Iron uptake in dicots depends on their ability to induce a set of responses in root cells including rhizosphere acidification through H(+) extrusion and apoplastic Fe(III) reduction by Fe(III)-chelate reductase. These responses must be sustained by metabolic rearrangements aimed at providing the required NAD(P)H, ATP and H(+). Previous results in Fe-deficient cucumber roots showed that high H(+) extrusion is accompanied by increased phosphoenolpyruvate carboxylase (PEPC) activity, involved in the cytosol pH-stat; moreover (31)P-NMR analysis revealed increased vacuolar pH and decreased vacuolar [inorganic phosphate (Pi)]. The opposite was found in soybean: low rhizosphere acidification, decreased PEPC activity, vacuole acidification, and increased vacuolar [Pi]. These findings, highlighting a different impact of the Fe deficiency responses on cytosolic pH in the two species, lead to hypothesize different roles for H(+) and Pi movements across the tonoplast in pH homeostasis. The role of vacuole in cytosolic pH-stat involves the vacuolar H(+)-ATPase (V-ATPase) and vacuolar H(+)-pyrophosphatase (V-PPase) activities, which generating the ΔpH and ΔΨ, mediate the transport of solutes, among which Pi, across the tonoplast. Fluxes of Pi itself in its two ionic forms, H2PO4 (-) predominating in the vacuole and HPO4 (2-) in the cytosol, may be involved in pH homeostasis owing to its pH-dependent protonation/deprotonation reactions. Tonoplast enriched fractions were obtained from cucumber and soybean roots grown with or without Fe. Both V-ATPase and V-PPase activities were analyzed and the enrichment and localization of the corresponding proteins in root tissues were determined by Western blot and immunolocalization. V-ATPase did not change its activity and expression level in response to Fe starvation in both species. V-PPase showed a different behavior: in cucumber roots its activity and abundance were decreased, while in Fe-deficient soybean roots they were increased. The distinct role of the two H(+) pumps in Pi fluxes between cytoplasm and vacuole in Fe-deficient cucumber and soybean root cells is discussed.
Fe deficiency differentially affects the vacuolar proton pumps in cucumber and soybean roots / M. Dell'Orto, P. De Nisi, G. Vigani, G. Zocchi. - In: FRONTIERS IN PLANT SCIENCE. - ISSN 1664-462X. - 4(2013 Aug 27), pp. 326.1-326.9.
|Titolo:||Fe deficiency differentially affects the vacuolar proton pumps in cucumber and soybean roots|
DELL'ORTO, MARTA (Primo)
DE NISI, PATRIZIA (Secondo)
VIGANI, GIANPIERO (Penultimo)
ZOCCHI, GRAZIANO (Ultimo)
|Parole Chiave:||Cucumber; Fe deficiency; Soybean; V-ATPase; V-PPase|
|Settore Scientifico Disciplinare:||Settore AGR/13 - Chimica Agraria|
|Data di pubblicazione:||27-ago-2013|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.3389/fpls.2013.00326|
|Appare nelle tipologie:||01 - Articolo su periodico|