Deciphering the biosynthesis pathway of gamma terpinene cuminaldehyde and para cymene in the fruit of Bunium persicum.

Persian cumin (Bunium persicum) is a widely used plant in Iranian cuisine, valued for its aromatic and therapeutic compounds, primarily monoterpenoids such as γ-terpinene, cuminaldehyde, and p-cymene. Many ambiguities surround the exact process by which monoterpenoids are synthesized in plants. This study investigates the key genes and biosynthetic pathways involved in monoterpenoid production during fruit development. To achieve this, RNA sequencing and GC-MS analysis were performed on two tissues (inflorescence and stem) to identify differentially expressed genes associated with volatile compound biosynthesis. Our findings revealed four highly expressed genes, terpinene synthetase (TPS1, and TPS2), and two geraniol hydroxylases-correlated with γ-terpinene and cuminaldehyde production. We also propose that cuminaldehyde biosynthesis from p-cymene likely involves two hydroxylation steps mediated by cytochrome P450 enzymes (CYP76B) family genes. Additionally, we identified other candidate genes, including those from the P450 family, alcohol dehydrogenases, and hydroxylases, that may contribute to the pathway of cuminaldehyde biosynthesis. Ultimately, this study presents a comprehensive analysis of Bunium persicum's transcriptome and proposes potential key genes involved in the biosynthesis of cuminaldehyde and γ-terpinene.