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Identification of an abscisic acid transporter by functional screening using the receptor complex as a sensor
- Kanno, Yuri, Hanada, Atsushi, Chiba, Yasutaka, Ichikawa, Takanari, Nakazawa, Miki, Matsui, Minami, Koshiba, Tomokazu, Kamiya, Yuji, Seo, Mitsunori
- Proceedings of the National Academy of Sciences of the United States of America 2012 v.109 no.24 pp. 9653-9658
- Arabidopsis, abscisic acid, biosynthesis, complementary DNA, gene overexpression, hypersensitivity, insects, leaves, mutants, nitrates, roots, screening, seed germination, stems, stomata, stomatal movement, surface temperature, two hybrid system techniques, vascular tissues, yeasts
- Movement of the plant hormone abscisic acid (ABA) within plants has been documented; however, the molecular mechanisms that regulate ABA transport are not fully understood. By using a modified yeast two-hybrid system, we screened Arabidopsis cDNAs capable of inducing interactions between the ABA receptor PYR/PYL/RCAR and PP2C protein phosphatase under low ABA concentrations. By using this approach, we identified four members of the NRT1/PTR family as candidates for ABA importers. Transport assays in yeast and insect cells demonstrated that at least one of the candidates ABA-IMPORTING TRANSPORTER (AIT) 1, which had been characterized as the low-affinity nitrate transporter NRT1.2, mediates cellular ABA uptake. Compared with WT, the ait1 / nrt1 . 2 mutants were less sensitive to exogenously applied ABA during seed germination and/or postgermination growth, whereas overexpression of AIT1 / NRT1 . 2 resulted in ABA hypersensitivity in the same conditions. Interestingly, the inflorescence stems of ait1 / nrt1 . 2 had a lower surface temperature than those of the WT because of excess water loss from open stomata. We detected promoter activities of AIT1 / NRT1 . 2 around vascular tissues in inflorescence stems, leaves, and roots. These data suggest that the function of AIT1 / NRT1 . 2 as an ABA importer at the site of ABA biosynthesis is important for the regulation of stomatal aperture in inflorescence stems.