Molecular and physiological characterization of vacuolar disaccharide and polyol transporters and of vacuolar monosaccharide transporter-like proteins

单糖和双糖以及环状和线性多元醇进出液泡的严格调控运输对于高等植物的最佳生长发育和抗逆性是必不可少的。在拟南芥中，至少有26种tono质体（TP）定位转运蛋白参与了这些转运过程的催化。到目前为止，只有少数这些蛋白质的功能特征，而且，令人惊讶的是，关于这些转运蛋白到TP的分类机制几乎一无所知。我们继续表征tp定位的肌醇转运蛋白（INT1）和几种su4型蔗糖转运蛋白，并开始表征两个tp定位的单糖转运蛋白：ERD6和ERDL3（同义：ESL1）。通过与研究单位的合作伙伴合作，我们可以从功能上表征拟南芥SUC4蛋白作为一种从液泡中释放蔗糖的转运体，并且我们为不同物种的SUC4蛋白亚细胞定位的矛盾数据提供了解决方案。此外，我们可以证明su4是通过适配器蛋白复合物3 （AP-3）靶向TP的。对于INT1，我们鉴定并鉴定了一个tono质体靶向序列，并揭示了该转运体使用第二种不依赖ap -3的途径到达TP。在ap-3突变体中，交换靶向信号允许tp通过int1途径靶向su4。现在，我们的目标是详细地揭示TP的这两种排序路径。我们将确定SUC4途径的分类基序和INT1途径的适配器复合体，我们将确定蛋白质磷酸化的可能作用，我们将研究研究部门分析的关于这两种分类途径的所有转运蛋白。同时，我们将继续并完成两种液泡单糖转运蛋白的表征。

The tightly regulated transport of mono- and disaccharides and of cyclic and linear polyols into and out of the vacuole is indispensable for optimal growth and development and for stress tolerance in higher plants. In Arabidopsis at least 26 tonoplast (TP)-localized transporters are involved in the catalysis of these transport processes. So far, only few of these proteins have been functionally characterized, and, surprisingly, next to nothing is known on the mechanisms involved in the sorting of any of these transporters to the TP. We continued the characterization of a TP-localized inositol transporter (INT1) and of several SUC4-type sucrose transporters and we initiated the characterization of two TP-localized monosaccharide transporters: ERD6 and ERDL3 (synonym: ESL1). In cooperation with partners of the Research Unit we could functionally characterize the Arabidopsis SUC4 protein as a transporter that releases sucrose from the vacuole, and we provided a solution to contradictory data on the subcellular localization of SUC4 proteins from different species. Moreover, we could demonstrate that SUC4 is targeted to the TP via the adapter protein complex 3 (AP-3). For INT1, we identified and characterized a tonoplast-targeting sequence and revealed that this transporter uses a second, AP-3-independent route to the TP. Exchanging targeting signals allowed TP-targeting of SUC4 via the INT1-route in an ap-3 mutant. Now we aim to unravel these two sorting routes to the TP in detail. We will identify the sorting motif for the SUC4 route and the adapter complex for the INT1 route, we will determine the possible role of protein phosphorylation, and we will study all transporters analyzed in the Research Unit with respect to these two sorting routes. In parallel we will continue and finish the characterizations of two vacuolar monosaccharide transporters.