Fig. 1.

Range of Al tolerance conservation in plants as conferred by Al-activated malate release encoded by ALMT1. (A) The ALMT1 protein is an Al-activated malate transporter located in the root cell plasma membrane of the tolerant genotype (6). (B) Genetic mapping indicates that functional ALMT1 homologs are present in Triticeae species (3, 8, 9, 10) and in rice (12). (C) Hoekenga et al. showed that functional conservation of ALMT1 extends to the dicot, Arabidopsis. The question mark on B indicates that a putative functional ALMT1 homolog (protein in red on the plasma membrane) has yet to be found in maize and sorghum. [Image in A reprinted with permission from ref. 19 (copyright 2004 by Annual Reviews, www.annualreviews.org).]