Molecular mechanism of electrogenic carrier- and pump-mediated vacuolar transport

液泡膜参与了溶质进出植物主要细胞器的运输。除了无机离子和代谢物外，大量的质子和糖也穿梭在膜上。两个质子泵，V-ATPase和VPPase，在液泡膜上产生质子和电梯度，驱动糖的积累和释放。不同基因家族的成员，如SUC、TMT和VGT，都与糖运输和调节液泡糖池的功能有关。在该联盟的第一个资助期内，我们研究了V型质子ATPase的作用方式和性质，并与糖载体SUC4和TMT1/2的作用方式和性质进行了对比。利用单液泡技术结合分子方法、瞬时过表达和拟南芥及其突变体的电生理分析，我们发现I.V-ATPase反馈pH梯度和跨液泡膜的膜电位。SUC4作为H+/蔗糖转运体从液泡III释放糖。TMT1/2代表了第一个能够将高容量葡萄糖和蔗糖装载到液泡中的质子偶联糖逆向转运蛋白。关于第二个术语的中心问题是，寒冷和盐如何改变不同液泡转运蛋白的运输周期。鉴于蛋白激酶Vik与TMT1相互作用，在接下来的研究中，我们将关注与TMT1相互作用的激酶是否以及如何调节糖转运蛋白的活性和选择性。随着我们对V-ATPase的进一步研究，我们将对第二个液泡质子泵-焦磷酸酶(PPase)进行比较研究。此外，我们将提请我们注意ERD6，ERDL6，ERD3和TLT1，它们是MST(类)超家族中可能在糖运输中起作用的两个亚类成员。

The vacuolar membrane is engaged with solute transport into and out of the major plant organelle. Besides inorganic ions and metabolites, large quantities of protons and sugars are shuttled across this membrane. Two proton pumps, the V-ATPase and the VPPase, generate a proton- and electrical gradient across the vacuolar membrane that drives accumulation and release of sugars. Members of different gene families such as SUC, TMT, and VGT have been associated with a function in sugar transport and modulation of the vacuolar sugar pool. In the first funding period within the consortium we have studied the mode of action and properties of the V-type proton ATPase side by side with those of the sugar carriers SUC4 and TMT1/2. Using single vacuole-techniques combined with molecular approaches, transient overexpression, and electrophysiological analysis with Arabidopsis thaliana and mutants thereof we found that I. V-ATPase feeds back on pH gradient and membrane potential across the vacuolar membraneII. SUC4 operates as a H+/sucrose symporter for sugar release from the vacuoleIII. TMT1/2 represents the first proton-coupled sugar antiporter capable of high capacity glucose and sucrose loading into the vacuole.The central question regarding the 2nd term is how cold and salt alter the transport cycle of distinct vacuolar transporters. Given that the protein kinase VIK interacts with TMT1, in the following research period we will draw our attention on whether and how the TMT1- interacting kinase tunes the activity and selectivity of the sugar transporter. Following up with our proceeding studies on the V-ATPase, we will perform comparative studies regarding the second vacuolar proton pump, the pyrophosphatase (PPase). Furthermore we will draw our attention to ERD6, ERDL6, ERD3 and TLT1 as members of two subclades within the MST(- like) superfamily with a probable function in sugar transport.