Disturbed nitrogen metabolism associated with the hyperhydric status of fully habituated callus of sugarbeet |
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Authors: | Fré dé rik Le,Dily ,Jean-Pierre Billard,Thomas Gaspar,Claude Huault |
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Affiliation: | Laboratoire de Physiologie et Biochimie Végéatales, associéI.N.R.A., Institut de Recherche en Biologie Appliquée, Univ. de Caen, F-14032 Caen, France;;Institut de Botanique B 22, Univ. de Liége, Sart Tilman, B-4000 Liége, Belgium. |
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Abstract: | The content of polyamines and proline was much lower in a normal (N) callus of Beta vulgaris L. than in a fully habituated hyperhydric (H) callus. The H callus also contained more glutamate and had a higher glutamate dehydrogenase activity. The excess of glutamate, in this chlorophyll-deficient callus, was linked to accumulation of proline and polyamines. Experiments with α-difluoromethylornithine (DFMO) and α-difluoromethylarginine (DFMA) showed that both ornithine decarboxylase and arginine decarboxylase participated in the synthesis of polyamines (especially spermidine and putrescine) and removal of ammonia. It is hypothesized that the H callus was subjected to ammonia stress from the start of the culture. Experiments with gabaculine, an inhibitor of ornithine aminotransferase, showed that this enzyme linked proline degradation to polyamine synthesis through the production of ornithine. This disturbed nitrogen metabolism appeared to be characteristic of the fully habituated callus and might explain the low growth of this hyperhydric tissue. |
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Keywords: | Beta vulgaris gabaculine hyperhydricity nitrogen metabolism ornithine aminotransferase polyamines proline sugarbeet |
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