Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: June 18, 2000
Publication Date: N/A
Technical Abstract: Aluminum (Al) toxicity is a primary limitation to agricultural productivity on acid soils, and is manifested primarily through an inhibition of root growth. Considerable evidence in the literature has accumulated associating Al tolerance with Al-induced exudation of organic acids from the root apex of tolerant genotypes. In Al tolerant wheat, Al exposure triggers rapid malate exudation from the root tip. The released malate is thought to chelate free Al3+ ions in the rhizosphere, thus preventing the entry of Al into the root tip (the site of Al toxicity). Al tolerant cultivars of wheat also exhibit reduced aluminum accumulation in the root apex relative to Al sensitive cultivars, supporting the concept of Al exclusion as a tolerance mechanism. Findings from other labs and ours have implicated plasma membrane anion channels as the class of transporter facilitating the organic acid exudation. In an effort to further our understanding of the molecular and physiological controls of Al-induced malate release, we are attempting to isolate anion channels from the root apices of an Al tolerant line of wheat (Atlas 66) exposed to Al. We have constructed a cDNA library from root apex mRNA from this line and are using Arabidopsis anion channel EST's as probes to conduct the hybridization screening. Cloned cDNAs will be expressed in heterologous systems (e.g. Xenopus oocytes) to examine transport properties and to investigate the nature of Al-induced channel activation. Results from this research will be discussed in the context of our overall program aimed at identifying Al tolerance genes from important food crops grown on acid soils (Supported by USDA-NRI Grant #97-35100-4501).