Delineating the redox signaling network under oxidative stress through over expression of Ecapx1 in Eleusine coracana
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Date
2018-12
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Global warming has emerged as one of the biggest threats to agriculture in the last two decades. In arid and semi-arid regions, where temperatures are already close to the physiological maxima for crops, higher temperatures may increase the incidence of heat stress in crops; negatively affecting the growth and productivity. Under such conditions, development of climate resilient crops is a dire need. As reactive oxygen species are a common denominator in the effect of various environmental stresses, therefore it is important to understand the signaling events in plants that are implicated in activating the anti-oxidative defense in plants and providing redox homeostasis. Towards this objective, we successfully developed Exapx1 over-expressing E. coracana plants. The transgenic lines were developed by using Agrobacterium mediated transformation method. The transgenic lines with increased ascorbate peroxidase activity where used to delineate the redox sensing mechanisms that are involved in providing protection from oxidative stress. The transgenic lines were morphologically similar to the wild type plants and had similar PS-II activity. Increased expression of apx1 gene in the transgenic lines could induce higher expression of superoxide dismutase and monodehydroascorbate reductase genes, under stress; but no significant increase in dehydroascorbate reductase and glutathione reductase gene expression was recorded. Over-expression of Ecapx1 gene could selectively (and not universally) induce the expression and activity of other anti-oxidant enzymes of the AsA-GSH pathway, indicting the existence of a cross talk or signaling mechanism in plants, for coordinated expression of these enzymes. On exposure to stress, the transgenic lines accumulated lesser H2O2 as compared to the wild type plants and also had lower proline levels. An effective control over H2O2 levels (through Ecapx1 over-expression) prevented undue activation of specific antioxidative enzymes like DHAR and GR, while helping to maintain the redox balance of the cells under stress. Incidentally, the transgenic lines had higher reduced to total ascorbate ratio, than the wild type plants, that was responsible for sensing the increased influx of ROS and activate the cellular anti-oxidative defense network, through down-stream signaling.
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