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 BoALMT1 (KF322104) was cloned from cabbage (Brassica oleracea). BoALMT1 showed higher expression in roots than in shoots. The expression of BoALMT1 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. Xenopus oocytes and Arabidopsis thaliana expressing BoALMT1 excreted more H+ under Al treatment. Overexpressing BoALMT1 in transgenic Arabidopsis resulted in enhanced Al tolerance and increased malate secretion. The results suggested that BoALMT1 functions as an Al-resistant gene and encodes a malate transporter. Expressing BoALMT1 in Xenopus oocytes or A. thaliana indicated that BoALMT1 could increase malate secretion and H+ efflux to resist Al tolerance.
Highlights
Al is the most abundant metal and the third most abundant element, making up around 7% of the earth’s crust (Tesfaye et al, 2001)
Overexpressing BoALMT1 in Arabidopsis resulted in enhanced Al tolerance and increased malate secretion. These results suggested that BoALMT1 has an important role in Al tolerance in cabbage
BLAST analysis revealed that the sequence of BoALMT1 was a 99% match to BnALMT1 from rape, 73% match to AtALMT1 from Arabidopsis, and 33% match to TaALMT1 from wheat
Summary
Al is the most abundant metal and the third most abundant element, making up around 7% of the earth’s crust (Tesfaye et al, 2001). When the soil pH value is lower than 5.0, the soluble aluminum in soil solutions is mostly present as the toxic Al3+, which inhibits root growth at micromolar concentrations in many species (Kochian et al, 2005). The most common OAs involved in the Al detoxification process are malate, citrate, and oxalate, depending on the plant. Malate is used in wheat (Delhaize et al, 1993) and Arabidopsis (Hoekenga et al, 2003), citrate is secreted in maize (Pellet et al, 1995), and oxalate is used in buckwheat (Zheng et al, 2005) and tomato (Yang et al, 2008)
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