Acquisition of aluminium tolerance by modification of a single gene in barley

Abstract

Originating from the Fertile Crescent in the Middle East, barley has now been cultivated widely on different soil types including acid soils, where aluminium toxicity is a major limiting factor. Here we show that the adaptation of barley to acid soils is achieved by the modification of a single gene (HvAACT1) encoding a citrate transporter. We find that the primary function of this protein is to release citrate from the root pericycle cells to the xylem to facilitate the translocation of iron from roots to shoots. However, a 1-kb insertion in the upstream of the HvAACT1 coding region occurring only in the Al-tolerant accessions, enhances its expression and alters the location of expression to the root tips. The altered HvAACT1 has an important role in detoxifying aluminium by secreting citrate to the rhizosphere. Thus, the insertion of a 1-kb sequence in the HvAACT1 upstream enables barley to adapt to acidic soils.

Natural variation underlies alterations in Nramp aluminum transporter ( NRAT1 ) expression and function that play a key role in rice aluminum tolerance

“…Further functional promoter studies are required to confirm/identify these SNPs as causative elements underlying elevated NRAT1 expression in the more tolerant rice lines. In addition to these five SNPs in the promoter region, we identified four SNPs in the coding region that were exclusively present in the nine sensitive aus lines and cause missense mutations (Table 1 and Table S2) (21). In this report we did conclusively demonstrate that each of these four SNPs in the sensitive aus allele significantly affects NRAT1's Al transport activity (Fig.…”

“…For instance, the size of a tourist-like miniature inverted repeat transposable element (MITE) in the promoter of the sorghum Al tolerance gene, SbMATE, is positively correlated with multidrug and toxic compound extrusion (SbMATE) expression (10), where increase in MITE size results in a greater number of sequence repeats in the MITE. Also, in barley, a 1-kb insertion in the promoter of the barley Al tolerance gene, aluminum-activated citrate transporter (HvAACT1), enhances HvAACT1 expression and alters the localization of HvAACT1 expression in roots so that it is expressed in the root tip epidermis, which is a novel feature of Al tolerance for this allele (21).…”

A Member of the Heavy Metal P-Type ATPase OsHMA5 Is Involved in Xylem Loading of Copper in Rice

“…The tissue-specific expression of OsHMA5 was examined with laser microdissection according to the described methods (Fujii et al, 2012). The segments at 1.75 to 2.25 cm from the root tip of 4-d-old seedlings of cv Nipponbare were collected for the tissue sections.…”

Review Genetic and molecular mechanisms of aluminum tolerance in plants

“…More recently, a distinct mechanism for regulating HvAACT1 expression was presented in barley (Fujii et al, 2012). An insertion of 1-kb sequence at 6 kb upstream from the HvAACT1 coding region added multiple transcriptional start sites, enhancing this gene expression in the root tips.…”

“…An insertion of 1-kb sequence at 6 kb upstream from the HvAACT1 coding region added multiple transcriptional start sites, enhancing this gene expression in the root tips. The modified HvAACT1 expression pattern resulted in a superior Al-induced citrate exudation that consequently improved Al tolerance in barley (Fujii et al, 2012).…”