Effect of NO3- transport and reduction on intracellular pH : An in vivo NMR study in maize roots
Articolo
Data di Pubblicazione:
2004
Citazione:
Effect of NO3- transport and reduction on intracellular pH : An in vivo NMR study in maize roots / L. Espen, F.F. Nocito, M. Cocucci. - In: JOURNAL OF EXPERIMENTAL BOTANY. - ISSN 0022-0957. - 55:405(2004), pp. 2053-2061.
Abstract:
The effect of NO3- uptake on cellular pH was studied in maize roots by an in vivo 31P-NMR technique. In order to
separate the effects on cytoplasmic pH due to NO3- uptake from those due to NO3- reduction, tungstate was used to inhibit nitrate reductase (NR). The results confirm that in maize roots tungstate inhibited NR activity. 15N-NMR in vivo experiments demonstrated the cessation of nitrogen flux from nitrate to organic compounds. Tungstate affected neither NO3- uptake nor the levels of the main phosphorylated compounds.
Slight changes in cytoplasmic pH were observed during NO3- uptake and reduction (i.e. control). By contrast, in the presence of tungstate, a consistent decrease in cytoplasmic pH occurred. The vacuolar pH did not change in any of the conditions tested. These data show that NO3- uptake is an acidifying process and suggest a possible involvement of NO3- reduction in pH homeostasis. In the presence of NO3-, a transient depolarization of transmembrane electric potential difference Em) was observed in all the conditions analysed.
However, in tungstate-treated roots, a lesser depolarization
accompanied by a greater ability to recover Em was found. This was related to a higher activity of the plasma membrane (PM) H+-ATPase. When NO3- was administered as potassium salt, its uptake increased and a greater depolarization of Em took place, whilst the changes in cytoplasmic pH were remarkably reduced, according to the central role played by K+ in the control of plasma membrane activities and cell pH homeostasis.
A possible involvement of cytoplasmic pH in the control of PM H+-ATPase expression during nitrate exposure is suggested.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
L. Espen, F.F. Nocito, M. Cocucci
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