Ectopic overexpression of the aluminum-induced protein gene from Panax ginseng enhances heavy metal tolerance in transgenic Arabidopsis

Abstract

Aluminum (Al), one of the most abundant metals in agricultural soils, significantly limits crop growth and productivity in acidic soil by inhibiting root elongation. Al ions, especially Al3+, have a toxic effect on both plant and animal cells under low-pH conditions. We first isolated and characterized aluminum-induced protein (AIP) cDNA from a 4-year-old root of Panax ginseng Meyer. This cDNA encodes an open reading frame of 711 bp with a deduced amino acid sequence of 236 residues. The calculated molecular mass of the mature protein is approximately 58.9 kDa with a predicated isoelectric point of 5.13. The Panax ginsengAIP (PgAIP) contains a domain also present in wheat aluminum-induced protein 7 (Wali7) and shares homology with the AIPs of other species, including Codonopis and Arabidopsis. The PgAIP gene was abundantly expressed in the plant’s leaves and was up-regulated by Al exposure. The functional role of PgAIP in Al tolerance was further validated through its overexpression in Arabidopsis. Transgenic Arabidopsis plants overexpressing the PgAIP gene showed enhanced Al tolerance in terms of root growth when compared to wild-type plants, suggesting PgAIP is important in plant defense against Al toxicity. Confocal analysis of CFP-tagging PgAIP in Arabidopsis showed subcellular localization in the plasma membrane. Our results suggest that PgAIP in the plasma membrane plays an important role in the protection of plant cells against heavy metal exposure