Photoperiod-dependent regulation of key triterpenoid biosynthesis genes in Gypsophila arrostii root cultures

This study was carried out to examine the effects of different photoperiod regimes on the expression of genes involved in triterpenoid saponin biosynthesis in Gypsophila arrostii root cultures. The responses of squalene epoxidase (SQE), cytochrome P450 716A12 (CYP716A12), and cytochrome P450 72A68 (CYP72A68) genes involved in triterpenoid biosynthesis were investigated under continuous darkness (CD), continuous light (CL), and a 16 h light/8 h dark (16L/8D) photoperiod. Gene expression analyses revealed that the activities of SQE and CYP716A12 varied significantly depending on the photoperiod regime, whereas CYP72A68 expression showed no statistically significant change. Notably, SQE gene activity increased approximately fourfold under CL and 16L/8D conditions, indicating that light exerts a stimulatory effect on the early steps of the saponin biosynthetic pathway. Similarly, the higher activity of CYP716A12 under illuminated conditions suggests that the oxidative modification steps of the triterpenoid backbone can be induced by light. Overall, these outcomes demonstrate that photoperiod plays a crucial regulatory role in plant gene expression and metabolic control. Accordingly, optimizing photoperiod conditions represents an effective biotechnological strategy to enhance the biosynthetic efficiency of targeted secondary metabolites in in vitro cultures.