A half-type AvABCG1 transporter derived from Andropogon virginicus L. confers aluminum tolerance

Aluminum (Al) induced genes were isolated from a wild plant, Andropogon virginicus L. by a method involving arbitrarily primed PCR-based RNA finger printing. One of the clones, AP18-2-1, was induced in both roots and shoots by Al and diamide treatments, and slightly by Cu and Zn treatments. Full-length cDNA (2287. bp) was obtained by RACE (rapid amplification of cDNA ends) PCR and DNA sequencing indicated that it encoded a half-type ABC transporter that was highly homologous to other ABCG family genes. The Al-induced transporter gene derived from A. virginicus L. was therefore designated AvABCG1. The AvABCG1 gene conferred tolerance to Al, Cu and diamide in Arabidopsis thaliana transformants. A fusion protein (AvABCG1::GFP) was localized in the cell membrane region. Immunohistological analysis of the native protein in A. virginicus L. indicated that it localized to both exodermis and endodermis in roots, and to the vascular bundle sheath and its extensions in both upper and lower epidermal cells in leaves. Fluorescent measurement showed that absorbed Al was detected in almost the same areas as the AvABCG1 protein in both root and leaf. We conclude that the AvABCG1 transporter may confer Al tolerance by accumulating absorbed Al ions in specific regions of the plant.