Structural classification, biosynthesis, metabolic engineering and ecological functions for the terpenes produced in tobacco

Tobacco is a globally economic industrial crop due to its distinctive flavor and important commercial value. Diseases, pests and insufficient aroma of tobacco are not only limited to affecting their quantity and quality but also affect their industrial availability. Terpenoid compounds are a large class of secondary metabolites present in tobacco ( Nicotiana genus), which can protect tobacco against biotic stress and influence the flavor and fragrance of tobacco products. This is the first systematic review of the chemical structures, biosynthesis, metabolic engineering and ecological functions of terpenes in tobacco. A total of 300 terpenes reported in tobacco were summarised and classified according to their chemical structure characteristics. A brief overview of the biosynthesis, key genes and metabolic strategies for terpenes in tobacco was carried out. Finally, the functions of terpenes in tobacco aroma and enhancing tobacco resistance against insect and disease have also been discussed.