BIOSYNTHETIC PATHWAYS AND METABOLIC ENGINEERING OF HIGH-VALUE PLANT SECONDARY METABOLITES

Plant secondary metabolites represent a vast and diverse array of compounds with significant pharmaceutical, nutritional, and industrial value. However, their natural abundance in planta is often exceedingly low, rendering traditional extraction methods insufficient to meet commercial demand. The elucidation of biosynthetic pathways and the application of metabolic engineering have emerged as transformative strategies to address this challenge. This review synthesizes recent breakthroughs in pathway elucidation, key enzyme characterization, and synthetic biology strategies for the sustainable, scalable production of high-value plant secondary metabolites. We critically examine advances in the biosynthesis of major compound classes, including terpenoids, alkaloids, flavonoids, and other specialized metabolites. Recent technological innovations—including single-cell RNA sequencing, multi-omics integration, and CRISPR/Cas9 genome editing—have dramatically accelerated pathway discovery and engineering capabilities. Furthermore, we evaluate the complementary roles of plant and microbial chassis for heterologous production, the emerging significance of biosynthetic gene clusters, and the application of synthetic biology approaches such as co-culture systems and cell-free platforms. Despite substantial progress, challenges persist in pathway complexity, enzyme characterization, and scalable production. This review identifies critical research gaps and discusses future directions for achieving commercially viable production of plant-derived natural products.