A novel transcription factor SgTCP24 positively regulates mogroside V biosynthesis by activating SgSQE, SgCS, and SgCYP87D18 expression in Siraitia grosvenorii

Siraitia grosvenorii, a important economic crop is now used as a sweetener because its bioactive compound, mogroside V, has high sweetness with zero calories. However, mogroside V only accumulates in S. grosvenorii fruits, and its content is low. Enhancing the production of mogroside V has become a major commercial and scientific endeavor. TEOSINTE BRANCHED 1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factors (TFs) have a key role in regulating secondary metabolite biosynthesis, however, their role in regulating mogroside V is unclear. In this study, twenty-four SgTCP genes were identified based on genome-wide analysis and classified into two subgroups according to phylogenetic analysis. Based on the expression levels in different fruit development stages, co-expression network showed that SgTCP24 had a strong positive correlation with SgSQE, SgCS, and SgCYP87D18. Through the subcellular localization, yeast one hybrid, dual-luciferase, and electrophoretic mobility shift assay it was shown that SgTCP24 can directly bind and activate the expression of these three genes. When SgTCP24 was over-expressed in S. grosvenorii fruits, the production of mogroside V increased. Conversely, the content of mogroside V decreased in lines subjected to virus induced silencing. Our results provide a major insight into the molecular mechanism of TCP TFs in regulating the mogroside V biosynthesis, and offers a new method for enhancing the content of mogroside V in plants.