Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

High-Resolution Mapping And Cloning Of AltSB, A Major Aluminum Tolerance Gene In Sorghum

Jurandir V Magalhaes¹ , Jiping Liu² , Vera M Alves¹ , Claudia T Guimaraes¹ , Yihong Wang^2,3 , Ubiraci G Lana¹ , Cintia M Coelho¹ , Robert E Schaffert¹ , Owen Hoekenga² , Patricia E Klein⁴ , Leon V Kochian²

¹  Embrapa Maize and Sorghum, Rod. MG 424, Km 65, 35701-970, Sete Lagoas, Brazil

²  U.S. Plant and Soil Nutrition Laboratory, Cornell University, Ithaca, NY 14853

³  Current Address: Biology Program, School of Science, Penn State Erie, the Behrend College, Erie, PA 16563

⁴  Institute for Plant Genomics and Biotechnology and Dept. of Horticulture, Texas A&M University, College Station, TX 77843

Breeding for aluminum (Al) tolerance has enable the agricultural utilization of large areas of acidic soils throughout the world, where Al toxicity is a major constraint.
However, a clear connection between the physiological basis of Al tolerance and the respective molecular determinants is only now being established. The comparatively small sorghum genome that lacks extensive duplications, and an apparent intrinsic ability to resist to adverse environments, make sorghum particularly adequate for the isolation of genes underlying abiotic stress tolerance in the grasses. Furthermore, its proximity to maize, rice and sugarcane is conducive to a comprehensive view of gene conservation in the grasses. High levels of recombination in the end region of sorghum chromosome 3, where the major Al tolerance gene AltSB is located, made it possible to define a 27 Kbp region where AltSB must reside. Sequence annotation as well as the expression pattern of the 3 ORFs in the region clearly indicated one of them as the best candidate to AltSB, which is involved with citrate efflux from the roots. Haplotype analysis of this ORF in the two reference alleles indicated that differential responses to Al are largely controlled by regulatory sequences affecting gene expression, rather than by polymorphisms in the coding region. Further analysis with an expanded sorghum panel suggested that a transposon insertion in the promoter region might be a key determinant of the phenotypic differences conditioned by the AltSB locus. Funding by USDA-NRI (#2001-35301-10647), the Generation Challenge Program and a McKnight Foundation CCRP grant.