Journal of Experimental Botany, Vol 49, 1855-1862, Copyright © 1998 by Oxford University Press
P Goupil, D Loncle, N Druart, A Bellettre and S Rambour
Young chicory plants transferred to abscisic acid (ABA)-containing media
displayed changes in nitrate and carbohydrate metabolism. The hormone
(10-7 M) rapidly promoted nitrate reductase
(NADH:NR, EC 1.6.6.1) activity (NRA) in roots. The hormonal effects on NRA
were not responsive to dose concentrations (10-8 to
10-4 M) and were not related to the intracellular
nitrate content. Furthermore, the ABA-regulated NRA was not modulated by a
phosphorylation/dephosphorylation mechanism.ELISA experiments using NR
antibodies showed that the NR protein accumulated in ABA-treated roots.
Northern blot analysis of NR mRNA indicated that the response to exogenous
ABA was, at least in part, at the level of transcription and the NR mRNA
accumulation was accompanied by cytosolic glutamine synthetase (GS1)
overexpression.Since NRA can be controlled by sucrose and the availability
of the reducing power, the carbohydrate metabolism was analysed
simultaneously in the chicory roots. HPLC analysis and invertase assays
showed that exogenous ABA modified the neutral invertase activity and the
carbohydrate levels as well. Sucrose hydrolysis was increased and the
levels of both glucose and fructose dramatically decreased in the presence
of ABA suggesting a relationship between both nitrate and sucrose
metabolism.Key words: Abscisic acid, carbohydrates,
Cichorium intybus L., glutamine synthetase, neutral
invertase, nitrate reductase.
ARTICLES
Influence of ABA on nitrate reductase activity and carbohydrate metabolism in chicory roots (Cichorium intybus L.)
Laboratoire de Physiologie et Génétique Moléculaire Végétales, and Laboratoire de Physiologie Cellulaire et Morphogenèse Végétales, Université des Sciences et Technologies de Lille, Bâtiment SN2, F-59655 Villeneuve d'Ascq Cedex, France; Corresponding author e-mail: Pascale.Goupil@pop.univ-lille1.fr
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