ARS | Publication request: HIGH RESOLUTION MAPPING AND CLONING OF ALTSB, A MAJOR ALUMINUM TOLERANCE GENE IN SORGHUM

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2006
Publication Date: July 1, 2006
Citation: Liu, J., Magalhaes, J., Guimaraes, C., Lana, U., Alves, V., Wang, Y., Klein, P., Schaffert, R., Hoekenga, O., Kochian, L.V. 2006. High resolution mapping and cloning of altsb, a major aluminum tolerance gene in sorghum [abstract]. American Society of Plant Biologists Annual Meeting. p. 109.

Technical Abstract: Aluminum (Al) toxicity on acid soils represent a major constraint for crop production as ~50% of the potentially arable soils worldwide are acidic. Therefore, understanding the genetic and molecular mechanisms underlying plant Al tolerance has been a major focus for a number of laboratories around the world. Here, we report on the isolation and characterization of AltSB, a major Al tolerance gene in sorghum. Through genetic mapping, we identified AltSB as a single Al tolerance gene on sorghum chromosome 3. Subsequent high resolution mapping of the genomic region spanning AltSB led to the identification of markers flanking AltSB that define a 27-kb region, which includes 3 putative ORFs. Information based on the physiological mechanism for sorghum Al tolerance along with sequence annotation of the 3 ORFs clearly led us to select one of the ORFs as the strongest candidate for AltSB. It encodes a membrane protein involved in the release of organic acids (Al chelators) from root cells into the rhizosphere, the major currently understood tolerance mechanism. Sequence analysis of alleles for AltSB derived from the parental lines, as well as a number of other sorghum genotypes differing in Al tolerance suggest that differences in gene expression and not protein function underlie differential sorghum Al tolerance conferred by AltSB. This is supported by studies of gene expression, which show that the candidate gene is expressed much more strongly in the root tip of Al tolerant lines and this expression is induced by Al exposure only in tolerant lines. The expression pattern for this gene in root tips correlates closely with differences in the identified physiological mechanism, Al-activated root citrate exudation. Additional follow-up studies will also be presented.