemed not to be enough to combat with Al-induced reactive oxygen species. Raj 3077 showed higher malate efflux and higher ALMT gene expression than Raj 4120. Further, root length of Raj 3077 seedlings was particularly affected in the presence of anion channel inhibitor, niflumic acid suggested that malate detoxification is required for providing Al-resistance in Raj 3077 in the root region. Thus, both Al induced antioxidant defensive and external malate detoxification systems provide strength to combat with Al toxicity in Raj 3077. © 2015 Elsevier B.V. Source

Sharma M.,Banasthali University | Sharma V.,Banasthali University | Tripathi B.N.,Banasthali University | Tripathi B.N.,Guru Ghasidas University | Tripathi B.N.,Academy of Innovative Research

The present study demonstrates the comparative response of two contrasting genotypes (aluminum (Al) tolerant and Al sensitive) of chick pea (Cicer arietinum) against Al stress. The Al-tolerant genotype (RSG 974) showed lesser inhibition of root growth as well as lower oxidative damages, measured in terms of the accumulation of H2O2 and lipid peroxidation compared to the Al-sensitive genotype (RSG 945). The accumulation of Al by roots of both genotypes was almost equal at 96 and 144 h after Al treatment; however, it was higher in Al-tolerant than Al-sensitive genotype at 48 h after Al treatment. Further, the Al-mediated induction of superoxide dismutase (SOD) activity was significantly higher in Al-tolerant than Al-sensitive genotype. Ascorbate peroxidase (APX) activity was almost similar in both genotypes. Al treatment promptly activated catalase activity in Al-tolerant genotype, and it was remarkably higher than that of Al-sensitive genotype. As another important Al detoxification mechanism, citrate efflux was almost equal in both genotypes except at 1000 μM Al treatment for 96 and 144 h. Further, citrate carrier and anion channel inhibitor experiment confirmed the contribution of citrate efflux in conferring Al tolerance in Al-tolerant genotype. Based on the available data, the present study concludes that rapid activation of catalase (also SOD) activity followed by citrate efflux effectively improves Al tolerance in chick pea. © 2015 Springer-Verlag Wien Source

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