Objective To identify members of the cycloartenol synthase (CAS) gene family (PgCAS) using the Panax ginseng transcriptome database, and analyze the expression patterns of PgCAS04-5 in overexpressed and RNAi-positive hair root materials), as well as explore the function of this gene in ginsenoside biosynthesis. Methods Bioinformatics approaches were adopted to characterize the chromosomal localization, conserved motifs, phylogenetic relationships and expression profiles, and the correlations with the gene expression of key saponin synthesis enzymes and the content of monomer saponin of PgCASs. The protein structure and subcellular localization of PgCAS04-5 were predicted. Meanwhile, the expression levels of key enzyme genes and variations in ginsenoside contents were detected in overexpression and RNAi-positive hairy root lines. Results A total of 20 PgCAS transcripts were identified from the P. ginseng transcriptome database. Chromosomal mapping showed that PgCAS genes were unevenly distributed on five chromosomes of P. ginseng. Phylogenetic tree analysis divided the PgCAS family into three subfamilies, and most PgCAS members belonged to subfamily Ⅱ and subfamily Ⅲ. The PgCAS genes displayed obvious spatiotemporal specificity in expression across different cultivars, growth years and tissues. Additionally, the PgCAS family formed an interaction network with key genes involved in ginsenoside biosynthesis, and their content was significantly correlated with the accumulation of monomeric ginsenosides. Subcellular localization prediction demonstrated that PgCAS04-5 was localized to chloroplasts. Moreover, the overexpression of this gene was inversely regulated with the expression of four genes including PgCAS04-5, PgDS-1, PgSE2-4 and PgCYP137 in RNAi positive materials, with significant differences. Conclusion A total of 20 members of the PgCAS gene family were identified in this study, and functional differentiation exists among PgCAS family members. PgCAS04-5 positively regulates the biosynthesis of ginsenosides Rg₂and Rf, and negatively modulates the synthesis of ginsenosides Rb₂and Rd. The results provide a valuable reference for further research on the PgCAS gene fami

Panax ginseng C. A. Mey  /  cycloartenol synthase  /  gene family  /  bioinformatics analysis  /  functional analysis