AtAzg1 and AtAzg2 comprise a novel family of purine transporters in Arabidopsis.

In plants, nucleobase biochemistry is highly compartmented relying upon a well-regulated and selective membrane transport system. In Arabidopsis two proteins, AtAzg1 and AtAzg2, show substantial amino acid sequence similarity to the adenine-guanine-hypoxanthine transporter AzgA of Aspergillus nidulans. Analysis of single and double mutant lines harboring T-DNA insertion alleles AtAzg1-1 and AtAzg2-1 reveal a marked resistance to growth in the presence of 8-azaadenine and 8-azaguanine but not to other toxic nucleobase analogues. Conversely, yeast strains expressing AtAzg1 and AtAzg2 gain heightened sensitivity to growth on 8-azaadenine and 8-azaguanine. Radio-labeled purine uptake experiments in yeast and in planta confirm the function of AtAzg1 and AtAzg2 as plant adenine-guanine transporters.