Regulatory mechanism of tree peony transcription factor PoPIF8 involved in luteoloside synthesis

Tree peony ( Paeonia section Moutan DC.), an important medicinal and ornamental plant, produces luteoloside, a key natural compound in its leaves with pharmacological activities such as anti-inflammatory, antitumor, and antioxidant effects. However, the mechanisms regulating luteoloside synthesis in plants remain unclear. In this study, we identified a basic helix–loop–helix transcription factor, PoPIF8, which plays a central role in luteoloside synthesis by directly activating expression of the flavone synthase ( PoFNS ) gene. Overexpression of PoPIF8 enhanced luteoloside accumulation in transiently transformed Nicotiana benthamiana leaves and in transgenic Nicotiana tabacum leaves. Conversely, silencing PoPIF8 in Paeonia ostii leaves reduced luteoloside content and suppressed several biosynthetic genes. Furthermore, we showed that PoPIF8 reinforced its regulation of luteoloside synthesis and PoFNS expression through recruitment of the cofactor PoPIF1. Together, these findings provide new insights into the regulation of luteoloside synthesis and highlight potential targets for genetic manipulation to increase luteoloside production in plants. • PoPIF8 is a potential key gene for regulating luteoloside synthesis. • PoPIF1 physically interacted with PoPIF8. • Overexpression of PoPIF8 and PoPIF1 increased luteoloside content. • Overexpression of PoPIF8 and PoPIF1 increased the expression and activity of FNS .