Objective To explore the key enzyme genes of the pentacyclic triterpene esters biosynthesis pathway in Balanophora subcupularis, which lays a certain research idea and theoretical foundation for its biosynthesis mechanism and the development and utilization of medicinal plant resources in the genus Balanophora. Methods Transcriptome sequencing and analysis was performed on the three tissues of the flowerstalk, rhizome and umbel of B. subcupularis, then searching the candidate enzyme genes involved in triterpene ester biosynthesis by PfamScan, constructing the yeast expression vector of BsubOSCs gene which was introduced into the Saccharomyces cerevisiae lanosterol synthase gene（erg7）-deficient mutant strain GIL77 for functional characterization. Results A total of 87 candidate genes involved in pentacyclic triterpene esters biosynthesis were identified from the transcriptome of B. subcupularis, most of them were highly expressed in umbel, suggesting that umbel may be the main site of synthesis of pentacyclic triterpene esters. The enzyme function of two BsubOSC genes were characterized, which was found that BsubOSC2 could catalyze 2, 3-oxidosqualene to form β-amyrin, but no catalytic product of BsubOSC1 was detected. Conclusion Based on transcriptome analysis, the key enzyme genes involved in pentacyclic triterpene esters biosynthesis were found in B. subcupularis, and BsubOSC2 is a β-amyrin synthetase gene, and is one of the key enzyme genes for the biosynthesis of balanophorin A. This study provides gene resources for further analysis of the biosynthesis pathway of triterpene ester compounds such as balanophorins, and facilitate the research on molecular breeding of B. subcupularis.

Balanophora subcupularis P. C. Tam  /  transcriptome  /  triterpene ester biosynthesis  /  oxidosqualene cyclase  /  acyltransferase