The ERF transcription factor OpCBR1 balances root growth and biosynthesis of the anticancer drug camptothecin in Ophiorrhiza pumila

Camptothecin is a chemotherapeutic drug widely used to treat various cancers. Ophiorrhiza pumila , a folk medicine in China, has evolved as an ideal model plant for studying the biosynthetic pathway of camptothecin as well as its regulation. Ethylene-responsive factor (ERF) transcription factors are conservatively widespread in the plant kingdom, and are well known to regulate secondary metabolism. However, their involvement in camptothecin production remains unclear. In this study, a total of 78 OpERF genes were identified in O. pumila , among which, OpCBR1 was found to have dual roles in regulating camptothecin biosynthesis and hairy root growth. Overexpression of OpCBR1 suppressed camptothecin biosynthesis but promoted root growth, conversely, its knockout produced opposite effects. Further analysis revealed OpCBR1 directly represses the OpIO promoter to reduce camptothecin accumulation. Meanwhile, it upregulates auxin- and cytokinin-related genes to enhance biomass, providing a genetic approach to improve camptothecin yield through biomass engineering. This study highlights ERF transcription factors as important regulators of plant metabolism and development. • OpCBR1 is a negative regulator of camptothecin biosynthesis. • OpCBR1 directly inhibits the expression of OpIO. • OpCBR1 positively regulates Ophiorrhiza pumila hairy root growth.