Tomato Trichomes as Metabolic Cell Factories: Specialized Metabolism, Developmental Regulation, and Defense Function

Tomato trichomes are dynamic interfaces for plant–environment interactions, serving as primary physical barriers against external stressors and as specialized cell factories for diverse metabolites. These highly specialized epidermal structures synthesize and sequester terpenoids, acylsugars, and methyl ketones, constructing a multidimensional defense line against herbivores and pathogens through physical entrapment and chemical repellency. Owing to their complex multicellular architecture, trichome morphogenesis and specialized metabolism are coordinated by intricate genetic regulatory networks. The SlWoolly-centered transcriptional complex, together with effector factors such as SlMYC1 and Hair, links cellular differentiation with substrate metabolic flux, rendering them an ideal model for studying the integration of cell fate determination and metabolic regulation. This review integrates current knowledge of specialized-metabolite biosynthesis, developmental regulation, and physiological functions in tomato trichomes, providing a framework for improving stress resistance and biomanufacturing potential through molecular-design breeding and for exploiting trichomes as controllable platforms for specialized-metabolite production.