Sugars will eventually be exported transporter 18 mediates glucose metabolism in Torreya grandis kernels

Sugars Will Eventually be Exported Transporters (SWEETs) are a novel class of sugar transporter proteins that play crucial roles in plant growth, development, physiological metabolism, and responses to environmental stresses. Previous studies have demonstrated that SWEET-mediated glucose metabolism plays a critical role in various developmental stages in plants like Arabidopsis and rice. However, their specific function in Torreya grandis, an economically important tree species, remain largely unknown. In this study, we identified 34 SWEET genes in T. grandis, which were distributed across 11 chromosomes. Expression patterns revealed that TgSWEET18 was highly expressed in the kernel, with a significant increase during kernel development. Functional assays confirmed that TgSWEET18 exhibited transport activity for hexose, such as glucose. Overexpression of TgSWEET18 in the kernel significantly increased both in TgSWEET18 expression and glucose content, while silencing TgSWEET18 led to reduced expression and glucose levels. Furthermore, we identified TgMYB1 as a transcription factor that directly binds to the TgSWEET18 promoter, upregulating its expression and enhancing glucose accumulation in the kernel. In summary, our findings reveal that TgMYB1 enhances glucose transport and accumulation in T. grandis kernel by directly activating TgSWEET18 expression.