A metabolic study of the regulation of proteolysis by sugars in maize root tips: effects of glycerol and dihydroxyacetone.
Sugars, the main growth substrates of plants, act as physiological signals in the complex regulatory network of sugar metabolism. To investigate the function of different glycolytic steps in sugar sensing and signaling we compared the effects of carbon starvation with those of glucose, glycerol and dihydroxyacetone on carbon metabolism, proteolysis, and protease expression in excised maize (Zea mays L.) root tips. Respiration, soluble proteins, protein turnover and proteolytic activities were monitored as a function of time, along with in vitro and in vivo analysis of a variety of metabolites (sugars, amino and organic acids, phosphoesters, adenine nucleotides...) using (13)C, (31)P and (1)H NMR spectroscopy. Our results indicate that, in maize root tips, endopeptidase activities and protease expression are induced in response to a decrease in carbon supply to the upper part of the glycolytic pathway, i.e. at the hexokinase step. Proteolysis would be controlled downstream glycolysis, probably at the level of the respiratory substrate supply to mitochondria.
Brouquisse
Renaud
R
Unité Mixte de Recherche de Physiologie et Biotechnologie Végétales, Institut National de la Recherche Agronomique, Université de Bordeaux 1, IFR 103, BP 81, 33883 Villenave d'Ornon cedex, France. renaud.brouquisse@cea.fr
Rolin
Dominique
D
Cortès
Sandra
S
Gaudillère
Monique
M
Evrard
Adeline
A
Roby
Claude
C
D002241:Carbohydrates / Q000494:pharmacology*; D004098:Dihydroxyacetone / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D006868:Hydrolysis / Q000187:drug effects; D009682:Magnetic Resonance Spectroscopy; D018519:Meristem / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013997:Time Factors; D003313:Zea mays / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D002241:Carbohydrates; D010940:Plant Proteins; D004098:Dihydroxyacetone; D005990:Glycerol