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The effect of biotic stress on nitrogen metabolism in tobacco plants
Fiala, Martin ; Ryšlavá, Helena (advisor) ; Müller, Karel (referee)
In this project the effect of viral infection on the metabolism of nitrogenous compounds in tobacco plants (Nicotiana tabacum L. cv. Petit Havana SR1) was studied. The tobacco plants were infected with Potato virus Y, strain NTN, ELISA confirmed the presence of the virus. Enzymes that participate in C4 plants in Hatch-Slack cycle fosfoenolpyruvate carboxylase (EC 4.1.1.31, PEPC), NADP-dependent malic enzyme (EC 1.1.1.40, NADP-ME), pyruvate, phosphate dikinase (EC 2.7.9.1, PPDK) are present also in C3 plants and are related to plant responses to stress conditions. As a result of viral infection, the activities of all these enzymes were increased. Infection caused by PVYNTN decreased activity of nitrate reductase (EC 1.7.1.1, NR), an enzyme catalyzing reduction of nitrates to nitrites. The activity of enzymes catalyzing the synthesis of glutamine from glutamate and ammonium ions: glutamine synthetase (EC 6.3.2.1, GS) and glutamate synthase (EC 1.4.1.14, GOGAT) was enhanced. In addition to this main route of nitrogen fixation the plant can still use glutamate dehydrogenase (EC 1.4.1.2, GDH). This enzyme can also catalyze the opposite reaction, deamination of glutamate. The direction of response depends on environmental conditions. In this case a significant increase of oxidative-deaminating activity...
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