TgWRKY25-TgSBP1 module promotes cell expansion in Torreya grandis cones

Sucrose-binding proteins (SBPs), a class of proteins in plants, are involved in sucrose transport and utilization, and play a vital contribution in regulating plant growth and development. As demonstrated by prior studies, in plants such as soybean and tobacco, SBP-mediated sucrose transport is crucial for both plant growth and development and carbohydrate partitioning. However, in comparison to the extensive research on the function of SBP in angiosperms, there is currently a lack of in-depth studies on the specific role of SBPs in gymnosperms. In the gymnosperm Torreya grandis, we identified that TgSBP1 may be involved in the cell expansion of its cones by mediating sucrose accumulation. In this study, we found that during cone development in T. grandis, the expression of TgSBP1 showed a significant upward trend. Heterologous expression in tomatoes and transient overexpression in T. grandis cones indicated that TgSBP1 positively modulated the expansion of cone cells. In contrast, transient silencing of TgSBP1 significantly diminished sucrose accumulation and reduced cell size. Furthermore, the WRKY transcription factor TgWRKY25 was identified to participate in regulating TgSBP1 expression. Further functional analysis revealed that TgWRKY25 directly bound to the promoter of TgSBP1 and upregulate its expression, which increased sucrose content in cones and led to a significant enlargement of cell size. Taken together, these findings indicate that TgWRKY25 modulates sucrose level by upregulating TgSBP1 expression, thereby promoting cone cell expansion in T. grandis.