经典蛋白质胞吐之旅始于高尔基体，经过反式高尔基网状体最终到达细胞膜或胞外。但是蛋白质经典胞吐途径并非其唯一外泌途径，非典型蛋白外泌作为经典途径的重要补充在细胞内发挥着重要的生物学功能。然而在植物细胞中，存在几种类型的非典型蛋白胞吐途径及其各自的调控机制与生物学功能都尚未研究清楚。本项目将以细胞壁合成过程中的关键酶——烟草果胶甲酯酶1 (NtPPME1) 为报告蛋白，来揭示一条决定细胞极性生长和分裂的非典型蛋白质外泌胞吐途径和其分子作用机理。初期研究结果显示，NtPPME1的外泌过程不依赖于经典的反式高尔基网状体且具有细胞极性。我们将深入研究NtPPME1的非典型极性胞吐过程和调控机制。通过各种细胞显微影像技术，结合药物处理响应反应，蛋白质动力学分析等来揭示NtPPME1的亚细胞定位。综合运用生物化学，遗传学和细胞器蛋白质组学等手段来阐明调控NtPPME1非典型胞吐途径的分子机理。

The conventional post-Golgi protein sorting and trafficking to plasma membrane (PM) is generally believed via the trans-Golgi network (TGN). Conventional protein exocytic secretion is not the sole pathway in cells. Unconventional protein exocytic pathways co-exist and play essential roles to complement the conventional pathway. However, how many different unconventional protein exocytic pathways exist in plant cells and their biological functions in regulating cell growth and development still remain largely unexplored. In this study, by using Nicotiana tabacum pectin methylesterase (NtPPME1) as a marker，we will identify a novel unconventional polar exocytosis pathway which mediates cell wall formation during cell expansion and cytokinesis. Our preliminary results show that NtPPME1-GFP resides on a TGN-independent polar exocytosis pathway. Further studies will focus on revealing the molecular mechanism of NtPPME1 mediated unconventional protein exocytosis pathway. Various microscopy imaging approaches, pharmaceutical treatments and protein dynamics analysis will be applied to identify the subcellular localization of NtPPME1. In addition, a combination of biochemistry, genetics and organelle proteomics analysis will be used to study the regulatory machinery of this unconventional exocytosis pathway.