Identification of Volatile Compounds and Terpene Synthase ( TPS ) Genes Reveals ZcTPS02 Involved in β -Ocimene Biosynthesis in Zephyranthes candida .

Zephyranthes candida is a frequently cultivated ornamental plant containing several secondary metabolites, including alkaloids, flavonoids, and volatile organic compounds (VOCs). However, extensive research has been conducted only on non-VOCs found in the plant, whereas the production of VOCs and the molecular mechanisms underlying the biosynthesis of terpenes remain poorly understood. In this study, 17 volatile compounds were identified from Z. candida flowers using gas chromatography-mass spectrometry (GC-MS), with 16 of them being terpenoids. Transcriptome sequencing resulted in the identification of 17 terpene synthase ( TPS ) genes; two TPS genes, ZcTPS01 and ZcTPS02, had high expression levels. Biochemical characterization of two enzymes encoded by both genes revealed that ZcTPS02 can catalyze geranyl diphosphate (GPP) into diverse products, among which is β -ocimene, which is the second most abundant compound found in Z. candida flowers. These results suggest that ZcTPS02 plays a vital role in β -ocimene biosynthesis, providing valuable insights into terpene biosynthesis pathways in Z. candida . Furthermore, the expression of ZcTPS02 was upregulated after 2 h of methyl jasmonate (MeJA) treatment and downregulated after 4 h of the same treatment.