C1 metabolism and chlorophyll synthesis: the Mg-protoporphyrin IX methyltransferase activity is dependent on the folate status.
* Tetrahydrofolate derivatives are central cofactors of C1 metabolism. Using methotrexate as a specific inhibitor of folate biosynthesis, we altered the folate status in 10-d-old etiolated pea (Pisum sativum) leaves and followed the rate of chlorophyll synthesis upon illumination. * In our conditions, the folate concentration decreased only from 5.7 to 4.2 nmol g(-1) FW, but the amount of chlorophyll after 24 h of illumination was reduced 2.5 times. Folate status and rate of chlorophyll synthesis were apparently correlated through the methyl cycle. * Indeed, we observed that methyl-tetrahydrofolate was the folate derivative most affected by the treatment; the decrease of methyl-tetrahydrofolate was associated with a sharp rise in homocysteine and S-adenosylhomocysteine concentrations, which are normally maintained at very low values, shifting the methylation index (S-adenosylmethionine/S-adenosylhomocysteine ratio) from 7 to 1; the decrease of the methylation index reduced by a factor of 3 the activity of the Mg-protoporphyrin IX methyltransferase (CHLM), an essential enzyme for chlorophyll synthesis. CHLM gene expression and protein concentration remained unchanged, suggesting that this inhibition relied essentially on metabolic regulation. * These results point out that an even moderate change in the folate status may affect plant development and adaptation.
Van Wilder
Valérie
V
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
De Brouwer
Veerle
V
Laboratory of Toxicology, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium.
Loizeau
Karen
K
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
Gambonnet
Bernadette
B
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
Albrieux
Catherine
C
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
Van Der Straeten
Dominique
D
Unit Plant Hormone Signaling and Bioimaging, Department of Molecular Genetics, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium.
Lambert
Willy E
WE
Laboratory of Toxicology, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium.
Douce
Roland
R
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
Block
Maryse A
MA
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
Rebeille
Fabrice
F
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
Ravanel
Stéphane
S
Laboratoire de Physiologie Cellulaire Végétale, UMR5168 CNRS-CEA-INRA-Université Joseph Fourier Grenoble I, Institut de Recherches en Technologies et Sciences pour le Vivant, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France.
D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D002244:Carbon / Q000378:metabolism*; D002734:Chlorophyll / Q000096:biosynthesis*; D005492:Folic Acid / Q000378:metabolism*; D008027:Light; D008727:Methotrexate / Q000494:pharmacology; D008745:Methylation / Q000187:drug effects / Q000528:radiation effects; D008780:Methyltransferases / Q000378:metabolism*; D018532:Pisum sativum / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D013763:Tetrahydrofolates / Q000737:chemistry / Q000378:metabolism
D013763:Tetrahydrofolates; D002734:Chlorophyll; D002244:Carbon; D005492:Folic Acid; D008780:Methyltransferases; C060234:magnesium-protoporphyrin methyltransferase; D008727:Methotrexate