Submitted to: Plant and Animal Genome VX Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/2/2006
Publication Date: 1/16/2006
Citation: Kochian, L.V., Magalhaes, J., Liu, J., Alves, V., Guimaraes, C., Wang, Y., Lana, U., Schaffert, R., Hoekenga, O., Klein, P. 2006. Map-based cloning and characterization of altsb, a major aluminum tolerance gene in sorghum [abstract]. Plant and Animal Genome VX Conference Abstracts. p. 33. Interpretive Summary:
Technical Abstract: Aluminum (Al) toxicity on acid soils that comprise ~50% of the world’s potentially arable lands is a major factor limiting crop production worldwide. Hence, there is considerable interest in elucidating the molecular and physiological mechanisms underlying plant Al tolerance. Here, we report on the identification and cloning of AltSB, a major Al tolerance gene in sorghum. High-resolution mapping led to the identification of markers flanking AltSB that defined a 27kb region on sorghum chromosome 3, which includes 3 putative open reading frames. Information based on the physiological mechanism for sorghum Al tolerance along with sequence annotation clearly led us to select one of the ORFs as the candidate for AltSB. This candidate gene encodes a putative membrane-bound protein that appears to mediate Al-activated root citrate efflux, which we have shown to be the mechanism of sorghum Al tolerance. Expression analysis showed that this gene is expressed almost exclusively in the root tips of an Al tolerant near isogenic line and expression is Al-inducible. The other two ORFs are expressed almost exclusively in shoots, and thus are not likely to be the AltSB gene. Sequence analysis of parental alleles of AltSB suggests that differences in gene expression and not protein structure/function are responsible for differential Al tolerance. The possible role of a transposon insertion in the promoter region for AltSB in this differential gene expression will also be discussed. This work is funded by USDA-NRI grant #2001-35301-10647, a CGIAR Generation Challenge grant, and a McKnight Foundation Collaborative Crop Research grant.