Heterologous expression of TuCAX1a and TuCAX1b enhances Ca2+ and Zn2+ translocation in Arabidopsis

Abstract

TuCAX1a and TuCAX1b improved Ca²⁺ and Zn²⁺ translocation and TuCAX1b enhanced Ca²⁺, Zn²⁺, Mn²⁺ and Fe²⁺ content when exposed to Cd²⁺; Cd²⁺ translocation was inhibited under Ca²⁺ and Zn²⁺. Cation/H⁺ antiporters (CAXs) are involved in the translocation of Ca²⁺ and various metal ions in higher plants. In the present study, TuCAX1a and TuCAX1b, two cation/H⁺ antiporters, were isolated from the diploid wheat Triticum urartu, and their metal cation translocation functions investigated. TuCAX1a and TuCAX1b showed abundant tissue-specific expression in the internode and beard, respectively, and their expression levels were increased in shoots exposed to Cd²⁺, Zn²⁺ and Ca²⁺. Plant phenotype analysis showed that overexpression of TuCAX1a and TuCAX1b could improve the tolerance of Arabidopsis to exogenous Ca²⁺ and Zn²⁺. In the plant shoots and roots, the contents of Ca²⁺ and Zn²⁺ were higher than wild-type plants under Ca²⁺ and Zn²⁺ treatments, indicating that TuCAX1a and TuCAX1b can enhance Ca²⁺ and Zn²⁺ translocation. Ca²⁺, Zn²⁺, Mn²⁺ and Fe²⁺ contents showed higher accumulation in TuCAX1b-transgenic Arabidopsis shoots than in wild-type plants exposed to Cd²⁺, and the translocation of Cd²⁺ was inhibited under Ca²⁺ and Zn²⁺. Overall, the present study provides a novel genetic resource for improving the uptake of microelements and reducing accumulation of toxic heavy metals in wheat.

Keywords: Heavy metal; Tolerance; Translocation; Triticum urartu; TuCAX1a; TuCAX1b.