Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Workshop: Abiotic Stress
            

ALUMINUM TOLERANCE IN ARABIDOPSIS THALIANA IS PHYSIOLOGICALLY SIMPLE BUT GENETICALLY COMPLEX

¹ Dept. of Plant Biology, Cornell University, 235 Fed Nut Lab, Ithaca, NY, 14853, USA

² Dept. of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA

³ Plant Sciences Institute, Iowa State University, Ames, IA, 50011, USA

⁴ USDA-ARS, Cornell Unversity, Ithaca, NY, 14853, USA

Aluminum is the third most abundant element in the earth's crust and toxic to plants if solubilized at acidic pH. Aluminum toxicity diminishes crop yield on approximately one-third of the world's arable land, primarily by inhibiting root growth and nutrient/water uptake. While increasing aluminum tolerance has been the objective of plant breeders worldwide for many years, no tolerance genes have been identified. The physiological mechanisms that underlie aluminum tolerance are somewhat better understood, where the best characterized mechanism involves an aluminum-activated release of small organic molecules (e.g. malate) that bind soluble aluminum and prevent it's uptake into the root. We have utilized a multidisciplinary approach to investigate the physiological and genetic bases for aluminum tolerance in Arabidopsis thaliana and will describe here the identification of two aluminum tolerance quantitative trait loci by composite interval mapping. Together, these QTLs explain appoximately 40% of the differences in tolerance observed between the recombinant inbred lines from the Columbia (tolerant) and Landsberg erecta (sensitive) RIL population. Next, we identified the mechanism by which tolerance is achieved; the two QTLs cosegregate with an aluminum-activated release of malate. With a second round of analysis, it is clear that malate release explains the majority of aluminum tolerance observed (adjusted R2 = 0.944) but is genetically complex, as only two of the factors involved are resolved as significant QTLs. Through the alternation of genetic and physiological approaches, we have made substantial in-roads to understanding the basis for the complex trait of aluminum tolerance in Arabidopsis thaliana .