Regulation of the Accumulation and Reduction of Nitrate by Nitrogen and Carbon Metabolites in Maize Seedlings.
AUTOR(ES)
Sivasankar, S.
RESUMO
The accumulation and reduction of nitrate in the presence of the nitrogen metabolites asparagine (Asn) and glutamine (Gln) and the carbon metabolite sucrose (Suc) were examined in maize (Zea mays L.) seedlings in an attempt to separate their effects on the nitrate uptake system and the nitrate reduction system. After 8 h of exposure to nitrate in the presence of 1 mM Asn, tissue nitrate accumulation was reduced at 250 [mu]M external nitrate, but not at 5 mM Asn. The induction of nitrate reductase (NR) activity was reduced at both external nitrate concentrations. In the presence of 1 mM Gln or 1% Suc, tissue nitrate concentration was not significantly altered, but the induction of root NR activity was reduced or enhanced, respectively. The induction of root nitrite reductase (NiR) activity was also reduced in the presence of Asn or Gln and enhanced in the presence of Suc. Transcript levels of NR and NiR in roots were reduced in the presence of the amides and enhanced in the presence of Suc. When Suc was present in combination with either amide, there was complete relief from the inhibition of NiR transcription observed in the presence of amide alone. In the case of NR, however, this relief from inhibition was negligible. The inhibition of the induction of NR and NiR activities in the presence of Gln and Asn is a direct effect and is not the result of altered nitrate uptake in the presence of these metabolites.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=158340Documentos Relacionados
- Genetic regulation and photocontrol of anthocyanin accumulation in maize seedlings.
- Relationships between Carbon Dioxide, Malate, and Nitrate Accumulation and Reduction in Corn (Zea mays L.) Seedlings 1
- Comparative Induction of Nitrate and Nitrite Uptake and Reduction Systems by Ambient Nitrate and Nitrite in Intact Roots of Barley (Hordeum vulgare L.) Seedlings.
- Relationship between Nitrate Uptake, Flux, and Reduction and the Accumulation of Reduced Nitrogen in Maize (Zea mays L.): II. EFFECT OF NUTRIENT NITRATE CONCENTRATION 1
- Effect of Carbon Dioxide on Nitrate Accumulation and Nitrate Reductase Induction in Corn Seedlings 1