Sugars are essential sources of energy and carbon and also function as key signalling molecules in plants. Sugar transport proteins (STP) are proton-coupled symporters responsible for uptake of glucose from the apoplast into plant cells. They are integral to organ development in symplastically isolated tissues such as seed, pollen and fruit. Additionally, STPs play a vital role in plant responses to stressors such as dehydration and prevalent fungal infections like rust and mildew. Here we present a structure of Arabidopsis thaliana STP10 in the inward-open conformation at 2.6 Å resolution and a structure of the outward-occluded conformation at improved 1.8 Å resolution, both with glucose and protons bound. The two structures describe key states in the STP transport cycle. Together with molecular dynamics simulations that establish protonation states and biochemical analysis, they pinpoint structural elements, conserved in all STPs, that clarify the basis of proton-to-glucose coupling. These results advance our understanding of monosaccharide uptake, which is essential for plant organ development, and set the stage for bioengineering strategies in crops.

糖是能量和碳的重要来源，也是植物中的关键信号分子。糖转运蛋白 (STP) 是质子偶联的同向转运蛋白，负责将葡萄糖从质外体摄取到植物细胞中。它们是种子、花粉和果实等共生分离组织中器官发育不可或缺的组成部分。此外，STP 在植物对脱水和普遍存在的真菌感染（如锈病和霉菌）的应激反应中起着至关重要的作用。在这里，我们展示了拟南芥的结构STP10 在 2.6 Å 分辨率下的向内开放构象和在改进的 1.8 Å 分辨率下的向外封闭构象结构，均结合葡萄糖和质子。这两个结构描述了 STP 传输周期中的关键状态。结合建立质子化状态和生化分析的分子动力学模拟，他们确定了所有 STP 中保守的结构元素，阐明了质子-葡萄糖偶联的基础。这些结果促进了我们对植物器官发育所必需的单糖摄取的理解，并为作物的生物工程策略奠定了基础。