Induction of the Root Cell Plasma Membrane Ferric Reductase (An Exclusive Role for Fe and Cu)

Abstract

Induction of ferric reductase activity in dicots and nongrass monocots is a well-recognized response to Fe deficiency. Recent evidence has shown that Cu deficiency also induces plasma membrane Fe reduction. In this study we investigated whether other nutrient deficiencies could also induce ferric reductase activity in roots of pea (Pisum sativum L. cv Sparkle) seedlings. Of the nutrient deficiencies tested (K, Mg, Ca, Mn, Zn, Fe, and Cu), only Cu and Fe deficiencies elicited a response. Cu deficiency induced an activity intermediate between Fe-deficient and control plant activities. To ascertain whether the same reductase is induced by Fe and Cu deficiency, concentration- and pH-dependent kinetics of root ferric reduction were compared in plants grown under control, -Fe, and -Cu conditions. Additionally, rhizosphere acidification, another process induced by Fe deficiency, was quantified in pea seedlings grown under the three regimes. Control, Fe-deficient, and Cu-deficient plants exhibited no major differences in pH optima or Km for the kinetics of ferric reduction. However, the Vmax for ferric reduction was dramatically influenced by plant nutrient status, increasing 16- to 38-fold under Fe deficiency and 1.5- to 4-fold under Cu deficiency, compared with that of control plants. These results are consistent with a model in which varying amounts of the same enzyme are deployed on the plasma membrane in response to plant Fe or Cu status. Rhizosphere acidification rates in the Cu-deficient plants were similarly intermediate between those of the control and Fe-deficient plants. These results suggest that Cu deficiency induces the same responses induced by Fe deficiency in peas.

Fortification of micronutrients for efficient agronomic production: a review

“…This process can involve competition among the micronutrient ions for entry into the plant, so that an otherwise beneficial process of nutrient accumulation becomes a limiting factor for efficient utilization of specific micronutrients (Cohen et al 1997;Alam et al 2001;Kim and Guerinot 2007;Ghasemi-Fasaei and Ronaghi 2008;Rietra et al 2015). Here, we will briefly highlight how micronutrients' uptake mechanisms can affect their accumulation in the plant. )…”

“…at the cell plasma membrane. Notably, this process, performed by members of a family of ferric reductases (FRO), is not only nonselective for the metal that is converted (Norvell et al 1993;Cohen et al 1997;Robinson et al 1999;Schaaf et al 2004;Johnson and Barton 2007;Martínez-Ballesta et al 2010;Dimkpa et al 2015a, b) but also occurs in both root and shoot cells (Mukherjee et al 2006;Martínez-Ballesta et al 2010). With Ni and Zn, uptake by plant is in the form of the divalent ions, even though Ni, but not Zn, participates in redox reactions.…”

Respuestas Del Sistema De Absorción De Hierro en Las Raíces De Los Cítricos Ante Diferentes Condiciones Clorosantes Del Medio

“…Como era de esperar, el bicarbonato estimuló la expresión de los genes FRO en las raíces de FA-5 que provocó el aumento de la actividad de la enzima FC-R, efecto mediado por la deficiencia inducida de hierro, que incrementa en gran medida la actividad del enzima en las raíces de los cítricos (Manthey et al, 1994), así como en otras plantas (Yi y Guerinot, 1996;Susín et al, 1996;Cohen et al, 1997;Robinson et al, 1999). Sin embargo, parece que existe cierta controversia en la bibliografía sobre el efecto del bicarbonato en la FC-R. En algunos informes, el tratamiento de plantas deficientes en Fe con bicarbonato no mejora la capacidad de reducción de Fe(III) de las raíces, como parece ocurrir en pepino, guisante, tomate y Arabidopsis (Romera et al, 1997;Lucena et al, 2007).…”

“…IV) Favorece la afinidad de la enzima FC-R por el sustrato, ya que neutraliza la carga negativa del quelato férrico y evita la repulsión con los centros de reducción (Cohen et al, 1997).…”

“…Esta reducción de los compuestos férricos ocurre a través de una enzima denominada quelato férrico reductasa, FC-R (Chaney et al, 1972;Bienfait, 1988a;Moog y Brüggemann, 1994), que es específica de la membrana plasmática de las células superficiales de la zona subapical de la raíz (Cohen et al, 1997). Este enzima toma electrones del NADH y reduce el Fe procedente de aceptores de alto potencial como el ferricianuro (+360 mV), así como de quelatos férricos sintéticos con potenciales menores, entre +100 y +250 mV (Nikolic, 1998).…”