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Developmental stage- and concentration-specific sodium nitroprusside application results in nitrate reductase regulation and the modification of nitrate metabolism in leaves of Medicago truncatula plants
Authors:Chrystalla Antoniou  Panagiota Filippou  Photini Mylona  Dionysia Fasoula  Ioannis Ioannides  Alexios Polidoros  Vasileios Fotopoulos
Institution:1.Department of Agricultural Sciences, Biotechnology and Food Science; Cyprus University of Technology; Limassol, Cyprus;2.Agricultural Research Center of Northern Greece; NAGREF; Thermi, Greece;3.The Agricultural Research Institute; Nicosia, Cyprus;4.Department of Genetics and Plant Breeding; School of Agriculture; Aristotle University of Thessaloniki; Thessaloniki, Greece
Abstract:Nitric oxide (NO) is a bioactive molecule involved in numerous biological events that has been reported to display both pro-oxidant and antioxidant properties in plants. Several reports exist which demonstrate the protective action of sodium nitroprusside (SNP), a widely used NO donor, which acts as a signal molecule in plants responsible for the expression regulation of many antioxidant enzymes. This study attempts to provide a novel insight into the effect of application of low (100 μΜ) and high (2.5 mM) concentrations of SNP on the nitrosative status and nitrate metabolism of mature (40 d) and senescing (65 d) Medicago truncatula plants. Higher concentrations of SNP resulted in increased NO content, cellular damage levels and reactive oxygen species (ROS) concentration, further induced in older tissues. Senescing M. truncatula plants demonstrated greater sensitivity to SNP-induced oxidative and nitrosative damage, suggesting a developmental stage-dependent suppression in the plant’s capacity to cope with free oxygen and nitrogen radicals. In addition, measurements of the activity of nitrate reductase (NR), a key enzyme involved in the generation of NO in plants, indicated a differential regulation in a dose and time-dependent manner. Furthermore, expression levels of NO-responsive genes (NR, nitrate/nitrite transporters) involved in nitrogen assimilation and NO production revealed significant induction of NR and nitrate transporter during long-term 2.5 mM SNP application in mature plants and overall gene suppression in senescing plants, supporting the differential nitrosative response of M. truncatula plants treated with different concentrations of SNP.
Keywords:sodium nitroprusside  nitrosative stress  oxidative stress  antioxidants  Medicago truncatula  hydrogen peroxide  nitric oxide  nitrate reductase
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