植物Na+,K+/H+反向交换体是调节细胞pH和离子平衡的重要蛋白，在植物生长发育的许多方面起着重要的作用。近年研究发现，AtNHX5和AtNHX6调控着植物的生长发育过程；它们在细胞扩展、细胞增殖、pH平衡和蛋白质运输等过程中起着重要的作用。然而目前对于AtNHX5和AtNHX6调控植物生长发育的分子机理尚无任何报道。同时，拟南芥存在一类定位于内质网的生长素运输蛋白PIN蛋白（ER-PINs）。目前关于ER-PINs调节细胞生长素平衡和植物生长发育的功能已有报道，但是关于ER-PINs 的作用机制和调节机理还很不清楚。本项目将二者联系起来，试图证明AtNHX5和AtNHX6是通过调控ER-PINs调节细胞生长素的平衡，进而调节植物的生长发育过程。本项目的研究将为认识AtNHX5和AtNHX6调控植物生长发育的分子机理，阐明ER-PINs的作用机制和调节机理奠定理论基础。

Plant Na+,K+/H+ antiporters (NHX) are critical players in cellular pH and ion homoeostasis, and play essential roles in many aspects of growth and development in plants. AtNHX5 and AtNHX6 which localize in the Golgi/TGN are members of the endosomal antiporters. A recent report indicates that AtNHX5 and AtNHX6 control Arabidopsis growth and development; AtNHX5 and AtNHX6 are critical for cell expansion, cell proliferation, pH homeostasis, and protein trafficking in Arabidopsis (Bassil et al., 2011). However, the molecular mechanism underlying the function of AtNHX5 and AtNHX6 in regulating plant growth and development remains largely unknown. Meanwhile, a new type of the auxin efflux carrier PIN proteins, including PIN5, PIN6 and PIN8, is found to be localized in the endoplasmic reticulum. Currently, the ER-localized PIN proteins (ER-PINs) have been demonstrated to function in auxin homeostasis as well as in plant growth and development. But their mode of action and regulating mechanism are not clear (Adamowski and Friml, 2015). In this study, by linking plant NHXs with PINs, we aim to demonstrate that AtNHX5 and AtNHX6 control plant growth and development through regulating the cellular auxin homeostasis maintained by the ER-PINs. We plan to study the role of AtNHX5 and AtNHX6 in regulating the activity and function of ER-PINs using molecular genetics and cell biological methods and techniques. Our study will pave the way for the understanding of the mechanism underlying the function of AtNHX5 and AtNHX6 in regulating plant growth and development as well as the mode of action of ER-PINs and their regulating mechanism in plants.