Metabolic engineering for tobacco quality improvement: Advances and perspectives

As a major cash crop, tobacco quality improvement is constrained by the limited effectiveness of conventional approaches, including traditional breeding and agronomic regulation. This review focuses on the application of metabolic engineering to enable precise and targeted modulation of tobacco quality traits. We first analyze the key factors and underlying mechanisms governing aroma, health-related components, functional metabolites, and combustion characteristics. We then summarize recent advances in metabolic engineering strategies, including pathway rewiring, metabolic flux redistribution, enzyme engineering, and regulatory-network modulation, for optimizing the biosynthesis and accumulation of target compounds such as terpenoids, polyphenols, and alkaloids. In addition, selected integrative approaches that support metabolic regulation and quality formation are briefly discussed. Finally, we highlight current challenges and outline future research directions to facilitate more precise and efficient improvement of tobacco quality.