Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2005
Publication Date: 10/18/2005
Citation: Raman, H., Zhang, K., Maron, L., Kochian, L.V., Garvin, D.F., Sasaki, T., Yamamoto, Y., Matsumoto, H., Delhaize, E., Ryan, P. 2005. Molecular characterization and mapping of almt1, the aluminum-tolerance gene of bread wheat (triticum aestivum l.). Genome. 48:781-791. Interpretive Summary: Large areas of land within the U.S. and over 40% of the world's arable lands are acidic. In these acid soils, aluminum (Al) toxicity is the primary factor limiting crop production via Al-induced inhibition of root growth. There is considerable genetic variation in tolerance to Al between different plant species and genotypes, yet the molecular, genetic, and physiological basis for Al tolerance is still poorly understood. Thus, we need a more complete understanding of the genetic and mechanistic basis for Al tolerance if we are going to be able to develop more Al tolerant crop plants for improved cultivation on acid soils. One strategy for improving crop Al tolerance is to isolate genes conferring tolerance, and characterize these genes to understand their function. Also, these genes could be an important resource for improving crop Al tolerance via biotechnology. In this paper, both physical and genetic mapping of a gene recently identified as a possible wheat Al tolerance was conducted in a number of different wheat mapping populations and genotypes. This gene was found to co-segregate with Al tolerance in all cases, strongly supporting the contention it is a bona fide Al tolerance gene. This provides a new molecular tool for use in improving the Al tolerance of sensitive cereal species such as barley, via both molecular breeding and biotechnology.
Technical Abstract: We determined the genomic structure of ALMT1, an aluminum (Al) tolerance gene of wheat that encodes an Al-activated malate transporter and found that it consists of 6 exons interrupted by 5 introns. Sequencing a range of wheat genotypes identified two haplotypes for ALMT1. One of these was identical to the ALMT1 gene from a Triticum tauschii accession, indicating that the occurrence of the ALMT1 haplotypes predates the evolution of hexaploid wheat. ALMT1 was mapped to chromosome 4DL using Chinese Spring deletion lines and loss of ALMT1 coincided with the loss of both Al tolerance and Al-activated malate efflux. Aluminum tolerance in each of five different doubled-haploid populations was found to be conditioned by single major genes. Where ALMT1 was polymorphic between the parental lines, QTL and linkage analyses indicated that ALMT1 mapped to chromosome 4DL and co-segregated with Al tolerance. In two populations examined, Al tolerance also segregated with a greater capacity for Al-activated malate efflux. Aluminum tolerance was not associated with a particular coding allele for ALMT1 but was significantly correlated with the relative level of ALMT1 expression. These findings suggest that the Al tolerance in a diverse range of wheat genotypes is primarily conditioned by ALMT1.