Potassium Transport to Shoot Organs by SHY3/AtKUP2

为了生长，植物细胞需要水分，这样产生的内部膨胀压力就可以推动细胞壁，使其伸展。水分吸收主要依赖于细胞内钾离子提供的渗透电位，因此钾离子的运输是植物细胞生长的关键。模式植物拟南芥（Arabidopsis thaliana）编码AtKUP2钾转运蛋白的基因发生突变，导致该植物的茎和叶细胞变小，这可能是由于向茎部输送钾的减少。这项资助采用三种方法来了解AtKUP2在植物钾运动中的确切作用。首先，研究哪些细胞会开启编码AtKUP2的基因，将揭示AtKUP2可能在哪些组织中介导K+摄取。其次，检查AtKUP2蛋白在这些细胞中的亚细胞定位将揭示转运蛋白是在质膜还是在内部储存液泡的膜中，以及蛋白质是否不对称定位。第三，对正常植物和突变植物中铷离子（Rb+，一种方便的K+替代品）运动动力学的研究将解决钾运动的假定障碍可能在哪里。这些实验将揭示AtKUP2转运体是否在根细胞或茎细胞中吸收钾，并为进一步研究K+营养和生长控制提供依据。

To grow, plant cells take up water so that the resulting internalturgor pressure can push against the cell wall, causing it to stretch.Water uptake depends on osmotic potential provided principally byintracellular potassium (K+) ions, and potassium transport is therefore keyto plant cell growth. A mutation in the gene encoding the AtKUP2 potassiumtransporter of the model plant Arabidopsis thaliana causes the plants tohave small cells in the stem and leaves, probably because of a decrease inpotassium delivery to the shoot. This grant takes three approaches tounderstand the precise role of AtKUP2 in potassium movements within theplant. First, study of which cells turn on the gene encoding AtKUP2 willreveal in which tissues AtKUP2 may mediate K+ uptake. Second, examinationof the subcellular localization of AtKUP2 protein in these cells willreveal whether the transporter is in the plasma membrane or in a membraneof an internal storage vacuole, and whether the protein is asymmetricallylocalized. Third, studies of the kinetics of movements of rubidium ions(Rb+, a convenient substitute for K+) in normal and mutant plants willaddress where the putative block in potassium movement may be. Theseexperiments will reveal whether the AtKUP2 transporter acts to take uppotassium in root or in shoot cells, and will lead to further studies of K+nutrition and growth control.