Sugar transport plays a pivotal role in determining the productivity of plants and their capacity to act as carbon sinks. In the major fruit crop grapevine (Vitis vinifera L.), the transporter gene Vitis vinifera Sugars Will Eventually be Exported Transporter 15 (VvSWEET15)is strongly expressed during berry ripening. However, the specific functions of VvSWEET15 and the mechanisms governing its transcriptional regulation remain largely unresolved. Here, we demonstrate that VvSWEET15 functions as a hexose transporter whose expression is associated with the strong sugar accumulation that starts at the véraison stage. We also characterize VvERF105 as a repressor that binds to the LTR-binding element in the VvSWEET15 promoter, thereby down-regulating its expression and inhibiting hexose accumulation at the pre-véraison stage. In contrast, VvNAC72 is an activator that binds to the VvNAC72-binding domain (CACATG) and promotes VvSWEET15 expression and hexose accumulation at post-véraison stages. Both transcription factors and VvSWEET15 are preferentially expressed in phloem cells. These results demonstrate that the balance between transcriptional activators and repressors is critical in regulating VvSWEET15 expression in sink organs. Further understanding of these processes will help improve plant productivity and their potential to be used as carbon sinks.

中文翻译：

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转录因子 ERF105 和 NAC72 调节葡萄中糖转运蛋白基因的表达和己糖积累


糖的运输在决定植物的生产力及其作为碳汇的能力方面起着关键作用。在主要水果作物葡萄藤 （Vitis vinifera L.） 中，转运蛋白基因 Vitis vinifera Sugars Will Eventually be Exporting Transporter 15 （VvSWEET15） 在浆果成熟过程中强烈表达。然而，VvSWEET15 的特定功能和控制其转录调控的机制在很大程度上仍未解决。在这里，我们证明 VvSWEET15 作为己糖转运蛋白发挥作用，其表达与从 véraison 阶段开始的强糖积累有关。我们还将 VvERF105 表征为与 VvSWEET15 启动子中的 LTR 结合元件结合的阻遏物，从而下调其表达并抑制 pre-véraison 阶段的己糖积累。相比之下，VvNAC72 是一种激活剂，可与 VvNAC72 结合结构域 （CACATG） 结合，并促进 VvSWEET15 表达和热后期己糖积累。转录因子和 VvSWEET15 均优先在韧皮部细胞中表达。这些结果表明，转录激活因子和抑制因子之间的平衡对于调节 VvSWEET15 在下沉器官中的表达至关重要。进一步了解这些过程将有助于提高植物生产力及其用作碳汇的潜力。