Physiological, biochemical and molecular analysis of sugar-starvation responses in tomato roots.
Two-month-old tomato plants were submitted to day/night cycles and to prolonged darkness in order to investigate the physiological and biochemical response to sugar starvation in sink organs. Roots appeared particularly sensitive to the cessation of photosynthesis, as revealed by the reduction of the growth rate and the decline of the carbohydrate and protein content. Therefore, excised tomato roots were used as a model to deepen the characterization of sugar starvation symptoms. In excised roots, the endogenous sugars were rapidly exhausted and significant degradation of protein was observed. Glutamine and asparagine accounted for most of the nitrogen released by protein breakdown. Respiration declined and proliferation- and growth-associated genes were repressed soon after the beginning of the sugar depletion. Among the genes studied, only the gene encoding asparagine synthetase was strongly induced. All the starvation symptoms were reversible when the roots were resupplied with sugar. When the culture conditions deteriorated, the metabolic and molecular changes led to the triggering of apoptosis of the root cells.
Devaux
Carine
C
Unité Mixte de Recherche en Physiologie et Biotechnologie Végétales, Institut de Biologie Végétale Moléculaire et Institut National de la Recherche Agronomique, Centre de Recherche de Bordeaux, BP 81, F-33883 Villenave d'Ornon Cedex, France.
Baldet
Pierre
P
Joubès
Jérome
J
Dieuaide-Noubhani
Martine
M
Just
Daniel
D
Chevalier
Christian
C
Raymond
Philippe
P
D000596:Amino Acids / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000494:pharmacology*; D019069:Cell Respiration / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018551:Solanum lycopersicum / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism
D000596:Amino Acids; D002241:Carbohydrates; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen