Molecular characterization and mapping ofALMT1, the aluminium-tolerance gene of bread wheat (Triticum aestivumL.)

Abstract

The major aluminum (Al) tolerance gene in wheat ALMT1 confers. An Al-activated efflux of malate from root apices. We determined the genomic structure of the ALMT1 gene and found it consists of 6 exons interrupted by 5 introns. Sequencing a range of wheat genotypes identified 3 alleles for ALMT1, 1 of which was identical to the ALMT1 gene from an Aegilops tauschii accession. The ALMT1 gene 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. Aluminium tolerance in each of 5 different doubled-haploid populations was found to be conditioned by a single major gene. When ALMT1 was polymorphic between the parental lines, QTL and linkage analyses indicated that ALMT1 mapped to chromosome 4DL and cosegregated with Al tolerance. In 2 populations examined, Al tolerance also segregated with a greater capacity for Al-activated malate efflux. Aluminium 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.

AtALMT1 , which encodes a malate transporter, is identified as one of several genes critical for aluminum tolerance in Arabidopsis

“…The gene is constitutively expressed in wheat root apices (11,12), whereas the ALMT1 protein is localized to the plasma membrane. These features are consistent with its role as a malate efflux transporter in roots (13).…”

Natural Variation of Root Traits: From Development to Nutrient Uptake

“…At the molecular level, this tolerance conferred by natural alleles of OsNRAT1 seems to be caused by higher expression of the transporter and more efficient translocation of aluminum from the root cell wall to the root cell and subsequently, in the vacuole, thus decreasing aluminum toxicity (Li et al, 2014). Several different natural variation approaches identified aluminum-activated malate transporter1 to underlie aluminum tolerance in wheat (Triticum aestivum; Sasaki et al, 2004;Raman et al, 2005;Zhou et al, 2007;Cai et al, 2008). More recently, GWASs in 1,055 wheat accessions identified known and many novel regions associated with aluminum resistance (Raman et al, 2010), supporting the notion of the power of the GWAS technique.…”

The roles of organic anion permeases in aluminium resistance and mineral nutrition

“…Evidence that TaALMT1 is the major gene for Al 3+ resistance in wheat includes the findings that it co-segregates with resistance, that its expression in several heterologous systems confers an Al 3+ -activated efflux of malate and when expressed in tobacco (Nicotiana tabacum) suspension cells and intact barley (Hordeum vulgare) plants, increases their Al 3+ resistance [6,7]. Furthermore, TaALMT1 is located within a single major quantitative trait locus (QTL) for Al 3+ resistance identified in several different doubled-haploid populations of wheat [8,9]. These observations coupled with previous findings that Al 3+ -activated efflux of malate is a general mechanism controlling Al 3+ resistance in wheat [10] suggests that TaALMT1 is a major and widespread gene for Al 3+ resistance in this species.…”

“…The alleles occur in both Al 3+ -resistant and Al 3+ -sensitive wheat genotypes indicating that the different amino acids do not confer differences in resistance. Instead, the level of expression of either allele appears to be the major determinant of Al 3+ resistance in wheat [8]. TaALMT1 is expressed constitutively in root apices and the level of expression in different genotypes correlates positively with Al 3+ resistance [14].…”