Nitrate reductase from <Emphasis Type="Italic">Triticum aestivum</Emphasis> leaves: Regulation of activity and possible role in production of nitric oxide |
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Authors: | E I Galeeva T V Trifonova A A Ponomareva L V Viktorova F V Minibayeva |
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Institution: | Kazan Institute of Biochemistry and Biophysics, Kazan Science Center, Russian Academy of Sciences, ul. Lobachevskogo 2/31, 420111 Kazan, Russia. |
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Abstract: | Nitrate reductase (NR) and peroxidase (POX) are important enzymes involved in the metabolism of reactive oxygen (ROS) and
nitrogen species in leaves of wheat (Triticum aestivum L.) seedlings. It has been confirmed that NR activity in wheat leaves depends on the light conditions and the presence of
nitrates during the cultivation of the seedlings, and it is regulated by the molybdenum cofactor and phosphorylation. In the
present study, confocal microscopy and EPR spectroscopy studies showed that the addition of nitrite, a product of NR, increased
the level of nitric oxide (NO). This increase was prevented by the addition of sodium azide, an inhibitor of NR. The results
suggest that in wheat leaves one of the key functions of NR is the formation of the signaling NO molecule. Cultivation of
green plants under conditions of prolonged (4 days) darkness, a strong stress factor for photosynthesizing cells, decreased
the activity of NR. Moreover, darkness induced significant elevation of the POX activity that was prevented by the addition
of nitrate to the growth medium. It is proposed that the changes in light conditions result in the competition between nitrate-
and ROS-metabolizing activities of POX in leaves, and a possible interaction between NR and POX controls the levels of NO
and ROS in the leaf tissue. |
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