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Biosynthesis of peroxidases: a role as interplay between primary and hormonal metabolisms
Gaspar, Thomas; Le Dily, Frédérique; Billard, Jean-Pierre et al.
2002In Acosta, M.; Rodriguez-lopez, J.-N.; Pedreno, Maria-A (Eds.) Plant perodixases - Biochemistry and physiology - VI international plant peroxidase symposium Proceedings
 

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Abstract :
[en] Hyperhydric, fully habituated (growth independent from exogenous auxin and cytokinin), fully heterotrophic (achlorophyllous, dependent on sucrose supply, nevertheless able to fix CO2 non-photosynthetically) and non-organogenic (complete loss of any organogenic totipotency) sugarbeet cells in culture were characterized by a very low peroxidase activity, among other deficient heme compounds. This deficiency resulted from the lack of synthesis of the precursor aminolevulinic acid (ALA) through the chloroplastic Beale pathway; the low productive unusual ALA synthesis through the mitochondrial Shemin pathway (commonly used by animals and fungi) functioned but further at a limited rate due to inhibition of ALA-dehydratase by benzoic derivatives, predominant among the phenolic acids of these cells (compared to normal ones). A thorough investigation of the metabolic and hormonal functioning of these neoplastic cells showed that the above deviation originated from a disturbed nitrogen metabolism that diverted glutamate from the Kreb's cycle into polyamine (over) synthesis, which had also as consequence a low ethylene production. The Kreb's cycle could be replenished by oxaloacetate and malate deriving from the anaplerotic fixation of CO2 onto phosphoenolpyruvate. A privileged pentose phosphate pathway (PPP) allowed the formation of substrates for a non-limited biosynthesis of (endogenous) auxins and cytokinins. The PPP, through NAD(P)H formation, enhanced nitrogen metabolism, but also, together with a putative H2O2 accumulation (originated from high superoxide dismutase activity and high polyamine oxidation combined with low catalase activity), favoured the alternative respiratory pathway. These results not only illustrate a novel view of integration of hormonal metabolisms with the C and N primary and secondary ones but also allow to consider the biosynthesis of peroxidases in an interplay or mediating role between them.
Disciplines :
Phytobiology (plant sciences, forestry, mycology...)
Author, co-author :
Gaspar, Thomas ;  Botanique, radiobotanique & serres expér.
Le Dily, Frédérique;  Université de Caen Basse-Normandie > Physiologie et Biochimie Végétales
Billard, Jean-Pierre;  Université de Caen Basse-Normandie > Physiologie et Biochimie Végétales
Huault, Claude;  Université de Caen Basse-Normandie > Physiologie et Biochimie Végétales
Bisbis, Badia;  Université de Liège - ULiège > Hormonologie végétale
Kevers, Claire ;  Université de Liège - ULiège > Département des sciences de la vie > Biologie moléculaire et biotechnologie végétales
Dommes, Jacques ;  Université de Liège - ULiège > Département des sciences de la vie > Biologie moléculaire et biotechnologie végétales
Language :
English
Title :
Biosynthesis of peroxidases: a role as interplay between primary and hormonal metabolisms
Publication date :
2002
Main work title :
Plant perodixases - Biochemistry and physiology - VI international plant peroxidase symposium Proceedings
Editor :
Acosta, M.
Rodriguez-lopez, J.-N.
Pedreno, Maria-A
Publisher :
servicio de publicationes. Universidad de Murcia, Murcia, Spain
ISBN/EAN :
84-8371-379-9
Pages :
169-185
Available on ORBi :
since 10 January 2009

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