|Hoekenga, Owen - CORNELL UNIVERSITY|
|Howell, Stephen - CORNELL UNIVERSITY|
Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2000
Publication Date: N/A
Technical Abstract: Aluminum (Al) is the third most abundant element in the earth's crust and toxic to plants if solubilized in acid soils. Al-toxicity diminishes crop yield on approximately one third of the world's arable land, primarily by inhibiting root growth and nutrient/water acquisition. Breeding crops with increased tolerance to aluminum stress has been a productive and active avenue of research. The underlying physiological and genetic bases for Al-tolerance are not well understood. Al-tolerance in a wide variety of plants is well correlated with an Al-inducible release of ligands (e.g. citrate) that may reduce Al uptake by roots. However, no genes important for Al-tolerance have been cloned and characterized in plants. We report on progress made to identify Al-tolerance genes in the model plant, Arabidopsis thaliana, utilizing two strategies. First, genes already known to be involved in Al-tolerance based on mutational analysis - the aluminum sensitive [als] and aluminum resistant [alr] mutants - were pursued by transposon-tagging using an Ac/Ds system. Several mutant lines exhibit normal root growth in the absence of Al, but exhibit a reduced tolerance to Al-stress. This phenotype strongly suggests that genes important for Al-tolerance have been compromised in the mutants. Cloning and characterizing the genomic sequences flanking the transposon insertion sites is underway. Second, four aluminum tolerance loci were identified using quantitative trait locus (QTL) mapping, using a recombinant inbred population constructed from the tolerant Col and sensitive Ler ecotypes. Three of the QTLs lie close to three als loci. Preliminary results suggest the fourth QTL, the major tolerance locus, regulates an Al-inducible citrate release. This research is supported by USDA-NRI #97-35100-5050.