Can genetic manipulation of plant nitrogen assimilation enzymes result in increased crop yield and greater N-use efficiency? An assessment |
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Authors: | M ANDREWS P J LEA J A RAVEN K LINDSEY |
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Affiliation: | School of Sciences, University of Sunderland, Sunderland SRI 3SD, UK;Department of Biological Sciences, Lancaster University, Lancaster, LAI 4YQ, UK;Division of Environmental and Applied Biology, University of Dundee at SCRI, Invergowrie, Dundee, DD2 5DA, UK;School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE, UK |
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Abstract: | The literature on the relations between plant nitrogen (N) assimilation enzymes and plant/crop N assimilation, growth and yield is reviewed to assess if genetic manipulation of the activities of N assimilation enzymes can result in increased yield and/or increased N use efficiency. The available data indicate that (I) levels of N assimilation enzymes do not limit primary N assimilation and hence yield; (II) root or shoot nitrate assimilation can have advantages under specific environmental conditions; (III) for cereals, cytosolic glutamine synthetase (GS1) is a key enzyme in the mobilisation of N from senescing leaves and its activity in senescing leaves is positively related to yield; and (TV) for rice (Oryza sativd), NADH-glutamate synthase (NADH-GOGAT) is important in the utilisation of N in grain filling and its activity in developing grains is positively related to yield. In our opinion, selection of plants, from either a genetically manipulated population or genetic resources, with expression of nitrate reductase/nitrite reductase primarily in the root or shoot should increase plant/crop growth and hence yield under specific environmental conditions. In addition for cereals the selection of plants with high GS1 in senescing leaves and in some cases high NADH-GOGAT in developing grains could help maximise the retrieval of plant N in seeds. |
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Keywords: | Nitrogen assimilation nitrogen use efficiency nitrate reductase nitrite reductase glutamine synthetase glutamate synthase genetic manipulation crop yield |
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