Advances in the Synthesis, Regulation, and Metabolic Engineering of Terpenoids in Tobacco

Terpenoids possess important application value in the pharmaceutical and chemical industries. Tobacco, primarily Nicotiana benthamiana and Nicotiana tabacum, has emerged as an ideal plant chassis for the synthesis of high-value terpenoids. This paper systematically reviews the types and properties of terpenoids in tobacco, elucidates their biosynthetic pathways and key enzymes, and discusses the complex regulatory network composed of transcription factors, phytohormones, and environmental factors. A special focus is placed on summarizing metabolic engineering strategies for using tobacco as a bioreactor, including gene expression regulation via transient expression and stable transformation, enzyme modification and subcellular localization, and product storage and secretion. Representative case studies are analyzed to demonstrate their application in enhancing the yields of target terpenoids. Finally, the current research challenges are analyzed, such as incompletely characterized metabolic networks, insufficient biosynthetic elements, and difficulties in balancing terpenoid yield with plant growth. Prospects for future research directions are outlined, including multi-omics integration, development of synthetic biology toolkits, construction of universal chassis, and industrial-scale deployment. This review aims to provide a theoretical reference for the innovative and high-value utilization of tobacco resources.