Sugar translocation between cells and between subcellular compartments in plants requires either plasmodesmata or a diverse array of sugar transporters. Interactions between plants and associated microorganisms also depend on sugar transporters. The sugars will eventually be exported transporter (SWEET) family is made up of conserved and essential transporters involved in many critical biological processes. The functional significance and small size of these proteins have motivated crystallographers to successfully capture several structures of SWEETs and their bacterial homologs in different conformations. These studies together with molecular dynamics simulations have provided unprecedented insights into sugar transport mechanisms in general and into substrate recognition of glucose and sucrose in particular. This review summarizes our current understanding of the SWEET family, from the atomic to the whole-plant level. We cover methods used for their characterization, theories about their evolutionary origins, biochemical properties, physiological functions, and regulation. We also include perspectives on the future work needed to translate basic research into higher crop yields.

 摘 要 

植物细胞间和亚细胞区室间的糖转运需要胞间连丝或多种糖转运蛋白。植物和相关微生物之间的相互作用也依赖于糖转运蛋白。糖转运蛋白SWEET家族包含了保守且必需的转运蛋白，参与了植物中许多的关键生物学过程。由于这些蛋白具有非常重要的功能，同时蛋白分子量较小，因此晶体学家成功地捕获了一些SWEETs蛋白及其在细菌中同源蛋白不同构象的晶体结构。这些研究与分子动力学模拟一起，为糖的转运机制，尤其是葡萄糖和蔗糖的底物识别提供了前所未有的见解。本文主要是总结了目前对于SWEET家族从原子水平到整个植物水平的理解。作者系统介绍了SWEET家族蛋白的特征、演化起源、生化特性、生理功能以及调节机制。另外，作者还展望了未来将基础研究转化为作物产量改良等实际应用所需的工作。

 Li-Qing Chen