BoALMT1, an Al-Induced Malate Transporter in Cabbage, Enhances Aluminum Tolerance in Arabidopsis thaliana

Abstract

Aluminum (Al) is present in approximately 50% of the arable land worldwide and is regarded as the main limiting factor of crop yield on acidic soil. Al-induced root malate efflux plays an important role in the Al tolerance of plants. Here, the aluminum induced malate transporter <i>BoALMT1</i> (KF322104) was cloned from cabbage (<i>Brassica oleracea</i>). <i>BoALMT1</i> showed higher expression in roots than in shoots. The expression of <i>BoALMT1</i> was specifically induced by Al treatment, but not the trivalent cations lanthanum (La), cadmium (Cd), zinc (Zn), or copper (Cu). Subcellular localization studies were performed in onion epidermal cells and revealed that BoALMT1 was localized at the plasma membrane. Scanning Ion-selective Electrode Technique was used to analyze H⁺ flux. <i>Xenopus</i> oocytes and <i>Arabidopsis thaliana</i> expressing <i>BoALMT1</i> excreted more H⁺ under Al treatment. Overexpressing <i>BoALMT1</i> in transgenic <i>Arabidopsis</i> resulted in enhanced Al tolerance and increased malate secretion. The results suggested that <i>BoALMT1</i> functions as an Al-resistant gene and encodes a malate transporter. Expressing <i>BoALMT1</i> in <i>Xenopus</i> oocytes or <i>A. thaliana</i> indicated that BoALMT1 could increase malate secretion and H+ efflux to resist Al tolerance.