Journal Article

Short‐term nitrogen‐induced modulation of phospho<i>enol</i>pyruvate carboxylase in tobacco and maize leaves

E.H. Murchie, S. Ferrario‐Méry, M‐H. Valadier and C.H. Foyer

in Journal of Experimental Botany

Volume 51, issue 349, pages 1349-1356
Published in print August 2000 | ISSN: 0022-0957
Published online August 2000 | e-ISSN: 1460-2431 | DOI:
Short‐term nitrogen‐induced modulation of phosphoenolpyruvate carboxylase in tobacco and maize leaves

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Untransformed maize and tobacco plants and tobacco plants constitutively expressing nitrate reductase were grown with sufficient [math] to support maximal growth. Four days prior to treatment the tobacco plants were deprived of nitrogen. Excised maize leaves and tobacco leaf discs were fed with either 40 mM KNO3 or 40 mM KCl (control) in the light. Phosphoenolpyruvate (PEP) carboxylase (Case) activity was measured at 0.3 mM and 3 mM PEP. The light‐ induced increase in PEPCase Vmax was greater in maize than tobacco. Furthermore light decreased malate sensitivity in maize (which was N‐replete) but not in N‐deficient tobacco. [math] treatment increased PEPCase Vmax values in both species and decreased the sensitivity to inhibition by malate, but effects of [math] were much more pronounced in tobacco than maize. PEPCase kinase activity was, however, greater in maize leaves fed [math] than in the Cl‐treated controls, suggesting that it is responsive to leaf nitrogen supply. A correlation between foliar glutamine content and PEPCase activity was observed. It is concluded that PEPCase is sensitive to N metabolites which favour increased flow through the anapleurotic pathway in both C3 and C4 plants.

Keywords: Anapleurotic pathway; nitrogen assimilation; protein kinase; C3 PEPCase; C4 PEPCase.; PEPCase, phosphoenolpyruvate carboxylase; PEP, phosphoenolpyruvate; OAA, oxaloacetic acid; CAM, Crassulacean acid metabolism; DTT, 1,4‐dithiothreitol; TRIS, tri‐(hydroxymethyl)aminomethane; PMSF, phenylmethylsulphonylfluoride; HEPES, N‐(2‐hydroxyethyl)piperazine‐N′‐2‐ethanesulphonic acid; PVPP, polyvinylpolypyrrolidone; SDS‐PAGE, sodium dodecylsulphate‐polyacrylamide gel electrophoresis; TCA, tricarboxylic acid.

Journal Article.  5559 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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