Identification of an abscisic acid transporter by functional screening using the receptor complex as a sensor
Identification of an abscisic acid transporter by functional screening using the receptor complex as a sensor
复制标题
DOI：
10.1073/pnas.1203567109
复制
发表时间：
2012-06-12
影响因子：
11.1
通讯作者：
Seo, Mitsunori
中科院分区：
文献类型：
--
作者：
Kanno, Yuri;Hanada, Atsushi;Seo, Mitsunori
植物激素脱落酸（ABA）在植物体内的运动已被记录；然而，调控ABA转运的分子机制尚不完全清楚。利用酵母双杂交系统筛选ABA受体PYR/PYL/RCAR与PP2C蛋白磷酸酶在低ABA浓度下相互作用的拟南芥cdna。通过使用这种方法，我们确定了NRT1/PTR家族的四个成员作为ABA进口商的候选人。在酵母和昆虫细胞中的转运实验表明，至少有一种候选的ABA进口转运蛋白（AIT） 1，被描述为低亲和力的硝酸盐转运蛋白NRT1.2，介导细胞对ABA的摄取。与WT相比，ait1/nrt1.2突变体在种子萌发和/或萌发后生长过程中对外源ABA不敏感，而在相同条件下，ait1/nrt1.2过表达导致ABA超敏感。有趣的是，ait1/nrt1.2的花序茎表面温度比WT低，这是由于开放气孔导致水分流失过多。我们检测了AIT1/NRT1.2在花序、茎、叶和根维管组织周围的启动子活性。这些数据表明，AIT1/NRT1.2在ABA合成位点作为ABA输入源的功能对花序茎气孔孔径的调控具有重要意义。
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.