Functional characterization of phosphatidylinositol transfer proteins in yeast and Arabidopsis and their potential use to increase aluminum tolerance in plants

磷脂酰肌醇（PtdIns）转移蛋白（PITPs）存在于所有真核生物中，在脂质代谢和膜运输之间的界面调节信号事件。Sec14，酵母主要的PITP需要协调磷脂（PL）代谢和反式高尔基网络（TGN）分泌囊泡的生物发生。我们最近在解决Sec14同源Sfh1与PtdIns，磷脂酰胆碱（PtdCho）和磷脂酰乙醇胺（PtdEtn）复合物的结构方面取得了突破，首次对Sec14蛋白如何结合其生理底物进行了结构鉴定，并提出了Sec14在与PtdCho的界面交换反应中将PtdIns呈现给脂质修饰酶的机制。这项研究是基于我们发现来自酵母和拟南芥的两个Sec14家族成员在酵母中异位表达时增加铝（Al）耐受性。铝对植物、动物和微生物有毒，是全球农作物生产的最大限制之一。我们将1)研究这些Sec14同源物的脂质结合如何转化为生物活性和增加铝耐受性，2)确定它们的下游脂质和蛋白质靶点，3)制定提高植物铝耐受性的策略。我们的功能研究将以脂质结合的结构信息为指导，并将包括无偏倚的基因组宽筛选。我们期望我们的工作将使我们对植物中脂质信号的调控和神秘的sec14蛋白家族的生物学有更多的了解。

Phosphatidylinositol (PtdIns) transfer proteins (PITPs), found in all eukaryotes, regulate signaling events at the interface between lipid metabolism and membrane trafficking. Sec14, the major yeast PITP is required to coordinate phospholipid (PL) metabolism with biogenesis of secretory vesicles at the trans-Golgi network (TGN). Our recent breakthrough in solving structures of Sec14 homolog Sfh1 in complex with PtdIns, phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) allowed for the first time a structural appreciation of how Sec14 proteins bind their physiological substrates and suggested a mechanism by which Sec14 presents PtdIns to a lipid-modifying enzyme during an interfacial exchange reaction with PtdCho. The proposed research is based on our discovery that two members of the Sec14 family from yeast and Arabidopsis increase aluminum (Al) tolerance when ectopically expressed in yeast. Aluminum is toxic to plants, animals and microbes and represents one of the biggest limitations to crop production worldwide. We will 1) investigate how lipid binding of these Sec14 homologues translates into biological activity and increased Al tolerance, 2) identify their downstream lipid and protein targets and 3) develop strategies to increase Al tolerance in plants. Our functional studies will be guided by the structural information on lipid binding and will include unbiased genome wide screens. We anticipate that our work will give us more insight on the regulation of lipid signaling and the biology of the enigmatic family of Sec14proteins in plants.