Carbon metabolism in in vitro cultures of date palm: the role of carboxylases (PEPC and RubisCO) |
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Authors: | Masmoudi Raja Rival Alain Nato Aimé Lavergne Danièle Drira Nourredine Ducreux Georges |
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Institution: | (1) Laboratoire de Physiologie Végétale, Faculté des Sciences de Sfax, 3038 Sfax, Tunisie;(2) Laboratoire GeneTrop, IRD ex ORSTOM/CIRAD-CP. Centre IRD, B.P. 5045, 34032 Montpellier Cedex 01, France;(3) Laboratoire de Morphogenèse Végétale Expérimentale, Université Paris Sud, Bat 360, 91405 Orsay Cedex, France |
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Abstract: | While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm
(Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate
carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic
cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active
isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic
(NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO2 h−1 mg−1 TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development
of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7
to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased
from 5.3 to 1.2 μmol CO2 h−1 mg−1 TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO2 h−1 mg−1
TSP
) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against
PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | carbon metabolism carboxylases CO2 fixation Phoenix dactylifera L somatic embryogenesis |
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