Role of BraSWEET12 in Regulating Flowering through Sucrose Transport in Flowering Chinese Cabbage

Abstract

We assessed the flowering Chinese cabbage (Brassica rapa var. parachinensis), a specialty vegetable found in southern China. The sugar content of the stem tip is closely related to bolting and flowering. Sugar Will Eventually be Exported Transporters (SWEETs) are bidirectional sugar transporter proteins involved in numerous plant growth and development processes. The expression of BraSWEET12 is positively correlated with sugar content. However, it is unclear whether BraSWEET12 is involved in bolting and flowering. In this study, we identified and characterized BraSWEET12. BraSWEET12 in flowering Chinese cabbage contains 288 amino acids and is located on the cell membrane as a sucrose transporter protein. BraSWEET12 is highly expressed in the petals and stem tips of flowering Chinese cabbage and is upregulated by gibberellin and low temperatures. Overexpression of BraSWEET12 in Arabidopsis can increase sucrose content at the stem tip, upregulate the expression of AtAP1 and AtLFY, and advance the flowering time. Subsequently, our results indicate that BraSWEET12 is involved in sucrose accumulation at the stem tip of flowering Chinese cabbage and plays a crucial role in flowering regulation. These results provide a reference for elucidating the regulatory mechanisms underlying flowering Chinese cabbage bolting and flowering.