The roles of organic anion permeases in aluminium resistance and mineral nutrition

Abstract

Soluble aluminium (Al 3+ ) is the major constraint to plant growth on acid soils. Plants have evolved mechanisms to tolerate Al 3+ and one type of mechanism relies on the efflux of organic anions that protect roots by chelating the Al 3+ . Al 3+ resistance genes of several species have now been isolated and found to encode membrane proteins that facilitate organic anion efflux from roots. These proteins belong to the Al 3+ -activated malate transporter (ALMT) and multi-drug and toxin extrusion (MATE) families. We review the roles of these proteins in Al 3+ resistance as well as their roles in other aspects of mineral nutrition.

AnALMT1Gene Cluster Controlling Aluminum Tolerance at theAlt4Locus of Rye (Secale cerealeL.)

“…Expression of M39.1 and M39.2 was also detected in leaves. Metal homeostasis, Al tolerance in the apoplast, and many important biochemical processes in plants involve transport of organic acids such as malate, or their metal complexes, between subcellular compartments (Holtum et al 2005;Kochian et al 2005;De Angeli et al 2007;Delhaize et al 2007;Haydon and Cobbett 2007). Potentially, rye ALMT1 proteins, or other members of the ALMT protein family , could be involved in these processes in root tips and other tissues.…”

“…A role for organic acid exudation as a mechanism of Al tolerance has been highlighted by the recent cloning of four Al-tolerance genes that all encode organic acid transporters. The TaALMT1 gene controlling tolerance at the Alt BH (Alt2) locus on wheat (Triticum aestivum L.) chromosome arm 4DL encodes the aluminumactivated malate transporter-1 (TaALMT1) protein representing the founding member of a family of plant-specific membrane-integral proteins Delhaize et al 2007). In Arabidopsis, a homolog of TaALMT1 (AtALMT1) makes a major contribution to the Al tolerance of wild-type plants (Hoekenga et al 2006).…”

Role of the plasma membrane H+-ATPase in the regulation of organic acid exudation under aluminum toxicity and phosphorus deficiency

“…Several genes encoding ALMT1 and MATE-family proteins have been identified from the roots of wheat, 13 Arabidopsis, 14 sorghum, 15 rice bean, 16 soybean, 17,18 and alfalfa, 19,20 And the identification and function of organic transporter genes in plant resistance to Al stress have been widely reviewed. [21][22][23] Beside on Al-induced organic acids transporter gene's expression, plasma membrane H C -ATPase is also involved in Al-induced organic acid process. In this review, we summarize what is understood about this field of study on the role of the plasma membrane H C -ATPase in organic acid exudation under Al toxicity and P deficiency conditions.…”

How do Citrus Crops Cope with Aluminum Toxicity?

“…Out of the several possible mechanisms, exclusion is widely accepted as the key contributor in preventing/minimizing Al toxicity in plant species (Delhaize et al, 2007;Garzon et al, 2011). As reported by many authors, exclusion is expected to occur as a result of one or combination of following processes; exudation of chelating ligands, formation of pH barrier at the rhizosphere or at root apoplasm, cell wall immobilization, selective permeability of the plasma membrane and Al efflux (Éva Darkó et al, 2004;Delhaize et al, 2007;Tolra et al, 2009).…”