The Green Factories: Medicinally Important Plant Secondary Metabolites Production by Callus Culture

Callus culture is a technique that is used in plant biotechnology. For the controlled production of important secondary metabolites with medicinal value, the callus culture technique is widely utilized. Callus is an unorganized cellular mass of totipotent plant cells with the ability of biosynthesizing bioactive secondary metabolites, such as alkaloids, phenolics, flavonoids, terpenoids, and steroids. This review emphasizes the historical developments in callus culture and recent advances in optimizing culture conditions, plant growth regulators, and elicitors to enhance metabolite accumulation. The callus induction by phytohormones, followed by stimulation of secondary metabolite production by biotic and abiotic elicitors are extensively discussed in this review. Further, the molecular mechanisms and insights underlying elicitor perception and signal transduction, including Ca²⁺ fluxes, ROS bursts, MAPK activation, and transcriptional regulation of genes involved in biosynthesis, are emphasized. This review also focuses on applications, limitations, and the possibilities for scaling up metabolite production using the callus culture technique. In conclusion, this review highlights that callus culture paves the way for a sustainable platform for the production of medicinally important secondary metabolites.