###### Abstract
The DCTAE conserved sequence is associated with substrate binding, while the QW characteristic sequence comprises negatively charged aromatic amino acids that play a stabilizing role during the cyclization reaction of 2,3-oxidized squalene [18]. With ongoing investigations into secondary metabolic pathways in plants, an increasing number of _OSC_ genes have been isolated, cloned, and functionally validated. To date, more than 200 _OSC_ genes have been identified across various plant species. Their catalytic functions have primarily been elucidated through heterologous expression studies conducted in yeast models including _Arabidopsis thaliana_[19], _P. ginseng_[20; 21], and _Glycyrrhiza alensis_[22]. The _OSC_ genes found in plants facilitate several reactions involving protonation, cyclization, rearrangement, and deprotonation processes on 2,3-oxidized squalene to produce diverse cyclic compounds such as cycloartenol, Ianosterol, dammarandienol, lupeol, \(\alpha\)-amyrin, \(\beta\)-amyrin, and other triterpene skeletons [23]. However, the structures and reaction mechanisms of various types of enzymes within the _OSC_ gene family remain incompletely understood. Consequently, the identification and analysis of _OSC_ family genes in medicinal plants, along with investigations into diverse OSC catalytic mechanisms, represent current trends and challenges for this gene family. In contrast to model plants, such as _Arabidopsis_ and rice, medicinal plants encompass a vast array of species, many of which possess unclear genetic backgrounds due to a lack of genomic and transcriptomic data as well as limited research on their functional genes. This deficiency significantly impedes advancements in the molecular biology of medicinal plants [24; 25]. Presently, more and more modern biotechnological methods are widely used in the molecular research of medicinal plants. Notably, next-generation high-throughput RNA sequencing technology is extensively utilized for transcriptome analyses and functional gene studies [26; 27; 28]. By examining variations in gene expression levels across different tissues, physiological states, and population distributions, it becomes possible to identify genes and regulatory factors associated with secondary metabolite biosynthesis pathways. This process plays a crucial role in inferring key enzyme genes involved in secondary metabolite biosynthesis within important medicinal plants while elucidating their metabolic pathways and regulatory mechanisms [29]. Benefiting from the previously obtained chromosomal-level whole-genome sequence of _G. pentaphyllum_[30], this study systematically identified and analyzed _OSC_ genes across the entire genome. Furthermore, it compared their expression levels in traditional medicinal plant _G. pentaphyllum_ from various regions using transcriptome sequencing technology and qRT-PCR experimental validation. The results will contribute to a deeper understanding of the systematic evolution of _OSC_ genes and the biosynthesis mechanisms of triterpenoids in _G. pentaphyllum_, which holds significant importance for elucidating the molecular mechanisms underlying dammarane-type triterpeneoid saponin formation in _G. pentaphyllum_.