A wheat gene encoding an aluminum‐activated malate transporter

TLDR

Toxic aluminum in acid soils inhibits root elongation, but some wheat cultivars tolerate it by exuding malate that complexes with Al, a mechanism hypothesized to underlie Al tolerance. The study aimed to clone the wheat gene ALMT1, which co‑segregates with Al tolerance in near‑isogenic lines. ALMT1 encodes a membrane protein expressed at higher levels in tolerant roots, and its heterologous expression in oocytes, rice, and tobacco cells induces Al‑activated malate efflux. The cloned ALMT1 gene encodes an Al‑activated malate transporter that confers Al tolerance to plant cells, as demonstrated by increased tolerance in tobacco cells.

Abstract

Summary The major constraint to plant growth in acid soils is the presence of toxic aluminum (Al) cations, which inhibit root elongation. The enhanced Al tolerance exhibited by some cultivars of wheat is associated with the Al‐dependent efflux of malate from root apices. Malate forms a stable complex with Al that is harmless to plants and, therefore, this efflux of malate forms the basis of a hypothesis to explain Al tolerance in wheat. Here, we report on the cloning of a wheat gene, ALMT1 ( al uminum‐activated m alate t ransporter), that co‐segregates with Al tolerance in F 2 and F 3 populations derived from crosses between near‐isogenic wheat lines that differ in Al tolerance. The ALMT1 gene encodes a membrane protein, which is constitutively expressed in the root apices of the Al‐tolerant line at greater levels than in the near‐isogenic but Al‐sensitive line. Heterologous expression of ALMT1 in Xenopus oocytes, rice and cultured tobacco cells conferred an Al‐activated malate efflux. Additionally, ALMT1 increased the tolerance of tobacco cells to Al treatment. These findings demonstrate that ALMT1 encodes an Al‐activated malate transporter that is capable of conferring Al tolerance to plant cells.