Journal Article

Nitrate acts as a signal to induce organic acid metabolism and repress starch metabolism in tobacco

Stitt M, Gonzalez Fontes A, Caboche M, Scheible W.R, Muller Rober B, Lauerer M

1997

Overview

Nia30(145) transformants with very low nitrate reductase activity provide an in vivo screen to identify processes that are regulated by nitrate. Nia30(145) resembles nitrate-limited wild-type plants with respect to growth rate and protein and amino acid content but accumulates large amounts of nitrate when it is grown on high nitrate. The transcripts for nitrate reductase (NR), nitrite reductase, cytosolic glutamine synthetase, and glutamate synthase increased; NR and nitrite reductase activity increased in leaves and roots; and glutamine synthetase activity increased in roots. The transcripts for phosphoenolpyruvate carboxylase, cytosolic pyruvate kinase, citrate synthase, and NADP-isocitrate dehydrogenase increased; phosphoenolpyruvate carboxylase activity increased; and malate, citrate, isocitrate, and alpha-oxoglutarate accumulated in leaves and roots. There was a decrease of the ADP-glucose pyrophosphorylase transcript and activity, and starch decreased in the leaves and roots. After adding 12 mM nitrate to nitrate-limited Nia30(145), the transcripts for NR and phosphoenolpyruvate carboxylase increased, and the transcripts for ADP-glucose pyrophosphorylase decreased within 2 and 4 hr, respectively. Starch was remobilized at almost the same rate as in wildtype plants, even though growth was not stimulated in Nia30(145). It is proposed that nitrate acts as a signal to initiate coordinated changes in carbon and nitrogen metabolism.

• Publisher: American Society of Plant Physiologists
• Subject: acide organique / acidos organicos / actividad enzimatica / activite enzymatique / almidon / amidon / arn mensajero / arn messager / carbohydrate metabolism / deficiency diseases / enfermedades carenciales / enzimas / enzyme / enzyme activity / enzyme deficiencies / enzymes / enzymic activity / expresion genica / expression des genes / feuille / gene expression / Gene expression regulation / hojas / Leaves / maladie de carence / messenger RNA / metabolism / metabolisme / metabolisme de l' azote / metabolisme des glucides / metabolismo / metabolismo de carbohidratos / metabolismo del nitrogeno / mutant / mutantes / mutants / Nicotiana tabacum / nitrate / nitrate reductase / Nitrates / nitrato reductasa / nitratos / Nitrogen metabolism / Organic acids / organic acids and salts / Plant cells / Plant growth regulators / Plant roots / plantas transgenicas / plante transgenique / Plants / starch / Starches / transgenic plants