Sugar Transporter Protein 1 (STP1) contributes to regulation of the genes involved in shoot branching via carbon partitioning in <i>Arabidopsis</i>

We previously demonstrated that alterations in sugar partitioning affect the expression of genes involved in hormone biosynthesis and responses, including BRANCHED1 (BRC1), resulting in enhanced shoot branching in transgenic <i>Arabidopsis</i> plants overexpressing cyanobacterial fructose-1,6-bisphosphatase-II in the cytosol (AcF). The exogenous treatment of wild-type <i>Arabidopsis</i> plants with sugars showed the same transcript characteristics, indicating that sugars act as a signal for branching. We also found that the reductions induced in <i>BRC1</i> expression levels in wild-type plants by the sugar treatments were suppressed in the knockout mutant of sugar transporter 1 (<i>stp1-1)</i>. Intracellular sugar contents were similar in <i>stp1-1</i> and wild-type plants following the sugar treatments, suggesting that STP1 acts as a factor for the regulation of shoot branching depending on extracellular sugar contents. <b>Abbreviations:</b> BRC1: BRABCHED1; FBP/SBPase: fructose-1,6-/sedoheptulose-1,7-bisphosphatase; Glc: glucose; HXK: hexokinase; SnRK1.1/AKIN10: SNF1-RELATED PROTEIN KINASE 1.1; Suc: sucrose; SnRK1: sucrose non-fermenting 1-related protein kinase; STP: sugar transporter protein Sugar Transporter Protein 1 (STP1) contributes to regulation of shoot branching.