Objective Terpenes are the substances with the highest number and content of volatile components in Michelia crassipes. This study aims to systematically identify TPS gene family members in M. crassipes, and elucidate their functional roles in terpenoid metabolism and floral aroma formation.

Methods Based on the transcriptome sequencing data of M.crassipes, the TPS genes family of M.crassipes was identified by bioinformatics methods. The data obtained by qRT-PCR, headspace solid-phase microextraction and gas chromatography-mass spectrometry were used to analyze the relationship between TPS genes expression level and terpene metabolic content in different stages.

Results A total of 10 TPS members were identified from the transcriptome data of M.crassipes. The molecular weight of the protein encoded by the TPS genes family members ranged from 57 810.20 to 113 803.45 Da, and the number of amino acids encoded ranged from 511 to 987. The results of phylogenetic analysis showed that the TPS gene family of M.crassipes was divided into three gene subfamilies. The TPS-e/f gene subfamily members lacked Motif 1, Motif 3 and Motif 5, and the TPS-a gene subfamily members contained 6 Motifs. The TPS-b gene subfamily member C41348.3 lacked Motif 3 and the remaining members contained 6 Motifs. TPS genes C41348.6 and C41348.3 were significantly highly expressed in stage V, while C31983.0 and C40582.0 also exhibited high expression at this stage. In terms of terpene content, A-ocimene, α-Caryophyllene, β-Ocimene, and cadinadiene were notably increased at stage IV. The content of δ-elemene, α-Caryophyllene, β-Ocimene increased in stage V. The correlation between gene expression and terpene content was analyzed. The TPS-b gene subfamily members C41348.3 and C41348.6 were correlated with the synthesis of the 1,2-bis(E)-prop-1-enyl cyclobutane. C31983.0 in the TPS-e/f gene subfamily of M.crassipes was positively correlated with three types of sweet fruit aroma compounds.

Conclusion The compounds A-ocimene, α-Caryophyllene, δ-elemene, and cadinadiene, may contribute to the fruity floral aroma characteristic of M. crassipes at stage IV, while β-elemene, α-caryophyllene, and δ-elemene are likely involved in aroma formation at stage V. TPS genes C41348.6 and C41348.3 may participate in the biosynthesis of 1,2-bis(E)-prop-1-enyl cyclobutane, whereas C31983.0 appears to regulate the formation of sweet fruity aroma-related compounds such as β-elemene, α-caryophyllene, and δ-elemene. Overall, the TPS gene family plays a crucial role in terpene biosynthesis. This study provides an in-depth characterization of TPS gene family members in M. crassipes, offering a theoretical foundation for future research on the key genes involved in terpenoid biosynthesis in its petals.