Objective To clone the full-length sequence,subcellular localization,and analyze the expression patterns of the β-caryophyllene synthase gene(AaCPS)of Artemisia argyi,in order to lay a foundation for the gene function analysis of sesquiterpene biosynthesis pathway in A.argyi.Methods The genes annotated as CPS were selected from the transcriptome data of A.argyi.The full-length cDNA sequence of the target gene was obtained by PCR,and the coding region was analyzed using bioinformatics.A prokaryotic expression vector was constructed and transformed into Escherichia coli competent cells to express recombinant protein.A green fluorescent protein(GFP)fused expression vector was constructed,and the subcellular localization of AaCPS was observed using Agrobacterium tumefaciens transient expression method in tobacco.Real-time quantitative PCR(qRT-PCR)was used to analyze the expression patterns of the AaCPS at different harvest times(April,May,June,July).Determination of β-caryophyllene by HS-SPME-GC-MS and correlation analysis.Results The AaCPS gene was cloned from A.argyi.The full-length open reading frame(ORF)was 1647 bp,encoding 548 amino acids.The molecular weight was 63 667 Da with a theoretical pI of 5.94.AaCPS contained conserved Terpen_synth and Terpen_synth_C domains.Phylogenetic analysis indicated that AaCPS was closely related to the CPS protein of Artemisia annua.SDS-PAGE showed the presence of target protein bands between 75 000-120 000 Da(containing 28 132 Da of the labeled protein),indicating successful expression of the AaCPS protein.The protein was found to be localized in the cytoplasm.As shown by qRT-PCR,the expression of AaCPS gene showed an upward trend,reaching the highest in July.The results of HS-SPME-GC-MS showed that the content of β-caryophyllene increased gradually from April to the highest in June.It is consistent with the trend of AaCPS gene expression from April to June.Conclusion Through the cloning and analysis of AaCPS gene,a foundation has been laid for further study of the functional identification of the AaCPS gene in the sesquiterpenes biosynthesis pathway in A.argyi.