Abstract:In order to understand the biosynthetic pathway of phytosterol in Dendrobium officinale, the transcriptome sequence of stems and leaves at two growth stages was analyzed by using Illumina HiSeq 4000 high-throughput sequencing method, and the expressions of key enzyme genes for phytosterois synthesis were compared. The results showed that a total of 43 085 Unigenes were obtained by transcriptome sequencing, of which 24 459 Unigenes were annotated in Nr, Swiss-prot, KOG and KEGG databases, and 7 333 were commonly annotated. KEGG metabolic pathway analysis showed that phytosterol biosynthesis of D. officinale could be divided into three stages with 50 Unigenes (30 enzymes) involved. The expressions of DXR and HMED were significantly higher in stems and leaves than that of MK and MVD. The expression of SMT1 at mature stage was higher than that at growth stage, while the expression of SMT2 was the opposite. The expressions of SMT1 and SMT2 were higher in leaves than that in stems at the same stage. These would be lay a foundation for the development and utilization of phytosterol and regulating phytosterol biosynthesis in D. officinale.